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Which battery to purchase, AGM? VRLA? Flooded? Lithium? 
Differences? Recommendations?
Filling a new 'flooded' battery & initializing it properly. 
Peculiarities of various types of batteries.
Rejuvenating.  Load-testing. 
Chargers (SMART and not). 
Maintenance voltages ...and other information.


This is a LONG article.  It covers VASTLY more than you probably ever thought you wanted to know.  I suggest that for your first reading of this article, that you read it ENTIRELY.   Make a note to come back SOON, and re-read the article, slowly. 

Copyright, 2014, R. Fleischer


You may want to read this:   The article has a some information on batteries that is NOT in the below article.

Vehicle batteries are no longer the simple flooded (slosh) batteries of my youth.  There are now many choices; even more are going to be seen in the near future.   No longer can an article, like this one, be relatively simple.  There is a LOT to know about battery chemistry, usage, purchase, maintenance, etc.  I advise you read this entire article.  Don't worry if you get confused WILL get plenty of information that will 'stick with you' ...and you can always read the article again!

The longest lasting batteries are still, OVER-ALL, ...taking into account all variables, the flooded (wet, slosh) types, in a quality brand.  The second longest batteries are likely the sealed or semi-sealed flooded types, which are very close-to, or even have the same reliability as the flooded types.  Properly taken care of, you can expect an AVERAGE of 5 to 8 years from these various types. 

Next is the AGM/VRLA batteries, with the Panasonic and Odyssey on top (maybe).  A really good brand is the Panasonic (I DO NOT MEAN a copy of the Panasonic). This is NOT the only such good brand; but the Panasonic batteries are ruggedly built and expected to last a long time.  These last about 4 to 7 years, some even longer.   It is possible for these batteries to exceed the life of the flooded batteries, if the Panasonic and Odyssey batteries are well-taken-care-of.

Of lesser life and reliability, below all the previous types, are the cheaper flooded & AGM and some gel types.

Note that when I list the average life here, I really do mean average life: useful life under a variety of conditions.  You might get less or more.  Keep in mind what AVERAGE is, mathematically.  If properly taken care of, the Odyssey, a brand often talked about, is a very good battery, but, like most AGM/VRLA types, one should pay attention to charging voltage/current & AVOID draining it too far at any time for any period of time.    I put the Panasonic battery in this category, although it MAY not be as sensitive to being heavily discharged, at least, or perhaps, for the short term.

BMW sells a battery they call a Gel type, which may be equal to the Panasonic in life expectancy, provided it is "properly taken care of", which really applies to ALL batteries.   HOWEVER:  gel batteries are NOT as good as non-gel, at low temperatures.  If you tend to start and operate your motorcycle in the Winter, with temperatures near or below freezing, where battery demands are high, the GEL type would NOT be recommended by me, particularly over the long term.   I put Lithium batteries in this same category.

The LiFePO4 (ONLY!) ... type of Lithium battery ... potentially COULD have THE longest life, but it has to be treated VERY correctly, as there are some  SERIOUS PROBLEMS AND VARIABLES.  See the LITHIUM batteries area below.

If ANY battery is not taken care of reasonably, its average life expectancy will be lower.  I have seen even high quality batteries that lasted LESS THAN ONE SEASON! ...due to neglect.  If you are the type of person that really does take care of your battery, you can get as much as 50% longer life than my averages, but you probably will only get more typical figures of 30% additional life.  50% longer would be UNusual; especially in colder climates (where you actually start and ride the motorcycle).  This is because motorcycle batteries are located in a poor environment for best life/longevity, such as heat/cold/vibration/poor re-charging/etc.

Below is a long discussion of Lithium batteries ...immediately afterwards are all the other types of batteries and information.

LITHIUM batteries:
I do NOT recommend the Shorai & other common Lithium type batteries for street use at this time. I have not tested any in-great-depth, because other folks HAVE, and their testing is well-done:

NOTE!  The LiFePO4 type, ONLY!! ... is being discussed here ... as all other lithium types are NOT to be used at all!

In my opinion the Lithium battery  being sold for motorcycles should be used only for racing, where the weight decrease and/or small size is or might be helpful. If you are building a Caf bike, you can also consider them. 
There are problems with these batteries if voltage gets too low or the temperature is near freezing; or if charging is improper, and certain other details, ALL of which I will set down in this section.

More problems if the actual AH of the particular battery is too small. 

There is a SERIOUS need for watching the charging process; ...particularly if using a Smart Charger that has a de-sulfation type of mode (charges to a rather high voltage for short periods).  I highly recommend you DO NOT USE such a mode.  Another problem occurs if the Smart Charger is the type that too soon reduces the charging level, & in particular if the very discharged battery is charged too quickly ...and some other things. LiFePO4 batteries are considered fully charged at 13.6 volts; & should not be charged to too high a voltage.  14.4 seems a good practical limit, although some literature might allow 14.6.  NEVER EVER exceed 14.6 volts will permanently damage the battery, even if overcharged briefly.  These batteries can ALSO be permanently damaged by being discharged too much, EVEN ONCE, although that damage need not be fatal (but can be).   They are different from lead-acid batteries in this respect ...a lead-acid battery can be fully discharged, even to zero volts, & if not heavily discharged for too long a period of time, is likely recoverable; this is ESPECIALLY so for FLOODED batteries.  The BIG thing with lithium batteries with respect to being heavily discharged, is that charging MUST be begun at a very LOW rate!   Many specialized chargers designed for these lithium batteries have special recovery modes, if the battery gets seriously drained.

The lithium batteries that are sold for bikes, to my present knowledge, do not have the INternal control circuitry to totally and completely equalize the cells.  However, this CAN be 'acceptable' in many instances. 

It is possible that some of the newer lithium chargers (see the manufacturer of your proposed battery, such as Shorai) have fully controlled chargers now available ...I've been expecting that to happen.  Chargers for lithium batteries are special, or should be, but need not be, but use with Smart Chargers will take some smarts on YOUR part.  High end lithium batteries, and possibly some bike types, have electronics assigned to EACH & EVERY CELL, to ensure equality of charging; holding charging currents & voltages to a tight specification.  You do NOT "have to" purchase a special charger, to make this clear; ...but you MUST BE CAREFUL using non-special chargers.

Lithium batteries can be VERY expensive in proper AH sizes, easy to seriously damage from being discharged, require special charging ...and have other problems ...depending on circumstances.   RACERS and caf riders may use them, and they will hold-up with some abuse, but not hardly a lot of abuse.  These are NOT the type of battery you want if you like to use your electrical system when the engine is off, and then start your bike near freezing, as power output of these batteries falls off very fast when they are cold; AND, bike batteries of the lithium type have VERY LOW ampere-hours (AH) ratings.   There are quite a few street riders now using these batteries. Just because some have good luck with them, does NOT MEAN YOU WILL.  Consider very carefully how they will be used, and under what conditions, etc.   These batteries are pricey even in the small AH sizes.  If you get one, I strongly suggest you NEVER let it get even near fully drained.

These batteries have a very flat voltage discharge curve.  On a practical basis, that means they work fine as they discharge, AND THEN, WITH NO NOTICE, WILL GO SUDDENLY DEAD ....AND, likely will be damaged.   They must then be charged at a VERY low VOLTAGE to begun with!!  This is quite different from other batteries, in which a light recharging CURRENT is needed the beginning.

If you do decide to get a Lithium battery:
Be SURE it is the LiFePO4 type. This stands for Lithium-Iron-Phosphate.  This type of battery is MUCH safer than the Lithium-Cobalt type.  The LiFePO4 type is much more thermally stable & it does not have the thermal-runaway problems of the Lithium Cobalt types, which can lead to a FIRE.   

When using a LiFePo4 type battery, be sure that its REAL ampere-hour (AH) rating is sufficient not get one too small in REAL ampere-hour rating, as while it may start your engine in decent weather, when it is cold the battery output is lower (this is common to ALL types of batteries) and if you have heated clothing and other loads, you may run the battery down very quickly, especially if the charging system is not working strongly, at, say, idle or just above idle. Watch out for 'equivalent to' ratings... xx AH ...Ampere that is MEANINGLESS!  If the battery is too small in REAL AH rating, it can be possibly be overwhelmed by a powerful charging system, although that is typically a lesser problem. Many people do NOT consider the charging rate possible from a motorcycle alternator, particularly the aftermarket larger ones, but even the stock Bosch 280 watt alternator can produce 20 amperes, of which as much as 14 might be available for charging.  An alternator rated at 450 watts, less normal bike loads, might have 375 (or bit more) watts available for your battery. That is over 25 amperes. Will the battery accept that amount of short-term charging rate without damage?   Many of these batteries have their REAL AH specification well-hidden in the literature, if you find it at all.  There may be a sticker on the bottom of the battery.  Some makers/sellers literature rates these batteries in watts ...tricky to properly understand, and NOT informative.   I recommend you do NOT get one that is rated at 6AH in actual capacity, as you can discharge it way too easily ...but, that is up to YOU ...and YOUR NEEDS, in YOUR real world usage.  Lithium battery ratings are often stated in a way that may make you think the seller/maker is comparing the battery to a lead-acid battery.  Be cautious!  You will also likely find that a Lithium-Iron-Phosphate battery of even half the AH rating of the common lead-acid batteries, CAN BE VERY PRICEY.  VERY!!!

ANY battery must not only deliver plentiful cranking amperes at any temperature you will try to start the bike at, but it must deliver much lower levels of electricity for long periods of time ...much longer than the high level needed when cranking the engine.  If you have to do a lot of cranking, especially if you ride in quite cold temperatures, and/or if you have lots of current-draining electrical goodies, or do a lot of stop and go riding, you could discharge the battery enough to not be able to start the engine.  This damages any battery, but can seriously damage or ruin a lithium battery.  If you have heated clothing, heated bars, gloves, vest, those draw current, sometimes substantial current.  It is worse if you have a larger wattage headlight or powerful auxiliary lighting. Especially bad is if you use the headlight during setting up a campsite; or use the battery to run accessories (that may be off-the-bike types...maybe a lamp on a cord).

Consider what a true 6AH lithium battery specification really means during cranking and other usage.  Even if the battery was capable of delivering the full 6 AH capacity at quite high drain levels, which it is not, let us assume here that it is capable of 6 AH at any drain level amount, to give the best possible rating for that battery ...and make calculations easy.

At room temperature, approximately, a LiFePO4 battery can likely deliver a HUGE amount of amperes, as its effective internal resistance is VERY low.  Unfortunately, that internal resistance effectively rises fast when the battery is near the temperature at which water freezes, which reduces its output capability.   The lithium battery is able to furnish very high currents for a short period of time at mild temperatures.   BUT, on a freezing morning with a cold engine, your Airhead may need 200 amperes of current for your starter motor to begin rotating the engine, and could need 100+ amperes to continue rotating.   If the engine started fairly quickly, there is likely not going to be a problem, unless the bike sits at idle for a long period of time, has stock or, worse, some added powerful lights, heated clothing, has been drained some (see above paragraphs)...etc., all of which plus ignition and whatever else is turned on, is draining the battery, from it not being recharged.   Battery charge tends to decrease in  stop and go traffic, typically rather quickly.   The storage or available capacity of that battery (6 AH), assuming no large other drains than just to start the engine, means that you could crank quite a number of times ...allowing the starter to cool off between starting attempts (the way you really should use a starter). So far so good, OK?

But (always are but's, eh?):
Let us say the starter did draw an average of 100 amperes all during the starting of the engine (that is actually possible) ...and you made six attempts at 10 seconds each.  You have used-up a fair amount of the battery's 6 AH capacity (probably over 30% in actuality) for cranking (on a practical basis, it will be considerably worse in cold weather).   That should, ideally, leave plenty for some idling time, then you can ride down the highway & hopefully the ride is long enough at a decent RPM to replenish the battery.  If you make a number of stop & go's, particularly short, say in busy traffic cities or traffic-backed-up freeway jams; maybe have more lighting & heated clothing; if the battery is not being replenished enough, the battery may not have enough charge to start your bike again. There is only so much total battery capacity.  AGM/VRLA/Flooded batteries have very much higher AH storage capacity (the Lithium batteries typically have low AH ratings for those sold for motorcycles) a more conventional batteries WILL give you a VERY much larger 'safety factor'.   This safety factor will be as much as 5 to 7 times on the larger BMW Airheads motorcycle battery size, and 3 to 4 times on the smaller battery size in common use on other Airheads.

Thus, while a true 6 AH battery might work OK for you, it might not.  Consider what the situation would be if you had a regular lead-acid battery, rated at 28 AH ...and changed it to a 6 AH.  You lost a high percentage of the stock battery capacity. 

The 6 AH lithium battery will run the engine, lighting, etc., for far less time, if you had an alternator system failure or marginal operation, used the battery at a campsite, did a lot of stop and go ...had heated clothing, large headlight ...and many other situations.  There is a reason BMW selected a certain battery size (in ampere-hours) for your bike;  many factors were considered.

It could be that a small capacity battery IS more than enough for you for all your starting and riding conditions.  Maybe.

If a LiFePO4 battery is discharged enough, it can be seriously damaged.  4 "cells" are used in a "12 volt system" in this type of battery. If the terminal voltage should fall below 2.5 volts per cell (10.0 volts at the terminals), the battery is being damaged.  Serious damage occurs below 8 volts.  So, make sure you never let the battery become discharged to or below 10.0 volts.  In addition, be aware that many Smart Chargers (that includes the Battery Tenders) may reduce their charging level too soon for the LiFePO4 batteries, if these batteries were fairly well discharged to begin with.  Mind what I said earlier about not charging a heavily discharged lithium battery initially at anything but a VERY low rate.  Guess what happens if you try to start the vehicle with a jumpered-battery, perhaps from another bike or a car, and you have a lithium battery..?   DAMAGE, & it can be BAD and EXPENSIVE DAMAGE.

The charging system in the Airheads will work fine with this type of battery (if not heavily discharged), and a small increase in charging voltage is appropriate ...just as it is for even the stock flooded battery, or any AGM/VRLA, because BMW set its stock voltage regulators fairly low, often around 13.8 volts.  BTW ...that is NOT enough to quickly or even moderately quickly, recharge any battery from such as cranking, sitting at traffic signals, stop and go, etc., but on a flooded battery, water use is lessened.   A much better voltage and compromise is 14.2 to 14.4 volts, which covers all conditions of usage reasonably well, and takes into account lamps life, battery types, etc.  

The lithium battery has other characteristics that differ from lead-acid batteries.  Just one is that after a complete and full charging (assuming the charging IS to proper high-enough voltage), lithium batteries will have a RESTING voltage (after several hours, for example) that is a bit higher than you are used to seeing, 12.8 or even slightly higher.  This resting voltage does not change very much as a light to moderate load is applied.  

LiFePO4 batteries are generally capable of more life-cycles (in practice, usually how many starts you get before the battery fails or starts to fail).  They can be charged faster than common lead-acid batteries. They will accept a faster charge without damage IF they are not already heavily discharged.  They do not have Peukert's losses ...the main article below gets into Peukert's a bit.   They also don't waste hardly any of the charging power in charging efficiency losses.

If your Lithium battery was discharged to nearly dead, the voltage being, perhaps, near or close to zero under a load; you really should begin charging at a FRACTION OF ONE VOLT.  I did NOT say amp, but VOLT. You are unlikely to have the equipment to do that.

I recommend that for lithium batteries you do NOT use a constantly-on and connected Smart Charger, as this will slowly damage them ...and the damage accelerates over time.   I suggest you charge the battery fully, then set it aside, with no load.  This is not practical if you want to ride your bike often!  If the drain of the motorcycle (clock, etc.) in not-running mode is going to discharge the battery very much, I suggest you recharge the battery now and then.  If the drain is excessive, or you want to eliminate it, simply DISCONNECT the battery after charging, store it, and once a year or so is enough for re-charging. There IS some evidence to show that using Smart Chargers continuously with ANY battery will adversely affect its life.

NEVER, EVER, jump start a bike with a discharged lithium battery.  This is effectively the same as HUGELY excessively charging the lithium battery ...and it may ruin the battery immediately; where, before, you might have had a chance at recovery.

Re-stating:  A deeply discharged lithium battery must be recharged at a VERY LOW RATE.

Am I totally against these LiFePO4 batteries?! ...not at all.  Just know what you are getting into.  Anyplace I'd recommend them?  Yes: racing & and minimalist caf bikes in particular ....AND a maybe-maybe for street riders who do not need the larger capacity of stock batteries and are willing to properly maintain and use the battery.

Back to lead-acid batteries:

What is the difference between a Flooded Battery; sealed & semi-sealed battery; AGM battery; VRLA battery?

1. The two basic types of lead-acid batteries are the type called FLOODED (an liquid sulfuric acid mixture is visible); and, the battery is sealed or semi-sealed or has cell top covers that can be removed in order to add distilled water, to a case-marked level-line. Construction methods can be wildly different.   Batteries of all types need VENTS, either a tube comes out, perhaps from the side near the top, or from a hole of some sort in the cell caps, or there is a seal that opens if pressure inside the     battery becomes high enough (typically from overcharging or way too rapid charging). Fully sealed batteries can not have water added, sealed there means sealed. SOME semi-sealed types can have water added if needed. The sealed batteries (and some semi-sealed batteries) differ from the types that have cell cap covers that are easily removed for addition of distilled water.  The difference is primarily in the plate chemistry (typically a calcium component)...I will get into this a bit next.

2. Fully sealed batteries, that you cannot open, are properly called VRLA, or Valve Regulated. These batteries have their plates made of a slightly different method and chemistry...similar to a semi-sealed calcium-containing battery.  These sealed batteries contain a ONE-WAY valve, and if gas pressure rises too much in the battery, from such as excessive temperature and/or charging, the valve opens, and gases escape. Enough of that and the battery begins to fail. In this respect, a VRLA battery can have other chemistries such as cadmium, iron, etc. However, all the batteries under discussion here are for those with some form of the element lead, and sulfuric acid as the electrolyte, whether in gelled form or liquid, or simply soaked into absorbent mats.

3. The VRLA group INCLUDES GEL and AGM. Thus, strictly speaking, fully sealed car batteries, which always have a gas pressure valve, are also VRLA types.

4. The sealed, and SOME semi-sealed batteries, which I will now call VRLA types, as they all ARE, use a chemistry called Recombinant. What happens in battery use, particularly charging (something similar, in reverse, happens under heavy drain) is that oxygen is formed at the positive (+) plate, and that oxygen reduces or eliminates the normally otherwise produced hydrogen at the negative (-) plate. The result is a cycle of gas>>>water>>>gas. This is overly simplified.

5. AGM is simply a type of VRLA. You could have APM....Absorbed Paper Mat, or many other things.

6. A valve vented lithium battery is also a VRLA, strictly speaking.

I will get into these things in depth, later in this article.

NOTE that voltages for 100% charge vary considerably with the type of battery.  The 'standing awhile' old standard flooded (slosh) lead-acid battery was about 12.6 volts at room temperature; the AGM/VRLA/GEL types up to 12.95; the lithium types about 13.6.  However, just how to use these voltages is not clear when you see these voltages in the literature the voltage during actual practical charging, is NOT that voltage ...not even that after the battery RESTS for a few hours AFTER charging.  I will get into these things deeper later in this article, about practical voltages.

Rejuvenating old tired lead-acid batteries, chemically:
These chemicals, such as EDTA, Epsom Salts, ETC., are often promoted with wild claims for them.  There is a lot of misunderstanding about the use of these chemicals.   Under the 'right' circumstances, these chemicals, if selected carefully, CAN or MIGHT rejuvenate, partially, old batteries of the flooded type. You need access to the insides.  IF it works, it typically works for a rather short time period.   What happens with batteries that are highly sulfated from being discharged or from very old age (just starting your engine causes very slight sulfation every time, & a battery that is partially or more discharged is going to sulfate more RAPIDLY, and perhaps way beyond hopes of recovery), is that EDTA, as an example, can chemically convert the sulfation.  UNfortunately, it can do NOTHING for the plate the sulfation was on.  The 'converted' product needs a place to go to.  That means it is in contact with the plate; maybe some falls to the bottom of the battery, assuming that the battery even has a no-plates area at the bottom for such deposits.   The active plate may have reasonable 'metal' (using that word generically here, to cover both types of plates in use in a battery) left to do something; OR NOT.  Typically, there is little if any useable active plate material left.  Critically, a sulfate coating caused by a discharge of the battery comes in two types.  What is called 'hard sulfate' from long term sulfate conditions is nearly totally unrecoverable.

My advice:  Don't even try using these 'products'.   Even if they work, which is very rarely, the battery is VERY likely to fail totally, and quickly, and in the meantime it is hard on the rest of the charging system.

Rejuvenating old tired lead-acid batteries, electrically:
If a battery has not been moderately to greatly discharged for too long a period of time, you may be able to resuscitate it.   It will not be fully rejuvenated, mostly depending on that TIME period for which it was discharged, but may be good enough to last a considerable period of time.  Flooded batteries that WERE in reasonably good condition, but have been considerably or fully discharged for not over a month, especially if they were at fairly cold temperatures, probably can be resuscitated.  For AGM/VRLA type batteries, perhaps somewhat longer than a month or so.   Contrary to popular belief, AGM/VRLA batteries do NOT like, not at all, being heavily discharged & then sitting that way for any period of time.  In many instances, these abused batteries, rejuvenated some, will draw a lot of charging current, and have other characteristics, that cause additional wear on your alternator charging system.

If the battery is quite discharged, terminal voltage may be too low to trigger a Smart Charger to turn-on.  If this happens, you can start the re-charging process by connecting a common low to moderate amperage (not over 12 amperes rated) common charger, NON-SMART type, for a long enough period of time until the terminal voltage rises above 10 (approximately).  Then disconnect that charger and connect the Smart Charger.  If you only have a simple charger, watch the terminal voltage. Do NOT let it get over 15. Watch the current flow too (if you have a meter ...too much current means excessive spot heating).  You may need to connect, disconnect for some hours, then reconnect, repeatedly, until you have 10 volts. If it is a flooded battery, and the water level is now quite low (below the level of the tops of the plates), add a quite modest amount of distilled water to each cell, as required to BARELY cover the plates, and charge at a low rate.  Watch the voltage. As the battery is seen to charge-up, the water level will probably rise some.  After the battery is FULLY charged, then add distilled water to the normal maximum level line. This can take a week with a low power Smart Charger (assuming it does turn on), and a day or two with a small non-smart charger.

Before putting the battery into use, & assuming you HAVE been able to charge the battery to at least 14.2 volts, disconnect the charger for a FEW hours.  Then, use a REAL battery load tester to analyze the battery's condition.  If you have no access to one, then CRANK the bike for 10 to 15 measured seconds, without starting the engine.  If the cranking is good, and terminal voltage over 9.5 DURING CRANKING ...use the battery, as it is probably OK.

FLOODED batteries: 
A "flooded" battery usually has removable cell covers, contains liquid you can (or should!) see if a cell cover is removed. Sometimes you can see through the case, or use a flashlight or other light through the case, to see the liquid. You have to add water occasionally to flooded batteries that have removable top covers.  Water type should be distilled, NEVER tap water. Walmart sells distilled water in 1 gallon plastic jugs for under a dollar, your supermarket probably is not much higher; ...a gallon will last a long time.

Flooded batteries are often, but NOT ALWAYS, shipped dry, & if dry-shipped it needs to be properly filled with acid electrolyte in the initialization process.  Sometimes these batteries are advertised as "pre-charged", which is very misleading. There are several problems involved with the purchase, initialization, and use of a brand-new flooded battery. 

There are types of batteries that are NOT normally considered 'flooded' types, that you DO add liquid too...ONCE. A particular version of Yuasa's Valve Regulated Battery (VRLA) is such a type ...but after adding the ELECTROLYTE you seal the holes.  That type is not specifically treated in this article; but is very similar in initialization and charging, etc.  Here is a link to that type of battery:

If "initialization" of any type of flooded battery is not done correctly, your battery will NEVER reach its full capacity; & WILL have a shortened life.   It is important that gas bubbles be eliminated now & then during the initialization period & a full & complete soaking of the internal parts accomplished before any high current charging.   This can NOT be done by filling & then immediately putting it into your bike & then you go for a ride.  That removes a substantial amount of life from your battery.

In general, old-fashioned flooded batteries are STILL the LONGEST LASTING batteries, assuming they were properly made & PROPERLY initialized and properly taken care of.

Flooded batteries; or any lead-acid battery under some conditions, can be extremely dangerous.   The hydrogen gas given off by flooded batteries (or, gross overcharging of others) can cause an explosion from such as a spark from a battery charger connection.  Acid can blind you.  Do NOT take this lightly.  Wear goggles.  Have a container of water available.   Even sealed batteries can be dangerous, if grossly overcharged or allowed to get quite hot, as they may pressurize and suddenly open their safety vent (VALVE Regulated batteries too).

The conventional flooded battery, with or without sealed battery chemistry, MUST be charged regularly, or kept on a maintenance charger, more often in warm weather.   These batteries SELF-DISCHARGE much more rapidly than other types. SOME types of lead-acid batteries self-discharge less rapidly, such as the types containing calcium in the plates.  The AGM and VRLA types have much less self-discharge than even those. 

Tongue-in-cheek (some!) scenarios regarding flooded batteries:

Scenario #1: Battery or motorcycle dealer fills the fresh "dry" battery with sulfuric acid electrolyte (one can hope of the correct strength ...German's use a slightly stronger electrolyte), & possibly charges it once, maybe not, probably does not rock the battery to eliminate pockets of gas ...and places it on the for-sale shelf.  OLD dealer stock is particularly bad here if the cell tops of the 'shipped dry' battery were not sealed against outside air during 'dry storage', air always contains moisture!

The battery begins to deteriorate from the moment of acid mixture installation.  The battery also deteriorates from unsealed tops before the battery has acid installed (although that deterioration is usually very slow).  The battery deteriorates especially fast if acid is installed & the battery is NOT properly "initiated".  The battery sits there deteriorating, awaiting YOU, the customer.  
  YOU arrive ...YOU need a new battery RIGHT NOW.   If you are lucky, the battery might have been charged & even kept charged.  Improperly initiated? ....your battery may already have lost a lot of capacity, & may already have a decreased life, sometimes a LARGE decrease.  If the battery is older, never had acid in it before, the cell top sealing was removed or never there in the first place, & the battery is stored in an area that has goodly temperature changes during the day/night, & higher humidity ....all these things will conspire to reduce battery life, once it does have acid put into it.  If not 'initialized' properly, it is worse.

Scenario #2: The dealer fills the battery while you wait, installs the battery, & you start your engine & off you go down the highway.  Such a battery has not properly absorbed the acid, will have bubbles as well as dry places at/in the plates ...all create hot spots & chemical reaction problem areas.  Your new battery will NOT have 100% of its plate areas initialized chemically nor electrically.  That battery will NOT last nearly as long as it should, certainly NOT give proper long life; nor will it operate to its rated capacity & performance.   This type of battery often fails in cold weather rather early; & in some instances can fail in mild weather.

Scenario #3:   The dealer fills a fresh battery (with no PRIOR air exposure since the cells WERE still capped & sealed) with acid mixture, initializes it in the way explained later in this article or reasonably similarly, & then connects it permanently to a Smart Charger on his shelf, whilst awaiting your purchase.  The dealer sells these shelf batteries within a few months.   Congratulations!

Scenario #4:   You purchase a battery at Wal-Mart or similar. It is probably a lawn equipment battery. It might even fit with the correct terminal types, size & polarity at the correct places, or you make wood, etc., pads. If the terminals are backwards, you 'make' it work in your bike, putting stress on the battery terminals, etc. ((Hopefully you never forget wire connection direction).   It either is already filled and deteriorating because Wal-Mart does not use chargers ...or, it is empty and YOU fill it with the acid that comes with it ...or you find at some other store.  The instructions that come with the battery are hardly complete regarding initialization.  The battery has no side vent nor hose; fumes are released UPwards from cell cap holes.    You find your seat and seat pan rotted-out and rusted-out a year or so later ...ugggh!  You also find the screws for the seat hinges have rusted into their hinge threads, and are the devil to remove.  If you have a K bike, you might find the fumes have caused intermittent problems with the 'computer'.  Do you have other electronics of some sort near that battery?  Did you talk to Wal-Mart before purchase about their battery WARRANTY DETAILS?  Do you know that if you return a failed battery in, let us say, 3 or 4 months, that the return $ allotment is VERY skimpy?

Scenario #5:  You did Scenario #4, but failed to notice that the battery has + & - terminals reversed. You connect the battery & do a LOT of damage to various electrical things in your motorcycle.  Since the battery does not fit correctly, you return to the store with the battery & find that batteries are covered not by exchange for a correct one (if they have such!), but by an allowance, & you lose a substantial amount of the money you paid for it yesterday.  Perhaps you monkey with the leads on your bike 'to make it fit', creating a possible fire hazard ...or a strain on the terminals ...which leads, eventually, to a sudden death internal disconnect ...and you can then complain about the battery quality, when it WAS ACTUALLY YOUR FAULT.

Scenario #6:   Back at Scenario #5 again return the battery as 'defective', and, LUCKY YOU get you money back 100% ...or, an exchange with the correct terminal placement.  This exchange battery also has no vent tube, and your seat rots out 3 years later, or maybe your bike's fuel injection computer or ABS computer fails.

Scenario #7:   You get the correct battery, with correct venting via an overflow & vent tube, initialize it yourself in the correct way, & probably obtain a reasonable life from it, since you also pay attention to maintenance.  Congratulations!

Scenario #8: You purchase a battery.  You use it far beyond what Snowbum says you should is now 7 years old, & fails on a dark & stormy night, very suddenly, in the middle of nowhere & it is Saturday evening.  All bike stores are closed the next two days.  It is raining.  You have no rain clothes, no tent, no sleeping bag.  "She" is on her first ride with you.  Things are becoming MUCH less fun.

Scenario #9:  You have had many years of use with no problems.  You report that situation, so all the world knows YOU have had no problems.  Anecdotal 'evidence'.   You continue to use that battery, no problems.  Doesn't make much difference what brand nor type it is.   Your alternator & diode board are wearing faster, your starter motor is wearing faster, even the voltage regulator is wearing faster.  All this faster wear is due to an old battery ...but it starts your bike problems (so far)!    If you have a K bike, suddenly, one day, an important relay has a problem ...its contacts are welded.  The starter continues to run, as you go down the highway ....GUESS WHAT IS NEXT?

Scenario #10: You purchase an AGM/VRLA type of battery whose terminals are on the correct side of the battery for your bike. These batteries come pre-charged.  Your purchased battery was not very old since original shipment to the seller. You check it on a Smart Charger or trickle charger while monitoring its terminal voltage.  You install it.   You make sure it is kept close to 100% charged.  You make sure it fits your battery holder/carrier, & that the tool tray does not excessively press down on it when you are seated on the motorcycle.  You usually perform a real load check every 6 months, but never beyond one year.  You replace the battery on a time/miles or load testing basis.

Battery types in common use:
Flooded batteries, by common use of that description (liquid sloshes around in them) are "lead-acid" batteries made in a few basic types.  They contain the element lead, in both a fairly pure form, as well as forms that contain other substances. There are positive & negative lead plates in the battery & they are not the same types of lead substances. The plates are porous. Some types of lead-acid batteries contain some calcium in the plates & those generally have a slower self-discharge, & can be a low or no maintenance type. These tend to WANT TO operate at a SLIGHTLY higher voltage, & will IF your voltage regulator is set properly.  Antimony is another substance often used in these batteries.

There are sealed batteries of several types available, besides conventional flooded batteries.  The conventional flooded battery (with or without sealed battery chemistry) MUST be charged regularly, or kept on a maintenance charger, more often in warm weather.  These batteries do not, generally, require special chargers ...and trickle chargers or standard lead-acid Smart Chargers are very convenient, and generally OK with them.

The absorbed mat sealed battery, often called AGM (absorbed glass mat), or VRLA (valve regulated) :
Contrary to information published in a few places, these really are the same type of battery.  The AGM is a subset of the VRLA type description. I am not sure where the confusion originally came from, but I suspect it was a German technical school, that taught that the VRLA battery was a flooded battery with absorbent glass mats.  The only battery that might be thought of this way are some from Yuasa (and maybe others?) which are shipped withOUT acid; you fill it; then you seal the battery ...although there is an over-pressure vent.     An example of a battery that is a VRLA/AGM, is the Panasonic brand (at one time, long ago, these were re-labeled as WestCo when sold by WestCo).  The VRLA simply means that the battery has a pressure vent.  Well, so does nearly every 'sealed' battery!

These AGM/VRLA batteries have very low internal electrical self-discharge and are usually shipped from the manufacturer fully charged, and probably will be OK on a dealers shelf for 6 months or so, unless the dealership battery storage area is quite warm.    Another popular brand is the Enersys-Odyssey, sold as a premium product.  An extra-premium version is available that has a metal case and it MAY be worth the additional cost as it protects the battery to a great extent at much higher temperatures than the none-metal case common versions.  The metal case version SHOULD BE AND IS MUCH less heat sensitive ON YOUR BIKE due to warping effects on the softer plastic case type, and the battery SHOULD AND WILL last MUCH longer.  A metal-cased VRLA battery might, in some circumstances, last a VERY long time ...over 8 years is really possible, even in engine starting usage ...I expect that, properly taken care of, an Odyssey in a metal case jacket (they do sell them like that) will last as much as a dozen years in proper use.

>>>MANY 'cheap' batteries are sold "using the Panasonic name" in the description. Some are a bit more honest and say they are the 'equivalent'.  If you want a Panasonic, be sure it comes as branded on the case as the Panasonic.  The Panasonic BRAND of battery is very well made internally. Yes, I have taken them apart (NASTY chore).

AGM/VRLA batteries are usually very tightly packed into their case.  They tend to be heavier, not lighter, than equivalent AH-rated flooded batteries. The only really important drawback is expansion/contraction with temperature changes (which are environmental and also from high current charging in the bike).  Many early designs failed from 'sudden death' due to internal cracks, and a few other problems.  With quality modern manufacture, most of these concerns are, or have, faded away, even with the common plastic-cased types.

WestCo stopped selling rebranded Panasonic batteries long ago, as far as I know.  In the long-ago past, one could remove the WestCo label & see the Panasonic label.   After the re-labeling was abandoned, the WestCo battery was probably a relabeled "BB" brand.

Another brand with a decent reputation is MotoBatt. They are hardly the only one.

Which to purchase:
I recommend you base your decision, on what fits, the CCA rating, warranty, quality built reputation; and as-delivered cost.  The cost of batteries is constantly changing.  Be sure to think of shipping charges.  You might be able to get a Panasonic VRLA battery from such as DigiKey, shipping free, if you know how to find the free shipping method, usually hidden, on the website.  DigiKey is a HUGE & reputable source for electronics & other electrical's.

The mats do not have to be glass fiber. There are many types of these batteries.  Ones specifically designed for engine starting were produced originally in only modest quantities.  There WERE versions NOT designed for engine starting, and the use of them originally gave the AGM batteries a bad name, and led to a LOT of confusion over the design. The Panasonic was a brand of AGM that was, unfortunately, caught up in this wrong-thinking by many in the motorcycling world, and they vigorously decried the brand, as NOT being for engine starting, which is absolutely backwards WRONG!  There were also BAD QUALITY AGM batteries sold, and this perpetuated the rumors about AGM. 

The modest quantity statement is no longer true; now there are MANY of them and they are made in HUGE quantities, many as original car batteries ...and as more cars are being produced with start-stop-start-stop type of engines, most will have AGM batteries of some sort.

Before these batteries were finalized in design for general public use for vehicle starting, they were developed for the Military and also for extremely long life ... float/maintenance charging was used with very specific voltages to be supplied to them.  These batteries were slightly later used for electronics and other back-up systems, often systems that are hardly, if ever, looked at.   Somewhat modified versions of these batteries were later made for engine starting and became very popular. Absorbed Mat batteries designed for vehicle starting & charging systems are used in CARS where demands on the vehicle battery are HIGH, typically higher than with flooded batteries.  QUALITY AGM/VRLA batteries are generally quite sturdy & very tightly compact internally. High heat and/or vehicle starting and/or high charging currents ...are all somewhat damaging to them, so once in awhile a catastrophic failure happens, suddenly the battery is essentially dead, due to an interconnection cracking failure. Generally, the car versions are in stiff cases, the motorcycle types not so much, so they have a somewhat more tendency to swell upon overcharging and high temperatures.  The reliability of the best brands is quite good.

MOTOR Magazine (a top source for Professionals, for everything about repairs & also industry trends)  confirmed previous estimates, that by the end of 2014 about 25% of all new cars and trucks would have AGM batteries, & they expected 40% by 2016.  One of the reasons is the ruggedness.  A MAJOR reason is the new idle-stop technology being rapidly introduced to improve fuel economy & reduce emissions.  In that mode of service, engines might be automatically stopped and restarted up to 50 times a day!  AGM batteries designed for vehicle starting & charging will handle three to four times the number of REASONABLE depth of discharge/charge cycles compared to conventional batteries; they will accept higher charge rates; operate better with lower charges, provide higher cranking performance, etc.   For MOTORCYCLE use, the designs are improving, and I expected they would soon not be known for their catastrophic failure modes as much as lasting longer than flooded batteries ...this seems to be happening. NOTE, however, that for automobile use, the alternator systems are big, rugged, will be often combined with the starter motor, and the battery is very likely to be ALWAYS charged, after the vehicle is parked. Thus, the battery will last longer than in bikes.

ALL the various types of lead-acid batteries, whether sealed, gel, lead-calcium, lead-antimony, VRLA, AGM, etc., have somewhat differing charge, discharge, float, self-discharge, temperature ...and other characteristics.  Some variances in charging voltages, particularly for various levels of charge, are also applicable. This article will get into these things, in some depth.

GEL vehicle batteries, TRUE gel that is, such as the $$ BMW (Exide) types, do not use the same absorbed glass mat construction of the VRLA Panasonic, AGM, etc.  Instead, they have a silica compound filled gel that supplies the electrolyte function.  The form of gel batteries used for low-drain security systems is NOT the same as the BMW gel battery.  The biggest problem, besides price, of the BMW Gel battery, is that it is being used in a standard charging system bike, but the problem is not all that serious.  If you use a maintenance Smart Charger on it, the specifications need to be relatively tightly controlled, & the voltage need is slightly higher.  When you think about this, it is a compromise, in MY opinion, for BMW to offer a GEL battery like this, for a bike with a standard charging system, often charging at too low a voltage, as set by BMW originally.  Luckily, the Classic K bike alternator VR is part of the brushes assembly, & easily changed to the higher voltage version. If you do NOT change that VR voltage, and the voltage at the battery terminals, during cruising, is in the stock area, say between 13.7 and 14.0, you will still get 'reasonable' life, just not quite as much life as if the charging voltage was 14.3 or 14.4.  NOTE ALSO, that GEL batteries are not as good as other lead-acid batteries, when the temperatures are near or at or below "freezing" ...that means water freezing temperature:  32F.  "Authorities" VR's are usually set to about 14.4.

Many of the specialty batteries, such as the AGM/VRLA types, are slightly taller, & often much less wide, than the stock motorcycle battery.   Some Panasonic and other batteries that are slightly taller than a stock BMW Mareg flooded battery, will be pressured by the Airhead tool tray ...not a great idea when you are sitting on the seat can possibly damage the battery over the long term.  There are several fixes I have  used for this.  How to deal with this varies.  The distance from the bottom of the battery box to the underside of the tool tray is not always the same. There are differences in the seat pans, rubber bumpers on them, & possibly some small but accumulative tolerances on other things, such as at the battery lower mounting, etc.  I advise you to consider the actual height of the battery you will be purchasing ...and your tool tray fitment.

Things to think about:
1.  Make a nice hold-down plate out of a nice piece of flat stainless steel.
2.  Sand down the UNthreaded part of the plastic hold-down knobs threaded hole area. That shortens them a bit.
3.  Turn the stock battery hold-down upside down. That also lowers the top of the knobs.
4.  If the knobs are NOT sanded, & just put in upside down, that sometimes works, but if you also put the hold-down upside down, that may make it less easy for your fingers to rotate the plastic knobs.
5.  Installations vary, so try what works for YOUR bike!  ALWAYS think SAFETY.  You do NOT want a metal hold-down to electrically short the  terminals.

I have also used combinations of these things, especially using both #2 and #3.  I have made a wood spacer for the narrower battery, painted it black; but later found out that normal hold-down pressure was plenty enough to keep the battery from moving, even in rough terrain.

DE-sulfating types of chargers:

There are smart chargers that have a de-sulfating mode.    These chargers are generally OK for use if the battery has ...MAYBE ...a quarter charge ...or more.  De-sulfation chargers work, sometimes, but if the battery charge was quite low for any goodly period of time, these chargers, IF THEY WORK, will be VERY UNLIKELY to give much more battery life, compared to you using a standard charger, or a smart charger without de-sulfation protocols, in trying to resurrect the battery.  

WARNING!!!!   If you use a de-sulfating charger on a battery that is fully connected to your bike's wiring system, the very high voltage (as much as 25 volts! ...and in some instances, much more of a 'spike' that is very short in time) from the charger CAN INJURE THE BIKE SYSTEMS.    THIS IS PARTICULARLY SO AND CAN BE VERY EXPENSIVE TO YOU ...ON CAN-BUS BIKES!!!  I highly recommend that you be very prudent & NEVER use de-sulfation MODE on a Can-Bus bike! ...and THINK before using that mode at all.  If you want to try the de-sulfating mode, DISCONNECT the battery from the bike!  IF you remove the battery from the bike, or at least disconnect it (all wires to the negative terminal will do), then there is NO problem with using a de-sulphating mode charger on ANY bike.  DO NOT use such a charge mode with LITHIUM batteries! ...NOT EVER!!


Whenever ANY form of lead-acid battery is at less than full-charge, there are chemical reactions going on that are causing MUCH FASTER deterioration. Much smaller deterioration is happening even at full charge. There are several types of deteriorations.  The one most commonly talked-about is SULFATION.  Sulfation occurs more and more as battery charge DEcreases.   Initially, the sulfate crystals are what are referred-to as 'soft'.  These 'soft' crystals are rather easily chemically converted by such as charging properly, which can very substantially remove/convert these sulfate crystals, which are otherwise being plated onto the battery plates.  Recharging the battery will usually recover almost all the original capacity & proper function of the battery.    As the battery charge reduces, over time, from the battery not being recharged, the sulfation gets worse.  Enough time at a reduced charge, particularly a deeply reduced charge, & the small sulfate crystals get much larger & these are vastly more difficult to remove or convert.    Eventually the battery is ruined.   On some vehicles, the alternator is not being spun fast enough, or is powerful enough, to fully recharge the battery; this is often seen on commuting vehicles ...short trips especially.  A few miles or short stop and go riding might hardly be enough to recharge the battery.  Regular use of a charger is a must to obtain good battery life in this type of service.

Various chargers on the market may promote their anti-sulfation or pulse modes, or other wordings.  Some do work fairly well; but, many, if not most, are only partially good at reducing sulfation; and hardly do much for the large crystal type of sulfation.  A LOT of the advertising is HYPE! If you want to try to desulfate a battery yourself, you can attach a quite small (very low output) battery charger & monitor the current & the voltage.  Because chargers vary so much in true output voltage & current (also depending on the battery!), it is impossible to give hard & fast rules.   Those with the know-how & the equipment can use an adjustable power supply, or a charger with a series resistance, or a quite small charger (1 ampere, perhaps, but some up to 3), or a larger charger with a method of reducing the charging current/voltage (a series connected lamp bulb perhaps, or Variac on the line side of the power source).   Whatever the method, the ideal way of trying to relatively quickly remove/convert sulfation to NEARLY the extent possible, is to charge the battery at about 0.150 ampere for a day or even three days.  Since there is no quite high charging pulse voltages in use, it is safe to do this with the battery still in the bike, and still connected.  Don't go over 16 volts at the battery.  You could do it faster by starting off with no more than 1 ampere, never exceed that amount, & keep raising the voltage as the charging current tapers off from the battery obtaining a charge.  The lower value stated above, 0.150 ampere, is best.  An even faster method than the no more than 1Ampere method, not quite as good, but still good enough, is to charge at a much higher rate, perhaps up to 6 amperes for a few minutes, then 3 amperes for a some time, all watching the terminal voltage.  When the voltage reaches about 14 to 14.5, reduce the charging current to 100 to 150 ma, for several days ...checking the current now and then, and adjusting the source if needed to maintain the proper current.

There are other types of deteriorating conditions, including one called stratification, where the acid & water mixture separate some, & the acid is near the bottom.  This situation is also helped by the very slow charging methods in the prior paragraph.

VERY long term charging can be done at 0.04 to 0.06 ampere. This is the type that might be considered for a very long storage period, besides de-sulfating.  A simple tiny low-output charger, with a series resistor, will do this. This extremely long term trickle charging is, as noted, done at 0.04 to 0.06 ampere.  You do not need a $$ smart charger to set up such a low charging amount ...if you don't know how, ask on the Airheads list or Kbmw list.   This method can sometimes be used with a Smart Charger after a complete and full charge. If not under 100 milliamperes, you should not keep it connected during the entire Winter storage time ...although the deterioration will NOT be excessive. Some Smart Chargers have cycling going on, periodically, so can be more hassle to measure and determine mode.  Thus, the very cheapest teeny chargers, with a series resistor (or lamp for that purpose) are really best for extreme long term storage. MANY just use a Smart Charger ...which will NOT deliver the longest life for your battery, as will the 0.04 to 0.06 ampere setup. I know of NO Smart Charger manufacturer that will tell you this!

Things you may want to know:

The higher the ambient temperature on ANY battery, the faster the self-discharge, and the more need for re-charging.   This can be critical for flooded batteries, which self-discharge rapidly in the Summer.   VRLA, AGM, Absorbed Matt, and Gel batteries are MUCH slower to self-discharge, although their self-discharge rate increases as the batteries age.

Some manufacturer's do NOT furnish really important specifications when promoting & selling their products.   Some, on purpose, try to cleverly avoid information such as Cold Cranking Amperes (CCA) by using other terms, that are of no importance, or even meaningless.  CCA is how many continuous amperes the battery will supply for 30 seconds at 0F ...before the battery voltage falls to 7.2; where its energy level is essentially zero.  True CCA, as far as real world use, will be somewhat less than the CCA as advertised, because the battery is not usable for starting the engine at 7.2 volts fact, under 10 volts is getting very iffy. Nitpicking aside ...the CCA test is real world.

CCA, combined with what is called Reserve Capacity, is what is important, besides quality. Reserve Capacity is specified for 10.5 volts, so it is real-world usable ...IF you can find that specification (and, find CCA).  CCA is obviously important in cold weather.  A brand-new battery will start deteriorating immediately after being put into service, which is one reason batteries should be tested yearly, at least, by a LOAD TESTER instrument.

"CA", a calculated value (as opposed to CCA), is done for 32F, and is pretty-much worthless.   Nerdy: On good quality batteries, CA is typically going to be CCA divided by 1.25.

I think a reasonable test, which is pretty much a common Load Test, is, at "room temperature", 10 to 15 seconds at 3 times the rated ampere-hours, at which the battery, still under the testing load, should read over 10 volts.  This means that if you load test a 30AH battery by having a load of 90 amperes, and maintain the load for 10 to 15 seconds, that battery is considered GOOD if the voltage is over 10 volts at the end of the load testing time (load STILL connected at that point). A good Load Tester has compensating charts or readout correction, for temperature.

Batteries deteriorate, fully charged or not.   Deterioration varies with temperature & type of battery.  In general, for every 15F ABOVE a nominal 77F the battery is stored or operated at, the battery life is reduced by HALF.

Batteries self-discharge.   In GENERAL, a flooded battery loses about 1/4% to 1% of its charge per DAY in VERY HOT Summer temperatures.  For an AGM, the loss is much lower, perhaps 1-3% per MONTH. These figures are for batteries being stored with NO loads attached (not even electro-mechanical clocks).

When you charge any type of battery, the conversion is not 100% efficient.   For flooded batteries, you must put into the battery about 15-20% more electrical energy than the battery will give back.   This 15-20% is converted to HEAT in the battery during charging.    For AGM's, the conversion is more efficient, perhaps as low as a 5% loss in efficiency (The lithium batteries may be even better).   Yes, it is true, this DOES mean a AGM-VRLA battery can be 'easier' on the charging system than a flooded type.

There is a peculiarity with ALL types of batteries ...that deals with a mathematical function called "Peukerts Exponent".   What it means (on a practical and simplified basis) is that some batteries can be discharged (there is a re-charge effect too) at a higher % of capacity rate than conventional flooded batteries, with a minimal loss of total capacity.  That does not seem to mean much, or, just requires you to sit here, and re-read it 10 times ...and still not understand it!, a reverse way of thinking about this is going to be explained here:

Let us suppose that you have a fully charged battery of any type & in good condition.  That battery has an ampere-hour rating, let's say 28 AH.   A 28 AH battery SHOULD, by simple mathematics (only), deliver 280 amperes for 6 minutes; or, 28 amperes for 1 hour; or, 2.8 amperes for 10 hours; or, 0.28 amperes for 100 hours ....and so on.   For clarity and no confusion, I shall NOT consider SUPER LOW discharge rates, where the load is nearing the battery self-discharge rate.

Batteries are LESS efficient as devices that use chemical change to produce electricity, as immediate current drain GOES UP.  Thus, a battery typically LOSES output capacity as the drain RATE increases.  This means that as the drain rate increases (you use more amperes for any given period of time), the Ampere-Hour capacity goes DOWN.  Your 28AH battery is NOT a 28AH battery when the drain is high.  Just 'what' is "high" depends on the manufacturer, but, as a general rule, anything over 10% of the AH rating, as a drain, reduces the AH available.  More or less, and depending on the battery type (and quality of design/manufacture).   The AGM and GEL batteries and lithium batteries are MUCH LESS affected by this than the flooded types.   Another way of thinking about Peukerts, is that a big/huge electrical load on a AGM battery will not effectively reduce the total ampere-hours capacity nearly as much, as on a flooded battery, because the Peukerts value is LESS for the AGM/GEL/VRLA, compared to the flooded type.  Even less, for lithium batteries.

There is another peculiarity, not directly a Peukerts thing ...
AGM/VRLA batteries can deliver somewhat higher voltage at the same time as having large loads.  Another way of looking at all this that the rated AH is more usable in high loading conditions ...such as repetitive cold weather use of the starter motor on hard-to-start bikes, over and over, within a minute or three, perhaps.

The voltage drop on many of these new-style batteries is flatter ...the voltage drops a bit very quickly; then remains on a rather slow downward curve, until it suddenly falls off steeply.  This is, for most, very good ...but you get less warning notice about the battery going dead. Lithium batteries have a particularly steep function; and go dead VERY FAST when the charge is depleted beyond a certain point, and the load continues.   We call such fast voltage drop-offs in a battery as the battery having 'a very steep discharge curve'.

HINT:  When a battery is getting old or getting closer to failure (even not very old batteries can start dying), if your stock BMW dash voltmeter is wildly swinging during use of the directional's flasher, & you have already checked the wiring and connections at various places, the battery may need replacing.  There can be other causes for the voltmeter swinging, especially poor switches and connections.  Check the battery using a LOAD TESTER.

PROPER way to fill & initialize a 'dry' shipped flooded battery:
This type of battery has visible liquid in it after you fill it.  While you should look at the manufacturer's information, the information in this section is BETTER than what most manufacturer's have in their printed instructions.

The battery MUST SIT overnight before being used in your motorcycle, and you SHOULD charge it overnight, but only carefully ...which is all explained here. Proper Initialization, which may here be somewhat more complex than the battery maker says, will lengthen battery life, with a small amount of extra effort.

1.  Put the battery on your workbench, floor, wherever (concrete floor problems are old wive's tales stemming from leaky wooden battery case days).   Put safety goggles on.  Fill the cells to the upper fluid level mark on the battery using the acid mixture provided.  Install the cell cover(s).   Let the battery stand 4 to 8 hours settle in and cool down ...because the acid installation causes some heat (worse in hot weather).  Some battery manufacturer's will say 1 hour minimum; that's not enough time in my opinion, to fully saturate every internal area.    During this ~half-day period, occasionally shake/rock the battery to get bubbles released.  I do this by rocking the battery back & forth, giving it a bit of a 'knock' on the table/etc., as the bottom bangs the table, lightly.  You want to dislodge bubbles that are formed & ensure all parts of the battery are fully wetted.

2.  At the end of the above 1/2 day, +-,  top off the battery cells again, to the same upper fluid level mark, using the ACID mixture.   Install the cell covers.  NOTE that this is likely the LAST time you will EVER add acid mixture to the battery ...but, don't throw the acid out as sometimes a battery may require topping up after being fully charged & after it then sits overnight.  I keep excess acid here for etching & other purposes, such as scale removal from metal.

3.  AFTER the above step 2, and when the battery is at or below baby bottle (luke-warm) temperature, THEN you may start charging it.   Connect the charger's battery leads carefully & securely, & THEN plug in the charger; this is to avoid sparks.   This is especially critical during anytime the time the cell caps are off, so be SURE the cell covers were replaced before using any charger.  Wear goggles.    NEVER connect or disconnect a battery charger unless its power plug is unplugged from the wall socket first ...that HELPS avoids sparks ...SOME chargers can have a tiny spark when they are connected even if the charger is not plugged-in, so be careful!  Have the cell caps in place when playing with the charger or other wiring! PLEASE PAY ATTENTION TO MY ADVICE HERE, FOR YOUR SAFETY!

4.  The rate for initial charging of a new FLOODED battery is officially a maximum of 10% of the battery ampere-hour capacity.  If you have a 28 ampere-hour battery, that means 2.8 maximum amperes.   I do not recommend small chargers rated below 1-1/2 amperes for initialization, although if that is all you have, use it.   On a practical basis, you will likely be able to use even a RATED 6 to 12 ampere car-type charger, so long as its meter indicated charge does not exceed 20% of ampere-hours rating for more than a FEW minutes before the charge rate tapers down.

5A.  Discontinue charging IF the battery warms up much over luke-warm, and then restart charging after the battery cools down.

5B. Some of the small ''wall-wort'' chargers (small black box chargers that plug directly into the wall receptacle without any power cord to the wall socket) will have internal circuit breakers that will constantly cycle on and off during initialization of SOME types of new batteries; and that can possibly burn out these low output wall units.   

6.  When a dry battery has acid mixture first put into it, the battery will automatically gain a certain 'charge'.  This is the  'dry-charged battery' effect.   For most batteries, that charge is close to 80%, if the battery was properly filled & let stand for some hours.  If you put the battery into immediate use on a motorcycle, without waiting, a number of bad things can happen, including spot area overheating which can loosen the lead compound mixture which is pressed into the plates grids. Even with waiting some hours, the motorcycle alternator MAY charge the battery at a vastly too high rate; or, the battery may be discharging if you have a bike with many lights or poor alternator output, etc.   I strongly advise you NOT put a new battery, of ANY kind, into service until you PROPERLY charge it fully.  For a typical lead-acid battery, this means that terminal voltage, battery NOT mounted in your bike but on the workbench, AFTER charging, & AFTER letting it sit for at least hour with charger turned off or disconnected, will be ~12.6 to ~12.7 volts.  12.5 is marginally acceptable.  The terminal voltage reached DURING charging; while important, and while it will be considerably higher than those voltages NOT the best criteria for when the battery has reached 100% of charge.   If the battery has been charged at a low rate (10% of AH or less) for a long period of time, and the voltage has risen to 14 (up to 14.9 on some types)...then the battery is likely fully charged.   A more accurate indication is the battery voltage 1 or 2 hours after being disconnected from the charger:  ~12.6 to ~12.7.

7A.  The amount of time necessary to charge a battery, considering chemical inefficiencies, CAN BE AS LONG AS, but not necessarily is, in hours, the rating of the battery divided by the AVERAGE charging rate, plus as much as 50%.   I have seen it even longer with constantly cycling wall-wart chargers.   Batteries vary with voltage rise during charging.  Be patient!  The last part of the charging process MAY take considerably longer than you may think it should.

7B.  The pricier Smart Chargers (lots of brands) are very nice, and most can be left turned on for extremely long periods (years in SOME situations). HOWEVER, such extremely long-term usage IS detrimental to battery life, unless the current flow is very low ...REALLY LOW! ...not much over the self-discharge rate. I have written about such very long term storage trickle charging earlier in this article, and how to do it safely.

8.  A MAJORITY of all the smart chargers I have seen have LITTLE TO NO temperature compensation; or, not enough. Because of this, many do not initialize a battery well, nor maintain it well, particularly in cold weather.  These smart chargers SEEM to be set for a compromise voltage. I prefer initialization of a new battery using a common type of NON-smart charger, IF you monitor the temperature and voltage of the battery. 

9.  I suggest that you MONITOR the new battery for temperature of the case (by feel is OK), just to be sure it is not overheating, & MONITOR the battery terminal voltage with an accurate digital meter now and then.  The battery terminal voltage will slowly rise as the battery charges.  This rise can be quite non-linear.  That is, it is possible for a rapid small increase, and then hardly any increase for long periods of time, until the battery finally reaches full charge and PERHAPS then the voltage soon spikes upwards.    The speed of voltage rise, and the voltage reached after many hours, is dependent on the internal characteristics of your charger, and the type of battery.  It takes a MINIMUM of 12.8 volts at the battery, for a VERY LONG time, to fully charge a battery; but this is NOT the same as initialization!  In general 12.8 is NOT nearly high enough to ensure a properly initialized battery and the voltage should be considerably higher, typically between 14.2 and 14.5.  This is at common 'room temperature'.

10A.  For both the flooded and VRLA/Absorbed Mat, etc., batteries, the maximum initializing is 13.8 volts, per many books.  In truth, up to 14.9 volts can be used, and for the AGM batteries, 14.7 at 25C is optimum!   IT IS BETTER if the charging current is modest. 

10B.  There is an official sweet spot, per the books, at 13.2-13.5 for FLOODED batteries.  You might as well disregard that, I find it WRONG for initial charging, and the whole idea of a 'sweet spot' is NOT EXPLAINED, so, forget it, EXCEPT that it IS the reasonable voltage for rather warm climates for the maintenance mode on a smart charger.  This has confused many a person.  I suggest you disregard it FOR INITIALIZATION OF A NEW BATTERY!

11.  Battery voltages for charging are typically quoted based on 25C temperatures (77F).     Battery charging is ...or can be ...controversial, with manufacturer's selling their own chargers that are touted as very special (some few are).   For flooded batteries, no matter the calcium or tin or antimony or selenium added to the chemistry of the plates (or not), when re-charging, it is a good idea to charge to at least 14.3 volts, and 14.5 is good.  I'd not go much higher; and I'd keep the battery at those voltages for quite awhile, for full stabilization/charge.  Then, float-maintenance charge can be in the 13.8 v. area.  Flooded batteries are quite tolerant.   For AGM/VRLA/ABS such as Panasonic, WestCo, most of the 'Chinese' AGM batteries, and the Odyssey, ETC. ...I recommend (for the very longest life) that the charger be capable of almost half the A-H capacity of the battery.  Most won't have that powerful a charger, but you will only loose a truly small amount of life if you do not.   For bike batteries in the 14 to 32 AH range, you really need a charger rated at 3 amperes or more; and ones under 2 amperes are NOT good for longest life from a battery.  This idea of a MINIMUM charger capability only applies here if the battery was heavily discharged when you started to recharge it.   This is a real peculiarity, but it is true.   If a battery is being initialized from brand-new, a 6 ampere to 12 ampere charger usually works quite well for a bike battery.  This usually is also applicable if the battery is deeply discharged. Keep in mind what I previously said about the TAPERING of the charge rate within minutes. If the battery has been in use for some time, and the discharge amount is not great, you can certainly use a much lower output charger.  If the battery is NOT new or deeply discharged, any common low power charger will suffice, even if well under 1 A rated.  Yes, again, a peculiarity of lead-acid batteries of all types.  I'd not go overboard on using this information though.

12.  A bit nerdy:  Once a battery is charged to ~14.0-14.5, it is NOT fully charged.  It is CLOSE, but NOT fully charged. There are various effects including "surface charge" going on in the battery.  In order to complete the charging, it is best to continue charging at a lower voltage, for a number of hours, perhaps overnight. That voltage is about 13.6.   Because of this, Smart Chargers get a bit extra life out of batteries just from that particular characteristic. FURTHER, any charger MUST BE capable of producing at least, during the initial charging ...a minimum ...of 14.2 volts, especially on the Odyssey.  Odyssey's have a peculiarity ...or, well, somewhat.  Let us say you have a quite well-maintained and not all that old Odyssey battery.  You use a small wal-wart charger, not a smart charger, every month or two, the battery is mounted in your bike, you have a clock that draws a teeny bit of power, maybe something else (or not).  The battery voltage may read quite well before charging, but you know that best practices are to charge to about 14.5 to 14.9, now and then.  When you start charging, the battery might be 12.3 to 12.55.  That voltage will rise very slowly, and then much faster rising will occur.  That's normal! Be sure to disconnect the charger, or unplug it, at 14.9 maximum on your digital meter.

My suggestion:  Charge relatively quickly to 14.7 volts, and then, IF USING A SMART CHARGER, float/maintain at ~13.6 volts.  No matter the type of charger, smart or not, you certainly can disconnect the charger if you want to, after the charge is at 14.7 and the current is maybe 100 ma.

MORE Nerdy: you can calculate the change in value, for other temperatures.  If the battery temperature is COLDER, the voltage need INcreases.  The calculation is 24 millivolts per degree Centigrade, referenced to 25C.  Thus, if the battery is 10 degrees warmer than 25C, the optimum voltage is DEcreased 240 mv.   I leave you to change to Fahrenheit, and calculate your conditions-effects.

Later in this article will be more about voltage/charging.

13A.  Going back to brand-new flooded type batteries, being INITIALIZED:
You have already filled the battery, done the rock/tapping, refilled as required, and the battery has sat for some time, ETC.

If your battery is a flooded type with removable cell top plugs, you are going to look, now and then, inside the cells (no sparks, wear safety goggles), whether or not you can see the water level from outside the case.  I HIGHLY RECOMMEND that if you look at the water level with cell caps removed, that you UNPLUG the charger from the WALL, first, as a safety measure, to avoid sparks.    After some hours (usually), the new flooded battery voltage will begin to rise close to 14 volts & the cells will have many small bubbles starting to rise; depending on the charging current.  The higher the charging rate, the more bubbles.  You may not see bubbles if the charging current is low; and, it may not happen anyway for quite some time.   ASSUMING a decent charge rate (current), and after an hour or two of bubbles rising, ALL THE CELLS SHOULD BE 'gassing-bubbling' at about the same rate.  The amount of gassing is absolutely current dependent, once the voltage is high enough.  More current, more gassing.   It may well be difficult to see ANY gassing-bubbles if your charging current is low, perhaps 0.25 to 1.0 ampere.  You do not have to see gassing/bubbles.  Your eyeball, with goggles on for safety! ...will easily notice if the bubbling is happening, & that it is about the same in all cells if the current is high enough (say 10% of AH capacity, which means 2.8 Amperes for a 28 AH battery).  Be patient.  Do NOT move the wires, ...AVOID causing sparks! 

When all cells are gassing (flooded type battery, with enough current flowing ), and/OR the voltage is perhaps 14.4 at room temperature (closer to 14.9 at 50F or colder) the battery is fully charged.   You can remove the charger, and let the battery sit an hour or two, THEN recheck the terminal voltage (accurately, please!),  ~12.6-12.8 volts.

For some batteries the gassing point might be reached a bit lower, or a bit higher.  Do NOT let ANY battery type get over 15.0 volts at room temperature.  Try to not let the battery get much over baby bottle temperature.   If the current is low, and you can't see gassing, use the voltage measurement, and allow extra TIME.   Conversely, if the bubbling is quite evident, and you are only at 14.4 volts, and the bubbling is the same in all cells, the battery is LIKELY fully-enough charged if the current is low, perhaps one-half ampere to as much as two amperes, depending on your charger.  Smart chargers are NOT in this category!

13B.  With sealed batteries you won't be looking for bubbles, but you WILL be monitoring the terminal voltage.  The exact point at which you stop the charging is not critical.  I recommend between 14 & 14.9 volts, AND this varies with battery construction, materials, and temperature.   Some Smart Chargers may not allow that much; or produce it then quickly go lower, and you might not see that happening, which is why I like NON-smart chargers for initializing and first charging.  

14.  Unplug the charger from the wall and THEN disconnect the charger from the battery.  This helps avoid sparks.    Sparks are VERY dangerous around flooded batteries ...and can be, even on some sealed batteries.

15.  For a flooded type battery, or a 'fill-it' type of AGM, etc., you can now install the battery into the motorcycle.  Mechanically (sandpaper?) clean the wires before attaching them TIGHTLY to the battery.  Be sure the battery terminals are clean. Be sure the wires are oriented to avoid shorts & sparks and avoiding strain on them and the terminals.  It is a good idea to purchase some of the goop in a tube (NCP2 or equivalent or at least Petroleum Jelly, called Vaseline, etc., in the USA),  coat the entire POSITIVE (+) terminal, and + wires metal ends, AFTER assembly; ...and, if the insulation is poor, force some into the wire/insulation junction.  Use an old hardware store 'acid brush' or toothbrush suitably modified for this application.  It is NOT necessary to goop the negative terminal area.  It is also OK to use clear silicone grease for this.  The best product might be the special anti-corrosion grease stuff for batteries, it does not depend on just the grease barrier, but incorporates anti-corrosives.

16A.  Monitor the BATTERY voltage AT the battery; start the bike.  As soon as the cylinders have some modest warmth, increase rpm, watching the voltage.  Allow a minute or two, depending on how much you used the starter motor.  If it does not reach 13.7 MINIMUM,,,,14.5 MAXIMUM (although 14.9 is OK on the sealed batteries at very cold temperatures) as the rpm gets higher & higher (might take 4000 rpm depending on the lights, etc. you have), then you have a problem with the charging system or excessive loads of your bike, which needs looking in to.   The voltage regulator should NOT be hot from a previously run engine for this test, unless you allow for that temperature.  A high VR temperature should show lower charging voltage ...up to a few tenths of a volt. The VR in K bikes is internal to the alternator, so you can't check its temperature by feel ...but the alternator case is good enough. 13.7 is LOW, and battery life WILL SUFFER.   For a good relative value, at 'room temperature', the engine not yet having heated up the regulator, or regulator inside the K-bike alternator not yet heated up, use 14.2 volts.  This is a truly good compromise between battery life, lamps life, etc., although 14.4 can be used.

16B.  It is typical for a BMW Airhead FAIRING voltmeter, to read 0.2-0.5 v. lower than an accurate digital meter at the battery itself would read.  If over .35 volt difference (headlight ON) you may want to check the fairing voltmeter calibration, & if OK, then check for resistance at various contacts, relays, & connections, beginning with the ignition switch. Be sure to check the small starter relay pass-through internal connections under the fuel tank, as all current flow to the system except the actual main starter motor power, flows through that relay's INTERNAL connections ...AND, its socket connections; BMW uses RED wires on those connections.  Check for voltage drop between red wires.

17.  On BMW Airheads, poor grounding connection at the diode board or not tight enough connections at the board or the alternator can cause charging problems ...especially with the HORRIBLE rubber mounts and grounding wires needed with those rubber mounts.  I STRONGLY suggest changing the mounts to aftermarket metal ones.  There are certain models that can have timing chest to engine problems with painted touching surfaces, etc.   Lots more in this website.  Here is a link:

18.  If you store your bike for the winter, removing the battery is usually not necessary, so long as you keep it reasonably charged.  A fully charged battery will not freeze in typical, even quite cold temperatures, 50 below zero F or more.  If the bike is stored in quite sub-freezing temperatures, and won't be recharged or used with a smart charger, you probably should remove it from the bike.  The colder the battery, the less often it requires recharging.  A small trickle charger is fine every month or so. A Smart Charger can be connected & plugged in all the time, according to many Smart Charger manufacturer's, but this IS NOT the very best for the battery, contrary to common belief.  BEST to use the Smart Charger every month or even three, for overnight. You CAN leave a Smart Charger on all the time, with only a small to modest decrease in battery life; something the charger makers NEVER tell you.  If you have a flooded battery, DO check the water level every two months, no matter what type of charger.  See 19 and 20, just below:

19. VERY Long term non-smart-charger trickle charging can be done, at 0.04 to 0.06 ampere.

20.  Many vehicles have small parasitic drains from clocks, computers, etc.  Failure to keep the battery charged will decrease battery life, possibly by quite a considerable amount.   ALLOW FOR THAT BY RECHARGING.

21.  If you test the battery with a real Load Tester every 6 months, or 1 year at the latest, you are unlikely to be surprised by a battery failure!


Battery prices climbed steeply for awhile, but prices are usually quite variable.  BEWARE, if you want a GENUINE Panasonic battery, because Chinese, etc., 'replicas' are on the market.  Watch the wording in the advertisements.    Be very sure that the battery you purchase, IF YOU WANT A PANASONIC, is going to come AS A REAL GENUINE PANASONIC BRAND, as some advertising is not very honest.  I have not ...yet...seen this advertising problem with the Odyssey...but it would not surprise me.

Panasonic Battery:
Panasonic made small changes in its battery part numbers, and there are several different versions of the battery posts Panasonic offers. The suffix P is the one you probably will prefer. On a genuine Panasonic battery, there are TWO COMMON POST TYPES.  Sometimes the screw post, which is usable on your Airhead, is cheaper.  Suffixes are AP and P; both will work in an Airhead.  The AP is a vertical threaded post.  The P is a conventional post.  I prefer the conventional post; the wires, to me, fit nicer.  The LC-X1228P is a conventional post 28 AH Panasonic battery.  It is 6.57" long x 5.0" wide x 6.97" tall, and 3 POUNDS heavier (weighs 24 pounds) than the flooded Mareg (of 28 or 30 AH). There is likely a small difference in the maximum height, as measured at the case top (& terminals stick up a wee amount too).  Information on how to deal with the extra height, & your tool tray are earlier in this article you are reading.

Float voltage is OK at 13.5.  Float voltage is NOT the bike system voltage under alternator charging is a floating voltage for storage, or after overnight SmartCharger use, with the SmartCharger still connected and powered.

Clean & shiny is necessary during the making/tightening of bike wire connections to the battery (and elsewhere's), as teensy voltage drops can upset the voltage regulator, or create other problems.  The LARGER (28AH) battery, does not generally fit the R65, GS,  /5, ST.  Smaller batteries are 17 to 20 ampere hours usually.  These batteries also fit the classic K bikes, some K bikes can use either size.

VRLA or AGM type batteries come fully charged (if fresh).  EVEN THOUGH these supposedly come fully charged, I suggest that you check the charge & put a trickle charger on it for the time necessary, before starting the engine.  Check the charge via a voltage reading.  You can also load test the battery if you wish. No matter what brand you get, be sure that the negative & positive terminals are on the correct side, & forward. That avoids wire strain and battery terminal strain, which can reflect back inside the battery, and try to break the innards; and, cause other ills. The self-discharge rate is quite low when the battery is new, so even if the battery sat for 3 months, it is PROBABLY still nearly fully charged. Probably sits around 12.6-12.7 Volts.  If under 12.5, be SURE to recharge it slowly.

Odyssey battery:  These are made in many sizes, two of which fit all Airheads.   I can recommend the metal-cased version of these batteries for the longest possible life, but at a cost increase.   I recommend that the voltage regulator be carefully adjusted on the motorcycle to obtain maximum performance and life for the battery. Further, I recommend that if the motorcycle is not operated often enough to keep the battery at close to 100% of charge, that either a proper Smart Charger be used ...OR, a small ~1 ampere non-smart type be used ...and for that type of charger, monitor the battery voltage, and shut the charger off when the terminal voltage reaches at least 14.7, but not over 14.9.  Snowbum has at least one bike that is not driven more than once every month or even three months.  He recharges the Odyssey with a 1 ampere unregulated wall-wart cheapo charger, once every month or two, to 14.7 to 14.9 volts.  It seldom takes more than a short time to reach that level.  The recharging takes care of battery self-discharge AND minor drains such as the clock, etc.

Do an Internet search for whatever type of battery you intend on purchasing.  ALWAYS check on shipping charges and taxes.  BE SURE you are getting the ACTUAL brand, size and terminals, etc., that YOU WANT.

I have DROPPED my previous very lengthy specific recommendations on where to buy specific batteries due to being unable to keep up with changes.  Do your own research on the Internet.  I will, however, mention some sources:

For Panasonic and Odyssey, try TNRBATTERY.COM as a starting place. Try your favorite bike shop too....especially try the independent service place you have established a relationship with, such as Beemershop, Tom Cutter's Rubber Chicken Racing Garage, and so on. Compare prices.  Try DIGIKEY.COM;  they do usually offer free shipping ...USUALLY you have to search their site find that discount.

Ted Porter's Beemershop:   Ted likes the Odyssey & also sealed Interstate batteries, such as models FAYIX30L & FAYTX20HL ...and get the plastic support plate.   (831) 438-1100.   34 Janis Way #E, Scotts Valley, CA  open Tuesday through Saturday.  Very knowledgeable BMW folks here.

Tom Cutter's Rubber Chicken Racing Garage: Tom likes the MotoBatt batteries, & stocks and sells those.   1360 Colony Way, Yardley, PA  19067  215-321-7944.  Very knowledgeable BMW guy.

WestCo Battery; 1620 Sunkist Street-Unit L; Anaheim, CA 92806; 714-938-5080; FAX 714-938-5307.
  small vertical terminal, a-la-WestCo.  That may have changed by now.

800-551-5645 Portable Power Systems

Yuasa, sealed battery, for Harley Davidsons, about 1 inch shorter; 335 CCA #YIX30L Yuasa, Allan Kohler 800-538-3627 (I have NOT confirmed this information).

Yuasa has a Y60N24AL-B battery.  NOT the YB18.

Some have used 'Garden tools' batteries.  Be careful with flooded types, as if no overflow/vent tube, you could see the fumes from the caps rot out your steel pan seat, mess with electronics, ETC., over many years.   The typical garden battery used is size U-1.  SOME sealed garden types will release corrosive gases.

***AVOID!!!! ...any flooded battery without a venting tube.  The short vent tube elbow must exist on flooded batteries to avoid problems.  It is used with a flexible plastic or rubber tube that directs fumes down to the ground, typically near the forward side area of the rear tire.  The STOCK place for BMW to put that tube is GOOD.   AVOID batteries with vented caps that do not have this venting outlet on on the side; that will allow acid fumes from the vented caps to ROT OUT YOUR SEAT, freeze/rust the seat screws ...etc.

***AVOID!!!!...any battery that has its + and - terminals reversed:   Trying to make YOUR cables reach and fit is a BAD idea.  Many problems from folks doing this; including the occasional $$ DAMAGE from reversed polarity connections.  In some situations, the side pressures cause acid fumes leakage, eventually.

I recommend you DO NOT use golf-cart and similar batteries!!!!

There are a large number of other sources.  Be careful about what you purchase.  I can't list all of these sources.  Ask about batteries on such as the Airheads LIST; the K bikes LIST, etc. Watch out for shipping charges.

Airheads hints:  

Adjusting the VR, if you have one that is adjustable:
Be sure that the various connections at the battery, at the diode board, at the alternator, internally at the ignition switch, ...ETC ...are all tight & good, and that no voltage drops that are excessive.  It does NO GOOD to adjust the VR, if these things are poor or bad.

Measure ONLY AT the battery terminals themselves. If you have a dash voltmeter you are probably going to want to NOTE what it reads in comparison to the digital voltmeter you are using at the battery, probably the dash voltmeter reads 0.3 volt less.  Be sure that your grounds, cables, brushes, wiring inside the timing chest, etc. ...are all properly tight and all grounds properly grounded and secure ...before adjusting the regulator. BE SURE you do these things!   Refer to in this website for LOTS more information.  At room temperature, try for 14.2-14.3 volts for the VR setting as a decent compromise, although up to but NOT EXCEEDING 14.9 is OK for the Panasonic or Odyssey battery, but lamps life will slightly suffer and battery life can suffer SOME in hot weather areas ...but 13.9 and under is also a bad idea.   For such as the Odyssey, I recommend 14.5 at room temperature (temperature measured at the VR case). As soon as the engine warms, the heat rises into the regulator causing the voltage to go down a tenth or three, so do checks and any adjustment before much heat develops. I start from a cool engine & adjust the regulator after a 1 or 2 minute engine warm-up, which is enough to allow me to go to 4000 rpm or so.  It is a GOOD idea, if you have rubber mounts on the diode board, to change them to aftermarket solid metal ones beforeadjusting the regulator. PIA to install, but a really good idea. Add the extra grounding wires too, see above linked article.  Motorrad Elektrik, Thunderchild, & Euromotoelectrics sell metal mounts.   My preference is for ROUND, not hexagon, metal mounts ...due to possible interferences.  sells adjustable regulators very reasonably priced; so does

Setting the regulator without knowing that all is OK ...wiring, mounts, diode board, connections, grounding ...etc. a waste of your time. 

NEVER ...EVER ...(unless you have an EnDuraLast permanent magnet alternator conversion) remove an Airhead timing chest outer cover without FIRST disconnecting the battery, typically by just removing all the wires at the negative post.  If only one big wire at that post, you can disconnect the battery at the speedometer cable bolt, which lug can be modified for easier removal in the future; with the smallest hole snip; be sure to use the stock washers on either side of the lug. 


There is nothing wrong with using a common battery charger, NON-smart type, if used properly.  This applies to any of the battery types:  absorbed mat (AGM) (also called Valve Regulated...VRLA), flooded (slosh), sealed, lithium, etc.   NON-smart type chargers can often be had QUITE CHEAPLY.  They are perfectly adequate for many of you.   Nothing wrong with turning on a common LOW output non-smart type once every month or two, for awhile. DO monitor the voltage!

I do NOT like Smart Chargers left on for many months, but we all know many will do that.  I prefer them to be used, perhaps overnight, once every 1 to 3 months, on the AGM/VRLA/Lithium types, & maybe monthly on the flooded types, or if the bike has small drains, such as from a clock, etc.

Money-saving HINT!    I haven't the foggiest idea why many do not know of this.    You may already own a small to modest sized charger that is NON-smart, and is not normally to be left connected for extended periods.   This type of charger, say up to 12 ampere rating (most are around 1 to 3 amperes for motorcycles), can be quite adequately used to maintain a battery over the Winter, when the motorcycle is not being used.  Simply connect it to the bike battery and then put a common cheap TIMER on the power plug.  Set the timer for a short time period.  If you can, set it for once a week; otherwise, perhaps a FEW minutes once a day ...or every few days.  Do check now and then that the timer still works!  If you do not use a timer, just connect the NON-smart charger once a month for an hour. Just how long to have it powered and connected depends on the type of battery, and the charger;
and your monitoring of of the voltage AT the battery terminals.  Keep in mind what I said earlier in this article about SELF DISCHARGE RATES for the various types of batteries.  Another way is to use this type of charger...OR a non-smart charger, & add a series resistor or proper lamp used as a series resistor, so that the VERY long-term charging does not exceed 0.060 ampere.  You can leave it on forever at 0.020 to 0.060 ampere.  CHECK THE TERMINAL VOLTAGE FOR ALL METHODS, BEFORE, DURING, AND AFTER THE CHARGING.  Check the fluid level once in a great while.

Smart chargers are called SMART because MOST of them recharge a battery first to a reasonably proper higher initial voltage.   That higher voltage (which they MAY call initialization, not the same as my use of the term in this article for preparing a new flooded battery for use) is NEEDED to recharge the battery fully. Once that voltage is reached they automatically drop the charging voltage to one or two lower levels, the final level is usually called the Float Level or Maintenance Level of charging ...which is just enough to maintain the charged condition; and that might be around 12.7 volts, some use higher. Some Smart Chargers have other modes for de-sulfation, pulse mode, and some have a final low level.   BEWARE OF DE-SULFATION CHARGERS ...see prior note on these!!!!

A true Smart Charger is ...or can be... the best charger for you; but do you REALLY (?) want several versions, if you have several types of batteries?  Super-smart-chargers have constant current and constant voltage modes, that are the very best, if the voltages they use are properly selected by the maker.  However, you need not purchase a fancy smart charger.   Understand that occasional use for awhile of any trickle charger or even a modest output charger, may do very well!  There are a few Smart Chargers that can be SET to specifically work with various types of batteries.  I have NOT, YET, seen any that are really good at doing this AUTOMATICALLY, only by setting for such manually.

The truth is that constant very long-term use of a commercial Smart-Charger can injure the battery.  That is NOT what the charger makers say, but it is the truth.  The bottom-line is that once or twice monthly use of a small cheap trickle charger on a FLOODED battery, perhaps overnight or half a day, will almost always keep the battery in quite good condition; without the need to spend $$ on a Smart Charger.   This assumes modest parasitic drains from clocks, etc.  A voltmeter will tell you.  Stop charging at 14.5 volts, if going higher, be cautious, never exceed 14.9 for any battery. I am NOT AGAINST SMART CHARGERS ...I OWN AND USE THEM (and have non-smart ones too, and I use one of them on my Odyssey)!

An AGM/VRLA might only need the charger every 3 months ...but do NOT fail to consider any clocks or other small drains ...they DO ADD UP!  The biggest advantage of a Smart Charger is that you plug it in, and pretty much forget about it until Spring arrives; although it is NOT the best way to use them, and can injure the battery a bit, especially if the smart charger output is high enough to cause appreciable water loss on a flooded battery; and it is not great for the AGM and other types either. The damage to flooded batteries is LOW, unless the battery fluid level is below the top of the plates.   You really need to check the water level now and then, and maybe the terminal voltage, NO MATTER what type of charger, on a flooded battery.  DO NOT add water immediately, or, add only a modest amount, if the water level is quite low and the battery somehow is discharged.  Give the battery a very slow charge first.  This is because a heavily discharged flooded battery absorbs the acid-water mixture, and the level might rise during charging.

The self-discharge effect is more important in quite hot weather.   ALL batteries lose charge by themselves, with nothing connected to them.  The self-discharge rate of ALL batteries RISES WITH TEMPERATURE.   You cannot expect full life out of a premium battery like the Odyssey if you store the battery where it is over 90F for many months; no matter the advertising.  The Odyssey is good at having a low self-discharge.  MOST ALL VRLA, AGM, and BMW GEL batteries are GOOD at having a low self-discharge ...but the RATE of self-discharge RISES with battery aging! ...and, as I noted, with increase in temperature.

Once in a great while someone asks about what to do if the bike is stored for a few YEARS.  Best would be to sell or give away the battery.  I used to have a second-best, to put it into your refrigerator (NOT freezer) and charge it every 6 months to yearly. I have decided that is not so good.  So, my second-best is to fill to highest level line or even a bit more, with distilled water (if a flooded type that can have water added); then connect a smart charger to it, with a series resistor to limit the current flow to 0.060 ampere, as measured after a full charge ...and keep it in relatively cool place.  Other ideas are same with no limiting resistor, and last best to just put a trickle charger on it now & then.  If you nor anyone else is around for YEARS, I suggest you get rid of the battery ....or, try the series resistor method.  BTW ...a common CHEAP wal-wart (that's not Walmart!; although they might sell them) ...NON-SMART charger can be used with the 0.060 ampere (MAXIMUM) method. 

Smart Chargers vary considerably in design.   SOME have safety features that can cause confusion and problems.    MOST of these chargers will have NO OUTPUT, therefore NO CHARGING!! ...unless the battery they are connected to has at least some voltage  (maybe 8v or greater??  for safety I have just used a figure of 10 volts, earlier in this article)  to begin with, and the voltage needed varies with the manufacturer and model.    IF your battery is drained very considerably, or is dead, and your Smart Charger does NOT begin to charge that battery, you have NO CHOICE but to use some other type of charger on that battery (or jumper to another battery for a few seconds), until the battery terminal voltage rises enough for the Smart Charger to then be connected, recognize the battery, and turn itself on.  Of course, the battery could be no good, but it will not hurt to try a conventional charger on the battery for awhile.   For a very dead battery, it usually takes only seconds of any other type of charger, even a momentary connection to a car battery put just enough of a charge into your bike battery to allow it to trigger the Smart Charger immediately afterwards.  

BEWARE of de-sulfation chargers!  This is especially so on Can-bus bikes, but also on any bike with electronics, and WORSE if the battery is quite dead to begin with, & then the charger goes into de-sulfation mode.  DO NOT USE THEM in de-sulfating mode on lithium batteries!

Miscl. section:
For folks that commute in cities such that the electrical system does not keep the battery fully charged, and you want to connect a battery charger every night, you PROBABLY should have a Smart charger, with an easy to plug-in setup. An easy attaching method is a good idea. The BMW accessory plug and socket works good for that purpose. There is supposed to be a 8 ampere fuse in that socket wiring. Mind cautions about the sockets possibly grounding the battery withOUT the battery ground wire at the speedometer bolt being connected. That can cause you problems in removing the front cover of an Airhead. Because of that, I recommend either ground-insulated jacks, OR; the black negative wire from the accessory outlet should be connected to the FRAME.

As a general rule, the largest size of battery charger that might be used AT ANY TIME safely with your Airhead's battery is one rated at 12 amperes. A smaller one is better for most folks, but ONLY if the battery never gets deeply  discharged. Even one as small as 1/4th ampere is often OK ...but NOT always, if the battery is deeply discharged. Nearly all 6 to 12 ampere rated chargers can be safely used on a bike battery rated over 10AH. Using chargers rated OVER 12 amps, things may get iffy, but SOME chargers even as high as 20 ampere chargers are OK for temporary recharging.  The reason they are probably OK is because while they start off with a moderately high ampere charge, they very quickly taper off, in a FEW MINUTES.

Nerdy: There is a peculiarity of deeply discharged batteries needing a fair amount of current to PROPERLY recharge the battery (this is NOT a matter of more hours on a smaller charger). Because of this peculiarity (except lithium batteries), I may put a jolting charge on a deeply discharged battery, for a very short period of time.  BESIDES that peculiarity, a charger that is too small may well not recharge the battery if it is well-drained from a day's commuting and you use the bike again the next morning. Many small motorcycle type chargers are rated at 0.5 to 2 amperes. DO NOT expect them to necessarily supply their rated current, often not very close to it, for YOUR battery, especially for very long. Most of the various types of chargers, especially the cheaper black-box types, that we call a 'wall-wart', that plug directly without a cord into your power socket, have a built in circuit breaker, that tends to constantly internally recycle (some sort of over-current circuit breaker) if the battery charge level is quite low ...or a cell or two are somewhat, or more than somewhat, failing ...these wal-warts tend to fail from that sort of recycling usage.

There are, or can be, important problems with large size chargers. Depending on the particular design, they MIGHT TEND TO overcharge the battery if left turned on for too long. It is NOT the current output CAPABILITY that causes this (at least up to the 10, sometimes the 12 or even 20 ampere size), but the internal resistance of the charger is lower, and so the output voltage also TENDS, by design, to be a bit higher under actual use, thus this type of charger TENDS to overcharge. NOT ALL will do this. If the charger is vigorous enough (not all will do this), then enough current flows into the battery, the battery will get hot, plates may buckle, the acid mixture & reaction causes hydrogen gas & water vapor laced with acid to escape, especially on the open vented flooded batteries. Putting such a charger on a sealed battery might well cause internal pressures that could cause a split case, etc.   I think 30% of capacity in ampere-hours, is OK as a maximum for the INITIAL FEW MINUTES of charging. Thus, if you have a 30 AH battery, you can start charging at as much as 9 amperes, which SHOULD taper off fast ...within a FEW minutes.

I think that owning a 6 to 12 ampere charger is very useful for bike batteries. I have tested some 20 amp chargers that would charge a well-discharged bike battery at 12 to 15 amperes, and within a minute taper off a whole lot, perhaps to a FEW amperes. I see no damage being done. If one does NOT taper off quickly, do not use it! SOME old-fashioned simple chargers are designed such that their output current does not taper off ENOUGH, as the battery terminal voltage rises from the charging. This is NOT universally true! I have a 10/12 ampere charger that works fine. Mine has an adjustable timer on it, a handy feature, but not really needed for most purposes. If I connect this charger to one of my Airheads in my garage that has a flooded type battery, once a month, it shows a 6 ampere charge for less than a minute, & is down to 4 amperes within three minutes, then slowly tapers to under 1 ampere as the battery is recharged. That type of operation is perfectly OK.  You don't want 6 or more amperes of charging for hours, minutes is OK. Even half an hour or sometimes a full hour is probably OK if the battery does not warm up much. Don't allow the battery voltage to be excessive at any time.

For the Odyssey, you can initialize at up to 50% of AH rating, per Odyssey; but I say 40% maximum, and 30% is better as a maximum.

An absorbed mat battery (AGM or VRLA) (WestCo/Panasonic/Digi-Key/Yuasa...ETC.) will USUALLY recharge far more quickly than a flooded type, as its internal self-discharge was much lower so the % charge loss is less; and the ability to more fully use the higher charging current is better. A Smart Charger might take overnight for any type, depending on the ampere rating & design of the smart charger. Smart Chargers are worthwhile, if you know the limitations. IF you use a common, NON-smart charger, MONITOR now & then the battery voltage. If it is a larger charger, monitor that the current does not stay up too high for very long. When the voltage reaches the fully charged amount, turn the charger off. Don't allow the battery to get much over baby bottle warmth. The range of voltage depends on the battery type & the temperature of the battery. For temperatures near freezing, that voltage might be as much as 14.9. For 70F temperature, the voltages will be somewhat lower. I like 14.3 on a flooded, 14.3-14.7 on an AGM a general rule, in any reasonable temperature. This conflicts only slightly with other voltages in this article.

If you use a larger conventional battery charger, many will have a meter that monitors the charging CURRENT. It is OK for that current to be initially rather some cases half the AH rating of the battery......IF!! ... that current level drops considerably within a VERY FEW minutes, & then decreases slowly downward. The rule of thumb that a battery should not be charged at a rate over 10% of its ampere-hour rating is a good rule, but not an absolutely strict one; as 15% is usually fine, and even twice that for short periods. What they don't usually tell you is that the so-called 10% rule is for 'continuous'. If your battery charger is still delivering 3 or more amperes & the terminal voltage of the battery is already over 14.2, then you want to be cautious about using that charger.

The use of old-fashioned service station quick chargers (typically 75 amperes & higher) is absolutely forbidden on bike batteries ...and is not good for large car batteries either. Huge charging currents will cause spot heating in the battery, plate buckling, steam, small to larger hot spots in the battery, & quite possibly the battery will be destroyed, and rather quickly. Excessive charging, over a long period of time, even if the excess charging is of a rather low level, will slowly cause oxidation of the inter-cell connections, eating them away, reducing battery life. The end result is a cracked inter-cell connector, and a catastrophic sudden failure to start the bike, yet lights MIGHT be OK. This is very much unknown for whatever reason. This is part of the reason for not leaving a Smart Charger connected & powered for years, during extended storage, & even 1 year is sometimes damaging. That is why a constant current at not over 0.060 ampere is better; after a full charge;...some Smart Chargers are like that though! Many anecdotal problems with sudden failures of AGM/VRLA batteries have come from people leaving them for long periods of time on Smart Chargers.

Battery life DEcreases vastly more quickly if not kept fully charged.

SULPHATION (sulfation, sulfated,...): Usually when a battery is well-sulfated, from age or being discharged for a long time, the battery is no good, & cannot be 'fixed'. There ARE exceptions. If you want to try to de-sulfate a battery, you can TRY by discharging it, if not already, to about 10.3 to 10.5 volts (the Odyssey type maybe MUCH lower). THEN, recharge with a substantial sized charger, to around 14.7 volts at room temperature.   The charger should be at least 6 ampere rating, but not over 20. Some chargers are advertised as having PULSE MODES (or similar), & that they will de-sulfate even a quite bad battery. PARTIALLY true. The pulse mode is better, but not worth a big premium. Use of the higher ampere rated charger the way described in this paragraph will probably help a sulfated battery MORE than a much lower de-sulfation mode in a Smart Charger. This will be denied by those trying to sell Smart Chargers. Still, the best method is the one described by me much earlier ....which is very different, and uses a very low current charging.  DO NOT USE desulfation charge modes on Can-bus nor Airheads, unless the battery is can damage the entire electrical system.

PRACTICAL advice on battery voltages for charging & float charging:
(Read all the previous information from the beginning of this article, if you have not already!)

Before getting into the PRACTICAL advice, I will share with you the OFFICIAL chart for battery charge, specific gravity, and open circuit voltage.  Conditions are for a vehicle starting type of battery containing antimony in the plates.  Readings are at 26C (78.8F).   The battery RESTED for 24 hours after charge or discharge; voltages are then measured.

You will be UNable to measure Specific Gravity of battery fluid (electrolyte) unless the flooded type with removal caps.

Approximate state of charge

**Average Specific Gravity

Open Circuit Voltage After resting
















Although I have given you rather specific advice in this long article on various voltages, the following is PRACTICAL advice, since voltage regulators on the various motorcycles will vary considerably ...or, you may want to know what is practical for setting yours if it is adjustable.   You might be interested in what settings are practical and useful for the three major battery types; and, a few other things. 

If the battery AND VOLTAGE REGULATOR are BOTH at ROOM temperature (70F approximately), then I would be OK with you setting your VR for 14.1-14.4 volts, before the engine heats up the VR.  This will probably result in a longer battery life, and only slightly less life for your incandescent lamps, which will be a wee bit brighter while going down the road.   On a really practical basis, ANY of these batteries will be "reasonably" OK with the motorcycle voltage regulator set for 13.8 to 14.5 volts under most any temperature you measure the battery at.   The lower portion of that range may not give you the best life from the battery.

In all situations, all types of lead-acid batteries, after a battery is charged, and the charger disconnected ...and this also applies to after the engine is shut off:   after a few hours of nothing connected as a load but maybe a clock, the battery should be ~12.6 volts.  If the battery/bike has been sitting for some days, etc. ...then, if under 12.5, be sure to recharge the battery. 

Additional information....and somewhat different viewpoint, etc:
I do not agree 100% with Anton, but I recommend reading it, and my nitpicks are hardly worth mentioning.

Load Tests:
Load Testing is THE best way to determine battery condition ...ANY TYPE OF BATTERY.

Voltage testing a battery to determine charge/condition; or, using a hydrometer on a flooded type battery for the same purpose, are NOT 100% checks on battery condition.   ONE of several reasons is that the battery could SEEM to charge up perfectly OK, if an open cell type the hydrometer could even show the battery as perfect ...and you might even check for correct voltage; and, let us assume that is fine ...and yet you have almost no output to run a load like a starter, sometimes yes for a headlight, ...all because an inter-cell connection was seriously cracked.  This is fairly common!  THIS IS JUST ONE of the possible problems if you only check the voltage or only hydrometer check, ...or both.   LOAD TESTING is a FAR better method of determining battery condition, as a load tester measures current output AND voltage, both WITH A SUBSTANTIAL LOAD.   A SLIGHTLY better method is a capacity test, but is not likely going to be what you do ...and is almost never really needed.  There are other types of testers:   A very sophisticated type of battery tester that measures conductance/impedance is available, these testers are hundreds to thousands of dollars.  They measure using a complicated formula used in conjunction with passing both low frequency A.C. and D.C. through the battery.    They are NOT further discussed here ...besides to tell you that they are absolutely NOT NEEDED.

Regarding load testing of the battery, voltage drop while cranking, etc:
You can use a digital voltmeter at the battery, & the motorcycle's starter motor, to perform a load test, with a VERY APPROXIMATE resulting guess of the battery condition.  Testing this way depends on the condition of the starter, the temperature of the engine, starter, battery; even the oil grade and if a high compression engine or not ...etc. The colder the temperature, the lower the voltage, due to higher current drains caused by increased friction and other losses, and the slower chemical activity of the battery.  Cold weather tests are also more demanding on the battery.  A problem is whether or not you do, or even could, know the REAL condition and ampere draw of the starter motor, and condition of peripherals like the solenoid switch, wiring, etc.

Load testers were traditionally only used by automotive service centers and sometimes available at places that sold batteries. NOW, Harbor Freight Company sells two types, a 100 ampere type and a larger 2-meters higher current type, and these are quite good for the low price, are often on sale ...and they DO work well.  I particularly like the two-meter larger one, I think it is much more versatile....and more accurate too.

1.  If you do NOT use a formal Load Tester, the following is a quickie way of doing load-testing, and it is an "sort-of-adequate" method:
It just so happens that the typical Airhead starter motor current drain, with a good starter, on a mild day, is going to average approximately 60-100 amperes DURING cranking; but is MORE when first starting the rotation of the engine; especially if the engine is cold, perhaps from an overnight storage. That means that the starter itself can be used as decent-enough load ...assuming the starter motor is OK, & same for connections & wires.  Remove the fuel (emptying the fuel bowls on Airheads is a good method), or disable the ignition (ground spark plug caps properly or disconnect coil PRIMARY) from the engine so the engine will not start. Be careful what method you use for the particular make & model of motorcycle.   Charge the battery FULLY while monitoring the battery terminal voltage. Disconnect the charger & let the battery sit for an hour or more.   If you think the battery is fully charged & does not need charging first, at least check the voltage first. 

Connect a voltmeter (digital type) directly to the battery terminals.  Crank the engine for 10 to 15 measured seconds.  At the end of the time period, while still cranking, note the voltage, see the voltage readings below. The large diameter leads from battery to frame or transmission ground; & to the starter motor solenoid, must be clean/tight, to avoid voltage drops at those points. You MUST measure the voltage at the battery terminals themselves.  DO NOT measure at any connection fastened to those terminals, or from frame, etc.

2.  If you DO use a Load Tester:  load tests on batteries are done at approximately THREE times the battery capacity in AH. Thus, a decent load test is done at about 90 amperes on a 30 AH battery.   The literature with the Load Tester will have more information.  Some literature, for some types of batteries, will show that the testing current should be 1/2 of CCA.  That is a very critical type of test; I advise you not to do it unless you know what you are doing AND how to interpret the results.  The regular type of test should last 10 to 15 seconds.  The 2-meter Harbor Freight unit is semi-automatic ...and HAS FULLY & CONTINUOUSLY adjustable load settings; just dial up the current immediately, then watch and let the unit do the automatic testing.

3.  For either 1 or 2, above:
A good battery will show the following voltages DURING THE TEST, at the 10 to 15 second point, and the temperature is that of the BATTERY prior to testing:
9.8 volts or higher at 70F
9.5 volts or higher at 50F
8.7 or 8.8 volts or higher at 0F.
A FAIR condition battery will show a few tenths less, and a top-notch battery will show higher.  The digital voltmeter should be connected to the battery terminal posts, NOT to the wires connected to those posts.  This will avoid slight voltage differences. Commercial LOAD TESTERS that are reasonably priced, such as the Harbor Freight unit, usually have a voltmeter built-in, or at least good-bad indication of some sort; and the way they do the voltage measurement is "OK", just not quite as accurate as the digital meter AT the battery TERMINALS.     I recommend you use an accurate digital voltmeter AT the BATTERY TERMINALS to compare to the load tester's analog meter, for more accurate information. You will probably find that the readings agree well-enough. If they do not....use the small meter adjusting screw on the Harbor Freight meter face to reset the meter needle slightly (it will then be off-zero).  The testing should always be done with the meter in the same horizontal or vertical position, to eliminate meter needle mechanical balance irregularities.

Starting problems?   Try this:

initial upload 02/04/2003 and initial copyright.
03/04/2005:  Update entire article to reflect latest information and include all prior revisions, greatly expand information.
04/13/2005:  note, on Advanced, possibly raising prices
05/03/2005:  REMOVE all information on company, due to non-responsiveness
11/26/2005:  update entire article
11/29/2005:  update digikey shipping information
02/13/2006:  Add information on WestCo's BB brand
03/02/2006:  update on Digikey
12/20/2006:  Re-edit entire article
03/21/2007:  expand upon charging efficiencies and self discharge losses.
04/15/2007:  Additional information on Yuasa and also garden type batteries
10/30/2008:  Remove pricing and methods of purchasing from Digikey, update a few other places (minor).
03/31/2009:  Update the article entirely, clarifying some things, reducing ugly color changes, etc.
06/05/2009:  Modest updates for clarity and add information on load testing and change title slightly to accommodate that.
03/30/2010:  Clean up appearance; make minor updates for clarity.
07/21/2010:  Add practical advice on voltages section.
03/03/2011:  Clean up article, add emphasis, straighten out confusion on voltages.
06/11/2012:  Clarify details, update for Odyssey somewhat more, etc.
10/11/2012:  Add QR code, add language button, update Google Ad-Sense code
12/19/2012:  Slight updating on AGM batteries regarding % of vehicle use; and expand slightly on conductance/impedance and minor other areas.
01/08/2013:  Clean up slightly, add a bit more on nerdy stuff to know.  Still a messy article. 
03/09/2013   Clean up a bit more; clarify a few details; add information on timer usage.
03/19/2013:  Revise and simplify the load testing procedure(s).
05/19/2013:  Clean up article quite a bit, also remove a lot of old outdated battery information.
05/22/2013:  Update the lithium battery information, condense it.
10/29/2013:  Update for clarity, add more cautions & information on DEsulfation mode problems.
12/14/2013:  More information on voltages, clean up article, add standard voltage information, clarify details.
04/27/2014:  Add note regarding poor battery and voltmeter swinging.
05/19/2014:  Update with more information on sulfation and rejuvenation.
11/17/2014:  Add note on purchasing batteries at very top area.
12/22/2014:  Add section on battery type descriptions at the top, from hosting on the Airheads LIST.
12/26/2014:   Minor tech changes.  Finish re-arranging the article, eliminating some redundancies, etc.
12/27/2014+:  Due to misunderstanding about battery capacity in A-H, in the area about small capacity Lithium batteries, I revised that section.  Slight update later this same day. Further small updates were done as I obtained more information, particularly on LiFePO4 types, on 03/01/2015 & 03/17/2015.
08/12/2015 and 08/28/2015:   Due to confusion, added more information & strict advice on Lithium batteries.
01/18/2016:  Updated the entire article.  Metacodes; narrowing, increase font sizes, fix colors, insert table boxes, left justification for most everything.  Still overly long and could use quite a bit of shortening.
03/09/2016:  Update meta-codes; layout, fonts, colors, clarifications, some simplifications, some redundancies. 
03/10/2016:  Fix so looks OK on IE and Chrome, as had some superfluous hidden tags.
09/16/2016:  Update metacodes, scripts, layout, content improvements for clarity.

Copyright, 2014, R. Fleischer

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Last check/edit: Friday, September 16, 2016