WetLeather Motorcycle Rider Information

Date: Fri, 18 Jul 2003 06:17:11 -0700
From: E. Gardner


> Anyone know of any FAQs regarding battery chargers? Especially the
> things to watch out for.

>
> Is the bubbling of a charging battery (2A mode) bad? normal?
>
> Clueless, but knowing what he doesn't know....
>
> --Adrian

The bubbling is both hydrogen and oxygen, because you are electrolyzing the water within the battery electrolyte into its components. When the bubbles rise to the top, they often pop and make a tiny mist of sulphuric acid which can be carried out of the battery along with the H and the O. The H and O want to burn back to water, and will do so given a good spark, if they are allowed to accumulate, but since the H wants to rise, any accumulation will be at the top of where the battery is being charged. A tiny moto battery is unlikely to generate enough volume of gas to be a hazard.

The primary recharging phase (called "bulk charging") causes little outgassing. As the battery approaches full charge the gassing increases, particularly if a "cheap" charger is used that does not properly control the voltage applied to the battery as charging current drops; a "good" charger, such as a Battery Tender, current limits during bulk charging, then voltage limits during the finish charging to prevent a lot of gassing; at the completion of this phase, the charger should shift to "float" mode, where it maintains approximately 13.2 volts across the cells indefinitely for long term storage.

A flooded cell battery (non gel, non AGM) should ideally periodically be "equalized" by charging the battery at a higher than normal voltage to stir the electrolyte with gassing and prevent stratification of the electrolyte; this is essential for static batteries that don't move, but less so with moto batteries which get shaken and stirred during riding. Needless to say, most moto batteries do not get treated ideally. They rarely get a full charge unless ridden for long distances or placed on a 3-stage charger that does bulk, finish, and float charging, but they still deliver adequate service life unless they are left for long times without being exposed to a charging situation.

Gel and AGM batteries are different birds; their electrolytes are trapped at the plates and do not need to be equalized and are easily damaged by overcharging. If you have one of these, you need to read the manufacturer's data sheets on them because they can vary in their needs. The typical "Freedom battery" (sealed) (low-maintenance) is NOT a gel or AGM battery, it is a flooded cell battery with an excess of extra electrolyte in the battery case. If overcharged and gassed, the extra electrolyte will be lost and eventually the battery will fail with no way to replace the lost (as H & O) water; be careful not to leave these batteries hookd up to a simple car or wall adapter type charger any longer than necessary to get it charged and working; i.e. when the charging current starts to drop, get it off the charger.

You can find some useful numbers here:

http://www.hupsolarone.com/about-batteries.htm

Ed Gardner

---

Date: Mon, 20 Oct 2003 21:51:54 -0700
From: Ed Gardner

> Will a desulphating battery charger/conditioner allow a larger
> capacity to be used?
>
> -ted
Once a battery has sulphated, that's pretty much "it". If you use the charger/conditioner BEFORE the battery has sulphated, then yes, the battery will last significantly longer. The only "conditioner" action I am aware of are actually called "equalizers", which periodically charge the battery at higher than normal voltage or with higher voltage pulses to equalize the state of charge uniformly across all cells. Sulphation is a different process from the normal shedding of active materials at the positive pole; a flooded battery that dies because of buildup of shed material until it shorts plates together is different from "sulphation", which can destroy even a new battery left discharged for very long. A float/trickle charger prevents sulphation damage by keeping the battery charged, not by "recovering" it after sulphation occurs. The capacity of the battery when fully charged will dwindle over time as active material is shed; it never gets better than when it is new, no matter what you do; keeping it fully charged simply allows you to use all of the capacity that is left at that point in its life cycle.

Wal-mart sells an inexpensive 1.5 amp charger with an automatic long-term float state for about $16; its the best "cheap" charger I have found; comes with both a "wire in place" harness to leave on the bike, and separate terminal clips harness, either of which plug into a polarized molex type connecter on the 6' DC cable. Its a good charge rate for a bike battery, and the whole thing is small and light enough to stash in a saddlebag.

Ed Gardner