Re: (ET) Golf cart batteries

["David Roden" <etpost drmm net>]

On 14 Jan 2009 at 12:48, Marcus wrote:

> an idle lead acid battery tends to sulfate while inactive. The sulphur  
> in the electrolite comes out of solution and deposits on the plates. 

I'm not so sure I agree with this.  The sulphur ions in the electrolyte's 
sulfuric acid do indeed combine chemically with the lead in the plates to 
form lead sulfate, but this is part of the normal chemical reaction when a 
battery is discharged.  No discharge, no sulfation.  

It's true that a lead battery will self discharge a bit.  That might be 
what 
you're thinking of here -- but in a good, well maintained battery, this 
effect is pretty minimal and fairly slow.

Sulfation (as the term is generally used) is in fact a relatively rare 
condition, much less common than the purveyors of magic snake oil 
additives 
and blinking gadgets would have you believe.  It's triggered by chronic 
undercharging, or allowing a discharged battery to sit for long periods of 
time (typically weeks).  The lead sulfate tends to form large crystals 
which 
resist being reconverted to lead and sulfuric acid.  After a while these 
crystals flake off the grids and fall to the bottom of the cell.  

This condition is not reversible, no matter what the salesmen tell you.  
But 
all you have to do to prevent it is fully charge the battery when it needs 
it. Sulfation is almost never a problem for a battery which is promptly 
and 
properly charged.

To get to your specific situation, the best treatment for idle batteries 
is 
to disconnect them from the vehicle if possible, clean them well, and 
store 
them in a cool, dry place.  There's no validity to the old myth that 
batteries left on a concrete floor will discharge, BTW.

Test them with a hydrometer every month or two and if it shows less than 
about 80% charged, charge them with a good quality charger, preferably an 
automatic one.

When you start using the batteries again, don't expect them to perform at 
full capacity until they've had several cycles of use.  Like humans, 
batteries stay in shape best when they're exercised regularly.  So I agree 
with Marcus that it'd be ideal to have someone use the vehicle now and 
then 
in your absence.

Battery maintainers are useful for batteries which have a small continuous 
load while idle, such as ICE starting batteries (the computers and gadgets 
in modern cars can discharge a battery in a month or two).  I suppose one 
might also be useful if you neglect your batteries and never clean them -- 
batteries CAN  discharge across damp, dirty tops.  Where there are no 
parasitic loads, though, maintainers generally do more harm than good. 

For future reference, the best (lead) batteries for EVs that sit idle for 
long periods are gel and AGM types.  They stay cleaner and thus need less 
fussing during storage.  They also have even lower self-discharge than 
flooded batteries.  I have several gel batteries that sit for months at a 
time, with no detectable loss of charge.