Re: (ET) Weird Battery Behavior

["David Roden (Akron OH USA)" <roden ald net>]

Battery chemistry varies among brands, so fully charged specific gravity 
and 
voltage will also vary.  A higher resting voltage isn't necessarily an 
indication that a battery is "better."  IMO, Trojan is a better battery 
than 
Exide (at least in golf car batteries), but I don't think the resting 
voltage is related to that.

Also, resting voltage won't be valid until the battery has been off charge 
for several hours -- at least overnight.  The amount of time that it takes 
for surface voltage to disappear might vary too, though I've never looked 
into that.  Specific gravity is always a better measure of state of charge 
than voltage.

It's vaguely possible that the previous owner reconcentrated the 
electrolyte 
in the Trojan to get a little more use out of it.  This is an old trick.  
It 
does seem to restore capacity, but it causes more depreciation in the long 
run.  Batteries are designed to have a certain balance between active 
material in the plates and electrolyte concentration.  The electrolyte 
turns 
to water and the voltage drops before the active material can be over-
discharged.  When you reconcentrate the electrolyte in an old battery,  it 
doesn't restore the lost active material to the plates, so they will tend 
to 
over-discharge and become damaged.

Disclaimer: I'm not an electrochemist, this is just my understanding of 
how 
batteries work.  


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1970 GE Elec-trak E15 36vdc
1974 Avco New Idea 36vdc
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