Date:         Thu, 20 Apr 1995 22:18:16 -0600 (MDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Jack Reed <jackr@fortnet.org>
Subject:      Re: Speaking of batteries...



On Thu, 20 Apr 1995, Alistair Bell wrote:

> 
> 
> Dug up the ol' chemical reaction that goes on in a battery.
> 
> Take a deep breath:
> 
> remember, the battery is made up of alternating lead and lead oxide plates,
> with sulfuric acid as an electrolyte.
> 
> the electrolyte contains hydrogen ions (H+) and sulphate ions (SO4--).
> During discharge, H+ ions react with the lead(IV) oxide to give
> lead(II)oxide and water;
> 
> 	PbO2 + 2H+ + 2e-  -> PbO + H2O
> 
> the reaction takes electrons from the plate, causing a positive charge.
> There is a further reaction to yield soft lead sulphate;
> 
> 	PbO + SO4-- + 2H+  -> PbSO4 + H2O + 2e-
> 
> electrons are released to the electrode, producing a negative charge.
> 
> You can see how the production of H2O accounts for the lower specific
> gravity in a discharged battery.
> 
> During charging the reactions are reversed;
> 
> 	PbSO4 + 2e-  ->  Pb + SO4--
> 	PbSO4 + 2H2O  -> PbO2 + 4H+ + SO4-- + 2e-
> 
> Now the specific gravity of the electrolyte (sulfuric acid) increases.
> 
> I still can't see where EDTA would fit in.
> I don't see any divalent cations...
> 
> Alistair
> 
> 
 
It's only effective when the battery is in a discharged state, if that's 
any help (still haven't located those papers, but I will)...

Jack