[Vwdiesel] Re: Alternator - Battery - jumpstart questions

[Anton Largiader]

Milton wrote:
>There is a chemical you can put in a battery cells that is
> supposed to reduce sulphide deposits.

Actually the deposits are lead sulphate (or sulfate).  During normal
operation the plates turn from PbO2 (positive) and Pb (negative) into PbSO4
(lead sulfate). If they stay that way (discharged for long enough) the
sulfate crystals become semi-permanent.

However, this isn't (in my experience) the failure mode that the additives
typically address, although they are touted as sulfation-reducers.  When the
battery is very discharged, the elemental lead in the plates becomes soluble
in the electrolyte (which is very nearly water when discharged). The
additives usually 'spike' the acid with other sulfates that keep the sulfate
concentration of the electrolyte high enough to prevent this from happening.
If it does happen, then the dissolved lead will soak through the separators,
and when the battery is charged (and the lead becomes suddenly insoluble)
the lead will precipitate out wherever it is, causing conductive paths
through the separators and subsequent shorting in the battery.

Shalyn wrote:
> Any of y'all ever hear of a battery life extender based on
> "Pulse Charge Technology"?

It's not a new concept and is used in manufacturing to improve efficiency.
I think there is something in it as far as breaking up existing
semipermanent sulfation in a battery, but I'm not sure it has much utility
for routine maintenance.


==============================================
Anton Largiader, Chester Springs, PA
'94 K75RT, '93 R100GSPD,  '94 R1100RSA, '98 Jetta TDI
largiader at worldlynx.net   http://members.aol.com/alargiader/
==============================================