Re: (ET) Update my my old "cooked" Trojan batteries

["David Roden" <etpost drmm net>]

On 27 Aug 2009 at 6:26, David Barden wrote:

> what is overcharging? 

Charging past the point where all cells in the battery are fully charged!

Typically with lead batteries you have to put back about 5% more energy 
than
you withdrew in use, to account for charge efficiency (this varies a bit
with different batteries).  Our ETs usually are less efficient than this,
because the battery is imbalanced by the use of lights and lift on taps, so
it needs equalization on every cycle.

Once the battery is fully charged, all further energy is wasted as heat and
electrolysis (splitting the water in the electrolyte into hydrogen and
oxygen).

The heat can cause serious immediate harm.  As a battery heats up, its
effective fully charged voltage falls.  The charge current begins to
increase.  The battery is now in thermal runaway.  If you don't stop the
charge, and the charger isn't smart enough to limit it, the battery can
eventually electrolyse all its water and commit suicide.  It can even catch
fire.

Also, by removing water from the electrolyte, electrolysis increases its
concentration, and this accelerates grid corrosion.


David Roden - Akron, Ohio, USA

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