Re: (ET) Battery chargers.

["David Roden" <etpost drmm net>]

On 29 Aug 2005 at 12:56, James Jarrett wrote:

> I'm sure [low current charging] is good on saving water in the battery, 
> but I'd question
> wether or not it is good for the batteries long term performance.

Batteries should generally be bulk (up to 80% SOC) charged at a minimum 
rate 
of C20/10 - that is, ((20-hour amp hour capacity) / (10 * hour)); e.g. a 
240 
ah battery should be charged at an initial bulk rate of 24 amps.  And 
there 
is ^almost^ no upper limit!  As long as temperature is monitored, a 
battery 
can accept charge about as fast as it can be discharged (that is, until 
it's 
80% charged).  Several experiments have shown that batteries actually 
perform better when charged at these rates for at least part of the charge 
cycle.

Don't ask me to explain why this is; I'm not an electrochemist and I don't 
understand it myself.

Some batteries need high current charging more than others.  Hawker 
Genesis 
batteries are infamous for this.  They tend to lose capacity fast if 
they're 
not whacked hard at least once in a while.

As for saving water, a smaller charger won't have much effect.  No 
electrolysis occurs until the battery is above gassing voltage.  By that 
time the current has usually fallen to C/20 or less anyway.

You should aim to have your battery 100% charged in 8-10 hours.


David Roden - Akron, Ohio, USA

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