Re: (ET) Three year plus batteries

["David Roden" <etpost drmm net>]

On 17 Sep 2006 at 17:48, Daniel Childress wrote:

> Is this normal when trying to charge an older battery?

If you have a battery that's been sitting for a long time and is dead-dead-
dead, its electrolyte is basically water and its internal resistance is 
very 
high.  When you first connect the charger, almost no current will flow - 
it 
will be measured in milliamps.

But if you can get even a little current to flow, the battery will 
g-r-a-d-u-
a-l-l-y charge.  Bit by bit, the resistance will fall and the current will 
rise. If you're lucky, eventually you can get it to reach an apparent full 
charge.

I say apparent because a battery that's been abused this way will usually 
have pretty low capacity.  You can "exercise" it and the capacity may come 
up but it will never be like new again.

That said, you may or may not actually have a "complete charge" on that 
battery.  I don't know how your charger determines what that is; it may be 
that the battery has fooled it.  The only really reliable way to tell the 
battery's state of charge is with a hydrometer, or by testing its capacity 
to see how long it will produce, say, 75 amps of current into a load.


David Roden - Akron, Ohio, USA

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