Loren,

Several folks already said this, and I agree: you don't want to discharge
a battery* more than 20 to 50 percent. "Deep cycle" batteries are exactly
that: they are designed for discharge to a deep point. Using a starting
battery ("shallow cycle") for house power applications results in a very
very short life.

Many *good* state-of-charge (amp-hour) meters will take into account the
above fact. Look for meters that are meant for alternative energy
installations. Most of them have enough brains for this.

*There are all sorts of new technologies in batteries that will supposedly
allow a "more complete" discharge than what we currently have. Hopefully
they will make it to the market soon.

Jon

On Tue, 20 Jun 2006, Loren Busch wrote:

> The answer to another question here on the list raised this question.  Given
> that we have the amp hour rating for a battery and also given that we don't
> want to draw it down below about 10.5 volts, about 80%.  Does that amp hour
> rating assume draw down to the 80% level, or draw down to 'dead', zero?
> I've always assumed that if I have a 50 amp hour battery that I can draw 1
> amp for 50 hours before reaching the point that will require charging, or
> will I only get 20% of that, 1 amp for 10 hours, before reaching the point
> where I need to recharge?
>