On Wed, 17 Oct 2007 11:59:26 -0000, Tim wrote:

accessory
battery is an 8-D "Cat" battery. I've run the 8-D battery almost dead
several times, and the alternator has charged well.

That battery is not actually intended for deep cycling, but is a
starting battery Running it down to flat will damage it, and it only
might only take a few times to do it in. Any battery should be charged
slowly: a ten hour rate is fast. And the slower the discharge rate,
the more total juice you get. I am pretty sure I will get the same
battery for my boat, and I will try not to discharge it to below 75%.
That is not a deep cycle. 25% is deep. Batteries have to be babied,
and if you find one that is more robust, it will be sure to cost more.

Casady