On 15 May 2006 07:50:23 -0700, in message
. com
" wrote:

The basic premise for calculating alternator size is 4:1. Your
alternator output in amps should be at least 1/4 the amp hour capacity
of the battery bank it is being asked to charge.

I have read this in all sorts of places but haven't seen a good
explanation for the why of it, other than the common sense notion that
it would be nice to get from 50% to 75% in not too much more than an
hour. I agree that it seems like a sensibly balanced rule of thumb.
I'm not sure I see why charging a 400 AH bank at 50 A would be a bad
idea. Maybe something about not running the alternator full out for
hours on end?

65 A into 200 AH seems to be working for me....

Ryk