A general electric tip / suggestion.
I have been very happy with Watt's Up meter.
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1634
(Most online hobby places or battery suppliers sell them for about $50)
I put the connector that I use on my batteries (was dean's now is powerpole) so that it sits inline with the battery.
Inside of a water tight box and I was able to put it in my ship and run with it, for a while I was using it all of the time in my Scharnhorst.
The meter measures from 0-50amps and will record the amp/hours and such.
Things I leaned:
At a dead short it capps out at 50 amps but does not blow up (mag throttle swtich failed)
My drive motor pulls 4-6 amps under load, about 2 dry on the bench.
Kip solenoids draw a little over one amp per, with three for the triples I'm about 3.5amps when the guns are firing.
In general for a local battle I would run 5-7 amp/hours, at NATS 7-10 amp/hours. The ship has 24amp/hours capacity so the voltage only drops a little bit.