[modmonster]

i know lots about batteries - i have custom built electric bikes.

for this application it is easiest to get cheap deep cycle batteries. however it would be best long term to go for nicd or nimh batterys.

it might be good to leave the normal battery untotched and have a relay system that disconnects alternator and switches to auxillery battery with one button press. then if you mess up you can always switch back to the normal battery.