Alternator "charge" wire

[ukm5]

The only benefit added with an extra battery, is the handling of peak loads, as long as long-term average load is less than alternator capacity.

Javier

i think u have misread why i and the other user want 2 batteries - i use it as a back up incase my main one goes flat, perhaps left the lights on etc... the other guy uses it to power a fridge without draining the main battery