wolfe10 wrote:
Amps is not the primary issue. Voltage drop, even if amps is rated way over actual could render the charge wire close to useless.
If voltage on the coach side of an isolator (wire run from batteries, fuse, etc is, say, 13.5 VDC and you loose .7 VDC across a diode-based isolator, you are NOT going to charge a toad battery with 12.8 VDC.
I agree, if you want/need it to be automatic, install a RELAY with an ignition-hot as the signal at the coach battery end. Fuse at coach chassis battery, fuse at toad battery and 8 gauge wire for hot and ground. DONE.
Most "modern" vehicle charging systems are only putting out 13.2V-13.5V AT THE FRONT BATTERY. YOU ARE
NEVER GOING TO GET ENOUGH VOLTAGE TO CHARGE YOUR HOUSE BATTERY !
What you really want is a DC-DC battery charger in your trailer. They typically will work with as little as 10V in.
