Join Date: Apr 2014
Location: Bozeman, Montana
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I have two golf cart batteries in series to make 12 volts -- 215 amp-hrs.
The most charging current I have seen is 38 amps and that only briefly -- so, probably fine with the 80 amp fuse. I would definitely not go lower. I am using 60 amps in that line for my two golf cart batteries (wire sized for 60 amps with small voltage drop).
You can use chassis grounds for the return paths to all the DC loads and to the van battery. I ran full size return wires for everything -- this was just for long term reliability. Ground connects to the chassis have to be very good, and even so, they can corrode over time and create electrical problems that are subtle. But, either scheme works. If you run return path wires, you still need to ground the neg terminal of the battery for safety reasons -- does not have to be a huge wire.
I would say that no matter what you do on other circuits, you do want a full size return on the run from the house battery to inverter -- the current is very large and just a little return (ground) path resistance is bad. Also good to place inverter as close to house battery as possible.
From your diagram, its hard to tell where you plan to put the van battery side fuse on the line from van battery to the ACR -- it should be as close to the van battery as possible, otherwise it does not protect the wire.
If you don't use an Inverter/Charger, then read up on where the AC side ground is tied to the neutral. When on shore power is back in the campground system when running off inverter, its inside the van. Inverter/Chargers do the shift automatically, but withe separate inverter and charger, you have to take of the switch over yourself via a transfer switch or the like. Its a safety issue, so you want to get it right.