So after much self-deliberation, here's my plan:
- Pick up a battery combiner. It looks like this
250A Xantrex Pathmaker is about the only one with a relay rated to handle a starting load.
- Mount it between starter/alt and main battery
- Run cable to back from second bank terminal of the combiner to battery mounted in rear
- Mount a fused distribution block and ground block in back to wire up inverter plus other DC accessories.
With the combiner you can mix battery types safely, it's automatic and lets the second battery be a starter backup. So I'd do an Optima yellow top for the second battery in back.
While I haven't yet picked a mount point for the battery (ship's idea of over the wheel well sounds nice if you can fab a cover).
The only things I haven't been able to figure out yet are:
- how heavy a wire to run from the combiner to second battery. Starter current may need to run along this in an emergency and it's going to be about 12-15 feet long!
- what kind of fusing is needed on this wire. Wouldn't this wire need overcurrent protection in both directions, in front for when normally charging, in back for when starting from backup battery?
Any electrical whiz with the answer on this last one? Maybe I'll finally need to break down and get a book.
Time to go buy stuff.