[B_and_D]

I've thought about wiring up the truck to be able to take a spare battery with us on day trips (like to the store, even), keep it in the tool box, and charge it while we're driving. It wouldn't be that hard to hook up. You could switch it back and forth with the house battery and that way keep them both charged up. When we camp, we hardly go a day when we don't drive somewhere.

Most TV's have a great recharging source - the alternator; some are better than others. The one in our Chevy truck seems to be a very good charger. However, the way most TM's and 7-prong plugs are wired, the charging doesn't always get to the TM house battery that efficiently through the 7-prong plug. In our 2720, the converter is way in the back, and then the power has to be transferred way into the front of the TM where the batteries are mounted. The wire gage and the length the charge has to travel makes a great deal of difference in how efficiently your batteries will charge. Take a look at how your battery in your TV is charged...it is through very heavy gage wire and short cables. Compare that gage of wire with the wires that connect your TM house battery to the TM! I believe that we could also mount a spare battery in the engine compartment of our Chevy 1500 which could be plugged into the TM at night. You would need an isolator or a manual cutoff switch to keep the main TV battery from draining. From what I understand, you can order a special bracket from GM to hold the extra battery in the Chevy trucks. We had an auxiliary battery in our old GMC with a camper, we would hardly ever run out of power, but we didn't have much to run back then, just a couple of lights, the water pump, and the Thetford. No phantom drains!

I highly recommend this book: RV Electrical Systems: A Basic Guide to Troubleshooting, Repair and Improvement, by Bill and Jan Moeller. I got our copy from Amazon.com.