Thank you all for the replies. This is what I expected, but didn't want to be missing something that could run the batteries down. I have a switch for very small wires (probably to a relay) coming up under the shower area sink that I have never found a use for. I occasionally stay in the trailer during the winter, and it is not extremely cold where I keep it (lower to mid 20's would be possible but rare), so I put the heater at 40 (its lowest setting) during cold snaps, and have a small, Thermocube activated heater pointed at the tanks and pipes for when I'm gone. So far, both tanks and batteries have survived.
JRMunn