Originally Posted by RichR

You could put a relay in line switched by the ignition switch.

Originally Posted by JackandJanet

Garry, I had a similar problem when we first got our trailer, brand new. Our first short trip (an overnight "dry camping" experience) was mostly uneventful except that the trailer battery was drawn down pretty heavily.

The second trip, into Colorado, to a "full hookup" camp followed by two dry camp points was quite different. The first dry camp found our trailer battery nearly dead, and I discovered the inline fuse on the charging circuit was blown. I replaced it and found it blown again when we camped the second night at a different place.

Later, I read in this forum that raising the top of the trailer with the trailer connected to the tow vehicle (and tow vehicle's engine running, so the charging circuit was connected) was likely the problem. The battery was on its last legs, due to the previous heavy discharges and raising the top put a heavy draw through the charging circuit, which was enough to blow the 30 Amp fuse that was protecting it. Essentially, the lift motor was getting its power from the TV battery, and the draw seems to be greater than 30 A.

This is different than what happens if you try to raise the top, with a dead battery, using shore power through the onboard converter. The circuitry in the converter simply does not deliver the 30+ Amps needed to power the motor.

So, I've learned to ALWAYS disconnect the trailer's power cord from the TV before raising the top to protect the charging circuit fuse. I've not had a blown fuse problem since then. I think simply shutting off the TV's ignition would provide similar protection, but it's just as easy to pull the plug.

- Jack

Originally Posted by RichR

Greg,
You would need an ammeter capable of measuring at least 15 amps, most muli-meters aren't that heavy duty.

What is going to happen is the fridge will draw from both the charge line and the trailer battery. So what the charge line doesn't supply the battery will. I have gone long distances with the fridge in 12 volt mode and arrived at the destination with plenty of battery to lift the top. But, I have dual batteries on the HiLo. You can go for quite a while with the fridge turned off if you pre-cool everything before you leave. I don't like running in gas mode, but many do.