Inverter vs Generator

The roof A/C draws around 200 amps from the battery. The truck likely doesn't put out 200 amps of DC power at idle, and it surely won't be charging your batteries at more than about 20-30 amps through a 10awg trailer plug wire at the rear bumper of the truck.

You're a brave man running air with a cheap MSW inverter and one battery. Hope things last.

How long can you run the air?

The fuse in the charge line (truck sending power to the trailer) is somewhere between 20 and 40 amps, the voltage drop from the trucks fuse box to the trailer batteries limits you to as well. There is a 0% chance you can run the trailers AC off the trucks charge line, not counting the trucks alternator puts out far less then 150-200 amps at idle that is needed by the inverter.
If you are going to plug the trailers power inlet into an inverter powered off the trailers batteries you will want to disable the onboard converter while you are doing it.

You may get 10-15 minutes off a single battery running the AC, but without putting it in a lot faster then 20-30 amps, the truck will only give you another minute or so of runtime. Then the trailers battery will be dead - no lights, no water pump, no propane detector, no fridge, etc.

Great start. Next is more battery and solar.

Was this a short experiment or have you overnighted with that setup?

I have not left the garage on this one. I did run the roof top unit for about 25 minutes but cooler weather might not have had the compressor running. Microwave seemed fine on heating a cup of water.So from recent comments another battery in series would possibly give say half an hour on a/c? In all reality my usage with the generator has been the microwave or tv or coffee machine. Our travel has been mostly in fall-spring and in parks at night. Very little a/c use.So this still might be a compromise, but looks like a win/win for us.

hvac wrote:
....So from recent comments another battery in series would possibly give say half an hour on a/c? .

Another battery in "series" will fry everything, including the 12v inverter, which won't like the 24 volts fed to it when you connect another battery in "series."

hvac wrote:
I have not left the garage on this one. I did run the roof top unit for about 25 minutes but cooler weather might not have had the compressor running. Microwave seemed fine on heating a cup of water.So from recent comments another battery in series would possibly give say half an hour on a/c? In all reality my usage with the generator has been the microwave or tv or coffee machine. Our travel has been mostly in fall-spring and in parks at night. Very little a/c use.So this still might be a compromise, but looks like a win/win for us.

We have four 6 volt batteries and would not even think about running the AC, but the wife can you her hair drier.

Here is a way to test the quality of the MSW inverter.

1. plug into shore power.
2. place 1 cup of water in microwave
3. run micro for 1 minute
4. measure the temperature of the water.
5. plug into inverter
6. place a cup of water in the microwave
7. run micro for 1 minute
8. measure the temperature of the water.

If the two temperature readings are identical--you are golden. If they are extremely close then you are only silver and I would not risk the roof air. If they are quite different (say ten degrees) then definitely don't run the (expensive to replace) roof air.

hvac wrote:
Microwave seemed fine on heating a cup of water.