Thank you all for all the posts. I've found all the switches and have everything working!! So, I need a generator to run the A/C and charge the battery, but I don't want to have to run the generator all the time. Will the inverter in the generator power the ac outlets, drawing on the battery, when the generator is not running?

Nope! The inverter just converts the generator output to AC power. It would be a DC device without it. I think if you want to use the A/C when boondocking, you're going to HAVE to run the generator.

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew

Thanks J&J,
I know I'll have to get a generator for A/C, and to recharge. I'm looking to add an inverter so we can run CPAPs all night on battery. I've done it in a tent with the built-in inverter in a Durango. Wait a minute, the generator I'm looking to buy already has an inverter. If it's plugged in to the battery, will it not invert the DC to AC? How could it know the difference between the 12V it puts out and the 12V from the battery?
Seems silly to buy an inverter when I already have one in the generator.

I don't know for sure, but I don't think there's any way to connect your generator's inverter to your trailer's battery. I know there's no way to do it on my Honda generator. My inverter generator is NOT a 2-way device. It only SENDS current to the trailer and/or battery.

If you want to run a CPAP from your trailer's battery, you'll need one that has an output Wattage that is somewhat more than what the CPAP is rated at. I'm no expert on this, so someone else might correct me, but I'd aim for something that has about 20% more capacity than the CPAP needs. This should keep the inverter running at a comfortable level. I think if you're very near the inverter's limit it might overheat and shut down.

With that Wattage pull, will your battery(s) last all night? What is the Watt rating of your CPAP machine? Watts are Volts x Amps. So since your battery will probably be around 12.5V under this demand, if the CPAP needed 200 Watts, you would be pulling 16 Amps from the battery to supply this demand. That's a very LARGE draw! I know the CPAP uses 120 Volts, but the Wattage is a constant. 12.5V DC and 16A would be converted to 120V AC and 1.67A to supply the 200 Watts needed. Forgive me, please, if I'm telling your things you already know - I'm just trying to keep you from being disappointed. Hopefully, the CPAP uses less Wattage, and you can figure out how you stand from that.

- Jack

Here is a CPAP reference point.

Our CPAP runs on 12VDC. We use a 120VAC to 12VDC power supply (just like a laptop power supply) at home or we run directly from a 12V cigarette lighter type output when camping. The CPAP label lists a current draw of 5.0A to 6.5A at 12VDC. The different amp draws likely come from different modes of operation.

If the CPAP runs for 8 hours a night, it consumes 40AHr to 50AHr of battery capacity.

The Amp-Hour capacity of the battery needed will depend on 1) how fully charged the battery is when the CPAP starts, 2) what else is running and 3) what battery technology is being used.

Hope this helps