Can you power an A/C from your 7-way plug?

Here’s a brief tutorial on why that won’t work….

Dear Mike,

On my 2019 Casita towed by a 2019 Subaru Ascent I have 325W solar panel, 3000W inverter and four Battle-Born 100W lithium ion batteries. If I’m boondocking and need AC at night, and I idle my car with trailer plugged into it, will it keep my batteries charged enough to use AC on low cool?

I know carbon monoxide would be an issue, so would park car in such a position that exhaust would be directed away, and of course windows and vents closed as well. - Betty

Dear Betty,

You’ll never get enough current though the 7-way plug on your vehicle (maybe 5 amps at 12 volts) to provide more than a few minutes of extra air conditioner time. That 5 amps at 12 volts run through an inverter (even at 100% efficiency) is only 1/2 amp of current at 120 volts, and you need at least 12 amps at 120-volts to power your A/C. So your 7-way plug doesn’t have a chance…

DC to DC chargers

You really need a DC-to-DC charger and heavy-duty wiring and an Anderson connector from your tow vehicle battery/alternator to your RV battery.

And without a heavy-duty alternator in your vehicle on high idle it will be difficult to get more than 80 amps of current at 12 volts for extended periods, and you need at least that plus a Hybrid Inverter to run an A/C indefinitely. So this project would be an expensive experiment with no guarantee of working.

The Gold Standard

If I were doing this and had the budget I would buy a Ford F-150 PowerBoost truck with the 7.2kW ProPower Onboard inverter generator. I tested an F-150 PowerBoost truck two summers ago and was able to power a 50-amp Airstream with two A/C units all day and night with the truck’s built-in 7.2kW inverter generator on idle. It’s not a big tow vehicle, but an F-150 PowerBoost is a great power source.

Let’s play safe out their- Mike