Tuesday, November 28, 2023


Why did my RV’s microwave stop working through the inverter?

Dear Dave,
I used to be able to operate my microwave through the inverter, but now that outlet has no power. If I turn on the generator or plug into shore power, then I can run the microwave. I have a Xantrex 12V, 125 amp hour battery. Could something have been rewired from the inverter? My battery also seems to be discharging quite rapidly with no systems running except the inverter and the fridge on propane. No lights are on, and the furnace is off. It went from 80 percent at night to 35 percent in the morning (about 6-8 hours). I have two 110-watt flexible solar panels. During the day under sunlight directly overhead, I was seeing only about an amp or 2 coming from solar. —Jesse, 2021 KZ Durango D348BHF

Dear Jesse,
There are several factors that come into play with the issues you have and we need more information. First, I assume you are talking about dry camping since you stated that you need to run the generator or plug into shoreline power for the microwave outlet to work. You state that your battery is a Xantrex 12-volt, 125 amp hour battery, which seems to be a lithium battery but you did not provide the make and model of the inverter. Most inverters are designed to provide 120-volt power to a residential refrigerator and other outlets, not just a microwave.

Do other 120-volt components on inverter work?

Have you identified what other 120-volt components are powered by the inverter and do they work? If not, then I would believe your inverter has a blown fuse or is defective. The reason things work when running the generator or plugged into shoreline power is most inverters have a pass-through feature that allows the 120-volt power to pass through the inverter to the components when plugged into shoreline or running the generator. Here is a photo of a Xantrex 1800 that was in the 2015 Thor Challenger we worked on.

It was mounted to the side of the upper storage compartment, and you can see the white 120-volt Romex wire at the top and bottom. On the back of the unit there is a positive and negative battery cable coming from the house battery that are inside the corrugated plastic tubing. There is a 15-amp fuse on the side of this unit that provides overload protection for the GFCI receptacles, which might be your issue. There is typically an inline fuse or circuit breaker between the battery and the inverter, so I would recommend checking for those and make sure they are reset.

Use a meter to verify volts

With the unit unplugged, use a 12-volt light meter or multimeter on the 12-volt setting to verify the batteries have 12.6 volts and there are 12.6 volts coming to the inverter. You can do this on the back side where the two cables come into the inverter. If there is no power, then it is somewhere between the batteries and the inverter. Some manufacturers install a battery disconnect inline on the positive cable, which you can also verify.

If you do have 12-volt power coming to the inverter, you can use the multimeter to verify if power is coming out of the inverter. This model was hard wired so it had no actual outlets. We had to remove the front panel and verify power. You can use a noncontact voltage tester placed on the wire to verify power.

If you have 12-volt power coming in to the inverter and the fuses are good, you should have 120-volt power coming out of the inverter. If not, the inverter is defective. Since it works when plugged into shoreline power, it would not be anything in the wiring from the inverter or the outlet. And, if you have not had any major work done to the unit, I doubt anything was rewired.

Rapid battery drain

If you do have the 125 amp hour Lithium Xantrex, it should last more than 6-8 hours unless it has been compromised. The cells in the lithium batteries can be damaged if they are drained to 100% and not recharged within a 48-hour time frame. Typically a Battery Management System (BMS) will shut things down prior to this happening.

You state that you only have the inverter on and the refrigerator is working on LP. However, there are other components running that you may not be aware of. The LP leak detector, roof vents, and lights, as well as the refrigerator draw 12-volt power on LP. And the furnace is a huge power hog due to the fan motor. 80% to 35% does seem to be a larger-than-normal drop. You need to do a power evaluation of what is actually running. It  would be wise to get an AC/DC clamp meter that you can put on the house battery cable and see how many amps are being used. Here is a very affordable one on Amazon.

This will verify how much power is drawing off the batteries and isolate if it’s a power drain or bad batteries.

Flexible solar panels

If you are getting only 1-2 amps charging from your panels, I believe they are doing nothing for charging and are most likely defective. Here is where it gets a little confusing and I’m still trying to figure out watts, voltage and amps. According to my sources at Go Power! and Zamp Solar, a 100-watt panel will produce 100 watts of DC output and 18 volts in ideal conditions. You then divide the watts (100) by the volts (18) and it should produce 5.5 amps. RVs do not want 18 volts as it would ruin batteries. So, hopefully, your flex panels have a charge controller that limits the voltage to under 16 and, if you have lithium batteries, 14.6 volts. So, let’s do the math: 110 watts divided by 12.6 volts would be 8.5 amps. Seems you have an issue with the panels.

 You might also enjoy this from Dave 

Can two 6-volt house batteries run a 2,000W inverter?

Dear Dave,
Will two 6-volt batteries connected in series run a 2000-watt invertor? —Pat, ’02 Lance 835 Lite

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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Dave Solberg
Dave Solberghttp://www.rv-seminars.com/
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.



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Neal Davis (@guest_243745)
4 months ago

Thank you, Dave! 🙂

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