Inverter problems ...or maybe not?

2018 R25-OB has a separate inverter and charger, not a combo unit. I have already replaced the charger. The inverter is behind the wall near the AC panel I believe. I have tried getting access to it and cannot figure out how to get the wall loose. The inverter is a Kisae model, not sure which one.

After owning the boat for a year I finally came upon a chance to use the inverter to run the microwave for a couple minutes. I turned the remote switch on, got a green light, then turned on the microwave. it ran for a few seconds then shut off. Several attempts had the same results. Three long beeps coming from the power panel then a shutdown. Voltage showed zero for a second, then it reset to 120 volts as it came back online.

When I got back home I tried a smaller load. A 3 speed oscillating fan, which ran fine with no beeping and no shutdown. With both the microwave and fan, there were no other breakers activated so these devices were the only load on the inverter.

Should the inverter be able to handle high loads like a microwave or even a toaster? Could my batteries be weak and need replacing, thus only accepting smaller loads? The microwave test was conducted with the engine running and voltage above 14 volts. Can anyone think of other diagnostic tests I can perform to help diagnose the problem? Or even how to remove that back wall to access the inverter?

Thanks in advance for your input.

I've recalled reading about inverter issues, searched and found these threads. https://www.tugnuts.com/threads/inverter-problem.21215/ https://www.tugnuts.com/threads/inverter-issues.26424/ https://www.tugnuts.com/threads/inverter-problem.5653/
One thing that comes to mind, from working with Martin, is the 2 house AGM batteries don't share a positive bus bar, so the loads don't equally draw. Martin can explain it better, I think its our era of model/wirering design. You may be loading one AGM battery more than another, causing the low volatge cutout. I'll admit that we rarely use the boats inverter, running the microwave on either shore power or from our Bluetti "similating" shore power.

Thanks Cliff,
I read every thread that I could find Labelled inverter and found out that I might not have enough battery to support the inverter. A positive battery bus would be a good idea.

John Cortesy said:

Thanks Cliff,
I read every thread that I could find Labelled inverter and found out that I might not have enough battery to support the inverter. A positive battery bus would be a good idea.

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The microwave can run off the inverter if they are in good health and only for a short time.

The beeping you hear is the inverter low voltage alarm at 11.8volts. At 11.5 volts the inverter will shut off.

Thanks Martin,
I may have to invest in a small, quiet generator.

John Cortesy said:

Thanks Martin,
I may have to invest in a small, quiet generator.

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John Cortesy said:

Thanks Martin,
I may have to invest in a small, quiet generator.

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I have a small Yamaha 1000w gen you could try to see if you like it?

Hi Martin, I am looking at the Anker LiFePo solix 1000 but AI says that it won’t be safe to use a 115v to 30amp shoe power adapter and I am wondering what Lemon Drop uses for her conversion from the unit to the R-27 shore power system?

If you run your engine while you run the microwave, does the inverter work just fine? When my house batteries are dipping towards the end of their capacity, it doesn't like running the microwave. How old are your house batteries?

SKing said:

If you run your engine while you run the microwave, does the inverter work just fine? When my house batteries are dipping towards the end of their capacity, it doesn't like running the microwave. How old are your house batteries?

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On a NW edition, which is what John's boat is... if you run the engine, turn on the inverter and run the microwave, the amp draw on the house bank is excessive ( around 1000 watts). That will cause the voltage to drop, a lot. As a result, the ACR between the house and engine will sense that voltage drop and will then open, to isolate the engine battery from the house, to protect the engine battery from the excessive load. Thus, the engine is running, the microwave is running, and the engine isn't helping the microwave.

I sulfated and destroyed my house bank 90 days after taking delivery of my boat doing this. But I was running the hot water heater with the engine running.

This mechanism exists in the other models as well which have AGM house bank batteries. A workaround is to simply engage the engine to house parallel switch, which bypasses the ACR's and does allow the engine to help. I've done this as well, but noticed that my engine battery was participating in the excessive load, acting as a deep cycle battery it wasn't designed for. Voltage on my engine battery I watched decrease, making this not a solution. I do not recommend using the parallel switch to bypass the ACR's for this function.

The microwave will pull about 90 amps at 12 volts via the inverter, the engine will only output 40amps at max. The math isn't there to run the microwave (or hot water heater) off the engine.

Start at timestamp 23:35.

So basically with that set up even if everything is new, the microwave is only usable at the dock.

SKing said:

So basically with that set up even if everything is new, the microwave is only usable at the dock.

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With AGM batteries that are healthy, we would run our microwave and cofee maker off the inverter on AGM batteries.
The microwave was used for a few minutes, same as coffee. It was able to handle that. Engine on or off, doesn't matter.

Hot water is what I was after, so I could take a shower. The water heater has to run for too long (45 minutes) to be of benefit, and the AGM's just can't do that.

For hot shower water, microwave, and toast, along with battery charging on cloudy days in late fall, I have decided to go with a gas powered generator. It is the cheapest, easiest solution to supplement my solar. Thanks for the responses everyone.