Community Forums

JavaJelly · 02-09-2008, 03:25 AM

The microwave would not heat, (barely warms) under inverted power even with the batteries at full charge and the engine running. Have to start the genset to get it to heat appropriately. First, I'm sure this is really bad for the microwave and second it should work under battery power no problem.

Two things:

I thought that my batteries were going bad. However, Newmar just checked all the batteries, adjusted the inverter and cleaned all the posts. They said the batteries were in great condition. They have an electronic piece of equipment that does a complete analysis. Also, specific gravity came in great.

Secondly, I do not believe there to have been any other major draws at the time of use, e.g. toaster, hair dryer. The only thing that might have been running is the HydroHot fans.

Any ideas out there?

JavaJelly · 02-09-2008, 03:25 AM

The microwave would not heat, (barely warms) under inverted power even with the batteries at full charge and the engine running. Have to start the genset to get it to heat appropriately. First, I'm sure this is really bad for the microwave and second it should work under battery power no problem.

Two things:

I thought that my batteries were going bad. However, Newmar just checked all the batteries, adjusted the inverter and cleaned all the posts. They said the batteries were in great condition. They have an electronic piece of equipment that does a complete analysis. Also, specific gravity came in great.

Secondly, I do not believe there to have been any other major draws at the time of use, e.g. toaster, hair dryer. The only thing that might have been running is the HydroHot fans.

Any ideas out there?

Route 66 · 02-09-2008, 03:34 AM

The first thing I would do is check the voltage at the microwave 120v receptacle, with the microwave on and off, and also on inverter power and shore power or generator power.

If you have a modified sine wave inverter, and you have the proper voltage, then I would think the microwave is damaged and will no longer work on a modified sine wave.

If you have a pure sine wave inverter, it almost has to be low voltage at the microwave receptacle when on inverter power.

The inverter will put out the proper voltage until it shuts down from low battery voltage.

bjbkkb · 02-09-2008, 04:21 AM

Just attended a seminar at the FMCA SEA rally on generators and electricity. The microwave lack of performance issue came up and it was said the first thing to do is check voltage.

JavaJelly · 02-09-2008, 04:24 AM

Gotta be a voltage issue as the microwave works great when on shore/genset power.

Gary RVRoamer · 02-10-2008, 04:47 PM

Microwaves are sensitive to the wave form of the AC power some may not perform well on modified sine inverters. Sometimes they do not work at all. But if the inverter was standard equipment in your Dutch Star, then the microwave should also be compatible and I would look elsewhere for the problem.

Microwaves are BIG power consumers and it is possible the large AC current draw is dropping the voltage in your batteries almost instantly. Can you monitor the battery voltage while the inverter is running and see what happens when the micro is on?

Dolph · 02-10-2008, 06:44 PM

Don't recall the source, but recently read that micowaves only receive approx. 60% of power from msw inverters. You may want to research that. Sorry that I can't be more helpful than that.

Gary RVRoamer · 02-11-2008, 02:00 PM

Yeah, I've seen the 60% power figure too. It probably applies to at least some brands, but not universally. It will depend on the design of the particular model. Just don't be surprised when things don't cook as rapidly when on the inverter.

Hillbilly2 · 02-12-2008, 03:03 PM

It could be the modified sine wave that causes the problem, with a true sine wave the peak voltage is something like 172 volts (can't remember off the top of my head what it actually is) and with the modified sine wave I think it caps at a much lower voltage which may not be enough to charge the high voltage capacitor in the microwave. Any engineers out there? They could explain it better, or at least confuse us more.

Gary RVRoamer · 02-12-2008, 04:10 PM

The lower peak voltage vs the capacitor is the explanation I read too. Makes sense to me, knowing a bit about how microwaves generate the radiation to cook with.

JerryKelly · 02-15-2008, 04:35 PM

Scott, my microwave makes a humming noise when powered by the inverter. I was told it was due to the MSW inverter. We only use the microwave when plugged in or the genset is running.

hamdave · 02-23-2008, 10:13 AM

I think you need to provide more info.
a)What size inverter
b)true sine or modified sine wave ?
c)What size uWave
Your factory info may not like modified sine wave.
Your inverter may be too small

????

Wayne Dohnal · 03-01-2008, 12:07 PM

As others have stated, if you have a 'modified sine wave' inverter, that explains the slow cooking. The microwave's cooking power is dependent on the peak voltage of the AC power, which is 162 with a 115 volt sine wave, and at best 140 with a 115 volt 'modified' sine wave.

**Petro** · 03-01-2008, 01:24 PM

Scott;

I have not tried ours strictly on battery alone but it works well while underway. We have a combination convection/microwave and we have used both while traveling.

Don