Microwave and Inverter don't play together well

[pascalG]

Using Modified sine inverters is hit or miss. Some thing work, others not so well. Power tool chargers are known to burn out on MSW. Years ago I used a microwave with a MSW Xantrex freedom and it worked although it made a different noise.

I have also use a Pure Sine Wave Magnum and everything worked great.

Pure sine is more $ but worth it especially when you consider the costs of the inverter bank,wiring etc.

[Pizzazz]

For those of us, who love the Freedom 1500/Link2000 setup, is there an inexpensive and efficient way to smooth out the modified some wave with a capacitor or something?

My microwave runs fine off the modified some wave inverter but the other day I tried a UV light air purifier and the bulb burned out immediately. I guess one way is to get a small pure some wave inverter for electronics but those are expensive as well.

Thanks,
Pizzazz

[DO335]

I have a square wave inverter and run my 1200 watt microwave all the time. What you are describing is what happens when the battery voltage is too low. Even if the voltage is above 12.1v dc it still might not run properly. Either wait until your batteries are fully charged (like 95%) or run your engine while operating microwave via inverter, the alternator will increase voltage above 13v and your microwave will work fine.

[DennisRyan]

My experience is exactly as DO335 describes.

[Dauntlessny]

Originally Posted by Stu Jackson

My Heart Freedom 15 is a modified sine wave unit, purchased in 1999. Xantrex bought Heart out shortly thereafter, but IIRC all Freedoms were modified sine waves. Manuals are available for older units on Xantrex's website. Ours runs a small, almost mini-microwave that was installed by the PO in the late 80s or early 90s, and they play well together. Could be that newer and/or bigger microwaves require pure sine wave, although in my readings there hasn't seemed to be a mandate --- seems some do, some don't.

Ditto. I have a Heart 2500 and out works fine with 90's microwave for the last 20 years.

Originally Posted by gbr

You have been misled. I run ours using our Victron Inverters all the time.

OP: You will almost certainly need a pure sine wave inverter for any microwave. Also, some coffee makers need pure sine wave as well. A lot of things with electric motors (depending on type) - need pure sine wave.

Might be an expensive proposition to replace your current inverter, but that is what I would do if you want a Microwave and not start your genny.

[smacksman]

I buy old boats in the US, have great holidays for 3/6 months then sell them.
I buy a cheap $100, 2000W inverter from Harbor Freight (square wave) and a $40, 700W microwave and a $50 'student' fridge from Walmart.
I run the engine for the few minutes the microwave takes to cook/heat water for coffee and while the fridge door has been open.
A tip is to use auto jump lead cables between the battery and the inverter to reduce voltage drop.
Works well.

[stormalong]

Originally Posted by smacksman

I buy old boats in the US, have great holidays for 3/6 months then sell them.
I buy a cheap $100, 2000W inverter from Harbor Freight (square wave) and a $40, 700W microwave and a $50 'student' fridge from Walmart.
I run the engine for the few minutes the microwave takes to cook/heat water for coffee and while the fridge door has been open.
A tip is to use auto jump lead cables between the battery and the inverter to reduce voltage drop.
Works well.

Auto jump cables come in a variety of gauges. Risky. What is even more risky would be to use them with their battery clips that are intended for temporary, monitored connections. Imagine what could happen if one of the clips attached to the inverter slipped off and shorted to the other cable.

[mitiempo]

Originally Posted by smacksman

I buy old boats in the US, have great holidays for 3/6 months then sell them.
I buy a cheap $100, 2000W inverter from Harbor Freight (square wave) and a $40, 700W microwave and a $50 'student' fridge from Walmart.
I run the engine for the few minutes the microwave takes to cook/heat water for coffee and while the fridge door has been open.
A tip is to use auto jump lead cables between the battery and the inverter to reduce voltage drop.
Works well.

I have never seen jumper cables large enough to run a 2000 watt inverter efficiently. A 2000 watt inverter will use 200 amps DC at its max. This requires 2/0 wire ideally.

[smacksman]

I don't know what 02 wire is but the jump start cables I buy are about 8 or 9mm dia. (about 3/8" dia. in old english) and yes, I solder on eye terminals and have the brains to trim the cable to length and put the balance in the spares locker. Then, in 10 years time, when the non-marine grade/ non-tinned cable needs to be replaced, the cable is to hand.

[mitiempo]

Originally Posted by smacksman

I don't know what 02 wire is but the jump start cables I buy are about 8 or 9mm dia. (about 3/8" dia. in old english) and yes, I solder on eye terminals and have the brains to trim the cable to length and put the balance in the spares locker. Then, in 10 years time, when the non-marine grade/ non-tinned cable needs to be replaced, the cable is to hand.

2/0 wire is about twice that size in area.

[transmitterdan]

So I boiled water for coffee on my one burner induction hob today. It draws 1100W and took 9 minutes to boil water. So an inverter will draw about 1250W from the battery. Round it off to 100A for 9 minutes and it takes about 15AH of 12V battery bank to make a liter of French press coffee.

[Pizzazz]

Originally Posted by transmitterdan

So I boiled water for coffee on my one burner induction hob today. It draws 1100W and took 9 minutes to boil water. So an inverter will draw about 1250W from the battery. Round it off to 100A for 9 minutes and it takes about 15AH of 12V battery bank to make a liter of French press coffee.

I have been thinking about this. If my calculations are correct, the minimum energy you need to raise the temp of 1 quart of water by, say 150F, is about 90 watts hrs or about 8 AHrs. So, you are 50% efficient, this includes the losses in the inverter, etc. I read somewhere that an electric kettle is 80% efficient, a microwave 50% efficient and a regular cooktop only 30% efficient due to losses to the surroundings. Bottomline:

Boil water in the kettle or in a pressure cooker. Alternatively, switch to an espresso machine and enjoy better coffee. Or drink tea I guess this is off topic but the idea that I have to run the engine for 15 min to replenish the energy for two cups of coffee [emoji27]

[Cheechako]

Originally Posted by Cheechako

My older Heart Interface Inverter/chargers worked well with a microwave.... and other ac appliances. I think I had them on 3 boats. Not sure how that helps, they were 80's -90's units. Microwaves are a huge draw though, I didn't have 1100 watters , had smaller units.

The draw was huge. Unless just using for just a minute or a little more to heat water, I started the engine.

[Stu Jackson]

Originally Posted by Cheechako

The draw was huge. Unless just using for just a minute or a little more to heat water, I started the engine.

Let's put this into perspective:


My small old microwave, that I reported on earlier in this thread, consumes 80A when running.


80A for a minute is all of 1.33 Ah. [80A * (1/60)] 10 minutes is all of 13 Ah. This is a very low load for my 390 Ah house bank.


Somebody wanna check my math?



I use the stove to make hot water. The longest run for my microwave is making frozen mac & cheese (Oh, Lordy, I did admit that in public?!?), that takes six or seven minutes. A whopping big ten Ah.


Even popcorn only takes four minutes.


I agree with Cheech that if the house bank was low I might start my engine, but then I'd do that anyway if the bank was low; I don't have solar. It then is a simple management issue: charge when heavily discharging - timing is everything!


[Freedom 15, 1500 watt inverter, MSW] Big 2/0 wiring.

[john61ct]

Yes, those for whom burning a bit of dino juice daily is NBD, then running a microwave or other home appliance is also NBD.

Those with no gennie who want silence on the hook for weeks at a time are a different use case.