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Microwave worked on 24V but not on 48V??

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Bex

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Oct 14, 2021
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We have been running our microwave on 24V system for over a year with no problems. 8 solar panels, for batteries.

We got 4 more batteries and have changed to a 48v system.

Microwave now triggers a fault on the inverter. We even brought a new microwave thinking the old one was broken!
Strange thing is it worked the first few times when we got the new one.
We run things with higher Watts all the time with no problems.
Any help would be much appreciated. Cheers
 
Different inverters have different abilities.
What 48v inverter are you using? What wattage is the microwave?
 
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I think the title is misleading. Presumably the microwave works on 120 volt AC and the difference must be in how the two inverters provide that power. My guess would be surge or less than perfect sine wave is causing the problem.
 
that watt inverter is minimal for a 1200 watt microwave. Just a bit of low battery or too much voltage drop will trigger the inverter protection circuits. The most recommended inverter for microwave use is two times the microwave watts for a sine wave inverter's watt rating.
 
Bex said:
Microwave now triggers a fault on the inverter.
Click to expand...
I am not familiar with the model of inverter you have ( I am in Europe), reading the instructions and specification it seems suitable for the microwave, specification suggest 4400 watts for 2 seconds.

I do not know the regs for 230v install in your country, (NZ?), but you may have a ground fault causing the trip, microwaves can have slight leakage to protective earth that may be causing issues. A system electrical test may identify the problem.

Other possible stuff that could cause problems.

You don't specify the batteries you have, lead or lithium? 6v, 12, 24, batteries?
There will be a lot more interconnections to check. Old batteries with new (lead acid) and series/parallel setup can cause unbalanced batteries.
If the batteries are drop in lithium there is often a limit of the series connection.

Mike
 
Thanks everyone, looks like we will be getting rid of the microwave ? oh well life goes on.
Appreciate all your helpful advice. Cheers
 
Bex said:
It was a 3000W inverter. When we ordered the new one we didn't double check the numbers ?‍♀️
Click to expand...
That would explain it. The microwave startup surge needed somewhere between the 2200W you have now and the 3000W you had before. I imagine the microwave is cheaper. Maybe get one that uses 1000W instead of 1200W.
 
I would certainly double check all of the connections and make sure there is not a problem somewhere. 2,200 watts is not a small inverter. That should fire up a reasonable microwave. Does the oven still work fine on grid power? 1,200 watt may also be the microwave output. Check the actual power draw. Does it come on at all, or trip out the instant it tries to cook?

Do you have anything else you can power up on the inverter that will pull near 1,000 watts for a minute or so? If you do, then check all of the connections for voltage drop or heat. Also measure the voltage at the inverter input with no load and the 1,000 watt load, to see how much droop you are getting. Most 48 volt inverters should stay running down to about 42 volts, but is your BMS shutting it down?? If you have just one weak cell, or a bad connection between cells, that might also be an issue.
 
GXMnow said:
I would certainly double check all of the connections and make sure there is not a problem somewhere. 2,200 watts is not a small inverter. That should fire up a reasonable microwave. Does the oven still work fine on grid power? 1,200 watt may also be the microwave output. Check the actual power draw. Does it come on at all, or trip out the instant it tries to cook?

Do you have anything else you can power up on the inverter that will pull near 1,000 watts for a minute or so? If you do, then check all of the connections for voltage drop or heat. Also measure the voltage at the inverter input with no load and the 1,000 watt load, to see how much droop you are getting. Most 48 volt inverters should stay running down to about 42 volts, but is your BMS shutting it down?? If you have just one weak cell, or a bad connection between cells, that might also be an issue.
Click to expand...
Thanks. We have given away the microwave. We are able to run a 1600W load no worries. So must be a hate relationship with our microwave.
Thanks again everyone
 
Keep in mind you can get microwaves that pull much less power. I'm pretty sure the one in my friends camper is like 600w lol

Takes a bit longer, but it does the job all the same.
 
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Bex said:
The 48V inverter is a nomad 2200W pure sinewave. Microwave input is 1200W
Click to expand...
Remember, a microwave output wattage is far less than the surge when he magnetron kicks in. A 1200W microwave can easily pull 2500W on startup… inductive loads from transformers are crazy at times.
 
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