Things take longer in the microwave to cook when on battery

Have a couple of clients say that things take longer to cook/heat up in the microwave and phones take longer to charge when there is load shedding and inverter is in ups mode, any thoughts on that

Which inverters? I find it unlikely. The pnones taking longer to charge is definitely not related to input power from the inverter.

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Very unlikely, but as @_a_a_a asked, which inverter is in question?

There is no difference by my (victron) installation…

one is a Sunsynk and the other is a Deye ( similar ), but that is 2 out of about 50 plus clients that made this observation

I’ve not noticed any difference my side. Could this be an output voltage thing?

It’s a placebo effect. Tell them to prove it: measure how long does it take to heat the same amount of water by the same temperature delta in the same cup in both cases. Or what is the temperature delta after heating a cup of water for 1 minute.

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FWIW the one time my in-laws used their microwave on their GoodWe they also noticed a similar effect (They only used it once because it tripped the little 2.3kw Backup of the GoodWe EM 5048 after 30 secs) again just anecdotal, nothing concrete.

For a Microwave, I may believe it, because the power is somewhat voltage related. If the inverter supplies 230V while the grid is closer to 240V (and since power is proportional to the square of the voltage), you may be able to observe a slight difference… but it certainly shouldn’t be overly obvious. A little more about this later.

For phones, I simply don’t believe it. All the modern phones have switch mode power supplies for charging. If the voltage is lower, they simply adjust their duty cycle to get to the same power level. That’s definitely placebo effect.

Back to microwaves. Depending on your habits, this can be easy to spot. My kids like Pronutro. I have the recipe down to the exact amount of milk and the number of minutes it needs in the microwave. Typically it’s 450ml of milk going into the microwave oven for 2 minutes and 22 seconds (why… because hitting the “2” button three times takes less effort and is close enough).

Then I go on holiday and I use whatever crappy Microwave is provided there (Bennet Read… ugh), and the milk came out just luke warm. The observation in this case (related to the actual power of the microwave) is accurate. So… it may be insightful to ask the complainant how they tested it.


Phone chargers would be impossible.

But microwave, maybe. Definitely the case at my house - but only because grid supply is crap. Frequently 250V+, which certainly perks up some appliances.

On this topic, there might be some true to the original poster.

I currenlty have a situation where, when the power is comming from the inverter, LF inverter not Victron, the microwave slound like it is really struggeling sometimes. But not all the time.
It not load dependant, as the microwave would sometimea be the only thing on the inverter, ok, then a small intex poolpump. (Ive remove the intex pool pump but that did not helped)

But the weirdest thing is the dishwasher.
For some reason the dishwasher dont want to go past the first cycle. It would do the first cycle of pumping out the water befor the wash, and then reset, just to start all over.
But as soon as i move to eskom or victron, it all works fine.

Hence im saying there might be some truth in the OP statement.

I would also sometimes get the flickering of led light/ clock radios on the inverter.

Weird but true.

What inverter? You say another LF inverter, but I’d have assumed they are all quite good, or do you mean a HF inverter?

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I know that your cheaper “modified sine wave” inverters can have this effect on appliances, heating the appliance a tad more and the food inside it a tad less. And I know it is possible to have LF design MSW inverters. Maybe?

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MLT inverter, a later model, about 60kg to mount on the wall.

That sounds like the heater is on and it’s trying to start the pump, but the inverter/battery cannot supply the surge current + heater.

All the cheap modified sine UPSs are also low frequency, so it’s definitely not a sign of quality.

The inverter is an MLT inverter. Really a good inverter. been running like a champ, Its doing all the “heavy” lifting in the house. I do have a MP2 3000va in the mix aswell.

So the company that I work for brings in Powerstations, and I’m on the quality/testing team.
One unit that we where testing had a similar effect on the frontloader.
We obviously use the cold wash, as it was only a 500w unit.
So in this case, it would go through all the stages, but at the very last stage, where is spins as full speed, the frontloader would get stuck at that cycle. Then suddently the 8 minuts left becomes half an hour!! unlit either the unit runs flat, or human intervention.
Needles to say, that unit never made it to market…

Agreed, but I thought we’re talking about “proper” inverters, not a UPS (since he is trying to run his dishwasher off it)…

Your observation makes sense that it is the heater + the pump, but then I’d imagine the inverter being very small. The pump in our dishwasher’s is quite a small load, about 300W, so lets say 1800W startup. Or 2400W worst case. The heater 2000W normally. Even a 3kW inverter should be able to start that up, unless it is really poor quality?

That is surprising, my understanding was that they are proper good quality stuff. For some reason I’ve considered them in the same light (or even more) than Victron.

My MP2 5kVA has zero issues starting up my 850W pool pump, during loadshedding (not piggy backing off the grid), when the 3kW geyser + 500W idle loads are on. Or the aircon, it isn’t even bothered.

i believe they are really solid units. I don’t think a lot of people can say that the inverter they have can run 2x aircon’s, microwave and a kettle at the same time! i have a 9000btu non inverter, 18000btu inverter ac. the MLT is solid. Just that is my only gripe with it. with all the LS going on, ive removed myself from the grid… Currently running my setup off Grid…

I did once (with my 3kVA Multi, under heavy load) see my frontloader struggle to start rotating the drum. You could hear it drone, with little action. These are of course universal motors with simple speed control that generally consists of firing a TRIAC at the relevant angle, so that I very much expect that a distorted sine wave must have an impact on operation.

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the issue is not that it is struggling to start those loads. It starts it all as normal. It’s just the dishwasher that is having that problem…