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stoneleigh asked

Induction Hob with Multiplus II 5Kw

I have recently bought a single pan portable induction hob as an experiment with a view to possibly changing our gas hob to an induction hob.

The Multiplus is configured as an ESS with solar and Pylontech batteries. At present all AC connections to the Multiplus are on the AC in (it will shortly be re-configured to use AC out 1 & 2). An ET112 is fitted immediately after the mains connection and is connected to the Cerbo GX.

We have noticed that when the 2kw induction hob is set to ‘simmer’ ie 1-2 / 8 the Cerbo indicates wild fluctuations of power going to or from the grid. Is this an ET112 limitation so that it cannot react quickly enough to the pulsing power requirement on low induction hob settings?

When we re-configure our AC to use AC out 1 & 2 my understanding is that we will no longer need the ET112, hence the Multiplus will need to react to the pulsing power requirement of the induction hob. Will it be quick enough?

We want to be able to use our 9.6Kwh batteries to power the induction hob, and not be sending power to, or drawing power from, the grid, which appears to be what is happening at the moment.

Any advice would be greatly appreciated.


Multiplus-II
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phoenix avatar image phoenix commented ·

I'd agree that there is some overshoot on the MP II when using devices that use a chunk of power, then stop (sometimes called bang-bang control) I have a cheap portable induction hob that does this. The induction hob installed in the kitchen (Hotpoint) uses proportional control and isnt too harsh on the MP. Power factor is pretty good - see attached graphs. It even looks as though the hob improves the PF generally. There were only about 75W of other loads - mainly LED lights and the router.

I'm running a MPII 24/3000 in ESS with a CT. It looks like the inverter was limited to 550VA (normal for me). You can see MP overshoot when the hob comes on, but is otherwise OK. Whilst not relevant to these graphs, the hob can be limited to its maximum draw at 3/4.5/6/9 kW and mine is set to 6kW but I've never seen the power draw anywhere near that.

hob-pf.png

hob-w.png

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stoneleigh avatar image stoneleigh phoenix commented ·
Thanks Pheonix, my portable hob is indeed a cheap one - £50 from Ikea! We like the induction cooking, we’ll see how the MP handles the power without the ET112, but it looks like we will need to buy a hob with proportional control. How can you tell whether hobs have this feature? (except that very cheap ones most likely won’t!)
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phoenix avatar image phoenix stoneleigh commented ·
I bought the hob before the MP, so I was lucky with it being proportional control. It's a Whirlpool, not Hotpoint as I posted before. I'm not sure how you'd know it's a proportional one- possibly the power limit feature?


A typical Sunday dinner will consume 1kWh with just the hob. I've only a 7kW battery so the hob is connected on the grid side and during power cuts we use a 2 ring gas hob.

The oven is a Samsung dual cavity and that is bang-bang control. 3.5kW for ~7 mins to get to temperature, then 1.5kW to maintain.

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Alexandra answered ·

@Stoneleigh

Most induction stoves totally mess with the sine wave. Sometimes electricity knocks about the place doing nothing. (There is a more technical term if you want to be more technical)

If you switch to inverting you will be able to test if it can handle the load. I am sure it will but the sound of the inverter will be different, sometimes sounds like there is fault with some of the hobs.

Just check your power factor on the hob as well. 2k is not always 2k. Especially if the Power factor is 0.5. Which alot of these appliances are these days (So 2k in watts is actually 4kVa).

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stoneleigh avatar image stoneleigh commented ·
Thanks Alexandra, I’ll try your inverting suggestion. As you say the MP ought to handle the max load, but it will be interesting to monitor how the MP reacts to the bang bang power demand.
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prein answered ·

On my boat I have a 12v 3000va multiplus 2. I have 8 kwh of batteries. My single ikea induction plate works great on any setting. Also purely on battery. I would rather like to get another induction hob with proportional control, just to ease the load on the multiplus a bit. But it works OK right now as well

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