Does the MultiPlus 3 kVA Inverter/Charger allow me to set an upper limit on the wattage?

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cw8 asked Apr 15, '21

Does the MultiPlus 3 kVA Inverter/Charger allow me to set an upper limit on the wattage?

I am considering the "MultiPlus 3 kVA Inverter/Charger" for my van build.

Due to battery constraints, what I really want is a 2.5-2.7 kVA inverter.

Is it possible to limit this inverter to something less than 3kVA? A setting that can be modified?

The other inverter I am considering, a Xantrex, does support this. ("Inverter Output Power Limit" - "The wattage setting value can be adjusted by 100-watt increments. Use with Inverter Output Power Limit Timer especially when pairing with a lithium ion battery. 0.1 is equivalent to 100 watts.").

I looked all through the Victron manual, but did not see anything about this.

I was hoping to go all-Victron, but this might preclude that.

Thanks!

MPPT Controllers Phoenix Inverter

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wkirby answered · Apr 16, 2021 at 08:43 AM

I have had a quick look at the datasheet for your battery.
It is saying maximum continuous discharge of 250A. So 250A x 12.8V (nominal) then that is 3200W DC. The minimum Voltage is 11.6V, so even then it's 2900W DC.
So then isn't a 3KVA inverter perfect for your needs? You'll only be close to this value when you are cooking a meal, most of the rest of the time you'll be well under this value.

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cw8 commented · Apr 16, 2021 at 02:37 PM

Thank you so much for looking into the battery. My thinking was that I am new to this, and did not want to go anywhere need the edge. I wanted to leave a lot of breathing room. This answer helps me feel much more comfortable going with 3KVA. Cheers!

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wkirby ♦♦ cw8 commented · Apr 16, 2021 at 06:11 PM

I also forgot to mention that you have good control when using an induction cook top.
You only really want full power from the cooker when bringing water to the boil, which is a short process. Once boiling, you need to reduce the cooking power. 1800W of induction cooking is far too much for normal cooking, you'll burn your food very quickly and damage your cookware.
500W - 750W for induction cooking is more in the normal power level for cooking.

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cw8 wkirby ♦♦ commented · Apr 16, 2021 at 10:09 PM

That makes sense. If I can keep it low, but... what would happen if I got the 2KVA inverter and put the hotplate on full 1800W and then someone (not me of course :-) added significant load? Can you set it up so that there is an audible alarm for example? If not, or if that audible alarm gets ignored, what would happen? In the system sense... Is there any danger of overheating? Or damaging something? Or would something just shut down? Or ??
Thanks again!

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swampbush cw8 commented · Apr 17, 2021 at 06:40 AM

You can use the relay function to set up an audible alarm based on wattage or low voltage and many other settings. I use a flashing beeping light that can not be ignored. Very rare that it is activated as we generally know how much we are using.

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ripper wkirby ♦♦ commented · Apr 18, 2021 at 07:09 AM

I dont know induction plates that can dial down that far. The ones I have seen go on 1000W 1 up to 10 seconds, off the rest of the 10 seconds. Here is stage 1 through 5. After that it modulates power.

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wkirby ♦♦ ripper commented · Apr 18, 2021 at 07:50 AM

It varies between models and brands. My one outputs 750W continuously on setting 3. Settings 1 and 2 are pulsed 33% and 66% at 750W. Settings 3 - 9 increase with constant output up to 2KW.
My friend has one which outputs constant power at 550W.

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Vance Mitchell answered · Apr 16, 2021 at 10:59 AM

Power output can be partially limited.

If you use AC2 for your outlets, you can program it to switch off if usage exceeds a set amount.

This would also allow you to keep sensitive loads on the AC1 running.

If you search the forum for information on diversion loads you will find information on assistants which might work for you.

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cw8 commented · Apr 16, 2021 at 02:33 PM

Thanks much. I looked a bit into diversion load, and now understand just the basics. That also helped me understand how the system works with/without AC coming in, so thanks for that.

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Answer 1 · 2021-04-15T21:29:29Z

wkirby answered · Apr 15, 2021 at 09:29 PM

There is no setting to limit the output power, you limit the output power by limiting the amount of load that you put on the output inverter.

Having a limit setting isn't very useful because its more of a nuisance than anything else.
If the output power is limited, what is supposed to happen when the limit is reached? Either the inverter cuts out, plunging the house into darkness or the current will need to be limited which would result in a Voltage drop and cause dimming and potential damage to equipment.

The best way is to "live within your means" and limit how much load you apply to the inverter and ultimately to the battery.
It just the same as living within the limits of your overall inverter power output, you need to live under 3KVA if you have a 3KVA inverter. Whatever the bottleneck of your system is, you need to be aware and keep within that limit.

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cw8 commented · Apr 15, 2021 at 09:49 PM

Thanks for the response wkirby. That makes sense, and that is how I originally planned to do it. However, I find myself somewhat in a corner...

I want to use one Lithionics GTX12V315A battery. I would like to use an 1800 watt double induction stove top, plus a few other miscellaneous small things, if possible, but I will dial down to a 1500 watt plate if necessary. I am exploring whether I can use that 1800w plate with that battery...

That battery can easily power a 2000W inverter, but 3000W is pushing it. A 2000W inverter would require me to drop down to the 1500w plate.

What I would really like is a 2500W (or so) inverter. But none of the companies I am looking at have one. So I wondered about 'detuning' one of the 3000W inverters, to 2500W for example.

For the record, this is for a van, so plunging my van into darkness is, offhand, not a big deal to me. Or does that do damage to some of the systems?

I would rather go dark than damage the battery. At least that was my thinking. I am brand new to this, so happy to hear what I missed or got wrong.

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tozz cw8 commented · Apr 18, 2021 at 01:29 PM

Others have already written this, but from your reply I get the feeling you don't fully understand it yet. The amount of power that the inverter is drawing from your batteries is determined from your load and your load only. If you turn on a 1500W water boiler, the inverter will draw 1500W (+some losses) from your battery. If you then also turn on your fridge, it will draw probably something like 1800W combined. The inverter will deliver 1800W. It cannot eg. limit output to 1000W and have your cooking and fridge work a little slower. It doesn't work like that.

If you tell an inverter 'Okay, never ever supply more than 1200W' (for whatever reason eg. it will exceed your battery's discharge rate or whatever) then the only thing the inverter can do is shutdown. It can't actually limit power to 1200W if connected equipment is demanding more. It would damage your equipment. Voltage would drop and you will get what is known as brown-outs.

So, if you want a certain type of induction stove, but you are worried you'll max out your batteries, then best thing to do is add a second battery in parallel.

If you would limit inverter power or choose a smaller inverter, it will shutdown whenever you'll exceed it's limit. There is no fun in that. Your RV will be in the dark and your cooking will stop.

So either dial down to a lower wattage induction stove or add batteries if you are worried that a single one isn't up for the job.

Limiting inverter power either by a setting or by choosing a lower wattage inverter is not the solution. It will only get you blackouts due to overloads

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Answer 2 · 2021-04-17T05:10:06Z

Paul B answered · Apr 17, 2021 at 05:10 AM

The battery has a automatic BMS off if you exceed its limit it will just turn off, then back on when the load is removed, no damage is done.

better to have a bigger inverter as you can always add a second battery at some time in the future

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