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Alexander Grieser avatar image
Alexander Grieser asked

Sizing question regarding MultiPlus / PowerAssist feature

I would have a short question regarding the sizing of MultiPlus hardware:

If I would like to operate it only to make use of the PowerAssist functionality (e.g. to run a 230v device with 8 amp peak power on a max. 6 amps AC socket, but never off the grid on the inverter alone), what system sizing will I need then?

Is it okay to count only the additional power delivered by the inverter (e.g. the 800VA model, to top off the "missing" 2 amps plus losses), or will I nevertheless need to go for a larger model covering the complete overall power consumption?

Would be perfect if one of the experienced users could help with this question.

Thanks a lot!

MultiPlus Quattro Inverter Chargerpowerassist
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4 Answers
blutow avatar image
blutow answered ·

The "power assist" amps is what is relevant to your rated inverter. The pass through amps have a separate rating. There is a combined limit also, but I seriously doubt you'll be up against that when on shore power, especially if you are limiting shore power.

I don't know what specific inverter you are using, but my muliplus 3000/12 can push out about 20a continuous through the inverter (~2500 watts at 120v). I can also pass through 50a from shore power. That doesn't mean it can do 70a total because there is a total system limit (I think 60a, but not sure) when using power assist. If the total system AC output max was 60a, I could get 40 from shore and 20a from inverter (or any combination where neither the inverter or shore power limits are not exceeded). There is an inverter limit, a shore power pass through limit, and a total AC output limit (which is not just adding the inverter and shore power together).

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Alexandra avatar image
Alexandra answered ·

@Alexander Grieser

Size the inverter to carry the full load. Including short peaks say for instance spikes from pump starting.

The inverter still has to pass through the whole current of the load even if it is only assisting.

8Ax 230v is 1840 Watts at least.

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Alexander Grieser avatar image
Alexander Grieser answered ·

Thanks for your valuable input, but I'm still not 100% convinced to be honest (sorry for that!).

In this document Victron explains how a 3000VA MultiPlus can be used to replace a 7.5kW generator by a 5kW one in a 6.5kW peak load scenario, by making use of the PowerAssist feature to add the missing power from the battery. So it seems to me that the passed-through AC current must NOT be taken into account for MultiPlus sizing in this situation, and the inverter must only be sized according to the power it has to add to the input current.

Following your argumentation at least a 6.5kW inverter would be needed due to the 6.5kW peak load?

Sorry for my skepticism, but this is still a bit confusing for me...

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Alexandra avatar image Alexandra ♦ commented ·

@Alexander Grieser

I did not see your reply sooner. And you are correct the linked document does describe what you are wanting to do. So does this blog.

https://www.victronenergy.com/blog/2016/08/29/multiplus-magic-small-generator-big-power/

blutow explained it better than what I did. The sizeing ratio you were proposing a red flag for me. Glad you found your solution.

Just be aware that if shore or genertor power gets kicked out/ trips for whatever reason that the inverter and batteries need to be able to take the load or the load must be cut off immediately.

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leenderthameete avatar image
leenderthameete answered ·

This quite an old question but I hope someone can help me with also a sizing question on a MultiPlus. We think off installing a Victron Mulitplus II 12/3000VA in a service van. A 230V welding device with will be used on this Victron Multiplus II 12/3000VA when a 2,3kW shorepower is present. So with the "Current Boost Factor" on 1.0 with both the Victron Multiplus II and the shorepower combined there is a 20A constant current available. In the specs off the welding machine there is stated that the max current will be 30A this will be present when the machine is switched on.afbeelding-van-whatsapp-op-2023-09-25-om-154030.jpg


Now my question is can the peak current off an extra 10A (30A instead off 20A) be absorbed by the Victron Multiplus II 12/3000VA?

Hope some


afbeelding-van-whatsapp-op-2023-09-25-om-154030.jpg (117.3 KiB)
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