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saboken avatar image
saboken asked

unknown Multi plus II behavior is It normal?

I'm still cleaning up a slightly botched install. Today I decided to test the Roof ACs on my camper. What I understand is if I run a high load device like an AC unit. And I have shore power the Inverter should just pass power through to handle the load. I started my Honda 3000 generator got it warmed up. The batteries were at 95% and getting 1600 watts from PV. When the AC started the Cerbo GX showed it cut power from the generator for about 10 seconds then started to take power from it to supplement the demand. I can confirm it did use the inverter and batterys to start and run the AC because the generator idled down. I had battle Born assist me in the settings they had me turn on the UPS function. I don't know if this is why this happens? The AC was pulling about 1200 watts after it started I'm sure it was a lot more during the start. I don't have a soft start on the AC units yet, I'm adding them later in the spring. But need to get this system working right not to damage anything. The system is a Multi plus II 3000 12v , 2 Game Changer batteries 540AH total. 1800 watts PV, Lynx shunt and distributor, I don't think anything else matters with this issue? If you need more information please ask I'll add to it. I just don't want to burn up the Multi plus with it taking on the entire surge. My camper has a 50a connection. The generator was running thru a 50a to 30a adapter. Could that be the cause? Also the one AC is 15000 BTU the other is 13500 BTU. They are each on a separate leg as wired by the camper manufacturer. I only ran one at a time because I knew the generator can't handle both without a soft start. I want to have the ability to run Both in the summer when I'm connected to 50a Shore power.

Multiplus-II
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4 Answers
snoobler avatar image
snoobler answered ·

Check this:

https://www.victronenergy.com/live/multiplus_faq

Check AC input current. This needs to be 22-25A to grab the full 3kW. If it goes over this, the inverter will take over with PowerAssist.

The sequence of events does not represent a problem.

When on 50A power, you will revise your input current limit to 50A, and this should never be an issue. The 2x unit always powers the second leg directly with the 2nd leg of the incoming 50A power. It can't use PowerAssist on the second leg.

When on 30A or single phase power, it passes through L1 to both legs of the panel and can provide PowerAssist to both legs.



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saboken avatar image saboken commented ·
Ok thanks that's probably the issue. Battle Born had me lower the input limit between 15-18 Amps. Why I don't know because I said I always have the Eco mode on unless I'm running an AC. I'll have to raise it and test it again.
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derrick thomas answered ·

Most likely there was enough of a voltage dip when the ac unit started that the ups function kicked in on the inverter. 3000 is a little small for starting a unit with no soft start capability. The inverter will be fine, it's doing what you asked it too. Do you have dynamic current limiter enabled in veconfig? That might keep the generator from kicking out on startup.

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saboken avatar image saboken commented ·
Yes the Dynamic is on . The generator never had a issue before I had the solar installed. So it definitely can handle it. I will have try adjusting some settings hopefully i can figure out why it does this. I found another appliance also causes the inverter to stop flow from the inverter. The 900 Watt microwave, I never had the generator running after the solar, until last night. It caused the same reaction. The Multi plus briefly switched to 100% battery for a few seconds then allowed both AC and Battery to share the Microwave load.
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derrick thomas avatar image
derrick thomas answered ·

Try turning off ups function. Ups function is more sensitive to voltage and frequency changes. Also tick the box for wide input frequency range. What is the low ac voltage cutoff set to?

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Kevin Windrem avatar image
Kevin Windrem answered ·

The Multi is more sensitive to incoming AC voltage than your appliances. That is a good thing. So the surge from the compressor start is just dropping the incoming AC voltage to the point the Multi rejects it. The inverter takes the load momentarily then accepts the AC and goes back to pass through / assist.

As Derrick says switching off the UPS function may allow the Multi to accept a wider incoming AC voltage.

All is well. No risk of damage.

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