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ourtimetorv avatar image
ourtimetorv asked

3000w Multiplus Won't Turn On and Results in 2 Volts Measured Across the System

I have just purchased several Victron components for my truck camper, one of which is a Victron MultiPlus 12/3000/120. It is paired with 2x206ahr SOK Lithium batteries. I have spent several days diagnosing a problem I am having and concluded the source is the inverter. It’s a very long story how I got here, but suffice it to say, when I remove the fuse on the Lynx Distribution bar for the Multiplus, the problem goes away. My problem is this.

I have expected voltage on the input side of the Blue Sea battery disconnect switch and nothing on the output side of the switch. When I first turn on the battery disconnect switch, I get a click in the Multiplus, then it shuts down. The result is readings (using a multi meter) of approximately 2 volts throughout the entire system, INCLUDING at the battery terminals and all the way down the system. When I shut the switch off and immediately back on, and all is well in the land. All my 120v and 12v devices work as expected. My 120v plugs test Good. I’ve even run the Air Conditioner off the system and also hooked it to shore power (15 Amp) and bulk charged the batteries for a short while. If I wait a short period of time (e.g. a few minutes) and turn the switch back on……just a click and 2 volts in the system. A quick Off and On of the switch, and all is well again. Any help would be appreciated.

MultiPlus Quattro Inverter Charger
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

It is a common problem with "drop-in" lithium batteries with build-in BMS.
They register the inrush current of the MultiPlus (or any other bigger inverter) as a short circuit and shut off.

An easy solution is to not always switch off the MultiPlus with a battery switch, use the switch at the MultiPlus instead. That way the capacitors wont discharge.

Or you need some kind of pre-charge circuit to charge the capacitors before switching the battery switch.

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ourtimetorv avatar image ourtimetorv commented ·
Thx Matthias. Given your profile, and plausibility of your response, I'll go with it. I don't expect to turn off the system for several once I hit the road and start traveling again. But I couldn't just ignore the situation not knowing if I might be doing harm to a bunch of expensive equipment. Thx again.
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ourtimetorv avatar image ourtimetorv commented ·
Matthias, I am considering the pre-charge circuit but have a question. Given my Multiplus and battery bank are already installed and connected, if I were to connect a resistor to the battery negative and negative of the inverter to perform the pre-charge, would it back-feed anything back thru the Lynx Distributor that would have ill effects on my MPPT, BMV712, or any other devices connected to the Lynx Distributor? In fact, I was thinking of using the resistor to connect the battery negative to the Lynx Distributor negative in order to send the charge downstream to the inverter capacitors. Any advice would be greatly appreciated.
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Rob Fijn avatar image
Rob Fijn answered ·

Hello, keep in mind the in-rush current that the Multi takes as it need to charge it's own capacitors.
Wat you see now could be a problem with your main Battery Switch, something inside is not going well at the moment this high in-rush current goes... When you switch OFF and ON a second time... the capacitors are full, so no in-rush current went thru to the Main Battery Switch.

Let us know what you find.

Rob

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ourtimetorv avatar image ourtimetorv commented ·

Thx Rob for the quick response. I had the same thoughts but did some other testing that I can’t quite correlate. Specifically, I have the same results with 2 new battery switches, albeit they are the same make and model (Blue Sea M-Series rated for 48V DC, 300 amp continuous, 500 intermittent and 900 cranking). Also, this is a fairly standard setup. Why is nobody else experiencing/reporting the same issues? I do appreciate your feedback. BTW, I have a buddy with another battery disconnect. I may try that and report back my findings.

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