Multiplus II: trips battery (no load)

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villychr asked Feb 18, '24

Multiplus II: trips battery (no load)

I am installing a (new out of the box) Multiplus II 12/3000 on my boat. I have only connected the DC plus and minus (in order to setup the Multiplus before connecting AC). As soon as I connect the DC breaker, the Multiplus trips the battery shortcut protection. The Multiplus on/off switch is off when this happens.

Any ideas?

Thanks,

Villy

PS. It's not reverse polarity.

Multiplus-II installation

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Answer 1 · 2024-02-18T04:39:01Z

JohnC answered · Feb 18 at 04:39 AM

Hi @villychr

This will be the Multi filling it's capacitors. They're large and take quite a hit.

If you have a spare 12V Pb battery handy, try jumpering it across to precharge them, then switch in your main battery. Usually comes with a spark.

If you're going to do this regularly you could arrange a precharge circuit, Some Li battery makers even have such in their product range, but it's just a resistor really.

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villychr commented · Feb 18 at 05:47 AM

Hi @JohnC, thanks. I connected the multiplus to a start battery, it held the voltage OK. Waited about five minutes but the inverter LED didn't come on (which I presume they should), and the Multiplus (Bus-connected) didn't show up in Victron Connect local). How long does it take to fill the capacitors?

With thanks

Villy

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JohnC ♦ villychr commented · Feb 18 at 06:03 AM

@villychr

A precharge done that way only takes the spark. Quick.

Does your bms need resetting or something? V on the Multi terminals? I don't know, you'll have to delve..

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villychr JohnC ♦ commented · Feb 18 at 06:07 AM

I still have it connected to the start battery. I guess my main question is: should there be light in the inverter LED when the Multiplus is connected?

If yes, I think I have a problem with the Multiplus.

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JohnC ♦ villychr commented · Feb 18 at 06:20 AM

Maybe it needs an ac load connected to show an inverter led?

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villychr JohnC ♦ commented · Feb 18 at 06:55 AM

@JohnC Ah, problem solved, silly me. The Multiplex initially tripped the battery while in off. When I connected to start battery -- it was still off. Turning it on helped. OK now. Thanks for your advice.

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nickdb ♦♦ villychr commented · Feb 18 at 06:27 AM

Possibly not, I don't think it would pass relay tests without being correctly wired. It's best to follow the instructions and wire it properly before jumping the gun and trying to make it work before it is ready.

Same applies for people trying to install it without batteries..

Even without lights, if you haven'r tripped your battery, you should be able to talk to it via a mk3 adapter and veflash.

It does sound like your battery BMS has not enjoyed the precharge, which will occur even if the multi is set to off.

Another common mistake, is having the rocker switch in the wrong "charger" position, instead of "on"

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