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elel avatar image
elel asked

Can a Multiplus II be started without battery connection?

I just bought a Multiplus II 48v/50VA and tried to do the setup via VictronConnect. I connected power to AC-in and had no connection in AC-out-1 and AC-out-2.. I didn’t connect it to batteries (they have not arrived yet). When I switched the Multiplus to ON, it stayed powered on (with Low Battery LED on) for a few seconds and then tripped my 32A circuit breaker. When I switched it on as charger (Main LED flashed), it also tripped my circuit breaker after a few seconds.


The manual doesn’t mention whether the MPII can be powered up without battery connection but I found this video (at 1:27) mentioned that it can be powered up either via AC-in or battery.

https://youtu.be/6lH3mF2cVaY

Howerer, it seemed that it is not the case from what I got.


Can a MPII actually not be powered up solely via AC-in? If it is the case, where can I find the related documentation. Or, there is some problem with my new MPII?


Thank you.




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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The MultiPlus is not designed to run without a battery.
What you see (tripping the cirtuit breaker) is the inrush current to charge the capacitors.

You should wait to have the batteries or connect another battery or power supply to the DC input.
You should be able to program the Multi with a lower voltage (24V or maybe 12V).

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elel avatar image elel commented ·
Hi @Matthias Lange - DE , thanks for the answer. I have 2 follow up questions:


1) I am not able to find any Victorn document/manual which mentions the fact that Multiplus is not designed to run without a battery (and the precautions that need to take due to this design). If there is one, can you direct me to that document? If no, would Victron Engery please consider documenting this fundamental and important design point.

2) After the MPII has been properly set up with both AC-in/out and battery connections, do I need to power off the MPII before disconnecting the battery? If yes, can you please let me know whether this important power-off / disconnect sequence is documented?


Thank you.

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Kevin Windrem avatar image Kevin Windrem commented ·
The Victron video linked in the OP clearly says AC or DC power. If this is not correct, the video should be updated immediately.

If the issue is inrush current charging the caps at the input to the DC input, they should be at least partially charged with the first surge. Immediately resetting the breaker and trying again should help.

You can also precharge the DC input caps with a small battery of the expected voltage (4 12 volts in series in this case) and a resistor to limit the inrush current. Once the DC input terminals reach 48 volts, there should be no AC inrush current. If there still is, something else is seriously wrong.

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Rob Duthie avatar image
Rob Duthie answered ·

Hi

Yes you can setup with mains power only to apply new firmware etc, this is what i do all the time with no issues, before i send then out to a clients project etc incase the site has no batteries or mains power or wifi onsite etc.

Regards
Rob D

NZ

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elel avatar image elel commented ·
Hi @Rob Duthie , thanks for your reply.


May I know the Amp rating of the circuit breaker that you used to connect to your multiplus (s) ?


Thank you.

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Rob Duthie avatar image Rob Duthie elel commented ·

Hi

Just a 20 Amp MCB with a 5kw multiplus2 for testing and firmware updating.

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