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Multiplus 24/1200/25 switching between charger and inverter

I have a Victron Multiplus 24/1200/25 hooked up to a set of series parallel Blue Nova BN13V-108-1.4k lithium iron phosphate batteries. I also make use of a Victron Battery Monitor BMV-702. I use the Multiplus as a backup/UPS to provide power during power outages at my house. I observe the following behaviour of the Multiplus:

• When AC power is lost, the Multiplus switches to the inverter and provides power, as expected.

• When the AC power is restored, the Multiplus starts charging the batteries, as expected.

• After a few minutes, the inverter will kick in again, and the fan will spin up.

• After a few seconds, the fan turns off, and the charger starts charging the batteries again.

• After a few minutes, the inverter and the fan turn on again.

• After a few seconds, the charger turns on again, but this time the fan remains on. The charger and fan remain on until the batteries are fully charged.

• Once the batteries are charged, the fan stops, and the charger goes into absorption mode.

This pattern consistently repeats itself each time the AC power is restored. This happens even if I unplug the Multiplus, and plug it in again after some use (ie, without an actual AC interruption from the utility). Is this pattern of switching between charging and inverting expected each time the AC power is restored? I would expect it to switch to charging only once, once AC power is restored. If this pattern is not expected, what could cause this?

battery chargingacups
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gianni-volpi avatar image gianni-volpi commented ·

I'm having this exact same problem as well. Also can't seem to figure out what is going on. I agree with the observation that it seems like when the fan is running while charging it is immune to the switching.

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frodob avatar image frodob gianni-volpi commented ·
Do you have the same model? I contacted my supplier, and they asked me to return the Multiplus back to them for inspection. I've not done that yet, but I'll let you know once I have and I've received some feedback.
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bruce-davidson avatar image bruce-davidson frodob commented ·

Having the exact same problem with my 12/800 Multiplus.

Did you perhaps return your unit to supplier for inspection? Did they find any issue?

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frodob avatar image frodob bruce-davidson commented ·
Not yet. I'm dependent on the unit so that I can work. We have daily loadshedding, so there's no opportunity to send it in. Currently, I've set it to charge at max 8A. At this setting, it charges perfectly without interruption. Any higher setting and the charging is interrupted, as mentioned in this thread.
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7 Answers
frodob avatar image
frodob answered ·

I returned the Multiplus to the dealer, and they sent me a new one after they tested it. Unfortunately I didn't receive a report as to what was wrong with it.

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Paul B answered ·

as the charger is coming on and suppling high amps to the battery, you maybe getting a mains input voltage drop and if it drops below the set min low mains voltage the inverter will disconnect from the mains. then as the load has stopped the voltage rises again and the grid is reconnected.

so check that out and see whats happening on that front

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frodob avatar image frodob commented ·
Thanks for the suggestion. I will spend some time observing what's happening there.
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frodob answered ·

I've checked as @Paul B suggested above, but from the Victron Connect app, everything looks good. I had set the charging current limit to 20A, which translates to about 2A at 230 volts on the AC input, which is not that much of a current draw at the AC input.

Today I dropped the charging current limit to 10A, and I see the charging disconnect/reconnect pattern continuously repeats itself. The charger disconnects each time the fan comes on, so I suppose the reason that the pattern repeats more at 10A is because the Multiplus does not get as hot as it does at 20A. But this leads me to believe this pattern is somehow related to the temperature/fan turning on. Is it possible that the charger could disconnect when a temperature threshold is reached?

It looks like similar symptoms are reported in this thread: https://community.victronenergy.com/questions/162/my-multiplus-123000-is-randomly-disconnecting-from.html

Today I updated the firmware to version 501, but there has been no change.

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frodob avatar image
frodob answered ·

Tonight I was drawing more than 500W whilst using the inverter, and as a result, the fan in the Multiplus was running. When the AC input was restored, the charger started, as expected, and the fan continued to run. As the fan was already running, the Multiplus has not switched between charging and inverting once. It's happily charging the batteries at the set limit. So it looks like the behaviour of switching back to the inverter occurrs when the fan activates.


Judging from the monitor in Victron Connect, when the Multiplus switches to inverter, it immediately detects the AC input, but only switches back to charging once the timeout occurs.

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frodob avatar image
frodob answered ·

I was observing the Multiplus again today, and I noticed the below "under voltage" log entries in VE Configure. These log entries appear each time the Multiplus briefly switches back to the inverter.

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1675782928276.png (32.9 KiB)
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vet avatar image
vet answered ·

As a suggestion: may be something wrong with the sinus form or frequency of your mains? Maybe unchecking "UPS function" will improve situation.

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frodob avatar image frodob commented ·
Thanks for the suggestion. I tried it tonight, but the behaviour is the same. I think we have pretty clean electricity here, for the most part.


It's strange, once the Multiplus has warmed up, the pass through/charger remain active until the battery is charged, which could take over an hour. The unexpected switching between pass through/charging and the inverter only occurs within the first 10 or so minutes of AC power being restored.
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frodob answered ·

As an additional observation, when I set the charging current to 8A, the Multiplus never gets hot enough for the fan to turn on. As a result, the switching between inverter and charging never occurs, and the batteries charge until full without interruption (albeit at a slow rate).

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Related Resources

VictronConnect VE.Bus charging manual  

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