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Bryan avatar image
Bryan asked

Quattro Stuck in Passthru

Hello, I’m hoping someone can help with my issue.

I have a 220/12/5000 Pair of Quattro’s running in Parallel. For the most part everything is operating as it should, and I don’t notice anything unusual. They’ve been in this configuration about 7 months now. It’s a marine configuration, so I’m not running anything related to ESS or anything requiring anti-islanding. The other questions / solutions I’ve seen with this issue all seem related to that system.

The issue has risen for a 3rd time now, and I’m really unsure how to proceed. At some point, the battery will get low enough that the inverter will shut off. Somewhere between 50 and 60% state of charge. This usually happens when theres an unexpected loss of power in the grid shore power, or generator breaker pops and we are unaware.

At this point, restoring grid power or generator power will put the quattros in passthru mode. The batteries will not charge. I usually have to wait until the MPPT’s charge the batteries back up enough to kick them out of the danger zone before I can get it back to normal.

Yesterday when this happened, I was able to remove the BMS assistant, and the BMS from the system and get it to kick into charging mode again...do I have an overall BMS problem? If I do, it will be the 3rd BMS in 7 months.


Thank you in advance for your help.



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

Do you have Victron lithium batteries with the VE.Bus BMS?
Have you connected the "AC mains detector" included with the VE.Bus BMS?

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Bryan avatar image Bryan commented ·

Sorry, I should have mentioned that yes...

I have 5 Victron 300ah Lithium Batteries, a Victron BMS, and an AC mains detector.

Currently without the assistant and without the BMS connected, it will charge. Overnight it used shore power to reach 100% which is where it’s sitting now in float.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ Bryan commented ·

Forcing to charge the batteries while the BMS seems to say "no" is a good way to kill (one of) your batteries.

Is/was there a red LED on the BMS?

If you have Smart batteries use VictronConnect to take a look "into" the batteries.
Maybe one of them have a problem and is stop the charging.
What temperature do you have at the batteries.

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Bryan avatar image Bryan Matthias Lange - DE ♦ commented ·

Thats a good point, I dont want to start doing any damage to batteries. I hadn’t followed down that path simply because they charge / discharge and act normally 99.9 percent of the time. It’s only this rare case where it gets low enough to cut the inverter (then the 12 volt system depletes it just enough that it wont charge when it comes back).

Looking at the device screen shows:

Allowed To Charge: No

Allowed To Discharge: No

BMS Error: Yes

There was also a red light on the BMS yes.

As an exercise, I went and checked a few cell voltages -

Battery 1: 3.55 | 3.55 | 3.49 | 3.39

Battery 2: 3.51 | 3.51 | 3.51 | 3.47

Battery 3: 3.53 | 3.53 | 3.53 | 3.51

Battery 4: 3.50 | 3.52 | 3.54 | 3.54


On battery 1 that 4th cell looks indeed out of wack. Is that enough difference to cause problems?

That batter temps right Now are about 30C

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seb71 avatar image
seb71 answered ·

What is the battery voltage when it cuts off?


Can you see/measure cell voltages? It could be a single bad cell (or way out of balance) which gets to a low voltage and then the BMS cuts the battery/switches the inverter off.

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Bryan avatar image Bryan commented ·

I can if I let it get low again, and I can see reported cell voltage though the VictronConnect app, but my issue isn't that it’s cutting off...

I assume that the cutoff is in line with the settings, my issue is that when mains power through the genset or shore power will not start it charging again. It will sit at low voltage in passthrough.

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seb71 avatar image seb71 Bryan commented ·

Did this ever worked as it should (when the BMS turns off the inverter because of low battery)?

If not:

Is the AC detector connected to the Quattro which is set up as Master?

Is the AC Detector wired correctly?

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Bryan avatar image Bryan seb71 commented ·

Yes, this works most of the time as it should, or it seemed to me that it was working as it should...if it wasn’t, I didn’t spot the difference.

The AC detector (Mains Detector) is connected to the master, and I believe it’s wired correctly; yes, including the pass through step from the RJ45 jack on the BMS to the mains detector, to the Quattro.

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Bryan avatar image
Bryan answered ·

As a follow-up to this. With the BMS disconnected, the quattro seemed to manage the charging from the MAINS without an issue. I let it get from about 55% SOC to 65% SOC and plugged the BMS back in, and reloaded the assistants in both quattro's and all is fine now....

I'm really curious what might be going on. If that one battery I mentioned above has a cell voltage that's getting too low, can someone comment? I can replace batteries if needed - but I would like it to be definitive.

Thanks All!!

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