question

botessj avatar image

Pylontech U3000 Overvoltage alarm at 89% SOC

Good day

I think this is quite a common point of discussion, but I need just need some confirmation that I understand correctly.

This installation is as follows:

  • 2 x Multiplus II 5kva 48V units set up in single phase parallel
  • CCGX unit
  • 4x Pylontech US3000 modules
  • No solar array installed as yet, purely back-up.

Setup and settings done exactly as per https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom


System was commissioned today and seems to function normally, except for a "Battery monitor (512)- High voltage" alarm.

Battery is at 89% SOC with voltage at 51.81V

Batteries were reasonably discharged (66% SOC) when turning on the system for the first time, so it stands to reason that they might have been standing for quite some time before we received them.

Am I correct in saying that this is a cell balancing issue, and should self-rectify? Or is there something I am missing?


Thank you in advance

BMV Battery MonitorCCGX Color ControlPylontechovervoltage
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4 Answers
cristimv avatar image
cristimv answered ·
Hi. I don't know if it's in the manual, but so far I've seen that most of the people recommend an initial battery balancing before connecting to the system. Take a look on this... https://www.youtube.com/watch?v=hTM-YMFiyns
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Thank very much. Very informative. Will definitely be going about it like this in the future.

Murray van Graan avatar image
Murray van Graan answered ·

Hi @botessj@gmail.com. I’ve had this happen a few times, and yes you’re most likely correct. I believe it is a cell balancing issue as the battery approaches 100% SOC. Best would be to set the system to keep batteries charged, reduce your charge current if you can, and wait it out. If this doesn’t rectify itself after a few hours at 52V, then one or more batteries might be faulty. I must add, this should not happen to a battery that’s been working a while. I’ve only seen this on power up

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An update. You are completely correct. I checked in again, and the SOC has increased to 92%. I think, as the link in Christian's mentions, one of the modules was most probably at a significant different SOC to the other modules, possibly causing the issue.

The Multi has automatically reduced the charge current to about 14A.

Thanks again for the advice


Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @botessj@gmail.com

Is there nothing in the Pylontech manual about initial balancing of the battery?

The batteries are always delivered at a storage voltage, this is better for the batteries.

At first use, the batteries have to balance for the first time, this can take a while, I'd expect the details to be in the battery manual?

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botessj avatar image
botessj answered ·

Hi Murray and Daniël

Thank you for the quick response.

I have just rechecked the manual. The only place where they make mention of cell balancing, is in the introduction. I quote " What's more, BMS can balance cells charging and discharging to extend cycle life".

Hopefully you are correct Murray, and the system rectifies itself. As you mentioned, it was on power on/first charge that the problem surfaced. In your experience, approximately how long would you allow the system to rectify? And what charging current would you suggest?


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