Pylontech U3000 Overvoltage alarm at 89% SOC

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botessj asked Feb 27, '20

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 Monitor CCGX Color Control Pylontech overvoltage

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Daniël Boekel (Victron Energy Staff) answered · Feb 27, 2020 at 05:59 PM

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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Murray van Graan answered · Feb 27, 2020 at 06:11 PM

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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botessj commented · Feb 27, 2020 at 07:36 PM

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

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CristiMV answered · Feb 27, 2020 at 06:52 PM

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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botessj commented · Feb 27, 2020 at 07:28 PM

Thank very much. Very informative. Will definitely be going about it like this in the future.

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Answer 1 · 2020-02-27T18:43:06Z

botessj answered · Feb 27, 2020 at 06:43 PM

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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