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perma-batteries avatar image

Pylontech abnormally high voltages after 2.60 update

Hello,


After more than one year of perfectly stable operation with a ESS system comprised of a Multi-II 5KVA and a MPPT 150/100, 2x US2000B Venus OS 2.60, always in keep batteries charged mode, (for back-up for critical appliances) we've been experiencing random high and low voltage alarms from the system, which are unusually high (almost 54VCC sometimes). No LED alarm whatsoever on the batteries. DVCC is activated, SVS is off, MPPT in slave/BMS controlled.


We're trying to figure out this for two weeks now, we're in touch with Pylontech but so far they're not giving us conclusive answers. We've changed the battery monitor from "automatic" to "Pylontech Can.Bus" today to see if it changes anything. One explanation might be that they're not designed to run under a 100% SOC for extended period of times and thus might be internal cell imbalances that are not corrected as they're not discharged and cycled. Anyone can chime in ?


Thanks in advance,



ESSPylontechbattery system voltage
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5 Answers
Izak (Victron Energy Staff) avatar image
Izak (Victron Energy Staff) answered ·

Hi @perma-batteries,

We raised the charge voltage of Pylontech batteries by 0.4V in Venus 2.60. This explains why you're starting to see the symptoms after this new release. It is noted in the release notes too. For the full reasoning, see the original issue: https://github.com/victronenergy/venus/issues/536

Secondly, the voltage we use is still on the lower end of what Pylontech wants. We've had only a hand full of cases out of thousands of installations.

Third thing I need to mention: The high voltage spike is often a symptom rather than the cause of the alarm. When the battery activates its internal protection to protect a cell, it disconnects that module from the DC bus. The voltage measurement on the DC bus is then different from the real battery voltage, so that the voltage mentioned in the alarm message will not necessarily reflect what really happened.

You are 100% correct that it has to do with the balance of the cells. The battery ideally needs to cycle for the balancer to do its job, since balancing is most efficient during charging after some of the cells reach 3.458V.

For a battery that is in imbalance, it can take several days, even weeks before it comes back into balance. So this would be the first half of my advice, you'll have to cycle the battery a little.

Secondly, Pylontech will be able to provide you with the software needed to communicate with the battery on its console port. That will give you more insight of what is happening internally, and the data can be used by Pylontech to determine whether you may have a warranty claim.

I hope this helps.

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @perma-batteries,

As a possible temporary work around, could you set the ESS mode back to Optimised (instead of Keep batteries charged), the SOC discharge limit to 90%, and then program a scheduled charge window to run every day for 23 hours to recharge to 95% (to recharge from the grid after an outage).

The Low battery alarm will be the battery disconnecting itself after the high voltage (or high current) alarm.

See if that corrects the alarms, and gives the batteries some opportunity balance (without approaching the very top end where a high voltage issue is more likely).

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perma-batteries avatar image
perma-batteries answered ·

As a side note, we've noticed that even if we activate "Limit inverter power" , the current drawn by the US2000 will still be ultimately determined by the DCL and BMS and NOT overriden by the "limit inverter power" option, which is worth noting (-68A sudden burst from 2x US2000, inverter power activated at 1200W).


So my guess is that the limit inverter power function is only working when you've got non managed (ie : lead acid, etc...) batteries with an ESS....






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Hi @perma-batteries

Please copy this into a new question, as it's quite different from the current title.

perma-batteries avatar image
perma-batteries answered ·

Izak,


Thanks for chiming in and the extra details, we're going to proceed according to your advices and Guy's and will keep you posted about the results.


Cheers !

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perma-batteries avatar image
perma-batteries answered ·

Hi Guy, thanks for the answer, will follow your advice, we've noticed that the system actually started to be faulty after we've upgraded to firmware 2.60 in Septembre.





We've switched to batterylife, SOC 90%, and we're going back to firmware 2.54 once the batteries have stabilised to switch back to keep batteries charged and see if it works fine again with the previous firmware.


Thanks !




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There was a change made in 2.60 to increase the charging voltage of the Pylontech.

You can read a bit more about it here - https://community.victronenergy.com/questions/62266/venus-os-v260-pylontech-batteries.html

I notified the developer of your report.