I have a system with a Multiplus 48/5000/70 V507, Cerbo V3.22 and 4x Pylontech US5000. During Summer I was using a script to charge to 100% every 3 weeks which worked fine.
Now if days are shorter I wanted to manually balance by setting minimum SOC to 100%.
I tried this for 2 days now but system stays below 100%. Voltage differnce bettwen lowest and highest Cell is 180mV … and stable (see screenshot).
Manual Limit on Battery charge voltage is OFF.
Has anybody seen such thing before?
Don’t use a min SOC of 100% it is not intended to be used that way, set ESS to Keep battery Charged instead.
Unbalanced batteries may not get to 100%, this is documented in the config guides, it should sort itself out if left long enough to charge properly.
With that cell difference, your 3 week charge seems to be insufficient, and you’re doing more harm than good.
@Nick
Thank you for your message. Very much appreciated. Last balance was in September and was looking good to me. That is why I kept this pattern as the system is running for 1 year like that. I will follow your advice and post the results.
Do the maths.
3.49-3.47 is 0.02v that is is pretty well balanced.
Even the previous post.
3.39 -3.36v is 0.03v also very well balanced.
Looks normal to me.
As an FYI pylontec do send a cell imbalance warning to the GX. So you will know if there is an issue that needs attention.
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180mv isn’t normal from the OP.
HV alarm is only generated when a cell hits 3.55V
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90% soc is where balancing starts or 52.4v?
None of the modules were blocking charge and the batteries weren’t taking charge. Seems like they sorted themselves out in further posts.
Indeed, but if the behaviour continues, something is off.
My posts were not in historical order. 1. post with the 180mV difference and the voltages not moving was from today. My second post was from Sept with 30mV difference.
The problem is in the 1. post as Nick correctly commented. I will use the “keep battery charged” this night and see if voltages are moving.
Ha right, didn’t see the forest for the trees…
My 2 cents…
This is what’s happening when some perpetuate the idea that for Pylontechs 52V is OK for bulk and 51V is OK for float.
The Pylontechs are made with pouch cells, not prismatic ones. This is why Pylontech sets the CVL at 53.2V.
Bulk and float are archaic things from the flooded batteries era. For LiFePO4 there is only one target voltage.
If you still want to be conservative, set all charging voltages (bulk, absorption and float) to 52.5V (3.5V per cell).
Charge as usual, without withholding below 100% SOC. Let the batteries hit 100% every time and allow them time to balance, even daily.
Don’t believe me, ask Pylontech technical department.
Also, according with the Pylontech factory config:
- HV alarm is triggered if any of the cells is hitting 3.6V, or the whole pack is hitting 53.7V (avg. 3.58V per cell)
- BMS starts to balance when all cells are above 3.36V and the difference between cells is 30mV or more.
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me again.
I now try to balance properly using Keep batteries charged.
I still face the issue that voltage of one cell drops to 3.349V after it was at 3.39. Will this cause balacing to stop?
Is there any way to tell from Batteryview if the battery is balancing?
Multi displays that it is in Absorption.
52V bulk, 51 float are only safety measures for when CAN communication breaks.
When BMS is connected, the GX always sets charge voltage to 52,4 V
You can type the command bat on the console when connected to that battery.
The BAL column will tell you which cells are balancing.
Also read this: https://communityarchive.victronenergy.com/questions/255172/pylontech-batteries-stop-charging-at-90.html
That cell voltage drops because the charging current drops when the battery pack voltage is reaching the CVL.
Probably if that battery will be left enough time to sit at the CVL, without cycling it anymore, it will balance.
You have a quite uneven cell voltages’ spread on that pack.
Pylontech balance is made with very small currents, so, at such unbalance, it may take even days.
The system is up to 100% SOC again. It took a little more than 24hrs to balance.
The issue was with one of the four batteries which was added this year in springtime. Cell difference when starting balance was approx 180mV 
Some things I observed during the long balance:
- using the console BAT command it lists the status of the cells. It did not indicate that is was balancing the problematic cell 13, but it was charging it anyways.
- Pylontech batteryview was helpful to better understand what is going on and get early indication that things are moving in the right direction.
- when SOC switched to 100% there was still a cell difference of 60mV. Leaving it 10 min more in ‘keep charged’ this reduced to the expected 30mV.
I will follow the advice to balance more often. A big thank you to everybody commenthing on this thread!
I had just this problem with falling solar levels the battery was not getting to 100% no balancing or absorbtion battery capacity fell so much that under load it was switching off, after a few days blaming the inverter suddenly it clicked.
Cycled the battery from 100% to below 10% twice cured the problem, then I set a scheduled charge to 100% once a month, I will increase that if needed.
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I thought it was resolved, a few days later it started reverting to sustain when a load was increased , eventually I found there was an assistant set on the VE bus that was set too high and overriding the settings on the VRM, lowered the assistant settings and so far it’s all good.
The whole issue is because I had not paid attention to the battery balancing, they do need to be charged to 100% and balanced frequently.
,
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Finally the people are starting to understand that it’s not so good to keep the batteries below 90% (supposedly to keep them healthy (?)) and must charge them to 100% and allow them to balance as much as possible.
In the end, this is the role of the BMS…
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Look at this
And too this