Can you possibly say what changes have been made to the Pylontech batteries?
Since version 3.50-15 the batteries only charge up to 51.8V, so the SOC is no longer set to 100%
It’s a consequence of the new algorithm introduced for protecting the batteries from over voltages.
Also keep an eye on this: Small omission in beta dvcc.py, maybe ?....
I read this post, but I find it strange that the charging voltage is limited and the SOC of 100% is no longer reached.
It’s just an optical thing because the batteries are full even at 99%, but I never had a problem with the batteries even at 52.4V (100%)
In my experience with the Pylontechs, the Voltage of 52.4V is to high, because of many high voltage alarms.
I then changed the max charge Voltage to 51.2V (if SOC is < 90%), and if the Voltage is reached (and the max diff Voltage from the cells are lower than 35mV) then i automatically increase the charge voltage by 0,1V until 51.6V. The max cell Voltage then is 3,45V - 3,47V.
With this algorythm you can also go to 52.4V step by step without any high voltage alarm.
I have it at 52.5V (3.5V per cell), the lower limit the Pylontech specify for charging the battery.
Even when there was an abrupt increase of cell voltage with an aggressive charging, the MaxCellVoltage was only 3.54V.
So never had an high voltage alarm, as the voltage for this is fixed by Pylontech at 3.6V per cell.
Hi everyone,
Indeed, the algorithm has changed, precisely because there are too many complaints about high voltage warnings. Once a battery is properly balanced, there are usually no problems, but I share @plastefuchs 's experience that even 52.4V can be just too high. Above 3.45V per cell, LFP cells become very spikey, even small amounts of charge can greatly increase the cell voltage. For this reason we want to keep the highest cell voltage to no more than 3.5V, which would indeed be 52.5V in a well-balanced battery.
Unfortunately there are quite a few batteries where the lower cells are just a little low. If, for example, you have 14 cells at 3.48V and one cell at 3.55V, that is still only 52.3V, and I think everyone will agree that battery is full!
To my knowledge – I can verify this with Pylontech as well – The BMS wants to see a cell voltage of 3.485V for balancing to work properly. In other words, 52.4V is pretty much as low as you can go as a generic charge voltage.
All the theory aside: Since this battery does not do dynamic voltage control, which really would have been the ideal here, this was an attempt to make it better. It worked alright at the two sites it was tested, but I knew more testing would be needed. So first of, thank you very much for the reports!
I made another improvement today, and this is currently in testing and will be released soon.
In the interim, if you prefer and don’t want to wait, you can reboot back to the previous beta to get the old behaviour back.
Edit: For the moment this is the result I’m getting, and aiming for. Comments welcome. Note how this battery has all its cells above 3.45V. This is a well-balanced battery. But the charge voltage still had to be lowered to 52.2V.
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Thank you Izak for your efforts.
Really appreciated, especially that you are sharing your views and experiences with us!
LE:
According with the settings programmed in the factory for any Pylontech pack, confirmed by one of their engineers, the pack will start to balance if the delta V between cells is more than 30mV and the voltage of all cells is above 3.36V.
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@Alex: I can confirm this and I observe this described behaviour on my Victron system connected to 5 US3000C.
And in addition: the Pylontech batteries must recognize at least a little bit over 52,00 V to set SOC back to 100 and to set charging current to 0. With 51,8 V this will never happens… The batteries will be slowly overcharged if you dont stop charging current!!! This will reduce lifetime of the batteries!!
To avoid overvoltage alarm, it would be better, to reduce the charging current if the first cell goes over 3,44 or 3,45V to for example 1-2 A per block.Than the weak balancers have enough time to balance the cells. This method i use in my Node Red flow, because I balance my batteries only max two times per month. All the other days they will be charged only to 80% SOC. Without it, it could sometimes happens, that one block gets an overvoltage alarm.
In my case, I’ve set the system to keep the Pylontechs at a constant 52.5V (3.5V per cell average)
And they stay in this way, at 100% SOC, in idle state, the entire time after charging, daily.
After the balancing period ends, they draw only about 40-50mA per pack, BMS necessary current.
Real life measured current, so, for sure, they will not get overcharged at that current.
After more than 8 months, in this kind of usage, the SOH is still at 100%.
And in the same consumption conditions, they supply the same amount of energy, measured over the same period of time. So no degradation here, because of the way of exploiting them.
Pylontech also confirmed during my discussions with them, that it’s OK how I treat the batteries and the main enemies are instead: high temperature, high currents and depth of discharge.
To enjoy their full lifespan, according to Pylontech, you should keep them:
- Between 20-30 deg.C during all conditions (charging / discharging / idle)
- Below 0.5C current during all conditions (charging / discharging)
- At any SOC above 20%, so maximum 80% DoD.
LE:
For example, here is a printscreen of the Pylontech status of my batteries. It is now at 84% SOC, discharging.
Observe that they are 6 packs and the minimum cell and maximum cell are of the same pack, pack no.1.
That means that the cells from all other packs are of the same values.
And the difference between minimum and maximum is just 1 (one) millivolt.
90 cells (!) with only 1mV difference between all of them.
That says something about the health and equilibrium of the cells, exploited like I’ve said above.
Today I had time to take a closer look at the batteries. The SOC has been at 99% (51.86V) for 3 hours.
I have 2 us5000 and 2 us2000c. The two us2000c are full and in standby. The two us5000 only have 5 LEDs on the SOC display and is charging.
The highest and lowest CELL is in one of the two US2000C 3.4680 and 3.441 i.e. 27mV
I’m going to load the beta today and will report back as well.
What can I expect to see when I go to the new beta? Voltage slowly settling to 52.5?
I have a well balanced bank of 3x UP5000s.
Current voltage at 100% is 52.8
Something is odd on your first graph…
Negative cell differences ??
I think it’s the Home Assistant or an overshoot…@izak may have better view…
I can confirm 52,5 V when the batteries are well balanced seem to work well on 4xUS3000C
Restricted max charge to 30A and have priority up to 75% after that they get what is left.
Snap shot at 69% under discharge
Reverting back to Main release… This is now happening with the voltage.
Note: the battery was full before the move to 3.50~15.
Beta release installed around 11:45
I can’t say this is bad but I didn’t get these voltage fluctuations on 3.41. I’ll send an update of the graph a bit later.
Immediately settled on 3.41.
generally I agree with you. But its not right to keep them at 52,5V independent what Pylontech staff says. It is a simple question of LiFePO4 chemistry. And chemistry is not different at Pylontech company. After balancing, the SOC switch to 100% and CCL by BMS to 0. That means not any current shall come from charger. After that the voltage will goes lower (one because of BMS consumption and because of natural voltage decrease by the cells itself). Thats what Pylontech programmed in their BMS. And Victron should follow this in my eyes.
I have a common SOH of 98%for all of them. they switched to 98 from 100 after two years.
Also my voltages are the same like yours at this stage:
Generally Im with you. I only want to confirm, that 51,8 V is to low.
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This all reaffirms, that, for optimal battery management you need both dynamic voltage and current control. Why so many BMS’s insist solely on current control, does not compute.
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For a certain SOC, the internal resistance is relatively constant. Then either the current or the voltage is enough.
Indeed, controlling both could be beneficial for fine tuning things, like balancing and overvoltages, but just one is generally enough.
Just observe the symmetry of the CVL and CCL. This is because the Ohm’s law (in this case the power formula) is a linear equation. When a smaller voltage is imposed, then a higher amperage is allowed. And vice-versa, when they increase the allowed voltage, it imposes a lower maximum current.
Just like the never-ending dispute between torque and power on cars. 
I went back to the beta ~15 today @ 09:30 when my battery voltage was below 51v to see what the effect was.
@100% SOC the battery is still up in the 52.8v+ and I was expecting this to be more like 52.5v per the beta change. @iburger Can you help with some expected voltage levels we should be looking for.
I also found the CC was fluctuating alot as the battery went from 90% upwards and also the CCL seemed to be ignored. This isn’t the case with the current production version.
@iburger Please feel free to dig in the data for my system if needed 
I have a 2 years off-grid system with 2 Pylontech US5000, SmartSolar 250/70, Multiplus II 5000/70 and Cerbo GX and looking at the history of battery voltage, my batteries never reached a voltage higher than 52,3V and I never had a voltage warning or alarm. It seems that Pylontech BMS do not allow a voltage charge higher than 52,3V (see last 30 days history attached). I always understood that was BMS who manages the inverter or solar charger.
