(No one has said to charge only from solar).

If your batteries are balanced, within 20mv is balanced, then that is not a problem and doing it for more than the time you have been doing it for is not required.

But if cells are going up to 3.62 volts before balancing then that does seems high. What was your charge voltage setting at that time?

Edited March 9, 20242 yr by Tinbum

Regardless if it is 52.5V or 53.2V. Since the modules are in parallel and the overall voltage rises, the module in question has to raise the voltage too.

I believe pylontech did a lousy job of matching cells. Because some cells in the module are raising their voltage slower, some others take the penalty and have to go to 3.62V. Those cells seem also “gutted” as they will stay at 3.46-3.47V for those 15-30min and then suddenly go to 3.53V. Check the pictures in the first post once more with this in mind, you will see it. 

Bellow 3.45V the cells are also balanced with that delta of 0.02V or less. Something happens above certain voltage.

So, if I would run them at 51.75V or less probably I will not see this behavior. Yet, that means no balancing as the balancer starts at 3.45V. 
 

Pylontech support said yesterday that they’ve passed my case to R&D and they’ve asked if there is a heating source next to the modules. I run my batteries in my garage, which is unheated. Thus, I insulate the rack and run some terrarium film heaters (20W) each to keep them at 23C when they are not charging, when needed. Spring-autumn I remove the insulation and heating, they operate at 18-27C.

Edited March 9, 20242 yr by onobeka

1 hour ago, onobeka said:

Regardless if it is 52.5V or 53.2V. Since the modules are in parallel and the overall voltage rises, the module in question has to raise the voltage too.

I believe pylontech did a lousy job of matching cells. Because some cells in the module are raising their voltage slower, some others take the penalty and have to go to 3.62V. Those cells seem also “gutted” as they will stay at 3.46-3.47V for those 15-30min and then suddenly go to 3.53V. Check the pictures in the first post once more with this in mind, you will see it. 

Bellow 3.45V the cells are also balanced with that delta of 0.02V or less. Something happens above certain voltage.

So, if I would run them at 51.75V or less probably I will not see this behavior. Yet, that means no balancing as the balancer starts at 3.45V. 
 

Pylontech support said yesterday that they’ve passed my case to R&D and they’ve asked if there is a heating source next to the modules. I run my batteries in my garage, which is unheated. Thus, I insulate the rack and run some terrarium film heaters (20W) each to keep them at 23C when they are not charging, when needed. Spring-autumn I remove the insulation and heating, they operate at 18-27C.

You really need to go back and understand how Li cells work.

Re 52.5 or 53.2v no one said anything about the module not raising its voltage.

The cells will look balanced below 3.45v.

No don't run them at 51.75v or less.

Low level heating sounds fine and sensible. As I and other have mentioned it looks like the ambient temp sensor is near the balance circuit, that's why the temp goes up when balancing.

I agree regarding the cells not being balanced well when manufactured.

 

I'll ask again what is your charge voltage when the cells go to 3.62v?

 

Tinbum, l’ve answered that already. Check the pictures if you want to see the exact voltage of the module when a cell is 3.62V.

Otherwise, if I run the maximum voltage at 53.2 or 52.5V, one (or more) cells will still go to 3.6 or beyond. It does not matter!!!

Why do you insist to go back and learn how lithium cells work? Where did I give the impression this is not known by me?

Edited March 9, 20242 yr by onobeka

Here si a picture of a lower module voltage:

and another one:

Sorry I missed the photo showing 53v but I can't see any at 52.5v with the cells at 3.62v.

 

Your comment "Bellow 3.45V the cells are also balanced with that delta of 0.02V or less. Something happens above certain voltage."

 

See you have now posted new photos.

I agree that the cells are badly matched and i do think pylotech should seriously look into it.

I want to help you have better control over your battery so that it does what you want it to do.

This starts by knowing what your battery settings are.

For example, my battery balance start voltage is 3.36V per cell which is too early for me. With a target of 3.5V per cell charge it started to discharge both the high cells and the low cells which made my 75mV delta V into 200mV in a matter of days. So I had to reduce my charge voltage closer to the balance voltage to correct this (which also took days). When delta V was 20mV I returned to the previous 3.5V charge per cell.

So lets get to know your battery...

config  =  battery settings

bat  =  battery status including which cell is in balance mode

This info will help to customize a fix for the battery

BTW nothing meaningful (re balancing) can happen in the flat part of the curve so it is ok to use your batteries at night.

@MeDat, thank you! Here is some information. The charging is already completed, I did not catch the 90-100% SOC.

 

 

So it seems the balancing not active right now. I need to be on guard when the drift happens and check then.

 

Edited March 10, 20242 yr by onobeka

Ok, so I discharged them a bit: 

And starting charging them back, you can see cells flagged with "Y" on balancing:

3mins later:

Another 3mins later:

3mins later, once more:

And ...3 mins later, balancing has stopped.

Probably I would need to catch a deeper discharge (next day) and catch the moment I am interested in, when one or more cells go to 3.6V+.

 

 

 

I think you are over analyzing things ,those figures look fine. 3,6V is not anything crazy ,there are batteries that only reach 100% soc when a cell hits 3,6V...  Deye batteries do this as example.   If the battery pulls full capacity when you discharge 95% without any issues i don't see the issue . As long as you are not keeping cells at 3,6V for weeks on end ,that's what causes damage.

Maybe I am, indeed. I do not like that transitory regime and it’s clear that it must not be this way: the other two modules. 

We are making progress!!!

This is a wealth of info to use to get better acquainted with your battery...

I think there is no need to jump to CODE RED at this time.

Give me some time to look over the info and share what your battery is doing and hopefully why.

 

No matter how I twist and turn the data it all comes back to the same result...your batteries are operating as intended (based on the supplied info).

There are a few "ghost in the walls" with bat 2 and bat 3 starting to balance with no clear reason. But this is not a cause for concern because

small balance current + large charge current = no real balance taking place.

When I got my batteries I used a power supply and set 52.5V charge voltage and left them until the charge current fell to 0.0A. This took a few hours (because they were new). Then I added them to the stack.

The battery settings tells you what is ok and what is not, so if something happens outside of that scope record it share it and we will work with you on a solution.

 

Thank you MeDat, that is probably correct, there are no errors stored. Today I might have a chance to catch the event of 3.6+V with some logs.

And here it is, this time there's no doubt. It is Over voltage.

I will look over the new data and let you know...

That cell nr 5 certainly is peaking pretty high , definitely not ideal. Will be interesting to see if they will warranty the battery for that(i would hope they do). looks like the BMS is handling the issue so if you weren't monitoring the cells you wouldn't know it existed! makes you wonder how many people have mismatched cells and are none the wiser...

They've asked to make this battery a slave and move it in the rack, to check if the temperature issue still happens. To me this is pointless as the temperature is a consequence of the overvoltage. In case the phenomena remains they said they will replace it. I've tried to make them realize this is irrelevant.

So, I guess I need to put in some elbow grease.

For now, I've lowered the float to 51.8V and bulk to 52V to see how it behaves. At 51.8V the balancing is active and that cell is not overshooting.

Edited March 14, 20242 yr by onobeka

1 hour ago, onobeka said:

They've asked to make this battery a slave and move it in the rack, to check if the temperature issue still happens. To me this is pointless as the temperature is a consequence of the overvoltage. In case the phenomena remains they said they will replace it. I've tried to make them realize this is irrelevant.

So, I guess I need to put in some elbow grease.

For now, I've lowered the float to 51.8V and bulk to 52V to see how it behaves. At 51.8V the balancing is active and that cell is not overshooting.

Moving it to being a slave would be a Band-Aid at best IMO. The temperate increase at the end is not from the overvoltage its from the balancing transistors working hard to dissipate the excess energy from the high cells ,this behavior is very common among many BMS brands and its totally normal and its baffling me how Pylontech themself would not know this .

I guess, they want to try to escape replacing the battery. Less hassle for them, more for me. Anyway, I've changed it and I wait for the phenomena to happen again, now in pack #2 :). 

1 hour ago, onobeka said:

For now, I've lowered the float to 51.8V and bulk to 52V to see how it behaves. At 51.8V the balancing is active and that cell is not overshooting.

I'd put it back to what it was when it showed the error so you can see the error in the new position otherwise they will say the position was the problem!

Edited March 14, 20242 yr by Tinbum

Yes, now they are back on 53.2V (PYL) mode. I am hunting now

If you are operating the battery within the parameters specified by the manufacturer and you are having issues then that is cause for a warantee replacement.

 It is important for you to decide if you want to keep it and find a reasonable compromise OR return it and demand your replacement.

If you decide to keep it, then I strongly advise not to stress the battery unnecessarily because you already know what the problem is.

You have discovered that a lower charge voltage helps and this is not a terrible thing because 52ish volts is still above the flat portion of the charge curve so you can achieve full charge with some more "absorption" and cell balancing along the way.

The only time module position is relevant...

New module with updated firmware = master battery in stack

So telling you to swap batteries around in the stack IS NO HELP AT ALL for your problem.

 

Edited March 17, 20242 yr by MeDat

MeDat, I know that they are buying time, they’ve said though to try that and if the phenomena is still there they will change it. So, I’ve sent new logs on Friday and yesterday. Obviously, nothing changed. I will wait for their answer next week. Until then, I am back on 51.7V float and 52V bulk. There was no balancing today, not that it needed to, voltages remained aligned. However, the BMS temperature spiked again to 38.5C. I have no idea why. 
It seems there are two issues with that module. I hope they will replace it.