Darek.S wrote:
If I receive a new battery and they do not request the return of the old one, I will of course include its detailed research here.
It also happened. First, I made an attempt to resuscitate the battery with a laboratory power supply. Voltage 21V, current 0.8A.
The battery received the current, but the voltage above 19V did not pop out. When charging is turned off, the voltage is a few volts. I connected the original charger and it started working, but after a few minutes the error. so I did the Battery section ...

It turned out that the two 2nd and 4th sections have zero voltage and damaged targets
(four links in total). They didn't load at all. The other targets were reloaded to 4.6V! And this is logical, although it poorly proves the work of the balancer, but on the other hand it worked in unnatural conditions (hence the original charger signaled an error.
So I disassembled the cells and temporarily soldered the used and a bit tight but working and full charged to 4.2V.
I even connected the hammer, but it worked only at the lowest speed, then it turned off, but not the cells themselves were a problem, only baskets with high resistance (up to 500m?

. This is clearly visible in the infrared image.
So I discharged the batteries a little with a resistor and charged them with a laboratory power supply set at 21V and 500mA. After a while, the current dropped and after a good time it reached a minimum. I checked the balancer and the voltage on the cells was 4.1 to 4.27V, but the cells were not the same and a bit worn.
Unfortunately, these tests showed that the two targets have a bit too high tension and from what I see in the sections that were scored. I did tests on various cells and in a rather weak condition and on a laboratory power supply. I also tried to replace the cells with the greatest differences (after slightly discharging the battery). The tensions leveled out a bit, but in the section where it was 4.27 it dropped to 4.22. In the section where I had 4.2 on the weaker link, it increased to 4.24.

After turning off the power, I had 4.27V on the cell for a while and it was discharged by the Balancer with a current of 50 mA. After the voltage on the cell to 4.24V, the current dropped to zero.
The next one was on the original Parkide links in half (one link per section because four were lost)) but in much better condition and the same.
The cells were charged with a Newell C4 Supra charger, therefore balanced.
The idea was to unload them with the resistor and then check the charging first in the laboratory and check the balancer, this time on the same cells, and then after another discharge with the original charger. And to my surprise, one of the cells fell to zero already at a relatively low discharge current. after the exchange, the second one fell, and it was at a relatively low current.
And so it happens similarly to the targets 2 and 4 before. On the last third attempt (I had to replace only one link with another one), the target 1 failed in the same way!
I have not tried on blue cells anymore.
Each time there was a small pop, ala a skip of a spark. Since I have a few other recovery cells, I did further discharge tests on them and nothing fell. It is worrying whether a defective BMS can be so damagingAt the same time, the cells did not succumb to permanent damage because they started working on new cells again (until the next cell failure) and nothing broke on the recovery ones? If it were so, it would be pointless to replace the cells with a new BMS. I should choose something. I realize that it is totally unprofitable (I bought the third battery for less than a hundred) but I do it out of curiosity. New links (from depots but not used) are on their way.
I took a closer look at this balancer. There is no BMS in this battery!
There is no Current Limit. There is only Balancer on the LGT8P22A chip.
The output is 5 cells in series with no transistor in series.
Balancing transistors are fleas that can balance small currents in the final stage of charging. If one were stuck short-circuiting the batteries it would be binding
with a multi-ampere current flow that would probably damage such a flea.
Another thing is that these baskets, as I measured them later, had a resistance of up to half ohm, so there is no question of such a large current even with a short circuit
and the 8 ampere current cannot damage the cells.

Anyway, later I soldered directly one of the cells that remained alive and it withstood a discharge with a current of 15A!
My fundamental question is whether this balancer could be the cause of the Parkside cell failure or was it simply defective.
Although the last three were overloaded, I use the remaining one in a device with a power consumption of over 10A and I have already unloaded them once ...
the question is important because I am afraid of new ...
Added after 5 [hours] 29 [minutes]: I changed the topic because the most important thing is what was really the cause of the failure, as if there was no new or at least little used equipment ...
1. Cells - unlikely, considering that the three that survived are doing well so far (although it is a short time, but the ones that died basically in the original battery). And I tested one of them with a discharge current of 15A ... but in the original system, the other cells did not die ...
2. Charger - hmm charged and the cells died during discharge. Both at work and during tests ... Although she could overload the cells ... What is likely
3. Balancer - The original Parkside links are dead, but gone. The first time with the original Owi charger, then charging from the laboratory and certainly reloading those who survived .... And the recovery during discharge somehow survived
... how to analyze the above points, one of them or maybe a few is right ... I have my type but I'm not sure. Asking for your opinions ... best regards