Pylontechs + DIY battery.. unexpected behaviour

[Tinbum]

I had one pack from new that a cell went to a high voltage. It didn't shut the pack down but I reduced the charge voltage down to 52.5 and left it like that for a good long time. It took some time to balance and the ambient temp sensor went up to about 40 degrees.

[Caesium]

I had one pack from new that a cell went to a high voltage. It didn't shut the pack down but I reduced the charge voltage down to 52.5 and left it like that for a good long time. It took some time to balance and the ambient temp sensor went up to about 40 degrees.

One of my packs has been doing this for a while as well so yesterday I took it out of my stack and put 52.5v across it from a bench supply, limited to 2A, hooked up some serial to monitor it, and left it to it.

Eventually it reached a state like this:

pylon>bat
bat
@
Battery  Volt     Curr     Tempr    Base State   Volt. State  Curr. State  Temp. State  Coulomb
0        3423     0        20000    Charge       Normal       Normal       Normal        94%      45637 mAH
1        3424     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
2        3623     0        20000    Charge       OV           Normal       Normal        99%      48064 mAH
3        3398     0        20000    Charge       Normal       Normal       Normal        89%      43209 mAH
4        3424     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
5        3423     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
6        3423     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
7        3423     0        20000    Charge       Normal       Normal       Normal        94%      45637 mAH
8        3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
9        3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
10       3424     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
11       3423     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
12       3425     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
13       3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
14       3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
Command completed successfully

pylon>pwr
pwr
@
Power Volt   Curr   Tempr  Tlow   Thigh  Vlow   Vhigh  Base.St  Volt.St  Curr.St  Temp.St  Coulomb  Time                 B.V.St   B.T.St
1     51530  0      24000  20000  20000  3398   3624   Charge   Normal   Normal   Normal   89%      2022-09-29 14:21:44  OV       Normal

So at this point its cut off charging (0 current to anything shown here, bench supply showing 50mA).

And its kind of sat there like that for about 12 hours now. The OV cell at 3.62v is veeeeery slowly dropping (it initially got to 3.69v or so) and when it reaches around 3.60v, it re-enables charging, the cells take 2A for a very brief few seconds, and the high cell shoots back up to 3.69v.

Each time this happens the other cells gain another few mAH so it is very slowly balancing them but I think it might take weeks..

Since the total pack voltage is only 51.53v I'm not sure if active balancing is kicking in. I think it has just cut off charging and is letting the OV cell fall of its own accord.

I'm tempted to open it up and put a 1ohm resistor across the high cell to bring it back down a bit..

[Stinsy]

I'm tempted to open it up and put a 1ohm resistor across the high cell to bring it back down a bit..

That is what I would do!

[Oldgreybeard]

My experience was that it took around 2 weeks of the whole pack regularly being charged to 100% for the whole lot to get in balance, and all I'd done is add three new US3000Cs to three that had been in use fora few weeks. Their cell balancing does seem to be very, very slow.

[Joeboy]

I had one pack from new that a cell went to a high voltage. It didn't shut the pack down but I reduced the charge voltage down to 52.5 and left it like that for a good long time. It took some time to balance and the ambient temp sensor went up to about 40 degrees.

One of my packs has been doing this for a while as well so yesterday I took it out of my stack and put 52.5v across it from a bench supply, limited to 2A, hooked up some serial to monitor it, and left it to it.

Eventually it reached a state like this:

pylon>bat
bat
@
Battery  Volt     Curr     Tempr    Base State   Volt. State  Curr. State  Temp. State  Coulomb
0        3423     0        20000    Charge       Normal       Normal       Normal        94%      45637 mAH
1        3424     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
2        3623     0        20000    Charge       OV           Normal       Normal        99%      48064 mAH
3        3398     0        20000    Charge       Normal       Normal       Normal        89%      43209 mAH
4        3424     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
5        3423     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
6        3423     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
7        3423     0        20000    Charge       Normal       Normal       Normal        94%      45637 mAH
8        3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
9        3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
10       3424     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
11       3423     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
12       3425     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
13       3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
14       3426     0        20000    Charge       Normal       Normal       Normal        95%      46122 mAH
Command completed successfully

pylon>pwr
pwr
@
Power Volt   Curr   Tempr  Tlow   Thigh  Vlow   Vhigh  Base.St  Volt.St  Curr.St  Temp.St  Coulomb  Time                 B.V.St   B.T.St
1     51530  0      24000  20000  20000  3398   3624   Charge   Normal   Normal   Normal   89%      2022-09-29 14:21:44  OV       Normal

So at this point its cut off charging (0 current to anything shown here, bench supply showing 50mA).

And its kind of sat there like that for about 12 hours now. The OV cell at 3.62v is veeeeery slowly dropping (it initially got to 3.69v or so) and when it reaches around 3.60v, it re-enables charging, the cells take 2A for a very brief few seconds, and the high cell shoots back up to 3.69v.

Each time this happens the other cells gain another few mAH so it is very slowly balancing them but I think it might take weeks..

Since the total pack voltage is only 51.53v I'm not sure if active balancing is kicking in. I think it has just cut off charging and is letting the OV cell fall of its own accord.

I'm tempted to open it up and put a 1ohm resistor across the high cell to bring it back down a bit..

Caesium, Have you balanced your Pylontechs recently? To do this, shut it all down, disconnect your incoming leads and leads going to you LFK280's. Disconnect your can cable. The packs will now all be interconnected for data/power with no outside leads? Turn the Pylontechs on again and press the top pack red button. You will see the green lights flashing, holding steady then going out as they discharge to each other to balance then shtting themselves off. Not sure how this works at prismatic pack level or if its across the whole unit? If you do open up a Pylontech i'd defo appreciate some photo's? Personally i'd give it a month and see how it plays out first but a balance is worth doing.

[nowty]

And its kind of sat there like that for about 12 hours now. The OV cell at 3.62v is veeeeery slowly dropping (it initially got to 3.69v or so) and when it reaches around 3.60v, it re-enables charging, the cells take 2A for a very brief few seconds, and the high cell shoots back up to 3.69v.

Each time this happens the other cells gain another few mAH so it is very slowly balancing them but I think it might take weeks..

Since the total pack voltage is only 51.53v I'm not sure if active balancing is kicking in. I think it has just cut off charging and is letting the OV cell fall of its own accord.

I'm tempted to open it up and put a 1ohm resistor across the high cell to bring it back down a bit..

From what @Caesium and @Tinbum have been saying, it looks like they work in a similar way to my high voltage cell protection boards I bought recently.


These work like this, they only come on very low operation between 3.60V and 3.63V. Then they come on full at around 3.65 to 3.68V. Once they are on, they seem to stay on until the cell has returned to around 3.60V.

Therefore, I reckon the cell protection will come on at any pack voltage if an individual cell exceeds 3.65V. Obviously the higher the pack voltage the more likely it is that the weakest cell will reach the cell protection voltage.

Personally, I would not open it up and manually balance it as its probably working as designed. If it went to a really worryingly high voltage, say 4V+ I would expect the pack to shut down.

[Tinbum]

Caesium, Have you balanced your Pylontechs recently? To do this, shut it all down, disconnect your incoming leads and leads going to you LFK280's. Disconnect your can cable. The packs will now all be interconnected for data/power with no outside leads? Turn the Pylontechs on again and press the top pack red button. You will see the green lights flashing, holding steady then going out as they discharge to each other to balance then shtting themselves off. Not sure how this works at prismatic pack level or if its across the whole unit? If you do open up a Pylontech i'd defo appreciate some photo's? Personally i'd give it a month and see how it plays out first but a balance is worth doing.

That is only for balancing between the packs when initially installing them.

[nowty]

Caesium, Have you balanced your Pylontechs recently? To do this, shut it all down, disconnect your incoming leads and leads going to you LFK280's. Disconnect your can cable. The packs will now all be interconnected for data/power with no outside leads? Turn the Pylontechs on again and press the top pack red button. You will see the green lights flashing, holding steady then going out as they discharge to each other to balance then shtting themselves off. Not sure how this works at prismatic pack level or if its across the whole unit? If you do open up a Pylontech i'd defo appreciate some photo's? Personally i'd give it a month and see how it plays out first but a balance is worth doing.

That is only for balancing between the packs when initially installing them.

+1, that can only balance up at a full voltage pack level.

[Tinbum]

Since the total pack voltage is only 51.53v I'm not sure if active balancing is kicking in. I think it has just cut off charging and is letting the OV cell fall of its own accord.

I'm tempted to open it up and put a 1ohm resistor across the high cell to bring it back down a bit..

That looks as if their may be a problem with that cell. If the battery is still in warranty I'd not open it an wait for it to fail or even put in a claim now.

[Stinsy]

Personally i'd give it a month and see how it plays out first but a balance is worth doing.

I'd definitely have give the new batteries and the pylontechs the opportunity to go through a few dozen cycles before taking action.