jerome_speedy
100 mW
Hi all,
I have an old problem that I want to fix with the help of people here (if they can/will). My battery is 10S 8P Li-Ion.
I've noticed for some time that It wouldn't take the charge anymore (displays 0A of charge current if I try). I have postponed the repair until I could afford to spend some time to research the cause of breakdown and fix it. I don't want to change the BMS if I can avoid it.
So far my tests:
B+/B- = B+/Cell- = 40,2 V
B+/LOAD = 34.4 V
B+/PACK- = 33.9 V
Cells0: 4,16 V
Cells1: 4,18V
Cells2: 4,17V
Cells3: 4,05V
Cells4: 3,98V
Cells5: 3,93V
Cells6: 3,90V
Cells7: 3,94V
Cells8: 3,93V
Cells9: 3,93V
I'm well aware that the cells are way out of balance but this is not the cause of my problem (I think). I used an active balancer at one point in time to get there (the balance was even worse before).
While "charging" at 42V (the charge socket being tied to a 42V voltage source), the (presumably) charge mosfet exhibits:
V G-Drain = 1,5 V
V Drain-Source = 1,9V
I think it's normal from that data that the BMS prevents the charge since the Gate-Drain voltage is too low (the threshold for activating the FET is around 3-4V if I recall correctly). So I suppose some part must be playing up and blocking the FET somehow. I checked the other "repair BMS" threads on this forum and concluded that it couldn't be that a sense wire is bad, judging from the cells voltage. But this is as far as I can go.
I checked the discharge FETs and they are willing to send "voltage" to the output, since:
V G-Drain = 5V and V Drain-Source = 5V (bizarre ?). I also noticed that when a suitable voltage (ie 42V or so) is applied to the charge socket, the discharge FETs shuts down (V G-Drain= 0V, V G-Source= 0V), so THAT BMS doesn't like charge and discharge at the same time (I noticed more recent chinese BMS accept that, usually).
If anyone has some more tests I could perform, I'm all hears... Thanks !
PS: I have a feeling the BMS could stop the charge because of too much imbalance of cells. Is that common in old BMS ? The next thing I want to try is charge the lowest cell to 4,2V, connect my active balancer, wait for a few hours and when the voltages are settled, try to charge the battery another time. What do you think of it ?
I have an old problem that I want to fix with the help of people here (if they can/will). My battery is 10S 8P Li-Ion.
I've noticed for some time that It wouldn't take the charge anymore (displays 0A of charge current if I try). I have postponed the repair until I could afford to spend some time to research the cause of breakdown and fix it. I don't want to change the BMS if I can avoid it.
So far my tests:
B+/B- = B+/Cell- = 40,2 V
B+/LOAD = 34.4 V
B+/PACK- = 33.9 V
Cells0: 4,16 V
Cells1: 4,18V
Cells2: 4,17V
Cells3: 4,05V
Cells4: 3,98V
Cells5: 3,93V
Cells6: 3,90V
Cells7: 3,94V
Cells8: 3,93V
Cells9: 3,93V
I'm well aware that the cells are way out of balance but this is not the cause of my problem (I think). I used an active balancer at one point in time to get there (the balance was even worse before).
While "charging" at 42V (the charge socket being tied to a 42V voltage source), the (presumably) charge mosfet exhibits:
V G-Drain = 1,5 V
V Drain-Source = 1,9V
I think it's normal from that data that the BMS prevents the charge since the Gate-Drain voltage is too low (the threshold for activating the FET is around 3-4V if I recall correctly). So I suppose some part must be playing up and blocking the FET somehow. I checked the other "repair BMS" threads on this forum and concluded that it couldn't be that a sense wire is bad, judging from the cells voltage. But this is as far as I can go.
I checked the discharge FETs and they are willing to send "voltage" to the output, since:
V G-Drain = 5V and V Drain-Source = 5V (bizarre ?). I also noticed that when a suitable voltage (ie 42V or so) is applied to the charge socket, the discharge FETs shuts down (V G-Drain= 0V, V G-Source= 0V), so THAT BMS doesn't like charge and discharge at the same time (I noticed more recent chinese BMS accept that, usually).
If anyone has some more tests I could perform, I'm all hears... Thanks !
PS: I have a feeling the BMS could stop the charge because of too much imbalance of cells. Is that common in old BMS ? The next thing I want to try is charge the lowest cell to 4,2V, connect my active balancer, wait for a few hours and when the voltages are settled, try to charge the battery another time. What do you think of it ?