I'm trying to change the cells in my wife Puch (Panasonic 26v) bike. Can anyone guide me? 7S5P 18650s as Joachim suggests. Does the BMS lock if I remove the old cells? what do I do about the small wires into the BMS? thanks for any help, links, guidance. cheers, derek
PANASONIC ebike battery change
- Thread starter osa57
- Start date
marceljack
1 µW
- Joined
- Jun 11, 2022
- Messages
- 2
Hi everybody,
I am new to this forum which has helped me in understanding Li-ion battery technology for e-bikes, and I would like to share with you my small experience with a faulty Panasonic battery (26 V / 12 Ah model NKY342 B2).
This battery is used on a Gitane e-bike which I did not use during about 6 monthes as it is in a vacation house.
When I wanted to reuse it, it seemed to work after a charge however the gauge on the battery was blinking over the 5 LEDs instead of a solid bar.
The gauge indication on the command unit was at full charge (3 LEDs), so I decided to have a small ride with the bike (about 5 km).
All seemed OK, except the bargraph on the battery which was still blinking when pressing the button.
The indication when on the charger was blinking as well ...
At the next riding tentative, everything stopped suddenly after a few seconds, no indications anymore on the bargraph and the battery refused to charge when put on the charger.
The voltages measured on the connector were 0V...
So I decide to open the battery, which requires a special Torx T20 screwdriver for "tamper proof" screws.
Once the battery open and extracted from its plastic bag with multiple adhesive tapes, I discovered its structure (7s 6p) and measured the voltages of each of the 7 groups.
Six groups seemed fully charged (4,15 volts) but one was at almost zero (0,7V) ...
Having a closer look, I discovered that one element of the faulty group had leaked (see photograh) and that most probably it was it which short-circuited the group.
I decided to disconnect it from the group and measured the voltage, it was already higher (more than 1V) and slowly increasing.
So I decided to try to charge this group separately from the rest with a cell phone charger delivering approximately 5,5V with a maximum current of 500 mA with a 68 ohms resistor in series at the beginning, then directly.
The voltage increased to 4,12V in less than 24 hours, so the BMS of the battery should have been happy with that condition, but pressing the charge indicator still gave nothing and there was still 0V on the connector ...
The BMS had to be reset but I did not know how to do it ...
Then I remembered to have seen on a forum that putting the battery on the charger could reset it, and bingo ! it worked !!!
Then I put the battery on the bike and switched it on with the on/off button of the command module and the 3 LEDs went on as well as the LED of the assistance level. I did not try the bike so far, I will do it soon.
I will also try to replace the defective element (I have to order a few but delivery is long).
I am new to this forum which has helped me in understanding Li-ion battery technology for e-bikes, and I would like to share with you my small experience with a faulty Panasonic battery (26 V / 12 Ah model NKY342 B2).
This battery is used on a Gitane e-bike which I did not use during about 6 monthes as it is in a vacation house.
When I wanted to reuse it, it seemed to work after a charge however the gauge on the battery was blinking over the 5 LEDs instead of a solid bar.
The gauge indication on the command unit was at full charge (3 LEDs), so I decided to have a small ride with the bike (about 5 km).
All seemed OK, except the bargraph on the battery which was still blinking when pressing the button.
The indication when on the charger was blinking as well ...
At the next riding tentative, everything stopped suddenly after a few seconds, no indications anymore on the bargraph and the battery refused to charge when put on the charger.
The voltages measured on the connector were 0V...
So I decide to open the battery, which requires a special Torx T20 screwdriver for "tamper proof" screws.
Once the battery open and extracted from its plastic bag with multiple adhesive tapes, I discovered its structure (7s 6p) and measured the voltages of each of the 7 groups.
Six groups seemed fully charged (4,15 volts) but one was at almost zero (0,7V) ...
Having a closer look, I discovered that one element of the faulty group had leaked (see photograh) and that most probably it was it which short-circuited the group.
I decided to disconnect it from the group and measured the voltage, it was already higher (more than 1V) and slowly increasing.
So I decided to try to charge this group separately from the rest with a cell phone charger delivering approximately 5,5V with a maximum current of 500 mA with a 68 ohms resistor in series at the beginning, then directly.
The voltage increased to 4,12V in less than 24 hours, so the BMS of the battery should have been happy with that condition, but pressing the charge indicator still gave nothing and there was still 0V on the connector ...
The BMS had to be reset but I did not know how to do it ...
Then I remembered to have seen on a forum that putting the battery on the charger could reset it, and bingo ! it worked !!!
Then I put the battery on the bike and switched it on with the on/off button of the command module and the 3 LEDs went on as well as the LED of the assistance level. I did not try the bike so far, I will do it soon.
I will also try to replace the defective element (I have to order a few but delivery is long).
marceljack
1 µW
- Joined
- Jun 11, 2022
- Messages
- 2
Hi everybody,
This morning I tested my e-bike with its "repaired" battery (7s 6p) which has now one element less in one of the 7 groups, so it has probably the capacity of a 7s 5p battery (10 Ah i.o. 12 Ah, assuming all elements are at 100% capacity which is certainly not the case).
I made a ride of 7 to 8 km wihout any trouble, however I used only the lowest assistance level.
The ride was not very difficult, with slopes on about 20% of the distance.
At arrival, the 3 LEDs of the control module were still "on" and the 5 LEDS of the battery were still lit when pressing the battery check button.
I placed then the battery on the charger, and it charged with the 5 LEDs "on", indicating the battery was not full.
This means probably that the indications are over-optimistic and that the BMS requires a recalibration.
The full charge (all LEDs off) took about 2 hours at 2 amps (1/6 of the original 12 Ah capacity of the battery), which would mean that the battery was still 5/6 full after this ride.
Wait and see for a more definitive repair...
This morning I tested my e-bike with its "repaired" battery (7s 6p) which has now one element less in one of the 7 groups, so it has probably the capacity of a 7s 5p battery (10 Ah i.o. 12 Ah, assuming all elements are at 100% capacity which is certainly not the case).
I made a ride of 7 to 8 km wihout any trouble, however I used only the lowest assistance level.
The ride was not very difficult, with slopes on about 20% of the distance.
At arrival, the 3 LEDs of the control module were still "on" and the 5 LEDS of the battery were still lit when pressing the battery check button.
I placed then the battery on the charger, and it charged with the 5 LEDs "on", indicating the battery was not full.
This means probably that the indications are over-optimistic and that the BMS requires a recalibration.
The full charge (all LEDs off) took about 2 hours at 2 amps (1/6 of the original 12 Ah capacity of the battery), which would mean that the battery was still 5/6 full after this ride.
Wait and see for a more definitive repair...
tom355
10 mW
- Joined
- Apr 9, 2021
- Messages
- 27
Did u continue working on that battery? I am about to buy a bike with a 36V Panasonic and refit the battery with new cells, but i heard that the BMS do not allow that. They seem to remember the reduced capacity and keep that also with the new cells around.