48v E-scooter it turns off at 48.6v and won't turn on until charge

[acidel]

Happy birthday to everyone and many achievements in life !
For more than a month I have a problem with my e-scooter, it cuts off the current when the e-scooter reaches 48.6v 4/5 lines (60%), I checked the battery and each series, I found some mismatched voltages, much too low. Some was 4v and some was 3.46v. I tried to balance them up to 3.7 - 3.8v and I have the same problem.
My question is, could be there a blown fuse somewhere in the display or other components? The controller has been changed and I also change the BMS but the new BMS does not charge the battery, probably because of the voltage differences. What do you guys think ?

 

[amberwolf]

If your cells are that different, the battery probably needs to be replaced. It means that the cells themselves are physically unmatched and will not all perform the same. Some will sag in voltage much more than others, and will cause the BMS to do it's job and protect them from damage that could lead to a fire by turning off the output.

(that's probably also why the new BMS wont' charge, it sees the cells are so different in characteristics (via the voltage difference) that they could be damaged or otherwise unsafe to use. Some of them are well-designed enough to prevent operation if the cells are too great a difference, the cutoff is often around 0.1v difference between any cells/groups).

The system otherwise sounds like it is doing exactly what it is supposed to do, other than the cells in the battery are just too old or are damaged or defective.

 

[acidel]

If your cells are that different, the battery probably needs to be replaced. It means that the cells themselves are physically unmatched and will not all perform the same. Some will sag in voltage much more than others, and will cause the BMS to do it's job and protect them from damage that could lead to a fire by turning off the output.

(that's probably also why the new BMS wont' charge, it sees the cells are so different in characteristics (via the voltage difference) that they could be damaged or otherwise unsafe to use. Some of them are well-designed enough to prevent operation if the cells are too great a difference, the cutoff is often around 0.1v difference between any cells/groups).

The system otherwise sounds like it is doing exactly what it is supposed to do, other than the cells in the battery are just too old or are damaged or defective.

The scooter is new, bought at the beginning of 2023, the battery was built in August 2022 with LGEBM261865 cells. The old BMS is charging perfectly the battery, new BMS is not charging and is different but same for 48v 25a. So, my problem is that the scooter turns off at 48.6v

 

[amberwolf]

And the answer is still the same: The cells are defective, damaged, or aged / used such that they are too different, so the BMSes are doing their job and protecting you from a failure.

If you want to know this for certain, you can buy cell testing equipment and test each cell or group of cells to see waht each one is capable of, and compare the data when testing is complete. This will show you which ones are different if you wish to replace them and buy the equipment to do that with (and learn how to safely and properly use it).

But it is likely to be cheaper to replace the entire battery, and certainly easier.


There is always the remote chance that there is a drain (high resistance short to something) from the cells that were lower than others, but this is unlikely; it's usually from corrosion or pinched wires, and tends to be visually obvious; alternately if the groups are made of multiple parallel cells, there could be interconnect problems.

Whether the new BMS is even working or not, couldn't say but the description is of correct operation for the situation.

 

[eee291]

If the cells drift apart very quickly, it might be because some spot welds broke, which decreased the capacity of some cells rows.
What you need to do is properly test the battery, and maybe add a Bluetooth BMS so you can monitor the cell voltages under load.