Hello, sorry to revive this old thread but i am desperately trying to find a “durable solution” to correct the voltage drifting in the P1 group and P10 group of my 10s4p 30q battery.
I charged them individually using 5v charger and JST connectors but the voltage keep dropping at a rate of 0.002V per hour for P10 and 0.001V per hour for P1.
I bought this battery 1 year ago and I’m ready to unwrap it. But i am looking for a guide or clear instructions on how to make a diagnosis and repair these groups which i can’t neither find on this forum nor on the internet.
Any help is greatly appreciated. Thanks a lot !
1st screenshot after the individual charge of P10 anf P1 (January 6th 2:16pm)
There are too many things that could be the issue and many won’t apply to your situation and would just take up a lot of time documenting.
You’ve confirmed that your BMS is functioning properly?
You’ll need to open the pack and confirm that you are reading the voltages accurately. If yes, you’ll need to remove those two p-groups, disassemble them, and find which cells are self-discharging so quickly. Or, you can just replace the two p-groups without trying to find the bad cells.
There are a large number of safety issues and precautions to take doing this so do not attempt to open your pack and replace the cells/p-groups unless you fully understand and accept the risks and will take all necessary safety precautions.
Hopefully others chime in with their thoughts too as there are different ways you can go at this.
Ok thank you for your help. BMS is fine. Voltage is drifting even if i disconnect the BMS.
Do you recommend a video / tutorial that explains how to replace the P group. (Problem is i don’t have a spot welder.)
Knowing that P1 and P10 are glued together at the extremity of the pack, is it possible that a mechanical shock caused this issue ?
(I already built a 7s3p battery pack for my daughter’s scooter, but i used NESE system.)
Thank you
Sorry, I don’t have one to recommend. If you don’t have a spot-welder and you have a spot-welded pack then I think you have a problem unless you are going to replace those p-groups with NESE groups.
It’s certainly a possibility. Verrrrrry carefully examine the spot welds for those groups. Be sure to cover (with something insulating) any other exposed p-groups while you do this. Dropping a metal flashlight or magnifier onto the pack could cause some real problems.
Last question before opening the pack: is there a technique to repair the 2 groups without a spot welder, if i notice that the spot Welds are damaged? Thank you
IMO, no.
You’d have to create some other method to connect to the cells if you do not have a spot-welder.
Since you have to open the pack anyway, just open it now.
The questions you need to ask will fall into place once you see what’s going on (or not going on).
Here are the photos, i was wrong group 1 and group 10 are on the opposite side…
I’m surprised to see that there are no fish tape & kapton tape for extra protection. And I asked the seller for a flexible pack but it doesn’t flex at all.
We can’t see 1/2 of the spot welds (centerline of the pack) so we don’t know if there are problems there or not. Unfortunately I cannot diagnose your pack from here. You’ll need to check the other welds, voltages, wiring, and maybe do more self-discharge testing.
If you don’t find anything wrong you have to the decide if you will remove/replace those two p-groups.
