Bottle battery can not be charge

[Tunk]

Hi
I have Tryed to fix a old bottle battery. I have replacing 4 cell. There are 40 battery in 10s 18650 2 ah. I have used same cell size on replacment cell. I have charge the 10 cell pack induvidial up to 3,1 to 3,5 V. I have ca 35 on battery pack.
When I try to charge it, The bms will not let the 41 go through bms and into battery pack.
I have not find fuse anywhere in bottle or on bms pcb.

Is There som trick to get bms to accept charging ?
1 3,56V
2 3,57
3 3,56
4 3,56
5 3,55
6 3,55
7 3,58
8 3,16
9 3,15
10 3,53

 

[trex]

You need to bring blocks 8 and 9's voltage nearer to the rest (3.55V) to get the BMS going.

 

[Tunk]

Thanks trex.
Now all are between 3,51V to 3,57 V. Charger push 41.3 to the bms, but no charging. Normaly charger goes from green to red on led, and goes green again when fully charge.
Still need a good trick too make the bms accept charger.
Maybe bms has some other problems. Have no technical drawings on bms so it is hard to know were too look.

 

[trex]

you may need to reset the BMS.
Unplug the balance wires and cut the B- wire. That the wire going from the - terminal of the first cell block to the BMS, it's usually marked as B- on the BMS.
Wait 5 minutes for the BMS to power down.
Reconnect the B-wire, plug in the balance wires then try charging again.

 

[Tunk]

Thanks again.
Then I will soldering it off, an then soldering it on again after 5 min.

 

[Tunk]

Tryed it, no change. Have soldering it off again, Then i try to connect B- then insert balance wire connector, then charge plug and at last powering charger.

Other sugestion ?

 

[Tunk]

Is There some of the smd components Who need a extra check on bms board, like a transient diode or simular component ?

 

[trex]

You usually have 3 FETs in parallel controlling the output and one FET the charging current. That one may have blown.
Worst case scenario, you may need a replacement BMS. Email Andy @ Woosh.

 

[Tunk]

Thanks again.
I have Now soldering off all wires and will take the bms to my jobb. There i have a elektro lab. If i am Lucky we got the right mosfet in stock.
I have tryed too find scematic drawings on pcb board, so i gess I have too do it old school. Resoldering/ touch up critical components etc.
Of course it is cheaper and takes less time to buy new bms, but I want to learn more.
I work with some electronics, but battery technology is new for me, exept bilding Hadway battery pack with 3 bms with 12V and 36V output. It has worked fine for aprox 4-5 years and Still working.