BMS Charging issues

[Moogster10]

Hi everyone - first time poster - enjoying solving the problems now. Am a bit stuck though

TLDR
1. Battery was not powering the motor
2. Installed a new BMS
3. Motor now works but the battery now does not charge

BMS
https://www.amazon.co.uk/10Series-Protection-Balancing-Li-ion-Battery/dp/B075MFBB23/ref=sr_1_3?crid=3U5DMDKYFDPQ5&keywords=36V+35A+10Series+BMS+PCB&qid=1648558641&s=electronics&sprefix=36v+35a+10series+bms+pcb%2Celectronics%2C80&sr=1-3

Battery
https://yosepower.com/collections/e-bike-battery/products/36v20-8ah-li-ion-e-bike-battery-electric-bicycle

Suspect it is a BMS issue

Not sure if
A.The BMS is wrong
B. BMS is installed incorrectly
B. Battery has an issue

The voltage across the cells is consistent (3.4V)
There is output from the battery if I bypass the BMS (34V)

The battery is quite run down as I was just using it hence the low voltage.

My thoughts are around taking the BMS off and re-installing but if it is the wrong type of BMS then this might be useless.

Options
- get new BMS
- reinstall BMS
- take off BMS and battery balance instead

Any tips / guidance welcome

Will post photos later tonight

 

[john61ct]

Try "waking up" the charging side with very low current input, voltage just above batt terminal V at rest, say overnight

Some have an on/off circuit?

Best to only buy BMSs with good docs and native English support available

 

[fechter]

Try measuring the cell voltages at the BMS connector. Make sure there isn't a broken wire or bad connection.

I use some solid strand wire the same size as the connector pins and insert it into the connector. The other end of the wire goes to my voltmeter.

 

[docw009]

Did you wire the output connector to positive and P- pad, and the charger connector to positive and the C- pad?


I would also do what Fechter told you. Check all voltages on the balance connector pins. You can do it behind the connector, or pull the plug and measure at the plug, With black probe on the B- pad, should get 3.4V on 2nd pin and increase steadily 3.4V per step up to 34 volts on the 11th pin.

 

[Moogster10]

Hi everyone - thanks for the replies. I was just waiting until I got my new multimeter through before I responded.

So
This may help - but I still don't actually know what the problem is.

Measuring each pin on the connector (black on B - red working through the pins)
3.47
6.92
10.42
13.90
17.36
20.82
24.3
27.7
31.2
34.9

Measured the charger also - there was 42v coming from that

Measured between black and red terminals on the battery (cutting out BMS) - 34.9v
Measured between red on battery and P- (blue wire) - 34.5v
Measured between red on battery and C (white wire) - 34.5 V

So still not sure what the issue is why its not charging
- is battery asleep?
- problem with where the charger plugs into battery?

Any ideas?

 

[Moogster10]

Is it probably best to just replace the BMS with a good quality one and that will hopefully work?

I toyed with the idea of using a balance charger / charging without a BMS but haven't tried that yet (not that I know how to)