Li-ion battery pack wont charge

[drummerdimitri]

I just finished assembling a Li-ion battery pack to be used for a powerbank project and although I was able to draw power from it, it doesn't seem to want to take any charge.

I am using a 3S BMS (3S6P pack) and my guess is that it is damaged. How can I test the BMS to make sure it's causing this issue?

[tunk]

How do you charge it? A BMS is generally not a charging circuit, only for protection.

[drummerdimitri]

How do you charge it? A BMS is generally not a charging circuit, only for protection.

This is the BMS I am using: https://www.aliexpress.com/item/32817897264.html

As you can see they state the the charging and discharging happens at the P+ and P- terminals which is what I've been using.

[tunk]

That board is for protection only - it does not control the charging itself.
You have to use the normal CC/CV/cut-off charging.
In your case constant current until it reaches 12.6V, then constant voltage
until it reaches 10% of the starting current. If you feed it with more than
13.05V (4.35*3) then the over-voltage protection will kick in.

[digsys]

.. As you can see they state the the charging and discharging happens at the P+ and P- terminals which is what I've been using

BMS activate method : Use 12.6V Li-ion  charger to charge it

errrr nope :-) very hard to understand their poor translation but - there is no way that is a charger as well ! It's a standard Vmax limiter .. all they are saying is - whether you are charging or discharging, the limiter is active.
For that price, I'd be surprised if the FETs or Transistors were genuine.

[drummerdimitri]

That board is for protection only - it does not control the charging itself.
You have to use the normal CC/CV/cut-off charging.
In your case constant current until it reaches 12.6V, then constant voltage
until it reaches 10% of the starting current. If you feed it with more than
13.05V (4.35*3) then the over-voltage protection will kick in.

I am using an external Li-ion charger for that purpose. This is only a protection board with some balancing functionality.

[drummerdimitri]

I got a new BMS but it seems to be designed for 4 batteries in series and not 3 as there is an extra tab to solder onto compared to my previous unit.

What could be B3-  . The others are self explanatory.