Active Cell Balancers Not Balancing?

[angrynorwegian13]

I recently installed 2 HiBMS active cell balancers from AliExpress but am running into a consistent issue with one cell in each of my 8s 24v batteries discharging quicker than the rest (the one connected to the main positive). This causes the BMS to rightfully shutdown due to low voltage on that one cell. I checked the active balancer various times throughout the discharge process and noticed that its never actually doing any balancing. Balance status is always off, and balance current is always 0.

Any ideas what might be going wrong? I know the language on these settings isn't always intuitive.

 

[sunshine_eggo]

Active balancers generally can't keep up with discharge demands.

It looks like you simply have one cell that's notably weaker than the others.

Have you confirmed all BMS cell measurements with a separate voltmeter?

What happens when you fully charge the battery?

 

[mikefitz]

I cannot see any advantage in performing cell balance whilst discharging. If you have a cell of significantly lower capacity than the rest, it is what it is.
In view of issues with the most positive cell , interconnection issues may exist in this area, check all conections to cells and balance leads .

 

[rbeudel]

You set the open balance voltage to 3,35V. That means it starts balancing over 3,35V off all your cells and the difference of 0,2V.

 

[angrynorwegian13]

Active balancers generally can't keep up with discharge demands.

It looks like you simply have one cell that's notably weaker than the others.

Have you confirmed all BMS cell measurements with a separate voltmeter?

What happens when you fully charge the battery?

Checking this morning with full charge it looks like balancing is indeed on, with a current of -.9 amps (Is this supposed to be negative?). Cells are all balanced. The interesting thing is the same cell on both of my 24v batteries is the one that discharges faster (cell 8, with the main positive connect). I did confirm with voltmeter.

You set the open balance voltage to 3,35V. That means it starts balancing over 3,35V off all your cells and the difference of 0,2V.

Ah I expected I was misinterpreting one or more of the settings. This helps. Thanks!

I will make sure to re-check all of my connections as well.

 

[sunshine_eggo]

Once top balanced at 3.45V/cell or higher:

1. Disable balancing completely. Discharge and see if the same cell shows up as the low cell at cut off.
2. Move cells in the battery and see if the issue moves.

 

[Lt.Dan]

It has been mentioned above, but I would also be looking at terminal torque. They might just be loose or have a weak connection.