Possible BMS issue?

[basssignal]

Hi All,

I have a 10S4P battery arrangement, each cell was charged and tested, and measurement of each cell was between 4.1v to 4.2v when done. I built the pack up and measured 41.5v across the output.

I bought one of these BMS:

10S 36V 30A Li-ion Cell 18650, GPS Accessories TMC Module Receivers Battery Protection BMS PCB Board With Balance Function Overcharge Over-discharge Over-current Protection : Amazon.co.uk: Electronics & Photo

10S 36V 30A Li-ion Cell 18650, GPS Accessories TMC Module Receivers Battery Protection BMS PCB Board With Balance Function Overcharge Over-discharge Over-current Protection : Amazon.co.uk: Electronics & Photo

www.amazon.co.uk

All wired correctly and double checked the balance wires. All appears ok.

Problem is, when the battery needs a charge, it appears to only charge to 38.5v volts. The external charger 42v,2A is red and turns green when the voltage of reaches 38.5v.

Any ideas why it's not reaching a little closer to 42v?

Thanks

 

[vfr400]

You didn't say whether you checked the voltage coming out of the charger, nor whether you confirmed that your meter is still reading correctly.

Assuming that they're OK, you need to check the cell voltages again as soon as the charger goes green.

 

[basssignal]

Hello, yes sorry the output voltage of the power supply is 42v measured with a fluke meter.

I measured each cell (C) group
C1 3.91v
C2 3.90v
C3 3.82v
C4 3.82v
C5 3.82v
C6 3.80v
C7 3.93v
C8 3.55v
C9 3.7v
C10 4.0v

C8 was the lowest voltage. I managed yesterday to charge all groups to at least 4.1v using my imax b6, so something isn't quite right somewhere.

 

[vfr400]

It's a long way out of balance. I'd rebalance it and see what happens.

 

[basssignal]

Yes, I was hoping that the BMS could manage that side of things but it doesn't want to play. Any suggestions?

 

[Nealh]

The voltage are to far out for the BMS to balance, they will balance if all are close even 0.1v is far out. One will have to manually balance each cell group first then see if they stay balanced.

 

[vfr400]

Yes, I was hoping that the BMS could manage that side of things but it doesn't want to play. Any suggestions?

Use your IMax. You'll have to get a couple of 5S connectors and som pinstrip to connect to the multipin connector.

 

[basssignal]

Use your IMax. You'll have to get a couple of 5S connectors and som pinstrip to connect to the multipin connector.

Yes, that's exactly what I've done. 1st set charged nicely to 20.4v. Measured with volt meter. Now charging the next side. Max stable charge current I could get out of the imax is 3A.

 

[WheezyRider]

Hello, yes sorry the output voltage of the power supply is 42v measured with a fluke meter.

I measured each cell (C) group
C1 3.91v
C2 3.90v
C3 3.82v
C4 3.82v
C5 3.82v
C6 3.80v
C7 3.93v
C8 3.55v
C9 3.7v
C10 4.0v

C8 was the lowest voltage. I managed yesterday to charge all groups to at least 4.1v using my imax b6, so something isn't quite right somewhere.

Looks badly out of balance. I would charge banks 8 and 9 individually to get them closer to the rest. Carefully connect a 1 amp 4.2V charger on bank 8, then bank 9.