JBD BMS Low Voltage Issues

[jkelly662]

EDIT: SOLVED. Please read my reply below.

Hi everyone,

This issue has me stumped after purchasing multiple JBD BMS and testing them with my 8S1P LF280K battery. Each JBD BMS I've tried reads low voltages on the first two cells, both in the Windows and Android app, which is strange. When I measure the cell voltages directly with my multimeter I measure the correct voltages. I have also wired a DC supply to the first channel (BC1) of the BMS, set it to 3.2VDC, but the the BMS still reads low around 0.5VDC. I have tried different ring terminals on the wires and different versions of the apps.

Summary of Problem:
1. Multiple brand new BMS read low voltages on the first two cells of my LF280K 8S1P battery (around 0.5VDc and 2.6VDC)

Things I've tried:
1. Two different JBD BMS from two different suppliers
2. Different versions of the Windows App
3. Different versions of the Android app
4. Re-terminating the ring lugs on the first two cells
5. Measuring the cells directly with a multimeter to confirm correct voltages
6. Wiring a DC supply to the first channel of the BMS to supply a known 3.2VDC.

Things I haven't tried (that I can think of):
1. Re-install the USB driver on my laptop, but the Android app reads the same low voltages which tells me it probably isn't the laptop driver
2. Tried a different laptop, but the Android app reads the same low voltages which tells me it probably isn't the laptop

Does anyone have any ideas here? Why would the (multiple) BMS read low voltages but I'm measuring correct voltages directly?

Hoping someone has some experience they can share.

Thanks,

 

[jkelly662]

Well I feel pretty dumb now. I had not been wiring the low side of the FETs to the battery, which is apparently required to properly sense cell voltages. I had incorrectly assumed that connection was strictly the FET low-side which does not appear to be the case. Upon connecting it to the low side of my battery the first two cells read properly.