BQ76940: BQ76940 to design the 15S BMS. I have one problem.cell 10,11,12,13 and 14 cell reading zero value

Hi Davayani,

This is not a normal behavior, so I am not sure what would cause the issue you are seeing. There are a number of important connections in the schematic that can be a little tricky. I recommend going through this video to see if it helps reveal anything: https://training.ti.com/how-create-schematic-bq76920-bq76930-and-bq76940

After going through the video, let me know if you are still not able to find the issue.

Best regards,

Matt

Dear Matt,

Thanks for feedback.

We have gone through video and verified all the connection as per guideline.

We have connected battery pack with 12Cell configuration and now we are able to read cell voltage as expected except cell 11,12 and 13 - we are reading 0.7V instead of 3.3V. rest of all cell voltage we are able to read properly using micro controller i2C line.

We have not turned on cell balancing yet. just we are reading cell voltage.

Please let me know what will be the issue,

We wanted to start production once this issue is resolved, we are really struggling to resolve this issue, 

Thanks,

Devayani

Hi Davayani,

If you can send your schematic, I can check it for connection issues. As I said, this is not normal behavior for the device, so there is likely an issue causing the upper cell group to not report voltages correctly.

Best regards,

Matt

Schematic Page-1.pdfSchematic Page-2.pdf

Dear Matt,

Please find attached schematic for your review.

after review can you conclude like area of problem . Hardware side or software side any improvements etc..

Thanks,

Devayani Bodar

Hi Devayani,

In your schematic it does not look like you are connecting unused cells as recommended by the datasheet. Please see Table 26 in the datasheet for how to connect a 12-cell application. 

Regards,

Matt