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BQ79616-Q1: Facing issues with BQ79616 communication and battery cell measurment.

Rakesh Gadde
Prodigy 20 points
Part Number: BQ79616-Q1
Other Parts Discussed in Thread: BQ79616,

Hello TI team,

 

Myself Rakesh developing a Complex Device Driver (CDD) for BQ79616 ASIC for an Battery Management System project.

I am facing few issues listed below while testing with BQ79616 devices, request you to look into it and provide me a quick feedback.

 

  • Accuracy of cell voltage measurement:

We observed that only VC0 pin is measuring accurate battery voltage where as other pins(VCx) are reading/measuring reduced battery voltage, difference is close to 1 volt.       

 

  • Comm diag errors:

 BQ79616 devices are continuously reporting SOF and Daisy chain crc error even with single read operation@10ms,

 

  • Fluctuation of VC pin measured voltages when CBFet open circuit diagnosis is performed.

  VC pin measured voltages are fluctuating(10%) whenever CBfet open circuit diagnosis are performed.

 

  • When cell balancing is active and if CB open circuit diagnosis is performed then it was observed devices are not responding. Do we need to pause cell balancing even for CBfet open circuit diagnosis?

 

 

I request you to provide a demo/sample code wherever possible which will accelerate/help our development activities.

Also guide us if we missed any preconditions or configurations.

  • 0
    TI__Prodigy 160 points

    Good morning Rakesh,

    Thank you for reaching out. In order to debug your issues, we need more information on your setup. Are you using the BQ79616-Q1 EVM?

    If you have access to the Mysecure folder, there exist documents with design recommendations as well as Sample code within the datasheet. Should you not have access, please submit the request via the main device page. I have attached a picture for navigation purposes.

    Regarding cell balancing, I recommend that you pause cell balancing when performing CBFET open circuit diagnosis. When performing CB, there will be an IR drop across the CBFET resistors giving rise to improper voltage readings in your diagnosis.

    Please provide the information/ schematic in order for us to assist with your queries.

    Best,

    Christian

  • 0 in reply to Christian Ammon
    TI__Genius 17440 points

    Hi Rakesh,

    I apologize, but I had to delete your reply. Please do not post the long version of the datasheet to the public forum. The datasheet is shared under NDA only. 

    If you'd prefer, please feel free to reach out to your FAE so we may discuss NDA restricted topics via email. Otherwise you may repost your questions and we will answer as much as we can publicly.

    Best Regards,

    Kristin Jones

  • 0 in reply to Kristin Jones93
    Prodigy 20 points

    Hi Kristin,

    Sorry i posted data sheet for reference, was not aware of TI policies.

    Can you provide me Email reference to discuss about datasheet versioning and as of now I am using Draft V1.18.

    I am facing major issue with communication to stack devices when ever CBFET diagnosis (verification and open ckt ) are getting executed.

    For both diagnosis it was ensured no cell balancing even then probably after 4-5 cycles of diagnosis execution BQ79616 devices are not  responding.

    As of now for testing purpose we enabled to open(VC/CB), Temp/cell measurment verification , CBFet verification every 250ms.

    If i disable CBfet open circuit and verification diagnosis then above problem was not seen at all.

  • 0 in reply to Rakesh Gadde
    TI__Prodigy 160 points

    Hi Rakesh,

    You will be able to request the updated data sheet along with other reference documents using the BQ79616-Q1 product page and following the 'request now' navigation as illustrated in my previous response. In order to properly dissect your situation, we require more information on your setup. Are you using the BQ796161-Q1 EVM?

    Regards,

    Christian 

  • 0 in reply to Christian Ammon
    Prodigy 20 points

    Dear Christian,

    Yes we are using BQ79616-Q1.

    I am referring SLUSE81 – AUGUST 2020 draft datasheet of same ASIC.

    As now we are facing issue with CBFET diagnosis.

    1) Stack is not responding after 5-10 cycles of CBFET diagnosis.

    2) Voltage is slightly fluctuating(5-10%) when ever software perform CBFET diagonsis.

    Any probes/pointers we need to look into?

    Regards,

    Rakesh Gadde.

  • 0 in reply to Rakesh Gadde
    TI__Prodigy 160 points

    Hi Rakesh,

    Thank you for your response. Does this issue only occur when using the CBFET diagnosis or does it also occur when you turn on Cell Balancing? If yes for both, then it may be a setup issue causing current limiting and therefore, too much current loss in communication. 

    May you also explain what is meant by a 'fluctuating' voltage? Is it 5-10% of the peak voltage or the mean voltage?

    It will be helpful if you can share your schematic along with applied voltages so that we can determine whether it is a hardware issue. If you prefer, you can send me a private message and we can discuss further or refer to your designated FAE (Field Applications Engineer).

    Regards,

    Christian