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BQ28Z610-R1: BQ28Z610-R1 capacity balance issue !

user3778223
Prodigy 10 points
Part Number: BQ28Z610-R1
Other Parts Discussed in Thread: BQ40Z50, BQ28Z610,

Tool/software:

Hello!
Currently, we are using BQ28Z610DRZR-R1 on the BMS of our 2S1P lithium iron phosphate battery. During the usage, we have found that your chip adopts the capacity difference balancing method. However, in actual use, BQ28Z610DRZR-R1 may misjudge the capacity difference, which leads to an increasingly larger voltage difference between the two battery cells. During the charging process, this may cause one cell to reach the overvoltage protection threshold prematurely,  making the battery never reach 100% SOC conditions.

Therefore, we hope to adopt the voltage balancing method. Previously, we also discovered the same drawback of using capacity difference for balancing on your BQ40Z50 chip. Later, you added the battery voltage balancing function in the BQ40Z50-R4 version. We solved the customer's problem by updating the program of BQ40Z50-R4. This time, we also hope that you can add the voltage balancing option in the BQ28Z610DRZR-R1 chip to facilitate us in resolving the problems we are currently encountering with the customers. Additionally, adding the voltage balancing option also increases the flexibility of your chip application and gives the customer the opportunity to make their own choice.

Thanks

Paul

  • 0
    TI__Mastermind 26401 points

    Hello Paul, 

    Thank you for your feedback, I will make note to the team. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 10 points

    Hello Jonny,

    Thank you for your reply! Our project is currently underway and we hope to resolve this issue as soon as possible.

    Best Regards

    Paul

  • 0 in reply to user3778223
    TI__Mastermind 31740 points

    Hello Paul,

    We have received your update and due to a back log of the queue we ask for some more time until we send a response.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 10 points

    Thank you very much for your reply. Currently, we are unable to further advance this project. If we were to produce it in large quantities, we are concerned that the risks would be relatively high. Therefore, the client is also very anxious, and we are also very anxious to resolve the client's problem as soon as possible. At present, we don't have any optimized solutions, so we can only hope that your company will add an option for voltage balancing to address the application of this product.

  • 0 in reply to user3778223
    TI__Mastermind 26401 points

    Hello, 

    Perhaps I misread your first comment. It is not necessarily clear what your question is above. Can you please elaborate your question? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 10 points

    Hello Jonny, 

    For first comment, you can see the detail from related picture, cell 1 voltage was only 3407mV, cell 2 voltage was 3713mV, but cell 1 Bat Time was 1838S, I have confirmed current balance channel by oscilatescope is cell1 channel when we charged the battery by charger. How to explain this balance issue? so we hope that your company can add an option of voltage balancing to solve the application of this product. 

    In fact, the first comment and the second comment have the same meaning. However, BQ40Z50, you have already added the voltage balancing option in the REV4 version. You can also learn why the voltage balancing option was added in the REV4 version for BQ40Z50. A similar problem was encountered on the BQ40Z50 REV2 version a few years ago. Later, this problem was solved by upgrading to the REV4 version through the upgrade program. There are discussion posts about this issue on the forum. It's something from a long time ago. If you're interested, you can search for it. But one of my projects that is about to go into mass production also encountered this problem. I need your help to solve it quickly so that the project can proceed smoothly.

    Thanks

    Best Regards

    Paul

  • 0 in reply to Jonny
    Prodigy 10 points

    Hi Jonny,

    Any feedback from you? When is your team planning to take a look at this issue that I consider to be quite important?

    I'm really looking forward to your prompt reply!

    Best Regards

    Paul

  • 0 in reply to Alan Frias
    Prodigy 10 points

    Hello Alan,

    Any feedback now?

  • 0 in reply to user3778223
    TI__Mastermind 26401 points

    Hello, 

    The BQ28Z610 does not offer a purely voltage based cell balancing. The exact nature of the cell balancing algorithm that is available within the BQ28Z610 is outlined in detail in Chapter 7 Cell Balancing in the device TRM. I believe the behavior you described can be explained from the cell balancing operation outlined in the aforementioned documentation. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 10 points

    Hello Jonny,

    I have read the technical documentation section on balancing at least five times. From the pictures, we can see that CELL1 = 3407mV and CELL2 = 3713mV. Could you please explain why CELL1 is in the balanced state but not CELL2? Also, have you confirmed with your team the reason why the BQ40Z50 REV4 has added the voltage balancing option?Additionally, could you please confirm if the balancing method for BQ40Z50 REV2 is similar to that of the current BQ28Z610-R1?

    Best Regards

    Paul