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BQ40Z50-R1: It seams that BQ40Z50-R1 stop working accidentally; weird!

andrew liu
Prodigy 110 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

Hello:

     We are using BQ40Z50-R1 in the BMS board of our battery（100WH), the schematic attached below:

     Now we found 10pcs failed battery : no output voltage（P+/P- in the schematic), and no any response when pressing the key(SW1 in the schematic);  and the failed battery can't be charged;

     we open the case, measure the power and some key signal:

          The voltage between B4 and B0 is 13.26V, it means the battery pack/cell was normal;

          The voltage on PIN32 of BQ40Z50 is 12.76V, normal;  the 

          The voltage on PIN8 of U1 is 3.3V; normal;

          The voltage of V3 is 12.76V, normal;

          But the voltage between CA5 is 0V;

           the voltage of CHG is about 8.5V;  the voltage of DSG is about 0V;

          when pulling  PIN4 of U1(MCU_RESET) to low, it even didn't response....;

          In the view that the voltage between CA5 is 0V, seams that BQ40Z50-R1 stop working..., 

          5pcs of them(10pcs), I just touched the ground line and socket(picture3) with pliers(picture4), it got to be normal(  voltage between CA5 = 12.76V, voltage on CHG and DSG =24.5V, LED flashing when pressing the key);

          But to be honest, before supplier ship them to us, supplier has charged them to full, and performed all test , check fully; a

          so these battery was normal when supplier chip them; and after we received them, when didn't do any on it(no charging, no discharing),  just pressing the key to see if it was okay( but no any response);

          Do you have experienced this kind of issue？   what reason can cause BQ40Z50-R1 to stop working like it?

thanks;

       

8037.4S2P_V3.3 SCH.pdf

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                                              3                                                                                                   4

  • 0
    TI__Guru** 102605 points

    Hello Andrew,

    Were you able to communicate with the gauge during this period with bqStudio?

    When the BAT+ voltage is applied to the PACK+ it will wakeup the gauge from shutdown, I'm not sure what SW1 on the schematic is design to do, but it's connected only to the MCU it looks like.

    Can you pull the .gg file from after the gauge wakes up? The lifetime/black box data may be helpful to determine is something turned off the gauge. What did the bqStudio dashboard look like when it was powered up? Does it return to that state, or does it stay in normal operation after it begins operating normally again?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    Hello Wyatt:

            Great thanks for your answer;

            During this period(when bq40z50r1 stop working), the Battery Management Studio can't communicate with the gauge(bq40z50r1）；

            Before the CNY holiday, some failed battery that has been waked up by touching the ground line/socket, but after the CNY holiday, they returned to that state(stop working) again;

            And today, for these failed battery that returned to that state, I inserted our charger onto it---to pull P+ to 14.45V, applying BAT+ voltage to the PACK+, it got to be normal again; and then I read it with Battery Management Studio;  the .gg file from after the gauge wakes up as "recoveFromStopWorking.gg" in attached file;  what the dashboard look like as picture0/1/2 in attached file;

            please review, have you ever experienced this kind of issue before?  what is the root cause?

    thanks;

          recoveFromStopWorking.gg.csv

          

  • 0 in reply to andrew liu
    Prodigy 110 points

    Hello Wyatt:

          I have tried all batteries with this issue, they have been waked up before CNY holiday; but got back to that state after CNY,

         Attached is the .gg of two more batteries;

         Please review;

    thanks;BT2.rarBT3.rar  

  • 0 in reply to andrew liu
    Prodigy 110 points

    By the way, all these batteries was just placed there, no charging and discharging, then after CNY, they all return to that state(stop working)

    thanks;

  • 0 in reply to andrew liu
    TI__Guru** 102605 points

    Hello Andrew,

    The only way to wakeup the gauge from shutdown is by applying voltage greater than the startup on the PACK pin. As I mentioned I'm not sure what the SW1 is doing in the schematic since it's tied to the MCU. From your testing (applying charger voltage on PACK pins wakes up the gauge) it makes me think that the SW1 functionality you have is not applying voltage to the PACK pin to wakeup the gauge.

    Sometimes if there is a secondary protector on the battery pack that disables the GND line from the battery this can cause issues, I'm not sure if this is the case for this.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    Hello Wyatt:

            thanks for your answer;

            I figure that this issue has nothing to do with the SW1 functionality, as I said in last messages, before CNY holiday(2 weeks) these failed batteries were all waked up,  but they all got back to shutdown state after CNY holiday, and in the CNY holiday these failed batteries were just placed there, no pressing SW1, no charging, no discharging;  

            and yesterday these failed batteries have been waked up by inserting charger, then I placed them there(no pressing SW1, no charging, no discharging), and today( 24hours passed) they are still normal(not get back into shutdown state), so it seams this issue has something to do with the time that the batteries was placed (idle)...;

            you said" Sometimes if there is a secondary protector on the battery pack that disables the GND line from the battery this can cause issues, I'm not sure if this is the case for this",

            What is the secondary proector on the battery pack?   

            Removing the GND line from the battery can cause this issue?  but when this issue happened in production line and the CNY holiday, the GND line was always on Battery, nobody removed it;

    thanks;

            

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    hello wyatt:

          As you said, disabling GND line from batteries can cause issue, so I also doubt that this issue has something to do with the ground or ground bounce;

          As the appearance discribed by me in the first message, when touched the ground line with  pliers, some failed batteries got to be normal; because it has ground bounce on ground when touched it with  pliers;

          Below picture is the PCB layout of our BMS board, the white highlight net is Ground, because the PCB is just two layer, so we have to route the ground trace and signal on the same layer, so the ground plane was not intergral, and we just tied the VSS pin of BQ40Z50 to the ground plane with two very narrow trace...;

          To be honest, I have measured the ground with oscillograph, when touching the ground with metal stuff( hold by hand), it did has ground bounce;

          And did you install PADS on your PC？ maybe I can share the schematic and PCB with you to check....

    thanks;

  • 0 in reply to andrew liu
    TI__Guru** 102605 points

    Hello Andrew,

    If you share the schematic and layout I can try to take a look.

    I think I've mentioned before on this thread (or the other thread) that this is not an ideal GND connection and it may be contributing to this issue.

    What are the voltages on the pack after wakeup? If the voltages degrade low enough during idle to cause shutdown of the pack you will need to apply a charger to enable the gauge again.

    I was mentioning the secondary protections because some batteries come with internal protectors that can disrupt the gauge if they activate. If your battery has an internal protector that is triggered the gauge will be disrupted.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    Hello Wyatt:

           Great thanks for your help;

           Could you share me your Mailbox? so that I can share the schematic and layout to you,

           open the PCB with PADS....

    thanks

  • 0 in reply to andrew liu
    TI__Guru** 102605 points

    Hello Andrew,

    I sent you a friend request. PM me.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    hello Wyatt:

       thanks for your help;

       How could I share the schematic and PCB with you?  by the friend request？

    thanks;

  • 0 in reply to andrew liu
    TI__Guru** 102605 points

    Hello Andrew,

    Send me a private message with the files.

    Sincerely,

    Wyatt Keller