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Original question:

BQ40Z80: It is required that the discharge MOSFET is turned off during charging. Can this be achieved?

BQ40Z80: bq40z80 7S Cannot exit shutdown mode when connected to the charger

jmyang
Expert 1186 points
Part Number: BQ40Z80

TI experts,

    we are now using bq40z80 to do a 7S  battery pack project, and we have a troublesome problem.

   When the battery voltage is 2V*7S=14V, the charger can be used to wake up and generate charging current, and the communication is normal.

  When the battery voltage is 2.5V*7S=17.5V, bq40z80 cannot exit the shutdown mode, nor can it generate charging current. The register interface flashes SDV and CUV and others repeatedly, But CHG and DSG are always green.bq40z80 7S Cannot exit shutdown mode when connected to the charger.zip

  • 0
    TI__Mastermind 19195 points

    Hi Jmyang,

    In your logs the voltage goes from 25V to 17.5V instantly can you explain this?

    Thanks,

  • 0 in reply to Nick Brylski
    Expert 1186 points

    Hi Brylski,

         We use the power simulation battery to test. Of course, our power supply can be programmed. In other words, we can set 25V, 17.5V, and other voltages.

  • 0 in reply to jmyang
    TI__Mastermind 19195 points

    Hi Jmyang,

    So you are not testing with real batteries? 

    Our device is intended to work with real battery, not battery simulator.

    Thanks,

  • 0 in reply to Nick Brylski
    Expert 1186 points

    Hi Brylski ,

          As shown in the attached data, we tried to use a battery pack for testing. When the 7S3P battery is at a shutdown voltage of 2.5V*7, it still cannot be charged and activated.

         From the data, it seems that bq40z80 reads an incorrect temperature & voltage value at the moment of charging and waking up.

         What's strange is that after programming the 7S Srec file to the 5S bq40z80-BMS, and then changing the Srec to 5S, everything is normal.

        However, if I program the Srec of 5S to the BMS of 7S, and then modify the Srec to 7S, then there will be a situation where 2.5V*7 cannot be charged and waked up.

       Is this situation related to the 12th pin (VC7SE)?  How should I solve it?

       

     

                   (Test with battery)bq40z80 7S Cannot exit shutdown mode when connected to the charger-2020-12-23.zip

  • 0 in reply to jmyang
    TI__Mastermind 19195 points

    Hi Jmyan,

    The image I attached in my last post is not normal battery behavior (battery voltage should not be jumping up and down). Can you try to replicate this issue with real cells?

    This part does not support 7s anymore. Sorry

    Best regards,

  • 0 in reply to Nick Brylski
    Expert 1186 points

    Hi Brylski ,

               After you mentioned not to use an analog power supply for the first time; I changed it to a 7S3P battery for the second time, and used bq40z80 for testing.

     

                The data I uploaded for the second time was tested with real batteries. You see the fluctuating voltage of the battery because the bq40z80 cannot wake up when the charger is connected, and then enters the shutdown (cannot log the voltage), this situation keeps on recurring, so the voltage you see is beating, the actual battery There is no jump in voltage.

                  Are you saying that the bq40z80 chip cannot support the use of 7S  batteries? I found that the bq40z80 technical reference file can be configured as 7S.

                

  • 0 in reply to jmyang
    TI__Mastermind 19195 points

    Hi Jmyang,

    Bq40z80 no longer supports 7s. Some discussion here: 

    Best regards.