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BQ25703A: BQ25703A can't charge

user6075775
Prodigy 40 points
Part Number: BQ25703A

Dear Specialists,

            BQ25703A can't charge 4S battery,L5 without voltage,but zhe Vsys have the 12.24V.What is wrong of my schematic diagram?

        

I appreciate your great help.

Best regards,

Ji

  • 0
    TI__Expert 3320 points

    Hi there:
        

         The 12.24V you see on VSYS is the default minimum system voltage, it is normal when you have a depleted battery voltage smaller than 12.24V.

         Please make sure your REG 03/02H are written correct fast charge current and REG05/04H are written correct maximum charge voltage for your 4S application. After you configure these parameters correctly, when battery voltage is below 12.24V, the charge current should be clamped at 384mA. 

        One more thing you need to double check is REG21/20H status bits to see if there is any fault or unusual status reported. 

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    Prodigy 40 points

    Hi，Shishuo

       Now the minimum system voltage is 15.6V,and the charge current is seting in 2A,but  Actually the charge current is19V 350mA,A minute later it becomes 0mA.What Settings should I change?

    Thank You!

  • 0 in reply to user6075775
    TI__Expert 3320 points

    Hi There:
        

        Thanks for providing detail results.

        Are you configuring in 4S setting? I find that the max charge voltage setting is 16.8V for 4S application. Battery voltage 19V is too high for 4S. The minimum system voltage 15.6V is only effective when battery voltage is lower than 15.6V.

        If you reduce battery voltage to 16V, the charge current should be 2A. The charge terminate because of watch dog timer.

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    Prodigy 40 points

    HI Shishuo:

       19V is the Input Voltage not the Charge Voltage.Should I set other registers?

    Thank You!

          

  • 0 in reply to user6075775
    TI__Expert 3320 points

    Hi There:
         

          I think your battery voltage should be lower than minimum system voltage 12.3V.  Therefore the charging current is clamped at 384mA. And the charge stops because of the watch dog timer trigger. Please follow below steps to achieve 2A charging:

        

          1, Increase battery voltage to be higher than 12.3V but lower than 16.8V then the charge current should be able to be regulated at 2A.

          2, Configure REG01X[6:5]=00 to disable Watch dog timer. Then the charging should not terminate by itself.

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    Prodigy 40 points

    Hi Shishuo Zhao ,thank you very much!