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BQ25713: Battery presence detection

Elder Costa17
Expert 2825 points
Part Number: BQ25713
Other Parts Discussed in Thread: BQSTUDIO

Is there a way to determine if the battery is present, before trying to apply a charging current to it? I could not find a flag for it.

One way I divised was checking if VBAT has a reasonable value. Vith no battery, register 0x2C is zeroed (inspecting with bqStudio), so I could use it. Another way would be simply trying to set a low charging current and see if the output voltage rises to the value programmed in the Charge Voltage Register. Is there a more straightforward way?

I thought of using the BATREMOVAL flag in Prochot Status Register. But it does not change when I connect/disconnect the battery. It is not clear to me how it works or if it can be used for battery detection.

  • 0 in reply to Elder Costa17
    TI__Mastermind 24075 points

    Hi Elder,

      You can use the BATREMOVAL flag, however it is set based off of CELL_BATPRESZ pin. CELL_BATPRESZ going low automatically sets the charge current to 0A, so you can detect battery presence using external logic, and use a FET to pull this pin low when no battery is connected. Note that the BATREMOVAL flag is good if making use of PROCHOT, otherwise pulling this pin low automatically sets charge current to 0A, so no further action would need to be taken to disable charge current.

  • 0 in reply to Kedar Manishankar
    Expert 2825 points

    Hello, Kedar.

    Unfortunately, this would require a hardware change. This is not an option, unfortunately. Moreover, I used the CELL_BATPRESZ pin to force the output to 12.5V (four cells) for a fail safe mode in my system and that must work even if a battery is not present.

    Would you have a more "soft" approach? One challenge I have assessing the cause of a low voltage on VBAT, whether due to a deeply discharged battery of no battery at all.

  • 0 in reply to Elder Costa17
    TI__Mastermind 24075 points

    Hi Elder,

       Unfortunately this part is not able to do battery absent detection through just software. The CELL_BATPRESZ pin is used for such a case, which is why pulling it low automatically disables charge, and why the BATREMOVAL is based off of this pin. With regards to low battery voltage, the auto_wakeup feature is for this case, so it can safely charge a deeply discharged battery.

    When this autowakeupEN bit is HIGH, if the battery is below minimum system voltage (REG0x0D/0C()), the device will automatically enable 128 mA charging current for 30 mins. When the battery is charged up above minimum system voltage, charge will terminate and the bit is reset to LOW.