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bq27500 current measurement with charger of bq24075

andy lee
Prodigy 20 points
Other Parts Discussed in Thread: BQ24075, BQ27500

Hi,

I have a platform that uses bq24075 to charge the battery, and uses the bq27500 for battery gauging,

here is my experiment data for reading the AverageCurrent() form bq27500:

CASE    |  bq24075 state                                    |   Flags() for bq27500 | AverageCurrent

CASE1 |  SYSOFF=High, with usb power      |   0x0138 (charging)    |  0

CASE2 |  SYSOFF=Low, with usb power       |   0x0138(charging)     |  482

CASE3 |  SYSOFF=Low, without usb power |   0x0139(discharging)| -70

My question is:

1.why case1's averageCurrent is 0 in charging mode?

2.does the averageCurrent in case2 mean output current for the battery to platform?

3. why case3's avargeCurrent is "-70"? 

Please help, thanks!

  • 0
    TI__Genius 14985 points

    The CHG bit does not mean that actual charge current is flowing.  It only means the temperature is normal so charging could be allowed.  Of course it doesn't control your charger.  It just sets a flag.

    The DSG bit does mean that discharge current is flowing and it is greater than your dataflash parameter (Dsg Current Threshold).

    To answer your questions:

    1. Current is 0.  It is not in charging mode.  CHG is set because temperature is normal.

    2. If AverageCurrent() is positive then it means current is flowing from your charger to the battery.

    3. If AverageCurrent() is negative then it means your battery is discharging.  Current is flowing from the battery to your system.

  • 0 in reply to dMax
    Prodigy 20 points

     I misunderstand the meaning of DSG bit, thanks a lot!!