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Smart Battery Charger reading simulated battery

George Mortimer
Expert 1205 points
Other Parts Discussed in Thread: BQ20Z90, BQ29330

I am implementing a Smart Battery Charger reading data from the SMBus in order to charge a bq20Z90/bq29330-equipped battery.  In order to test the performance of the charger, I am using a production battery PCBA with a power supply and balancing resistors to provide a simulated battery for the charger.  My problem is that one of the parameters the charger reads from the battery is Relative State of Charge (RSOC).  I cannot write to the SMBus from the tester firmware in order to get the battery simulator to communicate an appropriate RSOC (or Remaining Capacity) to the charger under test.  Does anybody have any suggestions on how I can get the charger to read the "correct" RSOC corresponding to the supplied test voltages?

  • 0
    TI__Guru* 76230 points

    the  gauge broad casts charging voltages and currents as well as alarms to the smart charger. RSOC is not one of them. The charger will have to read this from gauge. You just need to make sure the charger has that ability.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Expert 1205 points

    This I know.  The problem is not the charger reading RSOC (which it does), the problem is trying to load a value from the tester PIC into the battery simulator which will present an appropriate value to the charger when it reads the battery simulator's SMBus data values.

    Currently the tester sets the voltage of the battery simulator at 3 different levels (8V, 10V, and 12.6V), corresponding to 0% RSOC, or pre-charge; 50% RSOC, or fast-charge; and 95% RSOC, or maintenance-charge. With the current tester program, the charger reads the battery voltage and the RSOC.  After a period of use, the battery simulator calculates RSOC (I think) based on the current being supplied by the charger under test, and eventually sets the RSOC to a "fully charged" state, which interferes with the charger firmware's state calculation subroutine.  I can run a system reset on the battery simulator, which sets the RSOC back to zero.  Unfortunately when I do this, the battery simulator will not get back to a higher level of RSOC until a long time has passed (especially if the charger under test is only applying pre-charge current to the battery simulator.

    Again, is there some way to spoof the bq29330 into thinking the RSOC (or remaining capacity) has achieved the higher levels, then reset them for testing the next charger?