BQ27500 problems with environmental tests


We are having an issue with the BQ27500 after environmental testing, which includes shipping temperature extremes and moving quickly between them. The test goes from -20 to +60 degrees C. After the test the gas gauge reads zero state of charge until a reset command is sent. We do not want to reset the gauge if we can avoid it.

Could exceeding the limits of OT Chg and/or Suspend High Temp cause this behaviour? Any other ideas as to why the gas guage looses track of the battery?

Thanks and Best Regards, Tim Starr on behalf of DF@H

2 Replies

  • Genius 10845 points

    It's pretty normal that it would report 0% at -20degC since there probably is almost no _usable_ capacity in the battery at that low temperature due to the incredibly high internal impedance at low temperature.  However, the gauge should update the SOC after returning to normal temperatures.  On  newer firmware (not old ones like bq27500) it will automatically update if the temperature changes.  On older ones, though, it won't update (run a new simulation) until either a charge or discharge starts or until a "grid-point" during discharge is crossed.  Can you give more details about their test exact test sequence, please?

  • In reply to dMax:

    OK we tried moving the temperature limits beyond what we were testing to and this seems to have cleared the problem. We will keep on testing and let you know if we get any more failures, OK? Thanks!