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bq24123 charge status outputs

George Mortimer
Expert 1205 points
Other Parts Discussed in Thread: BQ24123, BQ20Z655-R1

Gentlemen:

I have a situation using the bq24123 charger to charge two Li-Ion cells in series.  When I first started charging the pack, the charger behaved normally, the In-Progress status light came on, and the gas gauge (bq20z655) indicated that the pack was charging.  When I came back to the pack after lunch, it should have been signaling between 50% and 75% charge, and either still have been in CC charge mode or have just switched over to CV mode.

What I found was that the pack was no longer drawing current, and instead of signaling fully charged (Complete indicator on), there appeared to be no activity.  I checked the battery voltage, and it was nowhere near fully charged.  Examination of the pack revealed that a jumper which I had soldered to the board to correct an artwork error had come loose from the pad.  I replaced the jumper, but still got no charging of the cells.  What I did see was the In-Progress (STAT1) output flashing at approximately 1 Hz.

What does this flashing indicate?  I cannot see this type of indication called out in the data sheet.

  • 0
    Expert 1205 points

    I think I found the answer myself.  Apparently the slow flash of the status light indicates a failure in the charge path.  What I had happening was that an intermittent connection in the charging circuit was causing the charge path to open up, and the battery protection circuit (bq20z655-R1) was shutting down the CHG FET as a result and not allowing the fault to clear after the failure was removed.  Once the intermittent was repaired and the protection circuit was reset, the charger returned to normal operation.