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BQ24123: Charge Complete

mike f
Prodigy 100 points
Part Number: BQ24123
Other Parts Discussed in Thread: BQ24125

Hello, we are in pre-production with a charger that uses the BQ24123 or BQ24125 (we have two variants of our design to address possible chip shortages).

We have been testing our charger for over a year with no issues, but this week a tester reported that when they installed a battery with low voltage (~7.3V), the STAT2 LED (charge complete) turned on immediately and the battery never charged. Upon reinstalling the battery, the system operated normally.

Our design uses three pogo pins, +, -, and NTC. The system is designed so that the NTC pin makes contact last (ideally).

Is there any explanation for how the BQ2412x could have mistakenly gotten into the charger complete state?

  • 0
    TI__Mastermind 29822 points

    Hi Mike, 

    Thank you for reaching out!

    What is the battery cell count of your design? What is the maximum battery voltage?

    mike f said:
    Upon reinstalling the battery, the system operated normally.

    Was the battery reinstalled immediately after? 

    Best Regards, 

    Aya Khedr 

  • 0 in reply to Aya Khedr
    TI__Guru**** 165766 points

    Hi Mike,

    I have not seen this issue in the past.  Is it easy to recreate?  If so, can you get a  scope capture of BAT and IIN when the battery is plugged in?  You might want to add a small capacitor at BAT to help prevent overvoltage spikes at hot plug of the battery.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 100 points

    Thank you for your response and the suggestion. 

    This fault was reported by a test user who was using a charger with a different charge IC that we have since moved away from. I apologize for the mistake!