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BQ24292I: Stopped charging when the current reached 128mA

Danilo A.
Mastermind 28560 points
Part Number: BQ24292I

Hi Team,

Can you please help us with our customer's inquiry below.

I have a board with this charger. Yesterday I charged battery to 100% (reported by fuel gauge) and I left it to discharge during the night.

The configuration of charger is as below:
charging voltage  = 4192mV
max_charging_current  = 2048mA
Termination_current = 128mA

Yesterday It charged correctly. So it started with CC mode and charged with 700mA, until the voltage rises to 4192. Then It switched to CV mode and keeps the voltage at this level when current was falling down.

When the current reached 128mA charger stopped charging.
Does it mean that the "charging current is below termination threshold and charge voltage is above recharge threshold" as mentioned at Section 8.3.3.1 of the datasheet?
Regards,

Danilo
  • +1
    TI__Mastermind 31090 points

    Hi Danilo, 

    Yes your understanding is correct. After the charger IC switches from CC mode to CV mode charge voltage will be regulated to 4192mV and charge current decays as battery gets closer to full charge. Charge will terminate when current reduces to the termination threshold (128mA in customers case) when the device is in CV mode. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    TI__Mastermind 28560 points

    Hi Garret,

    Our customer provided more details about the issue. Please see his email below.

    I will try to describe as precisely as I am able to:

    I made a board with charger bq24292i. On the same board I have a fuel gauge to monitor the state of a battery that I would like to charge. 

    The configuration of charger is as below: 
    charging_voltage = 4192mV
    max_charging_current = 2048mA
    termination_current = 128mA 

    Yesterday I charged my battery from 70% up to 100% and it was in sequence: 
    1. Charger was charging with constant current 600mA.  CC mode 
    2. When the voltage rises to 4192mV charger kept the voltage and the current slowly fall down. CV mode 
    3. When the current reached 128mA charger stopped charging (and fuel gauge reported 100%) 

    I disconnected the power source from the board and let it discharging the battery. 

    Today morning fuel gauge reported 92% and the battery voltage was 4070mV. 
    I connected the power source to charge it back to 100% but then charger start generating unlimited interrupts and charged the battery with 4140mV and only 50mA. Which is much below the termination_current and it should stop.  
    It did not matter how many times I disconnected and connected the power source. It looked like charger is in CC mode with only 50mA. 

    Later I disconnected the power source and the battery. I wait a minute to let the board discharge all capacitance and connect the battery and power source back.
    Now it charges with 4192mV and 480mA. So it is in CV mode. 

    Why I had to disconnect the battery from the device (and power source)? Is sounds like the charger bq24292i was in a wrong state or something. 

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Mastermind 31090 points

    Hi Danilo, 

    Without further information it is hard to determine a root cause for the unusual behavior the customer observed. It seems the device was either having some sort of fault or potentially having issues with the input source. We would need to see the status and fault register readings along with waveform captures of VBUS, VBAT, and SYS during the reported behavior.

    Danilo A. said:
    Why I had to disconnect the battery from the device (and power source)?

    Disconnecting both battery and input source allowed the device to do a full power cycle. Upon restart the device was able to correctly detect the battery voltage below the recharge threshold and perform a charge cycle. 

    Regards,

    Garrett