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BQ24192: Battery not able to recover/not charging after Overdischarge

mrausol
Intellectual 690 points
Part Number: BQ24192
Other Parts Discussed in Thread: BQ27531-G1, , BQ27531EVM, BQSTUDIO

Hi,

We are using BQ24192 charger IC with BQ27531-G1 Fuel Gauge IC in our system.

During test, an overdischarged battery (0V because protection was triggered) connected to our System cannot recover when recharged via USB. Shouldn't the charger IC be able to handle this scenario? Which registers are needed to be configured to enable the charger to recover dead batteries? Any thoughts? 

CE is always pulled low in our system. The battery terminat voltage spec is 2.5V.

I do however notice that charging the dead batt using the BQ27531EVM demo board would wake up the battery.

Thanks,

  • 0
    TI__Expert 8230 points

    Hello,

    When a deeply discharged battery is connected to the bq24192, VBAT <2V, the device applies a trickle charge of approximately ~100mA to attempt to wake up the protection FETs and begin charging the battery. This is done automatically, assuming charging is enabled and the charger conditions are correct (input current limit, no faults on the charger, etc.).

    During your testing, is your load current present when attempting to charge the dead battery? If so, what's the load current?

    Can you also confirm what's the input current limit of the 192 when the USB is plugged in?

    You also mentioned it works on the EVM, what's different between your board and the EVM?

  • 0 in reply to Fernando Lopez
    Intellectual 690 points

    Hi,

    Charging enabled  - you mean the CE pin is low and Reg 01 [5:4] is 01? Note that we are using the Fuel Gauge. Does the Fuel gauge control the charger IC register value at this scenario (vbat<2v)? Or this register is set to the Charger drfault value which is 01?

    Our PSEL and OTG are pulled high with the PSEL to VBUS and OTG to Sys, so the inlim of the charger should be set to 500mA. The Fuel Gauge inlim is also set to 500mA. Our system eats up around 250mA.

    When I attempt to charge the battery, my reading is 0A.

  • 0 in reply to mrausol
    TI__Expert 8230 points

    Hello,

    The trickle charge current setting of 100mA is a default value and doesn't need to be set up by either the charger or gauge. 

    I recommend verifying the following:

    • Actual input current limit setting via I2C, make sure the charger is set to 500mA.
    • Verify the state of USB_IN_DEF bit on the gauge. By default this bit is set to 0, which corresponds to a 100mA input current limit when an USB host is detected as the input.
    • Verify the status register of the 192, REG08, and the fault register, REG09. I'm looking to see if any faults tripped or if the device is in DPM (either VINDPM or INDPM).
    • Repeat the test with a sourcemeter acting like the battery to rule out the protection FETs not turning on as the issue.
    • Verify of the charger if the BATFET is not turned off, REG07[5]. This wouldn't allow charge current to flow.

  • 0 in reply to Fernando Lopez
    Intellectual 690 points
    Thank you for your recommendations. I will let you know once I tried those.

    If the battery is dead, how will I verify those settings? I usually view it via BQStudio but when the battery is below 2.5V the BQstudio wouldn't recognize the system because the Fuel Gauge would be reset. Do you mean to verify those registers before the battery dies?
  • 0 in reply to mrausol
    TI__Expert 8230 points
    Hello,

    You can verify the state of the charger before the fuel gauge turns off or if VBUS is applied, you should be able to communicate with the charger without battery if the I2C pullups are powered externally.

    If the charger has VBUS applied and no battery connected, you should see the STAT pin flicker since it will be toggling between Fast Charging and Charge Done states.