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BQ25798: BQ25798 Battery Present Check and not fully charging

Matthew Reed
Prodigy 20 points
Part Number: BQ25798

Tool/software:

Hi There,

I'm following the datasheet where it states "the host must periodically disable charge, force IBAT discharge current and then read the ADC BAT pin voltage" I'm doing this every 30 sec only if we are not charging and determine if we should enable or disable the charger. This works fine, but it seems every time we do this the charge cycle gets restarted? 

Every 5min I also do a rough battery voltage check where I set FORCE_IBATDIS for 300ms and then take ADC reading and then reset FORCE_IBATDIS back to 0. Does setting FORCE_IBATDIS also restart the charging cycle? 

I have 3s LiIon 18650 and have VREG set to 12.6V but at 11.9V the charging goes from CC to CV and then terminates at around 12.2V ( termination current is set to 120ma ) for some reason the battery never reaches 12.6V. We do get to the top off timer which I have set at 30min... charges at about 80ma. The issue is we never reach the end of the charge... stayed in top off state for > 2 hours which indicates the charge cycle is be restarted. 

  • 0
    TI__Guru**** 166576 points

    Hi Matthew,

    The charge cycle is restarted when the /CE pin or CE bit disables then re-enables charge.  FORCE_IBATDIS does not restart charge cycle.  If the battery voltage measured at BATP pin drops below the VRCH threshold, charge is also restarted.  Charge termination is disabled if the charger is in DPM, TREG or TS WARM/COOL.  The issue could be PFM switching noise at light load make interfering with the charge current measurement.  If  you disable PFM, does the charger terminate?

    Regards,

    Jeff