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BQ40Z50-R1: [FD] [FC] protection flags

Mariano
Intellectual 370 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ24600

hi, we are developing a QSBMS software driver for a batteries packs with a BQ40Z50-R1 and we have some questions:

when battery is charging, if [FC] flag is set , is this a failure condition? or always  this flag is set when you charge the battery?, can we use this flag to stop charging (charger is BQ24600 - NO SMBus level 3 charger)? 

when battery is discharging, if [FD] flag is set, is this a failure condition? or always  this flag is set when you discharge the battery?, i mean is normal use case?, we must wait for [FD] flag in order to change to other battery?.

We have a battery that after set [FD] flag couldn´t been charge but after many tries of the charger finally charge was allowed, why could it be?

thanks.

  • 0
    TI__Mastermind 42535 points
    Your question has been assigned to an AE, you will receive a reply in 1 week or less.
  • 0 in reply to Batt
    TI__Mastermind 42535 points
    FC and FD are flags indicating full charge or full discharged state. They will be set depending on the voltage conditions of your cell and also when your protections like overcharge or overvoltage have been set. Please refer to the TRM for further details.
  • 0 in reply to Batt
    Intellectual 370 points
    hi, thanks you for reply,

    * i understand the conditions that set this flags, but isn´t clear for me when unconnect a battery from power path, is ok to wait [FD] flag set ? or i have to use other condition like charge level ?.

    * We have a battery that after set [FD] flag couldn´t been charge but after many tries of the charger finally charge was allowed, why could it be?

    thanks.
  • 0 in reply to Mariano
    TI__Expert 6575 points
    Hi,
    In general, you can use RSOC or [FD] to stop the discharge by the host. This should not cause any issues.
    The issue where you noticed the pack unable to charge after a full discharge i.e. [FD] was set, it should not be due to the [FD] bit being set. You may have to check the other status bits, especially the Safety Alert/Status to see fi there was a protection event that is preventing charging.
    It is also possible that the gauge is in a Pre-Charge voltage range and is disabling the charge FET and enabling the Pre-Charge FET, so if you are not using a separate pre-charge path, you may need to set the [PCHG_COMM] bit in your "Fet Options" setting.
    Regards,
    Swami