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BQ34Z100-G1: VOK doesn't set 1 when charging start

luo neo
Prodigy 210 points
Part Number: BQ34Z100-G1

Hi TI team

The TI document says "VOK: This bit tracks when the gauge measures the battery's voltage. This bit is normally set when charging/discharging starts, and is cleared when discharging stops. The gauge has detected that the battery voltage has stabilized, and has taken the OCV measurement. It is a good way to track when OCV measurements occur.

I find that in some case(randomly),  the VOK will not set 1 when charging start. This will cause Qmax will not be updated after full charge. Could you tell which condition will cause VOK doesn't set 1?

Thanks,

Neo

  • 0
    TI__Genius 11535 points

    Hi Neo,

    If VOK is never set, then this means that the learning cycle did not start with an empty battery, it did not fully charge the battery, or the charge cycle was disturbed in some way. Also make sure IT_ENABLE is set.

    Best,

    Jessica

  • 0 in reply to Jessica H.
    Prodigy 210 points

    Hi Jessica

    Thanks for your reply.

    I am sure that

    1. battery has been charge to full(FC = 1), and 

    2. the charge cycle wasn't disturbed, and 

    3, IT_Enable has been set (ITEN in LearnedStatus set 1).

     

    Now, we will review the battery voltage when charge start between these unit with VOK set/unset. Could you tell what is the threshold of "empty battery", eg, battery voltage < xxxx mV, or SOC < xx%, or other conditions

    Thanks,

    Neo

  • 0 in reply to Jessica H.
    Prodigy 100 points

    Hi Jessica,

    Just want to understand that if set the quit current higher than charger current threshold in gg file, whether this will cause VOK not set when charge started.

    Regards

    Sam

  • 0 in reply to Jessica H.
    Prodigy 100 points

    Hi Jessica,

    It is mentioned in TI document  SLUA903 chapter 3.2.1, the resistance update should be disabled during the initial discharge, could you please kindly let me know if RDIS is not set, what will happen?

    Neo and I are from the same team, we have some issue for learning cycle, the VOK is not set after the battery full discharged and relaxed with OCVTAKEN=1.

    Regards

    Sam

  • 0 in reply to luo neo
    Prodigy 210 points

    Hi Jessica

     

    Our project are pending by this issue. Appreciate if you could share us some comment.

    Neo

  • 0 in reply to luo neo
    TI__Genius 11535 points

    Hi Neo and Sam,

    The threshold for an "empty battery" would be when battery voltage < cell terminate voltage and SOC is at 0%.

    Quit current should definitely be lower than the charge current threshold so that could be blocking the VOK from setting. 

    Can you send me a gg and log that captures VOK not getting set?

    Best,

    Jessica

  • 0 in reply to Jessica H.
    Prodigy 210 points

    Hi Jessica

    Thanks for your reply. The policy of our company forbidden me to share our design document into a public forum.

    Could you share me you email or add me into your friend list, then I could send the gg file and log to you by private message. 

    Thanks,

    Neo

  • 0 in reply to Jessica H.
    Prodigy 100 points

    Hi Jessica,

    Thanks for your response on this, could you please let us know more about the mechanism on how the wrongly setting of quit current impact the VOK setting?

    Regards

    Sam 

  • 0 in reply to Sam Gao1
    TI__Guru** 105760 points

    Hello Same,

    The quit current must be higher than the standby current of the system and less than any charger taper currents or light loads expected in the system.

    The Quit Current threshold is used to go in and out of relax mode where OCV more strongly affects gauging. 

    Sincerely,

    Wyatt Keller