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BQ35100: What does "the high load pulse" indicate?

K.Yaita
Guru 29690 points
Part Number: BQ35100

Hi Team,

My customer considers EOS Mode with Li-SOCl2 battery.
Regarding page 19 8.2.2.2.1.2, what does "the high load pulse" indicate?
Does it mean we have to pull the high load pulse by intention?



Best Regards,
Yaita

  • +1
    TI__Guru** 102465 points

    Hello Yaita,

    The bq35100 is designed to gauge pulse with an amplitude of tens of mA (~50mA+) that last for tens of mSec (~100mS+).

    The intent is the pulse should be measured in mA and the length should be measured in mSec. 

    Essentially we usually want to see around 100mV drop for 100mS or longer for the pulse.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Guru 29690 points

    Hi Wyatt-san,

    Is that a requirement to measure impedance when EOS mode?
    In addition, I believe the system needs to know when the load pulse will occur in advance.
    Otherwise, I think the system can't send GAUGE_START.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29690 points

    Hi

    I would like to know how to use the device properly, so may I have your reply?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29690 points

    May I have your reply?

    Best Regards,
    Yaita

  • +1 in reply to K.Yaita
    TI__Genius 10370 points

    Yaita,

    You are correct the system does need to know when the load is being applied in order to work. the correct flow is 

    1) GE pin high when the battery has been resting for a long time

    2) Send GaugeStart command

    3) Apply load and remove load. 

    4) Send Gauge stop command

    5) Wait for GDone bit set

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Guru 29690 points

    Hi Eric-san,

    Thank you for your support. I understand.
    I would like to ask an additional question.
    The datasheet shows the following on page 1.

    (datasheet page 1)
    The BQ35100 device provides accurate results with ultra-low average power consumption where less than 2 µA can be achieved through host control via the GAUGE ENABLE (GE) pin. The device is only required to be powered long enough, at a system-determined update frequency, to gather data and to make calculations to support the selected algorithm. A typical system may need to only be updated once every 8 hours as the gauge is not required to be powered to measure all discharge activity.

    Could you tell me what the blue part indicates?
    Especially, I would like to know the background that the sentence uses specific "8 hours".

    Best Regards,
    Yaita

  • +1 in reply to K.Yaita
    TI__Genius 10370 points

    Yaita,

    The comment is tailored as an example. We expect this application to be at rest for long periods of time with short bursts of power. The original application is for a water meter which is radio burst the usage a few times a day. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Guru 29690 points

    Hi Eric-san,

    Thank you for your support. I understand.
    I believe there is no recommendation period of measurement cycle for BQ35100 and it is application dependant.
    Is my understanding correct?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29690 points

    Is my understanding correct?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10370 points

    Yaita,

    There is a minimum time of at least 32mSec. The converter runs every 8mSec alternating between voltage and current. So it needs at least 2 samples of each. Ideally around 100mSec-1sec is ideal. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Guru 29690 points

    Hi Eric-san,

    Thank you for your reply.
    Could you tell me where is it written on the datasheet? I would like to check it on the datasheet.

    My customer considers reading BatteryStatus() once a day. Is it reasonable?
    I believe there is no correlation between measurement frequency and measurement accuracy as long as we follow the minimum time.
    Is my understanding correct?

    Best Regards,
    Yaita 

  • +1 in reply to K.Yaita
    TI__Genius 10370 points

    Yaita,

    I must have misunderstood the question. The frequency you need to wake the gauge over the life of the device depends on the number of samples you want to feed into the EOS filters. I would say a minimum of 500 wake events are needed over the life. 

    Due to the passivation layer buildup on these types of cells the amount of time between readings needs to be as consistent as possible. The bq35100 thrives on load consistency. 

    You do need to make sure the battery is at the best OCV state prior to waking. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Guru 29690 points

    Hi Eric-san,

    Thank you for your support.

    >You do need to make sure the battery is at the best OCV state prior to waking. 
    Regarding the above, I believe "the best OCV state" means "the load should be as small as possible (nearly relaxed state)".
    Is my understanding correct?

    Best Regards,
    Yaita

  • +1 in reply to K.Yaita
    TI__Genius 10370 points

    Yaita,

    Load need to be the smallest possible for an extended amount of time. Normally 5 hours+

    Thanks,

    Eric Vos