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BQ40Z60: Cycle count

Robert Ploeg
Prodigy 240 points
Part Number: BQ40Z60

Hi,

In the BQ40Z60 the preset for the cycle count is 90%. Does this means it needs to see a delta of 90% in the learned capacity, for example charged up to 95% and discharged to 5%, or does it always has to be charged to a 100%?

Thanks,

Rob

  • 0
    TI__Mastermind 34775 points

    Hi Rob,

    It's threshold need to be exceed for the calculation/increment of the cycle count. The gauge needs to be discharge to below 10% and charge to above 90% (which is user defined) to be considered as a cycle.

    The lower threshold is always 10% of design capacity, but the upper 90% threshold can be configured to be 90% of design capacity or full charge capacity by CCT bit in settings >>  IT Gauging Configuration.

  • 0 in reply to Damian Lewis
    Prodigy 240 points

    Hi Damian,

    Thanks. Petty the lower threshold can't be set also.

    Rob

  • 0 in reply to Damian Lewis
    Prodigy 240 points

    Hi Damian,

    is there a way to increase the minimum level of 10%? We advise our customers to change the batteries when the remaining capacity drops below the 20% and underline this with an external display changing colour from green to yellow to orange. In case they follow our advice, their batteries will never count a cycle.

    Thanks,

    Rob

  • 0 in reply to Robert Ploeg
    TI__Guru 73830 points
    Robert
    There seems to be some confusion as to how the CycleCount works. The Cycle Count Percentage can be set from 0 to 100%. You can set the CCT bit to select whether this is 0 to 100% of FCC or 0 to 100% of DesignCapacity. If you select FCC then the lowest percentage of FCC that can cause CycleCount to increment is 10% of DesignCapacity. It is set this way to set a minimum level internally, since FCC changes. Once the Cycle Count Percentage has been chosen, then the gauge monitors the accumulates Passed Charge during discharge. Passed Charge changes during charge do not affect the accumulation and the accumulation does not have to occur in the same discharge cycle. The CycleCount will increment after the accumulated Passed Charge exceeds the Cycle Count Percentage of FCC or DesignCapacity. Here are a couple of examples. Suppose that we set the Cycle Count Percentage and CCT bit to select 90% of FCC. We will let FCC = 1000mAh in these examples. We charge to the pack to full and then fully discharge the pack. The CycleCount will increment after 900mA of Passed Charge has been removed from the pack. This should occur at about the 10% SOC point. For the second example, assume that we charge the pack to full and discharge it to 50% SOC. Approximately 500mAh of Passed Charge were accumulated during the discharge. Now charge the pack to full and discharge to 50% again. The CycleCount will increment after 400 mAh of Passed Charge has been removed from the pack during the second discharge. (500 mAh in the 1st cycle + 400 mAh in the 2nd cycle) This should occur at about 60% SOC.

    Tom
  • 0 in reply to ThomasCosby
    Prodigy 240 points

    Hi Tom,

    thanks for the explanation, this makes it a lot clearer but rises another question:

    If the Cycle Count Percentage is, for example, set to 30% FCC does that mean a 100% discharge causes 3 cycle counts? In your example with FCC = 1000mAh, battery charged to 100%, a cycle is counted during discharge at 700mAh, 400mAh and 100mAh.

    Thanks,

    Rob

  • 0 in reply to Robert Ploeg
    TI__Guru 73830 points
    Yes, that would be the expectation.