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BQ27Z561: Question about the FCC curve in the datasheet

Wayne Wang20
Expert 4380 points
Part Number: BQ27Z561

Hi team,

My customer is evaluating BQ27Z561. They have a question about below curve in our datasheet.

How to understand the third curve 'true_FCC' in below picture? From my understanding, the capacity should gradually drop along with the current output. But why it is a stepping waveform in below picture and sometimes steps up and sometimes steps down?

By the way, customer also has below question:

1. How does the gauge determine if there is a valid battery connected?

2. Can the gauge  know how many cycles has the battery charged and discharged? If it can, which parameter does it use to calculate the cycle? 

Thanks.

Best regards,

Wayne

  • 0
    TI__Guru* 76230 points
    Hi Wayne
    True FCC is dependent of the current. A high current will give less FCC than a low current. This is an inherent characteristic of a battery. Also, the gauge runs rem cap simualtions, so depending on the current used to run the simulation and the ra table, the device will estimate what the FCC is based off that simulation. So it is expected to see slight variations in FCC.

    1. This is a pack side gauge, there is no system present pin. The gauge does not detect battery insertion.
    2. Pls see the cycle count and cc threshold parameters in the TRM.

    thanks
    Onyx