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Partial charging

Diego Zamberlan
Prodigy 40 points
Other Parts Discussed in Thread: BQ34Z100

Hello,

we are designing a multicell, Li-ion battery pack with bq34z100-based gas gauging. We need the charging voltage (thus the resulting capacity) to be variable, that is, before initiating every charge, the applied charging voltage is chosen. For example, choosing a 4.1V per cell instead of 4.2V would result in a final remaining capacity of, say, 90% instead of 100%.

I was trying to understand if this could be a problem for the gas gauging algorithms and for their accuracy and if we need to reconfigure from time to time some parameters (e.g. Charging Voltage).

Thanks,

DZ

  • 0
    TI__Guru 73830 points

    Diego,

    The bq34z100 can compensate for charging the cells to a lower voltage. You should run an optimization (learning) cycle at that charging voltage to allow the device to estimate the most accurate Qmax for the pack.

    Regards

    Tom

  • 0 in reply to ThomasCosby
    Prodigy 40 points

    Thank you Tom.

    Qmax is referred to as the "maximum chemical capacity" of the battery. So, if I'm planning to charge the battery with a user-selectable charging voltage, should I run an optimization cycle for every charging condition (4.2V and 4.1V in the example above)? Or just for the highest voltage/capacity, as usual?

    DZ

  • 0 in reply to Diego Zamberlan
    TI__Guru 73830 points

    Diego,

    You would run the learning cycle with the highest charging voltage and the device will compensate when you charge it to a lower voltage. It will eventually update Qmax to match the charging voltage that you are using.

    Regards

    Tom