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BQ40Z50-R1: When measuring small current, SOC deviation？

Arvin jie
Prodigy 60 points
Part Number: BQ40Z50-R1

Hi:

I use this chip to design mainly for capacity test of lithium battery (3800mah).

The current of the battery is 10A under normal operation.

But now I need to use 10mA current to discharge the full battery continuously.

Under such a small current, whether the current collected by the sampling circuit can be calculated into the coulometer will have a greater impact on SOC.

If 10 mA current is used to discharge the fully charged battery (SOC = 100%) for 7.9 consecutive days, the battery will discharge 1900 MAH theoretically, and the SOC should be updated to 50%. What is the SOC when the sampling deviation is taken into account? Can you give us an approximate reference value? Thank you！！！

  • 0 in reply to Arvin jie
    TI__Genius 12215 points

    The Gauge calculates the capacity with OCV, Ra and nominated load rate, temperature when the battery is in relax mode(Current < Quit Current), each time the new SOC is calculated during relax, a register value, DODPassedQ will be cleared, if you log the data during discharge, you can see this register. At meantime, you will see True Remaining Capacity, True Full Charge Capacity update. If smooth function is disabled, same change can be observed for Remaining Capacity, Full Charge Capacity register.

    If you log the data when the battery is discharge with 10mA current for 8 days, I think you will be able to the True RSOC reach 50% or so at the end of test.