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Original question:

BQ40Z50-R2: Tell me about the changes in SOH and Ra

BQ40Z50-R2: Tell me about the changes in SOH and Ra(continued)

user5768972
Intellectual 450 points
Part Number: BQ40Z50-R2

Tool/software:

Thanks for the answer.

Question 1.
I understand that there is a V-reading error problem with Ra=V-OCV(DOD,T)/I.

But the answer to question 2.
>Since voltage readings are not accurate, SOH and Ra table values should be disregarded.
I don't think this explanation explains the phenomenon where SOH worsens at low charge/discharge cycle numbers and then returns to normal as the number of cycles increases. Because if the voltage readings are not accurate, then wouldn't the Ra table be disregarded at low cycle numbers? I think this is a good idea.

Could you please explain?

  • 0
    TI__Mastermind 28430 points

    Hello,

    If there is an issue with the Ra table based on the measured voltage being wrong at the time, the gauge will use the current Ra values, but will not update them with the new values. The resistance measurement from the new (wrong) voltage would need to be negative for the update to be disabled. If the resistance is not negative and meets all requirements, it will be updated. More information regarding the calculation can be found in the document below:

    https://www.ti.com/lit/an/slua364b/slua364b.pdf 

    We recommend for voltage calibration to be accomplished to avoid this situation.

    Regards,

    Anthony