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BQ40Z50-R3-DEVICE-FW: Reserve Cap-mAh

Zhihan Zhang
Expert 1100 points

Part Number: BQ40Z50-R3-DEVICE-FW

Hi TI Team,

I have couple questions about Reserve Cap-mAh. When I set e.g. 500mAh to reserve, I found that the full charge capacity will decrease pretty much the same amount right away. In this case,

Do I need to decrease the Design Capacity setting with the same amount (500mAh) as well?

When I change the setting for either Reserve Cap-mAh or design capacity, do I need to re-run a learn cycle to generate a new golden sample?

I also found that if not change the design capacity, ASOC is deceased but SOH is still 100%. Why SOH is not affected since SOH ~= FCC/DC while FCC is decreased?

I would appreciate it very much if someone could answer my questions!

Best Regards,

Zhihan

  • 0
    TI__Guru** 105590 points

    Hello Zhihan,

    The Reserve-Cap function allows you to keep enough battery charge to perform a controlled shutdown with your system. Your system will basically report 0% SOC when the reserve capacity amount has been reached.

    Yes, if you have changed some of the parameters you will need a new golden image, when you get the final output files you want them to be the exact configuration as you plan on using in other systems.

    SOH is concerned with the longevity of your system of many cycles, if it is a new battery the SOH should still be 100% not dependent upon your reserve capacity.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Expert 1100 points

    Hi Wyatt,

    Thank you so much for your answers! 

    So when I adjust Reserve Cap-mAh, I don't really need to adjust Design Capacity accordingly? For example, with Reserve Cap-mAh = 0, design capacity is set to 3000mAh based on the measurement. But if I change Reserve Cap-mAh = 500mAh, do I need to change design capacity to 2500mAh as well?

    Speaking of SOH, can you please explain a little bit more how SOH is calculated? Because I did find that even for a new battery, the SOH could be just 95% not 100%. Is that still a normal case?

    Thanks,

    Zhihan

  • 0 in reply to Zhihan Zhang
    TI__Guru 52115 points

    See my comments below.

    But if I change Reserve Cap-mAh = 500mAh, do I need to change design capacity to 2500mAh as well?

    [Andy] No.

    Speaking of SOH, can you please explain a little bit more how SOH is calculated? Because I did find that even for a new battery, the SOH could be just 95% not 100%. Is that still a normal case?

    [Andy]  You can find some details on Section 6.7 of BQ40z50-R3 TRM.

    Andy