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BQ27Z746: BQ27Z746- Charge at low temperature 0℃ and discharge at normal temperature 25℃

q h
Intellectual 260 points
Part Number: BQ27Z746
Other Parts Discussed in Thread: GPCRB

Tool/software:

Hi ti team

7870.Gauge settings_Panasonic_NCR2170M_ID7473_KAYO_20250106.gg.csvI have a product using the BQ27Z746. It is in a 1S2P configuration with a voltage of 4.2V and a capacity of 9100mAh at room temperature. However, when I charge the battery to 4.2V in a low-temperature environment of 0°C, due to the low temperature, the capacity of the battery when charged to 4.2V at 100% SOC is only about 7500mAh. When I restore the temperature to 25°C and start discharging, the BQ27Z746 will mistakenly think that the full charge capacity (FCC) is 9100mAh. But in fact, at this time, only about 7500mAh of capacity can be discharged. This will cause the state of charge (SOC) to jump. I would like to ask if there is any way to solve this scenario where charging is done at 0°C in a low-temperature environment and discharging is carried out at 25°C in a high-temperature environment.

Thanks

  • 0
    TI__Mastermind 26395 points

    Hello q h,

    q h said:
    solve this scenario where charging is done at 0°C in a low-temperature environment and discharging is carried out at 25°C in a high-temperature environment.

    This scenario is very difficult to solve and this is where expectation of battery gauge algorithm should be understood, since FCC will update depending on the temperature and since SOC is calculated as RemCap/FCC * 100 since the dependent variable of FCC is constantly updating you will see some jumps with SOC. We do have smoothing parameter subclass that you can use to lessen the amount of SOC jumps but if you are gradually bring the device to temperature than there should be huge SOC jumps. Lastly another way to improve the accuracies of your cells SOC in low temperature environment you can use the GPCRB tool attached below.

    GPCRB:
    https://www.ti.com/tool/GPCRB

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Intellectual 260 points

    Hi  Alan 

    We can effectively improve the accuracy of the State of Charge (SOC) in the scenarios of charging at room temperature and discharging at low temperature by using GPCRB. However, it doesn't effectively improve the situation in the scenarios of charging at a low temperature of 0℃ and discharging at a room temperature of 25℃. Does Texas Instruments (TI) have any countermeasures in this regard?

  • 0 in reply to q h
    TI__Mastermind 26395 points

    Hello qh,

    We don't have any countermeasures either than GPCRB tool, I would reach out to the cell manufacture since the battery gauge can't influence the cells capacity or Qmax during temperature shifts it is only able to read the current SOC. 

    Thank you,
    Alan