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BQ27Z561-R2: RSOC jump

Hailiang Zhang
Expert 4725 points
Part Number: BQ27Z561-R2
Other Parts Discussed in Thread: GPCRB

Hi Team,

The customer programmed 2 fuel gauges with the same configuration, the cell voltage is 3.9V, and the RSOC is 50%.

  • One of the battery packs is in relax state, and the ambient temperature is cooled to -20°, and the RSOC of this battery pack is gradually reduced from 50% to 18%. See the LOG data and GG file below; the current set parameters are RELAX_SMOOTH_OK=1, RELAX_JUMP_OK=0, why is it still jumping?

NT02_GPCRB_7105_20230301bq27z561R2.gg.csv

NT02_minus20degC_simulation_20230317.log

  • The other battery pack was charged to 100% at room temperature and left to stand, and then the ambient temperature was lowered to -20°. The RSOC of this battery pack did not jump during the cooling process; why is this?

Regards,
Hailiang

  • 0
    TI__Guru 57747 points

    Hello Hailiang,

    Most batteries self heat during discharge. The self heating can result in battery delivering more current than it normally would at lower temperature. Since the second battery is fully charged, it may be able to sustain a longer discharge. This is determined by the temperature compensation which is obtained using the data submitted for GPCRB.

    Smoothing prevents a sudden jump. Instead of the sudden jump it will spread it out over time which is what is observed.

  • 0 in reply to Shirish
    TI__Expert 4725 points

    Hi Shirish，

    The customer observed that the RSOC decreases as the temperature decreases when the battery pack is relax (discharge current is 0). In the latest test, the RSOC is 49% at room temperature, and decreases to 27% as the temperature decreases. Is this normal? If not, how should it be optimized?

    Pls see the gg file and log below.

    NT02_GPCRB_7105_20230301bq27z561R2(├╪├▄).gg.csv

    NT02_minus20degC_Simulation_20230329.xls

    Regards,

    HL

  • 0 in reply to Hailiang Zhang
    TI__Guru 57747 points

    Hello HL,

    The terminate voltage is set at 3300mV. Capacity reduces at lower temperatures and as you can see a sudden current causes the voltage to drop below this and causes Remcap to drop to 0.

    Term voltage, Load mode and load select  need to be selected carefully to match the application.