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Original question:

BQ27750: Technical Reference Manual Update?

BQ27750: Technical Reference Manual Update?

Andrew Elgar
Prodigy 110 points

Part Number: BQ27750

Hello,

I have found that other TRM's in the bq27XXX family explicitly describe whether or not factory calibration is needed. bq27546-G1 requires calibration (Appendix A), bq27542-G1 shouldn't require but can be calibrated (Section 14.1), bq27426-G1 doesn't require & can't be calibrated (Section 7.4.5.2), etc.

I haven't found this information in the bq27750 TRM, does this particular gauge require factory calibration for voltage, current, and/or temperature?

Thank you,

Andrew Elgar

  • 0
    TI__Intellectual 1840 points
    The bq27750 has a auto-calibration feature where if there is no communication activity for about 5 s, the voltage, current, and temperature will auto-calibrate.
  • 0 in reply to Nabil M
    Prodigy 110 points

    I am aware of auto CC offset calibration, but auto calibration for voltage, current and temperature is news to me. If I'm following your claim correctly, this would mean that an incorrectly calibrated fuel gauge can self-correct despite only having its own incorrect readings for reference. To test this, I adjusted the cell gain parameter so that the voltage reading would be 10mV lower than actual cell voltage. I disconnected the pack from the EV2400 for approximately five minutes and when I reconnected the pack the voltage reading error was still 10mV and the Cell Gain parameter had not changed. (CC offset did though, as expected)

  • 0 in reply to Andrew Elgar
    TI__Mastermind 24870 points
    Hello Andrew,

    The gas gauge does not adjust for calibration or measurement type errors. You will need to calibrate the voltage using bqStudio's voltage calibration plug-in to zero out the error.

    The gas gauge will take OCV measurements assuming a correctly calibrated voltage, current, and temperature measurement to "calibrate" the SOC error and the coulomb counting drift error for gauging accuracy.

    In terms of V, I, T measurement, the gas gauge relies solely on the offsets as you have described.