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BQ34z100EVM calibration

Peter Upczak
Intellectual 965 points

On Page 8 of the EVM user manual covering Battery Management Studio,  it states:

3.3.1 Voltage Calibration
• Measure the voltage from BAT+ to BAT– and enter this value in the Applied Voltage field and select
the Calibrate Voltage box.
• Press the Calibrate Gas Gauge button to calibrate the voltage measurement system.
• Deselect the Calibrate Voltage boxes after voltage calibration has completed.

I am evaluating the BQ with a K2Energy 8-series 4-parallel LiFePO (PO4 / LPF26650) 25.6V battery pack.

However, for the 8 series-cell pack @ 25.6V total (3.2/cell) 25600 mv for this field exceeds the determined range for the chemistry (ChemID 401).

I read elsewhere on the bq34 forum that the chip internally calculates based on 1 cell then uses the value from # series cells data-memory  to finalize the internal calculations. So is it then correct that for an 8 series cell pack, the Voltage Calibration input is the measured volts as directed, but as V / 8 ?

This seems to work in that Battery Management Studio accepts the scaled range and allows me to calibrate the other parameters and a subsequent discharge run seems to track actual measurements, but I've not found a definitive explanation for this.

thanks!

  • 0
    TI__Guru 73830 points

    Peter
    Are you using the TI EVM? If so, do you have the voltage selection jumper set in the 32V location? Can you export an srec file and send it to me? I can check the calibration parameters.

    All calculations in the device are handled at a 1S level. The gauge takes the Voltage reading and divides it by the number of series cells and uses this value for voltage in the firmware.


    Tom