BQ40Z80: BQStudio limits for CC/Capacity Gain too tight

Mohammed Kabir

Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO

I'm working with a high discharge pack (current scale factor = 3), and running CC calibration through BQStudio yields a CC Gain of ~0.645.

However, the Dataflash Memory tab doesn't like this and fails to write the CC Gain and Capacity Gain parameters with the error message "Value is beyond maximum value defined for parameter: Calibration.Current.CC Gain". The calibration interface can write them just fine, but the dataflash interface cannot. Once calibrated, the BMS's current measurement matches the external measurement over a wide range of currents, so I'm confident that the calibration value itself is correct.

This is currently preventing us from writing a single gg.csv file to multiple packs, and looks identical to e2e.ti.com/.../bq76930-bq76930-bq78350-r2-and-currents-of-200a-with-7s5p-battery-pack-rsense-value

Any help would be appreciated!

over 4 years ago

0 Vos over 4 years ago

TI__Genius 10370 points

Mohammed,

For calibration you should never just write the datamemory page stand alone. The true value stored in the gauge is 4 bytes where as the ~0.645 value you are seeing is to make it readable. Writing 0.645 does not give the same accuracy and resolution you are needing. You should use the calibration plug-in then export a "golden srec" from the device to flash into other devices.

Or if needed. You can use the I2C advanced communication screen to manually write that address.

Thanks,

Eric Vos

Power management

Power management forum

BQ40Z80: BQStudio limits for CC/Capacity Gain too tight