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BQ40Z60: Current sensor not working

Olivier Witteman
Prodigy 30 points
Part Number: BQ40Z60
Other Parts Discussed in Thread: BQSTUDIO

Hi TI Community,

I have a BQ40Z60 evaluation board (BQ40Z60EVM) and I have downloaded the corresponding TI Battery Manager Software. I am unable to sense the current, as the current register is always reading an incorrect value. This is a screenshot at 1A - the current is only reading at 304mA. Even at a changing current, it stays at 304mA or fluctuates within 1mA of this value:


I have attached the configuration file for reference: conf_b1.gg.csv

Thank you for your help!

Note: This post is not about the board I previously posted about, the FETs work on this board and there are no problems charging or discharging.

  • 0
    TI__Genius 11535 points

    Hi Olivier,

    Did you follow all of the steps outlined in the EVM User's Guide?  What is your battery setup like?

    Best,

    Jessica

  • 0
    Prodigy 30 points

    Hi Jessica,

    I just looked through the steps again and don’t see anything we missed. Voltage and temperature readings already corresponded to the actual state, so we skipped the calibration of those.

    Currently, we simulate the battery with a power supply (at 15V) and 4 1.2kOhm resistors and have a variable power sink attached as load. 

    Best regards,

    Olivier

  • 0 in reply to Olivier Witteman
    TI__Genius 10370 points

    Oliver,

    Depending on the setup you could have lots of IR loss and the current could actually be 300mA. Have you measured the voltage directly across the senseR to do the manual calculation to confirm if the current is off? 

    If it is just the gauge reported that is incorrect it is most likely due to calibration in some form. i recommend using an external power supply to force voltage directly across the senseR to simulate a 1A load. then use the bqStudio calibration screen to perform the calibration. I would not use a resistor becuase the gauge expects a very stable load current when doing the cal. 

    Thanks,

    Eric Vos

  • 0
    Prodigy 10 points

    Hi Vos,

    I am a colleague of Olivier also working on this project. Despite the recommended calibration method, the current value does not change and remains fairly static. Is there any possibility of a current bypass in the circuit?

    Thank you!

    Brontë

  • 0 in reply to Bronte Kolar
    TI__Genius 10370 points

    Bronte,

    Does the CC Gain and Capacity Gain values in the calibration section roughly match the size senseR you are using? for example 2.003 for a 2mOhm sense. If you manually adjust these parameters does the current value change?

    Thanks,

    Eric Vos