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Original question:

BQ40Z50: Retrieving data from a fuel gauge

BQ40Z50: SoC response in big steps and not smooth

Bjorn Olsen
Prodigy 50 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hello,

I am working with BQ40Z50 (or more specifically the dev kit -EVM). I have 3 3.7V batteries - ca 12V.

I read the SoC every 5 seconds. I can read the SoC - all good.

But it seems to not give me fine grained response. Discharge takes around 50hrs with my application.

The SoC will show 100%, then aroun 90%, then maybe 78%, next 43% or similar. I was exepecting a smooth response over time.

What is going on?

Bjorn

  • 0
    TI__Mastermind 29245 points

    Hello Bjorn, 

    Can you send a .log file of the event to view how SOC is being affected based on your load.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 50 points

    Hello,


    export_batterytest_20250508_085300.csv

    Thank you for your quick response. Here is a log of the battery SoC over time. As you can see, it skips down.
    The load is pretty much constant at 1 W. The battery is connected to a 30W heater. I am regulating the heater using PWM - controlling a fixed temperature target.

    I don't (yet) have the capability to read the actual load, but given that the battery is 50Wh, and everything else is constant (e.g. temperature)... 

    I am wondering if the PWM could be the culprit here. We are just finalizing our custom PCBa, so it would be good to know if there are some HW tricks I need to do.


    Bjorn
     

  • 0 in reply to Bjorn Olsen
    TI__Mastermind 29245 points

    Hello Bjorn,

    The file you sent didn't appear to been exported from BQStudio, typically we would be able to see all the different registers and how they interact with each other during the charge/discharge cycles. Could you resubmit a log file with the proper registers within it .


    *Example of what I am expecting

    Thank you,
    Alan