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BQ27742-G1: Problem to get accurate result of SOC while battery discharging

Reena Patel
Intellectual 375 points
Part Number: BQ27742-G1
Other Parts Discussed in Thread: BQSTUDIO, GPCCHEM

Hey Dear all,

Please check my last post. I urgent need help from TI community. There is one project which i am working now and i do not get required output from it.

For my project which is basically based on fuel gauge(BQ27742-G1). and for my set-up i simply done I2C communication with stm32L053C8 by connecting SDA,SCL and GND pin with left open my Pack+ pin.

And made simple program for I2C communication to get BATTERY voltage and SOC. Battery is Tenergy 3.7v 1400mAh Li-ion. and to discharge battery voltage i connect one 15ohm resistor in parallel with battery.

and start to check my voltage and SOC in debug mode. As battery discharge gradually i observe change in voltage output in debug mode(it update by itself). But There is no change in SOC(state of charge) basically it does not update at all as voltage does. But when i plug-in my battery in socket and wake-up it. i get True value of both soc and voltage.

But while discharging SOC does not update with voltage. And If i remove my battery from socket and plug-in again. i am able to get true value of SOC and voltage.

So please help me to find out my problem where i make mistake. can i connect 15ohm resistor parallel with Battery to get output. ??????

and if i made right coonection of my set-up ,why my SOC and Remaining capacity does not update while discharging battery ???? and why it updates after i connect battery again.

Please solve my problem as soon as possible.

I want to clarify one thing, i did not made any change through EVM board and BQstudio (actually i do not have this things to make any change in fuel gauge) . So one more question do i need unseal my gauge and make changes to get right output ?? or i can get by itself??

If you want see my code. Please reply me for that.  

Thanking you in advance,

Regards,

Reena Patel

 

  • 0
    TI__Guru* 76230 points
    Hi Reena,
    Why do you have the resistor in parallel with the battery? What purpose does that servce? That is not recommended.
    Also, have you performed a chem id identification for your batttery and a learning cycle? We have a lot of material online on how to do both

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 375 points
    Hello onxy sir,

    Thank you so much for your answer. And now i have already started step as you have told me. And for that first i made whole setup with EVM module and BQ27742 EVM circuit. As i do not have correct chem id for my battery (Tenergy 3.7v 1400mah 18500 Li-ion battery) , i start rel-discharge-rel step for chem id. I will post it on GPCCHEM tool for correct chem id.

    And after i will get chem id i will have to do calibrate my gauge and re-enter data memory . and then i will have to do learning step. As i do not have much knowledge of this whole process maybe i will need your help. Please guide me with all step.

    One question for you, is that any step which i missed and i need to do that ?? please mention that.

    Thanking you in advance,
    Regards,
    Reena Patel.
  • 0 in reply to Reena Patel
    TI__Guru* 76230 points
    Hi Reena,
    You can refer to this document for doing the learning cycle. even though written for a different gauge, it is similar.

    www.ti.com/.../slua902

    thanks
    Onyx