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BQ40Z80: battery percentage shows wrong.

Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO

Hello Team ,

We are using the 3 cell setup and have the cell type US18650VTC5A , we flashed the chemid  to our board with the suppport of BQstudio (2161 is the chemid).

I saw the terminal volatge set as 8.9V  , but the battery shows it have 10.2 V  , but the percentage of charging shows as 0 percentage.

Terminate Voltage, this is essentially the empty pack voltage where the gauge should ensure 0% state of charge is reported.

why this chnage is occured in battery , if battery have the remaining voltage , why it is shown as 0 %.

i tested with 0x0E and 0x0F command both returns 0 value.

Could you please help me why this issue is happend , venthough battery have sufficient


  • Hello Mohan,

    You have not completed a learning cycle, no gauge related information will be accurate until the gauge is fully optimized.

    Please follow the guide on the product page for learning cycle information:


    Wyatt Keller

  • Hello Wyatt ,

    We already know our chemid , then what was the usage of the learning cycle.

    if we don't know the chemid only we need to do the learning cycle , that is my understanding am i right ?.

    The below is our chemid we flashed the chemid to the device .

    retriving the chemid is right only. Let me know then what was the issue  showing battery percentage wrong.


  • This is our battery spec , as per the battery spec the chemid is 2161  , i findout from the BQstudio and programmed.

    and export bq.fz image from device and using to our other device , we want to know what was the issue in showing the different percentage ?

  • Hello Mohan,

    You need to perform a learning cycle after you have programmed the chem ID, a learning cycle is always needed for impedance track gauging. I reviewed your .gg file and it shows update status is not learned so you must complete the learning cycle first following the guide I sent previously.

    Make sure your terminate voltage is set correctly for your application as well, this is what the gauge uses to determine 0% SOC.


    Wyatt Keller

  • Hello Wyatt ,

    As per your suggestion  i need to flash the chemid first using BQstudio.

    Then i need to perform learning cycle , means initally the battery discharge to empty  with C/10 rate , then need to put 5 hours  relax and put charging C/2 rate  . then put 2 hours discharging again i need to put the dicharging and 5 hours relax.

    am i right ???   after that already know chemid so i hope log i dont want to send to ti  (GPCCCHEM also not required) after that i need to export the image from the device.

    let me know my understanding is right or not  ??

    Could you please suggest charging rate and dischagring rate for this battery .

  • Hello Mohan,

    In general yes that's the correct flow for a learning cycle. You can also check the bits of VOK, REST and RDIS to make sure the process is successful at each step. The application note I linked has all the information in it to do the learning cycle. After you fully configure all the settings and the pack is fully learned you would export the SREC or flash stream file for production programming.

    The C rate is the design capacity, you should set your parameters based on the C/10 rate.


    Wyatt Keller