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Battery gauge bq40z50-R1 design question

Mario Moraes
Prodigy 90 points
Other Parts Discussed in Thread: BQ40Z50-R1, BQSTUDIO, BQ27742-G1, BQ20Z65, BQ40Z50

We are designing a new product and want to integrate a Li-Ion battery ( 2 cells in series) with battery gauge. The product will have one mother board with power circuits and several other circuits for all different functions in the unit.

Should we include the bq40z50-R1 gauge circuits in the mother board or design a separate small board just for the bq40z50-R1? 

Thank you,

Mario 

  • 0
    TI__Mastermind 27135 points
    Hi Mario,

    This is a pack-side gauge so it will need to be connected to your battery stack at all times. As long as this requirement is satisfied, you have the option to do either. If you choose to include it on your motherboard, you will want to be careful with your high current paths.

    This TI reference design might be useful to you. It's an example of a separate, small board with the bq40z50-R1: www.ti.com/.../TIDA-00883

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 90 points
    Hello Ben,
    The battery will be connected to the gauge in the mother board all the time. The only time that it will be disconnected is if we need to service and change the battery. I am afraid about the chemical fuse that is recommended in the reference design. If it permanently opens and we need to replace or there is any way to reset the fuse.

    I am also having a hard time to make the EVM works. I can't make it start and keep the voltage at the pack+ output.
    1. The Present connection to the pack - should be connected all the time or just a quick connection?

    I press the wake-up button, the voltage appears in the pack+ but it returns to 0V as soon I release the wake-up button.

    Thank you for your help.
    Best Regards,
    Mario
  • 0 in reply to Mario Moraes
    TI__Mastermind 27135 points
    Mario,

    1. There is not a way to reset the fuse but you can disable this feature in data memory.

    2. System Present connection should be connected to Pack- at all times.

    3. The default configuration of the EVM is for 3 cells. In the DA Configuration register, make sure CC1 is set to 0 and CC0 is set to 1 if you haven't done so already.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 90 points
    Hello Ben,

    We are not being able to start the gauge. WE set a 3 cells battery to test and still not holding the voltage in the Bat+ pack when the wake-up is removed.

    Also when we place a small 1K resistor between pack- and pack+ to simulate a load, the voltage at pack+ is only 0.9V when pressing the wake-up.

    Also we are not being able to communicate with the EVM using the BQ Studio and the EVM2300. It does not recognize the EVM.

    We connected a charger with 12.6V from pack- to pack+ and still with same problems above.

    How can we troubleshoot the EVM?

    Any test point voltage to measure?

    Thank you,
    Regards,
    Mario
  • 0 in reply to Mario Moraes
    TI__Mastermind 27135 points
    Mario,

    Here are the steps I normally take to setup a bq40z50EVM:

    1. Wire terminal block J1/J5 according to figure 2 of the evm user manual
    2. Short SysPres to Pack-
    3. Connect a power supply to Pack+ and Pack-
    4. Connect the EV2300
    5. Apply ~14 V to Pack+/Pack- pins
    6. Open bqstudio. Software should recognize the connected gauge.
    7. Set the DA Configuration register accordingly. Also set values for design capacity, design energy, etc.

    You can now remove the power supply and connect your charger. At this stage, you cannot remove the battery without losing your settings.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 90 points
    Hello Ben,

    I did all the steps above. When I open the bqstudio, it does not recognize the EVM.

    We used the bqstudio and the EV2300 to test and develop the bq27742-g1 and bq20z65 EVM and was working fine.

    Our initial design for this product was using the bq20z65 and migrated to the bq40z50 by suggestion of the TI support for new designs.

    What test point voltages can I measure in the bq40z50 EVM to troubleshoot this problem?

    Thank you,
    Best Regards,
    Mario
  • 0 in reply to Mario Moraes
    TI__Mastermind 27135 points
    Hi Mario,

    What version of bqstudio are you using?

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 180 points
    Hello Ben,

    I am working with Mario on this project.

    We are currently using version 1.3.52.

    Thank you,

    Pedro
  • 0 in reply to PEDRO M.
    TI__Mastermind 27135 points
    Thanks Pedro,

    I would confirm that you see your battery voltage at the BAT test point and you see the CHG/DSG test points go to ~12V when you press the wake button. Try holding down the wake button when you are opening bqstudio if it is still not recognizing your device. Also just confirm you are connected to the SMB port on the EV2300.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 180 points
    We measured the voltages as got the following:

    Wakeup Not Pressed:

    - BATT: 10.38
    - CHG: 5.57
    - DSG: 13.67

    Wakeup Pressed:

    - BATT: 10.37
    - CHG: 5.57
    - DSG: 13.68

    I have verified that the connection to EV2300 is SMB and tried opening BQStudio with the Wake Up button pressed, it is still not recognizing the gauge.

    Thank you,

    Pedro
  • 0 in reply to PEDRO M.
    TI__Mastermind 27135 points
    Pedro,

    It looks like your charge fet is not turning on. Using a scope, do you see voltage pulses across the thermisters? You should see pulses every 250 ms if the gauge firmware is running.

    If you do not see pulses,apply 12 V to pack+ using a power supply and try connecting to the gauge with bqstudio. Also let me know what voltage you see at the BATT, CHG, DSG test points and if you see pulses on the thermisters when you are applying 12 V across Pack+/Pack-.

    Best Regards,
    Ben Lough