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Original question:

BQ40Z50: Troubleshooting Vgs Voltage and FET Control Issues with BQ40Z50 on Second PCB

BQ40Z50: Assistance Required for BMS Wake-Up Issue with bq40z50 for 4S3P Battery Pack

Sumedh Saptarshi
Prodigy 70 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Tool/software:

Dear Technical Support Team,
We have developed a Battery Management System (BMS) utilizing the bq40z50 for a 4-series, 3-parallel (4S3P) battery pack(14.8V 6600mAh) configuration. We are encountering an issue where the battery pack, upon discharging below its threshold voltage(Threshold Voltage - 13.5V and discharging current - 600mA), fails to wake up or initiate charging. Despite attempting various commands through BQStudio, we have been unable to reactivate the pack.As this condition battery will be connected to the load as it is.
Could you please provide guidance or recommend specific solutions to address this issue? Also tell us when Battery goes to protection mode how to recover from it without using bqStudio software.

Any insights into potential configuration adjustments, firmware settings, or diagnostic steps would be greatly appreciated.
Thank you for your assistance.

  • 0
    TI__Mastermind 25725 points

    Hello Sumedh,

    This question has been assigned and will be reviewed when possible.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 70 points

    Thank you Alan.

  • 0
    TI__Intellectual 902 points

    Hello Sumedh,

    • Do you have a datalog and the gg file you are using for this application?
    • Is gauge still communicating with your device?

    -Miguel

  • 0 in reply to Miguel Castro Gonzalez
    Prodigy 70 points

    Hello Miguel,
    1.Sorry, I don't have the datalog and the gg for this application.

    2.Yes gauge is communicating with my device.

  • 0 in reply to Sumedh Saptarshi
    TI__Intellectual 902 points

    There is chance you could be triggering a protection when the load is applied as a transient. The gauge has two types of protections:

    • The gauge has several FW protection thresholds. The state of these bits can be seen in bqstudio. If any of those bits is set high (Red), then you will not be able to turn on the CHG or DSG FETS.
    • There is also HW protections (AOLD, ASCC, ASCD1, ASCD2) which are always on and will turn off the FETs even if the BQstudio is saying they are on. 

    A way to confirm this is by disabling the FW protections and maxing the HW protections (HW protection cannot be turned off).

  • 0 in reply to Miguel Castro Gonzalez
    Prodigy 70 points

    Dear Miguel,

    This means bq40z50 is going into the protection mode but if it goes into protection mode then how we can recover from this protection mode , is there any command for this because I have use the RESET command for it but it didn't work.

    - You are saying a way to confirm this by disabling the FW protections but how to disable it?

    - I need another kind help from your side this is very urgent to me , I am posting my question here only

    We have developed the BMS for the 4S3P battery pack using bq40z50 IC for testing purpose we are using evaluation board EV2400 the problem is that -

    - SMBUS communication is not happening properly means when we short the 3P and the pack+ for the 3S Battery (not momentary short) then only we can able to communicate with the BQStudio.It will show the status of the battery using BQStudio. But when we disconnect the short then it is not communicating.

    - Same happening for the 4S Battery we need to continuing short the 4P and the pack+.

    Some observations of the voltages of the IC , I am sending you the schematic for your reference also

    1.Voltages at pack+ and gnd is showing 0V , but it should be ~12V

    2.Voltages at R20 is 0V , but it should be ~12V.

    3.Voltages at the bq40z50 pin CHG(Pin no 31) and DSG(Pin no 28) are 0V but it should be ~24V.

    I am sending you the schematic 3554.0043-08-7081 sch.pdffor your reference.

  • 0 in reply to Sumedh Saptarshi
    TI__Intellectual 902 points
    Sumedh Saptarshi said:
    You are saying a way to confirm this by disabling the FW protections but how to disable it?

    Set all the Enabled Protection A/B/C/D to zero. This will disable all protections.

    The AFE protection is temperaly after a delay. Please see section 2.7 in the Technical Reference Manual for a detailed description of the Hardware Protection.

    I will get back to you about the other later topic today

  • 0 in reply to Miguel Castro Gonzalez
    Prodigy 70 points

    Thanks Miguel I will go through it.Please spare some time for the 2nd query also it would be a great help.

  • 0 in reply to Sumedh Saptarshi
    TI__Intellectual 902 points

    Hello Sumedh,

    In your schematic, you are using the same FETs for DSG &CHG. This is not correct. It should be a NFET and PFET, so they cannot be the same.