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Original question:

BQ40Z50-R2: Application issues

BQ40Z50-R2: Turning off discharge MOS leads to inability to charge

lan xin
Prodigy 190 points
Part Number: BQ40Z50-R2

Tool/software:

Hi，I have found the reason why it cannot be charged. After overcurrent, the discharge MOS is turned off, and the charging voltage can enter through the diode of the discharge MOS. However, after passing through the diode, a voltage drop of 0.2V will be generated. Because my battery pack is 2S1P, the full charge voltage is 8.8V, and the total voltage in series is 8.65V, the original charging voltage of 8.8V becomes 8.6V, and the total voltage of the battery pack is higher, resulting in the inability to charge. I tried discharging to reduce the total voltage of the battery pack and was able to clear the overcurrent state through charging, thereby turning on the discharge MOS. Additionally, I tested manually turning off the charging MOS, turning on the discharging MOS, and using a load to discharge. Turning on the discharging MOS will automatically turn on the charging MOS. Is this related to a certain parameter configuration? Can the discharging MOS be directly turned on during charging?

2474.test_ocd.zip

  • 0
    TI__Mastermind 26595 points

    Hello Ian,

    Your question has been received and will be answered promptly.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    TI__Mastermind 28480 points

    Hi Ian,

    The DSG FET will be turned on if the charging current is greater than the CHG Current Threshold for bypass protection purposes. This will happen even if there is a protection triggered to turn off the DSG FET, if the gauge recognizes it is in charge mode then it will allow the DSG FET to become active. This will also happen in discharge, if a current less than the DSG Current Threshold is observed then the CHG FET will also become active.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 190 points

    Hi，The attachment I sent earlier includes my. gg.csv file and the log data that I want to charge after triggering OCD protection. From the configuration file, it can be seen that the CHG Current Threshold is 50mA. According to your reply, as long as the charging current is greater than 50, the DSG FET will be turned on. However, I am currently unable to charge because the DSG FET is turned off, and my charging voltage has dropped through the diode of the DSG FET, resulting in a charging current of 0, which cannot meet the conditions for entering charging mode. My circuit schematic is as follows:

  • 0 in reply to lan xin
    TI__Mastermind 26595 points

    Hello Ian,

    Could you send a .log file to see what your battery gauge sees during this event? I can verified that you have set your chg current threshold to 50mA but with the .log we can better see what is happening within the gauge. Also verifying that VC1 goes to the first cell in series positive terminal? Everything marked green is good and please ignore the orange that was a mistake on my end.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 190 points

    Hi，The compressed file contains log data and configuration files that trigger OCD protection before recharging

    1682.test_ocd.zip

  • 0 in reply to lan xin
    TI__Mastermind 26595 points

    Hello Ian, 

    The log file you sent just shows the battery gauges being discharge for a very small window and then at rest for a short period of time. This .log file is too short and what we are looking for is you pushing 50mA to the battery gauge and seeing how your "RemCap" changes during this period of time. You would need the cell no be fully charge in order to see this and the longer .log file the better.

    Thank you,
    Alan