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BQ28Z610-DEVICE-FW: Unexpected Charging Cutoff Behavior on BQ28Z610 in 1S2P Li-ion UPS Design

Tarek Sharbo
Prodigy 70 points
Part Number: BQ28Z610-DEVICE-FW
Other Parts Discussed in Thread: BQ28Z610, BQSTUDIO, EV2400, GPCCHEM

Tool/software:

Dear TI Support Team,

I have designed a UPS system with a 12V input/output, using a 1S2P Li-ion battery pack. For battery management, I selected the BQ28Z610 IC. Initially, I programmed the BMS using open-source Arduino code to activate the CHG and DCHG FETs, and the system was able to charge and discharge the battery normally.

However, I encountered a critical issue during operation:

  • When keeping the power plugged in to fully charge the battery, the BMS stops the charging process before the battery is fully charged.

  • After the charging FET turns off, if I unplug and reconnect the power, the BMS does not resume the charging process, even I reprogramming it again to be able to charge agian.

To diagnose further, I ordered the TI EV2400 programmer and used BQStudio to monitor the BMS behavior during charging and discharging. I observed the following:

  • The BMS considers the battery fully charged at voltages significantly lower than expected for Li-ion chemistry (e.g., 7.9V or 7.6V for a 2-cell configuration, instead of reaching ~8.4V).

  • I tried using different batteries but faced the same issue.

  • I downloaded the latest firmware for the BQ28Z610 from the TI website and reprogrammed the IC, but the behavior remained unchanged.

  • I have tried to turn on balancin, but it doesn't turned on.
  • I have balance the battery manule and insert them into the device and faced similar issue.

I have attached screenshots from BQStudio showing the charging data graphs and register snapshots during these events.

I would highly appreciate your support in identifying the root cause of this issue and guiding me on how to correctly configure or debug the BMS to achieve proper charging operation.

Thank you very much for your assistance.

Best regards,

Sr. Electroncis Desig Engineer / Engineering Manager
Tarek Sharbo

  • 0
    TI__Mastermind 24685 points

    Hello Tarek,

    This question has been assigned and is currently being worked on.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    TI__Mastermind 24531 points

    Hello, 

    Please ensure you have correctly matched your chemID using the GPCCHEM tool. Additionally please ensure you have successfully completed the learning cycle, the process for the learning cycle is outlined here. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 70 points

    Hello Jonny,

    Thank you for your message.

    I’m currently in the process of identifying the correct ChemID for my battery using the GPCCHEM tool. Since I couldn’t find a matching ChemID directly, I’ve studied the process of new ChemID identification and the learning cycle, and I’m following the steps using BQStudio.

    I’ve completed the first step of the learning cycle ("relax-discharge-relax") for a 2-series Li-Ion battery pack. I uploaded the resulting log file to the GPCCHEM online tool but initially encountered an error. Upon reviewing the data, I realized the error was due to not completing the initial relax stage properly, which is required to capture the correct OCV value before starting the discharge.

    However, I also noticed that the pack voltage dropped below the configured termination voltage (set to 6V in BQStudio) and reached as low as 5V. I’d appreciate your guidance on whether this could be contributing to the issue. Additionally, could you please clarify which specific parameter in BQStudio determines the termination voltage?

    Here’s a summary of the procedure I followed:

    • Fully charged the battery pack and allowed it to rest for approximately 2 hours.

    • Enabled the gauge using Gauge_EN and toggled DSG_FET, then pressed RESET.

    • Connected an electronic load and discharged at a C/10 rate.

    • Logged the data and generated the GPCPackage files using the GPCCHEM tool.

    Could you please confirm whether the procedure I followed is correct?

    One final point I need clarification on: I’m using a 2-series cell pack, but the TI documentation states to enter "1" for Number of Series Cell in the GPCCHEM tool. Could you please confirm whether I should input "1" or "2" in this case?

    Looking forward to your advice.

    Best regards,
    Tarek



  • 0 in reply to Tarek Sharbo
    TI__Mastermind 24531 points

    Hello, 

    To properly obtain the data needed for the GPCCHEM tool, please follow the GPCCHEM user's guide. 

    Regards, 

    Jonny.