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BQ30Z554-R1: How to manually quit maintenance charge?

John Griffith
Mastermind 21811 points
Part Number: BQ30Z554-R1

Hello,

My customer has their equipment placed on the charger and they are using the Terminate Charge Alarm to disable the CHGFET when they get close to their full charge voltage of 8.40V (2S Li-Ion). They ran into a test condition where the TCA bit was enabled (after a valid charge termination), and the system was slowly floating/discharging and the CHGFET was off as expected. However, the charger lost power (due to A/C power loss), and restarted. The charger saw that the battery was less than what it considered 100% charge, now at 8.3V, and attempted to charge the system to 100%. This didn’t occur and the device timed out after 3 hours of trying since the TCA was enabled and CHGFET was turned off.

They would like to know a way that the MCU on their equipment can kick the BQ out of Maintenance Charge with GaugingStatus[TCA] = 1. The equipment is awoken from sleep when the charger resets so they have the opportunity to do something.

Is there a way to set GaugingStatus[TCA] = 0 or do something else to have the same effect? The charger will be powering the equipment during this condition so the BQ sees low discharge current. So far the only way they have been able to recover is to issue a BQ Reset command (0x00 0x12) but they recall there was hesitation in handling issues this way in past.

Let me know if you need anything else and thank you in advance! 

John

  • 0
    TI__Guru 52115 points

    Hi John,

    Can you ask the customer to provide their gg file? We would like to check their settings.

     
    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Mastermind 21811 points

    Hi Andy,

    I have sent you the gg file separately to keep my customer's information confidential. 

    The GG file allows a valid charge termination to open the CHG MOSFET. If the charger then momentarily looses power (resets) the charger will then try to charge the battery, but because the CHG MOSFET is open, no energy will enter the cells. After a time limit of 3 hours for a complete charge expires the charger will signal a failure (red- light).

    What they want to know: If they add software to recognize this situation and as a result of this detection send the battery BMS chip (bq30z554) a reset command (x0012). This reset command will reset the CHG MOSFET to the “ON” condition which is our desired action. Would this command (x0012) cause any other changes or conditions that we don’t intend other than to turn on the CHG MOSFET?

    Thanks!

    John

  • 0 in reply to John Griffith
    TI__Guru 52115 points
    Hi John,
    The gauge should not be reset or even power cycled unless the power supply to the gauge drops below the minimum required for the gauge to work.
    Let me check with our firmware team and see if there is a proper way to solve their issue.
    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Mastermind 21811 points

    Hi Andy,

    Thanks for the quick follow up. Can you expand a little on why the customer does not want to reset the device? What are the negative consequences? My only thought is that all the cell learning will be reset. Is there anything else?

    Thanks for checking into what other ways there are to solve the issue. 

    John

  • 0 in reply to John Griffith
    TI__Guru 52115 points

    Hi John,

    Below is the feedback I got from our firmware team.

    Basically, they think that is just the way the gauge works and their workaround is not a good idea.
    They mentioned two possible workarounds.
    a) Not to turn the CHG FET off when the TCA sets.  They can set the Charging Configuration[CHGFET] to 0. 
    b) Clear the charger’s failure flag or otherwise find a way to ignore it in this case.

    Andy

  • 0 in reply to Andy Liu (BMS)
    TI__Mastermind 21811 points

    Hi Andy,

    Thanks for following up! Are you able to expand a little on why the customer does not want to just reset the device? What are the negative consequences? My only thought is that all the cell learning will be reset. Is there anything else?

    Thanks,

    John

  • 0 in reply to John Griffith
    TI__Mastermind 24870 points

    Hello John,

    You are correct that the cell learning will be reset, but the gauge could also get a bad initialization. This will mean the first cycle may not be as accurate. The RSOC will recover once the gauge takes a dv/dt condition.