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BQ34Z100-G1: BQ34Z100-G1 Remaining Capacity will slowly decline

XIE XiChun
Prodigy 100 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQSTUDIO

Our company produced several 14-series battery packs. After all batteries are assembled, calibrate and turn on IT_Enable, the battery power is basically around 72%.The batteries were left in the warehouse for 2 days, and it was found that the SOC of almost all the batteries was reduced by at least 15%, and quite a few  reduced more than 20%.During this process, the current value was always zero, and the voltage and temperature do not changed.

To troubleshoot problems, they took one piece of batteries do test,  send x0041, SOC will return to 72%, and then  use BQstdio continuously log the battery data, I found that RemainingCapacity fell by a numerical every 30 minutes.Now,The batteries have been storing  in the warehouse for 12 days, and some have dropped to 0 percent with the same voltage. And some batteries have Cycle count become 1.

There's a small number of batteries SOC goes down for a while, and all of a sudden it goes back up to about 72%, and then it goes down again, and the Cyclecount has increased by 1.

In addition, There are a few batteries whose RemainingCapacity and SOC does not change after the reset operation.

Our ChemID is 2106.This ID is calculated by GPC CHEM tool.Our learning cycle was successful. I do not know why the  RemainingCapacity is going down.

One more point, the maximum current in our battery is around 120Amp, which is much more than 32Amp, so we scaled the current by 20 times.

The figure 1 shows the RaTable:

This problem has been bothering us for a long time, please help us.Thanks!

Regards,

Xie

  • 0
    TI__Genius 12215 points

    Xichun

        It could be caused by ghost current. You can check a register read by bqStudio with the name of "DOD PassedQ", the ghost current would cause this register increment or decrement slowly overtime.

       If this is the case, you need to recalibrate the gauge until you do not see the DOD PassedQ increment or decrement. If you can not make this, then you need to modify the private dataflash value cc deadband. And I need to create a bqz file which opens this item for you to modify.

  • 0 in reply to Steven Yao
    Prodigy 100 points

    Hi Steven:

    As you said, the register named DOD PassedQ did change one value, and then the remaining capacity dropped by one value.There is relevant data in the log file I uploaded.

    0245.data.log

      I have modify the private dataflash value cc deadband(increases the value of cc deadband).Then, the register named DOD PassedQ still changed.

      You said that I need to create a bqz file which opens this item for me to modify.I do not know how to do it.Could you please gave me more information?And Do you know how the ghost current  is generated?

    Thanks!

  • 0 in reply to XIE XiChun
    TI__Genius 12215 points

    Hi, Xichun

         Since you can already modify the cc deadband, then you do not need to create another bqz file. Are you sure the value you modified is CC Deadband? because this item is default to private, which means no accessible without special bqz file.

        The ghost current is typically caused by noise coupled into the current sensing circuit. the area sensing circuit to the sense resistor should be as small as possible, the to sensing trace from sense resistor to the IC should be routed symmetrically, and kevin rule should be followed to current sensing trace to the sense resistor.

        If you can not modify your circuit, then you have modify cc deadband until you do not see DOD PassedQ increment or decrement.

  • 0 in reply to Steven Yao
    Prodigy 100 points

    Hi Steven:

    I modified the value of CC Deadband showing in the figure.Is that the CC Deadband as you were talking about? I can just modify this value.I tried to modify some of the values.It doesn't work at the moment.I don't know if it's the right way.

    I don't know exactly what Kevin rule is.You can see my PCB Layout as showing in the figure.


    the R82 is a 0 ohm resistor used to connect BAT- and GND.Can you see if I did something wrong in my design?

    Thanks a lot!

     

     

  • 0 in reply to XIE XiChun
    TI__Mastermind 24870 points

    Hello,

    It seems like your sense resistor is below the recommended minimum for this device. It looks to be 2.5 mOhm. In this case, we should increase the deadband settings as suggested and re-test to see if the Qpass ticks go away when there is no current flow in or out of the battery cells.

  • 0 in reply to Kang Kang
    Prodigy 100 points

    Hello Kang Kang ,

    Do I modify cc deadband directly on the BQStdio or I need to re-burn the srec firmware?

  • 0 in reply to XIE XiChun
    TI__Mastermind 24870 points

    Hello Xie,

    bqStudio can generate a new srec after you modify cc deadband.