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Connection error during cemistry select cycling

Thomas Sauer
Prodigy 50 points
Other Parts Discussed in Thread: BQ27500

Hi,

I'm using the latest bqEASY-Software together with the bq27500 EVM. Because I don't know the correct type of the battery I'm using, I wanted to find this out via using the "Chemistry select cycling". So I set up the circuit as shown at the top of part 4C and started. Everything works fine until step 6 of 7. Near completion of step 6 the execution stops and the following error occurs:

"Communication with the target device could not be established. Please check the connections. bqEasy cannot operate without a SMBus connection to the device. Do you wish to ignore future errors?"

Selecting "No" causes the same error pop up again and again. Selecting "Yes" makes the program run until completion, but at the end no battery can be selected due to a too great failure-rate.

I tried to run the "Chemistry select cycling" about 5 times - even with different values for minimum cell voltage. Every time the same error occurs.

Can someone help me with this problem?

Thank you,

Tom

  • 0
    TI__Intellectual 2100 points

    Tom,

    I apologize for the delay.

    First, check to see what your battery voltage is when it says it can't communicate.  If it drops below POR (~2.2V), the gauge will turn off, causing this error.  In this case, there is a configuration problem with autocycle.

    The program is kind of stupid, and an mis-entry in bqEASY will cause the autocycle module to load the battery until the voltage crashes to 0V, but the program never detects this condition and just complains that the gauge stopped talking.

    In my case, it was because I had not read units correctly and entered 3mV instead of 3000mV as my terminate voltage.

    Let me know if this helps,

    Charles

  • 0 in reply to Charles Herder
    Prodigy 50 points

    Hi Charles,

    thank you for your answer.

    The battery has a charging electronic which prevents the battery's voltage from dropping under 3 V. So POR will never be reached.

     

    Therefore I chose the following values:

    (Cell characteristics) Nom. capacity: 2400 mAh

    (Cell characteristics) min. rated cell voltage: 3100 mV

    (Charge parameters) max. cell voltage allowed: 2400 mV

    (Charge parameters) max. taper current: 100 mA

    (Discharge parameters) mincell voltage: 3100 mV

    (Discharge parameters) min. average discharge current: 100 mA

    (Discharge parameters) max. discharge current: 1600 mA

    (Reserve capacity) 250 mAh

    For the remaining values I left the standard settings.

     

    Any ideas?

    Tom

     

  • 0 in reply to Thomas Sauer
    Prodigy 50 points

    Hi,

    last night I did one more chemistry select cycling to see at what voltage the program stops.

     

    The measured values are:

    RSOC = -0,11%

    V = 3112 mV

     

    This voltage is even higher than the battery's cutoff voltage.

  • 0 in reply to Thomas Sauer
    TI__Intellectual 2100 points

    During that cycle, did the gauge stop responding?

    bqEASY relies on the gauge information to determine battery voltage, so this would mean that the gauge communication is intermittant (otherwise, the software would never be able to read the voltage and terminate).

    Is this correct?

  • 0 in reply to Charles Herder
    Prodigy 50 points

    I did not notice anything abnormal until the error occured I mentioned in my first post.

    Of course I was not able to watch the execution all the time but there was no message or something else.

  • 0
    Prodigy 90 points

    Hi,

    I have the same problem with BQ20z75- V160. 

    Everything works fine until step 6 of 7. Near completion of step 6 the execution stops and the same error.

    Process time about 27h ,Voltage ~ 6000mV for two cell

    Best regards

    Wojtek

  • 0 in reply to Thomas Sauer
    TI__Intellectual 2100 points

    Tom,

    Can you post your bqEASY project file? (the .ezy file in your projects directory)?  I should be able to try your cycle here (with a different cell).

    Thanks,
    Charles

  • 0 in reply to Charles Herder
    Prodigy 50 points

    Hi Charles,

     

    this ist the content of the bqEASY project file:

    [Device]
    Type=0500
    Version=0108
    [Setup]
    1A_Proj_Name.Project_Name=IndoorCycling
    1B_Load_DFI_File.DFI_Filename=C:\Programme\Texas Instruments\bq Evaluation Software\Plugins\Device Defaults\bq27500_1_08.dfi
    [Project]
    Name=IndoorCycling
    [Completion]
    1B=True
    2A=True
    2B=True
    2C=True
    2D=True
    2E=True
    2F=True
    2G=False
    2H=False
    3A=False
    3B=False
    3C=False
    3D=False
    3E=False
    3F=False
    4A=True
    4B=True
    4C=False
    5A=False
    5B=False
    1A=False
    [Configuration]
    2A_Cell_Char.Num_Parallel_Cells=1
    2A_Cell_Char.Nom_Cell_Capacity=2400
    2A_Cell_Char.Min_Cell_Vltg=3100
    2B_Chg_Params.Max_Chg_Cell_Vltg=4200
    2B_Chg_Params.Max_Chg_Taper_Curr=100
    2B_Chg_Params.Max_Chg_Temperature=55
    2B_Chg_Params.Min_Chg_Temperature=-5
    2C_Dsg_Params.Min_Dsg_Cell_Vltg=3110
    2C_Dsg_Params.Max_Dsg_Temperature=60
    2C_Dsg_Params.Max_Steady_Dsg_Current=1600
    2C_Dsg_Params.Min_Active_Dsg_Current=150
    2C_Dsg_Params.Initial_Standby_Current=10
    2C_Dsg_Params.SOC1_THRSH=150
    2C_Dsg_Params.SOCF_SET=90
    2C_Dsg_Params.SOCF_CLEAR=120
    2D_Reserve_Capacity.Capacity=250
    2D_Reserve_Capacity.Capacity_Units_mAh?=True
    2E_Load_Characteristic.Is_Constant_Current?=False
    2F_Application_Configuration.PFC_Code=1
    2F_Application_Configuration.Bat_Low_Active_Low?=False
    2F_Application_Configuration.Bat_Gd_Active_Low?=True
    2G_Rem_Capacity_Method.Is_Constant_Load?=False
    2H_Misc_Info.CurrentSenseResistor=10
    2H_Misc_Info.ThermistorConfig=0
    2H_Misc_Info.Int_Focv=0
    2H_Misc_Info.Int_Brem=0
    2H_Misc_Info.Soc_Int_Pol=-1
    2H_Misc_Info.OpcfgB_Wrtemp=-1
    2H_Misc_Info.OpcfgB_Bie=-1
    2A_Cell_Char.Num_Parallel_Cells_2=1
    2A_Cell_Char.Nom_Cell_Capacity_2=1500
    2A_Cell_Char.Min_Cell_Vltg_2=3000
    2F_Application_Configuration.Low_Bat_Active_Low?=False

     

    Thank your for your help,

    Tom