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BQ34Z100 VOK bit

sridevi krishnamoorthy
Prodigy 160 points
Other Parts Discussed in Thread: BQ34Z100, BQEVSW, BQSTUDIO, BQ34Z100-G1

hi,

I'm using 6S1P battery with BQ34Z100 as fuel gauge. I'm sending IT_ENABLE command, now VOK bit is set. then i started charging. After charge relaxation OCVTAKEN bit is set and VOK bit is also set. Then i'm discharging the battery to 20.5V and after discharge relaxation OCVTAKEN bit is set and VOK bit is cleared. This behaviour happens when i do the charging using bench power supply.

 

But when i put the battery in my customized PSU, after IT_ENABE command charging and  charge relaxation OCVTAKEN bit is set and VOK bit is also set. Then i'm discharging the battery to 20.5V and after discharge relaxation OCVTAKEN bit is set but VOK bit is not cleared.

 

As per SLUA597, VOK bit should get cleared after discharge relaxation. Why VOK bit is not cleared i my customized PSU??? what could be the possible reason for this??

 

  • 0
    TI__Guru 73830 points

    Sridevi,

    Was the time from charge complete to the OCVTAKEN flag about the same for both cases? The VOK flag may not clear if there was not a valid DOD point set before the charge or discharge started.

    Regards

    Tom

  • 0 in reply to ThomasCosby
    Intellectual 670 points

    Hi, sorry for digging up this grave but I'm also having problem with VOK not being cleared. After a full charge, FC and OCVTAKEN are set, I then disconnected the charger and OCVTAKEN flag is clear, full charge capacity (not sure this is Qmax) and DOD0 updated (reset to 0). I have been waiting for 2 hours but VOK is still not set, is it because I disconnect the charger too soon?

  • 0 in reply to Hac Le
    TI__Guru 73830 points

    The OCVTAKEN flag may clear at the end of charge and then you have to let the pack rest until is sets again. The VOK flag should not have cleared after you removed the charger, but it will clear after the rest. Qmax probably will not update at this point. Can you send the log file?

  • 0 in reply to ThomasCosby
    Intellectual 670 points

    Hi Tom, my OCVTAKEN has been set after a really long period of resting, way longer than a normal 5 hr, I guess it's because my battery is of lead acid chemistry. Anyway, the update status still stay at 0x04, I chose a 12V 26Ah chemID (ID 803) for my 12V 24Ah, chances are the chemID is way off for my battery. Since the calculated parameters are wrong, what should I do to reset the entire chip to factory settings to start another fresh learning curve?

    Our next plan is to use BQ34Z100 for monitoring a 12V 200Ah. Is there any way that I can use BQ34Z100 and BQEVSW combination to characterize the battery and create a new chemID?

    Thank you for replies Thomas.

  • 0 in reply to Hac Le
    TI__Guru 73830 points
    Hac
    The gauge has a 48 hour timeout after charge and a 5 hour timeout after discharge. You will not be able to create a new ChemID, but you can use our online GPC Chem tool to try to find a better match.

    www.ti.com/.../GPCCHEM

    If you have a log file, then I can review it to see if I can find the problem.
    Tom
  • 0 in reply to ThomasCosby
    Intellectual 670 points

    Hi Tom,

    Please find the log file in the attachment. From what I have been searching around the forums, It seems that battery characterization can be done using a battery tester such as Arbin's, is it correct? Since we want to mass produce BQ34Z100 and commercialize it, battery characterization is of great importance to us. 12v24Ah_dis.log

  • 0 in reply to Hac Le
    TI__Guru 73830 points
    Hac
    Your discharge log looks good. The VOK and OCVTAKEN flags are operating as they should, but the DOD0 point did not get set after discharge. This could be a ChemID problem. Can you export a .senc file, so that I can check the setup?
    Tom
  • 0 in reply to ThomasCosby
    Intellectual 670 points

    Hi Tom,

    I can't export the senc with BQEVSW (error 772) but I managed to export SREC FF and FS files via BQSTUDIO. Please have a look.

    OutputFiles.zip

  • 0 in reply to Hac Le
    TI__Guru 73830 points

    Hac

    I loaded your srec file and checked some of the parameters. ChemID 803 is loaded. The Cell Terminate Voltage is set to -15360mV , so it looks like this parameter got corrupted at some point. Try changing it to the terminate voltage that you would like to use. Maybe something in the 1800 mV range.

    Tom

  • 0 in reply to ThomasCosby
    Intellectual 670 points
    Hi Tom,

    Lead acid termination voltages are around 10500 mV, so Cell Termination Voltage should be 10500/6 = 1750 mV. I set this value to the Cell Termination Voltage entry in the "Gas Gauging" tab but get rejected be cause minimum voltage is 2500 mV (while Cell BL Threshold allows this value).
  • 0 in reply to ThomasCosby
    Intellectual 670 points

    Hi Tom, I loaded BQ34Z100-G1 srec file able to set term voltage to 1750 mV. OCVTAKEN and VOK bit seem to behave correctly although UPDATE STATUS still stay at 04. Could you please examine the attached log file and gg file?

    fiam_26Ah.log.zip

  • 0 in reply to Hac Le
    TI__Guru 73830 points

    Hac,

    The VOK flag was not set before the first discharge cycle, so Qmax did not update. It was set before the second discharge, but there is not rest period after the discharge so I cannot determine why it failed. Your discharge rate is also high for running an optimization cycle on a PbA cell. I would use this process.

    • Charge the pack to full and allow it to taper to a C/20 taper current.
    • Allow the pack to rest until the OCVTAKEN flag has set.
    • Discharge it at a C/8 rate to the Termination Voltage.
    • Allow the pack to rest until the OCVTAKEN flag has set. Check to see if the Update Status has incremented to 05.

    If it does increment, then repeat this process to update the Ra table. If it does not update, then send me the log file.

    Tom