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Bq34z100 Qmax learning problem

ALAN WRIGHT1
Prodigy 140 points
Other Parts Discussed in Thread: BQ34Z100, BQSTUDIO, BQ24170

Hi

I'm currently trying to the operation for Qmax, i have followed the calibration process and now  the Qmax learning procedure. below is one of the few i have found on this forum

1. Send an IT Enable (21) command to turn ON FETs. Send a Reset command (41) to disable Ra-table updates.
2. Discharge to empty
3. Wait 5 hours
4. Send IT Enable command to set a DOD0 reference point.
5. Charge to full
6. Wait 2 hours Qmax will be learned at this step. You should see VOK turn green after Qmax has learned. You should see Update Status change to a 05.
7. Discharge at typical low rate of target application (usually C/5 for notebooks) down to Term Voltage. Using low rate will allow to update resistance points at deep states of discharge. Rate of discharge must be higher than C/10 rate, otherwise resistance will not update.
8. Wait 5 hours for relaxation. You should see Update Status change to a 06 during the rest period.
9. Repeat steps 5-8 while running EV Software log to verify accuracy.

Questions

1

all is going well until step 6. when i turn on the Qmax learning the VOK bit stays low.  my question is what are the factors that must be correct for VOK to go high ? does the discharge have to be of a certain rate ? also i let the battery relax for at least 2 days while i was still connected to the bq34z100 (not in sleep mode).

sorry, i have a few more questions whose answers will help clarify things for me.

2.

if i need to leave Qmax learning mode, how do i do that if there is only a command to enter it (21) ?

3

I have a 4 serial  x 2 parallel battery configuration which gives me a nominal voltage of 14.8V at 4.5A, its max charging voltage is 16.8V.my charger is set for 16.8 volts, which value do i use for the highest expected battery voltage for the 'voltage divider' entry  (step 3 in design steps on page 29 of BQ34z100 datasheet)

4.

on the bq gas gauge evaluation software 'DataRAM' screen, should the 'Full charge capacity' show the total capacity of one cell of the battery pack or of the whole pack ?

5.

is the Qmax Cell 0 value the value of one cell of the battery pack or of the whole pack (4500mA) ?

thanks for any help given. I know some of these questions may seem straightforward but i just want to clarify i have certain things correct.

many thanks

Alan

  • 0
    TI__Guru 73830 points

    Alan,

    Here are some comments.

    I modified your optimization cycle to tailor it to the bq34z100.

    Set your Flash Update OK voltage to 2000mV. Set the FConvEn bit to 0 in the Pack Cfg B register.

    1. Send an IT Enable (21) command to turn ON FETs. Send a Reset command (41) to disable Ra-table updates.
    2. Discharge to empty
    3. Wait until the OCVTAKEN flag turns red.
    4. Send IT Enable command to set a DOD0 reference point.
    5. Charge to full (FC bit set.)
    6. Wait until the OCVTAKEN flag turns red. You should see VOK turn green after Qmax has learned. You should see Update Status change to a 05.
    7. Discharge at a C/8 rate down to Term Voltage.
    8. Wait until the OCVTAKEN flag turns red. You should see Update Status change to a 06 during the rest period.

    (2) You cannot disable IT after the 21 command has been send, but a reset 41 command will disqualify the DOD point and prevent Qmax from updating and the Ra table from updating.

    (3) You should set the resistor / divider for the maxium voltage that will be applied. It will be 16.8V in this case.

    (4) and (5) All parameters in the device are cell based. The Design Capacity and Qmax max will be set to the number of parallel cells. It will be 2 times the capacity for one cell in your case.

    Regards

    Tom


  • 0 in reply to ThomasCosby
    Prodigy 40 points
    Hello,

    i have also problems with a calibration of the Qmax of the battery.
    I use the bq34z100 with bqStudio 1.3.45 and the Charger is a bq24170.

    The Battery properties are:
    7Cells parallel Panasonic NCR18650B.
    Capacity: 22.4Ah
    Energy: 82.2Wh

    At the beginning I have calibrated the offset of the board and set the Chemistry-ID to 2012.

    Configuration of the FuelGauge:
    Taper current: 224mA
    Design Capacity: 22400 mAh
    Design Energy: 8220mWh
    Design Energy Scale: 10

    Then I started with your commented steps.
    But the OCVTAKEN flag on step 3 does'nt go to red and also the RUP_DIS, QEN flags are red and the QEN is green.
    I am waiting for 8 hours and there are no changes.

    What is wrong?

    Thanks for help,
    Daniel
  • 0 in reply to Daniel Huhn
    TI__Guru 73830 points

    Daniel

    You will need to verify that you have a good ChemID match to your cells and we have an online tool to help with that.

    www.ti.com/.../GPCCHEM

    This will be a better optimization cycle for the bq34z100. Be sure to log data through the entire process.

    •   Configure the dataflash with appropriate parameters suitable for your application; configure pack's chemistry and perform calibration.
    •    Activate impedance track.
    •    Charge the pack to charge termination.
    •    Allow the pack to rest until the OCVTAKEN flag sets.
    •    Discharge the pack at a C/10 to C/5 rate to the Termination Voltage.
    •    Allow the pack to rest until the OCVTAKEN flag sets. Qmax should update and Update Status should increment to 05.
    •    Fully charge the pack to charge termination.
    •    Allow the pack to rest until the OCVTAKEN flag sets.
    •    Discharge the pack at a C/10 to C/5 rate to the Termination Voltage.
    •    Allow the pack to rest until the OCVTAKEN flag sets. The Ra table should update and Update Status should increment to 06.

    You can then run a couple for cycles to check the gauging performance and then move forward to creating the golden file that can be used to program additional packs.

    Tom

  • 0 in reply to ThomasCosby
    Prodigy 70 points

    Hi Tom,

    I am performing an optimization for the following battery pack:

    LiFePO4 Battery

    15 in series

    3.2V

    40Ah

    I performed the optimization cycle you posted above but after step 3 (charge the pack to termination), the OCVTAKEN bit will not set. I have been waiting more than 12hrs and the bit still has not set. Attached are the configuration files and log files of the cycle.

    Thanks,

    Chek

    Calibration Start from Discharged 1.logBQ34Z100G1 Config.gg.rar

  • 0 in reply to Chek Castillo
    Prodigy 70 points

    4251.BQ34Z100G1 Config.gg.rarRe-uploading the zip file to include the log data.

  • 0 in reply to Chek Castillo
    TI__Guru* 76230 points
    Chek
    I would recommend you always start a new post for your own issues to ensure you get a timely response. For LFP cells, the relaxation after charge tends to be quite lengthy due to the nature/characteristics of the cell. Did you set the LFP_relax flag in IT gauging configuration? Also did you ensure that you are using a correct chem id?

    thanks
    Onyx
  • 0 in reply to ThomasCosby
    Prodigy 170 points

    Hello Tom,

    I'm running through the first learning cycle. My question is if is it crucial to reach FC set in step5? In my battery I have reached the charging voltage and the current has dropped below C/100, but SOC shows only ~90%. (It's a brand new Panasonic LC-P1220P pack and the config is setup according to the datasheet.) Should I increase the charging voltage and let more charge into the battery or will the gauge learn that this is the Qmax?

    Best regards,
    KornelEVM_Pana_LC-P1220P_02.gg.zip

  • 0 in reply to Kornel Straub
    TI__Guru* 76230 points
    Hi Kornel.
    I would recommend always starting a new post for your own issue.
    In response to your question, make sure you are charging to the max voltage stated by the cell maker in the DS and make sure you are terminating discharge to the min voltage stated as well. It is important to have FC flag gettting set during the learning cycle. You need to set your taper current appropriately to ensure charge termination is detected by the gauge. Make sure FC set is set to -1 to have charge termination is detected by the gauge based on taper conditions. SOC is of no consequence until learning has completed., ie you can't use the SOC reported by the gauge unless your learning completed successfully.

    thanks
    Onyx