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BQ40Z60: Learning Cycle - Settings for 2 cells

Thomas Albrecht46
Prodigy 240 points
Part Number: BQ40Z60
Other Parts Discussed in Thread: BQSTUDIO,

Hi there,

i am trying to perfom a succesful manual learning cycle with a two cell setting. The hardware I am using is the bq40z60EVM-578.

I've calculated the "advanced charge algorithm setting" according to the app-note SLUA750.

I would like to have a fully charged voltage of 8400mV. I am using the charge settings shown below. My problem is that the TC-bit is never(I am using the option when doing the learning cycle)  set as the charging process stops too early. ( That's at least what I think.  Any suggestion what the problem might be. Wrong calculated values? When is the TC-bit set?

My second question is about the gauge. Even if bqStudio shows 100% charged only 2 LEDs are on. Do I need to perfom a whole learning cycle to get proper indication? I am using two Panasonic NCR18650B cells. Is the Design Capacity (3350mAh, 2412cWh) and design voltage of 7400mV correct?

Thank you very much

Best regards

Thomas

  • 0
    TI__Expert 6575 points
    Hi,
    It is difficult to tell from the bqStudio screen shots.
    It will be easier if you can post your bqStudio log and your gg file to look into this further.
    Regards,
  • 0 in reply to Swaminathan Ramanathan75031
    Prodigy 240 points

    Hi,

    I've attached the gg.file of my configuration.

    I not quite sure what kind of log file you want and how to create it. If you let me know I would kindly provide it.

    Thank you very much

    Thomas

    ti_review.gg.rar

  • 0 in reply to Thomas Albrecht46
    TI__Expert 6575 points
    Hi Thomas,
    In the "Register" screen of bqStudio, there is a "Start Log" button next to the "Scan" button.
    It will prompt you for a file name, and you log the data from the gauge during your Charge->Rest(2hrs)->Discharge(At around C/7)->Rest(5hrs)
    You can then stop the logging, and attach it in this post after compressing it.
    Regards,
    Swami
  • 0 in reply to Swaminathan Ramanathan75031
    Prodigy 240 points

    Thanks for your answer Swami.

    As TC/FC is never set during the charge process when exectuting the learning cycle I neither reach the relax state of the charge progress nor the discharge progress. However I've attached the .gg- and log-file of my latest learning cycle. 

    Thank you very much for your help

    Best regards,

    Thomas

    6138.ti.rar

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    I did find that you were reaching relaxation during dsg. This is indicated by RDIS clearing and REST flag getting set when ITStatus changes to 0x11. However, your battery is not reaching charge termination. This is because your rec chg v in adv chg algorithm section is set to 4100mV while your TC and FC settings are for 4200mV. Please change it to 4200mV and restart your test.
  • 0 in reply to Batt
    Prodigy 240 points

    Thanks Batt for you answer,

    I tested it with the change in the register. Still the same. I'am going to make another log.

    What I noticed is that the "OC" Bit in the "Safety Alert C+D Register is set and then the charging process stops of course. I couldnt find out what's the reason for this is. In the  application node "sluua04d" it only says over current.

    Thank you very much

    Thomas

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    OC means overcharge. It can happen if your charging beyond design capacity. Please try your test with a fully discharged battery, then reset and wait for RDIS to clear and then start charging.
  • 0 in reply to Batt
    Prodigy 240 points

    Hi Batt,

    just to confirm what I should have done(all was done manually - so no learning cycle):

    1. I discharged my battery till 5600mV (is this fully discharged? The TD-Bit was set / FD not yet)

    2. I did a Reset so RDIS-Bit was set.

    3. I waited till RDIS was cleared

    4. Started the charging process

    I ended up with the same result. I've added the log.

    Thank you very much8623.ti.rar

    Best regards,

    Thomas

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    This may take me some time to debug. I'll try to look into it today, if not, you will have a reply sometime next week.
  • 0 in reply to Batt
    TI__Mastermind 42535 points
    Your charging is all over the place. There is again no proper taper. We need a CC/CV style of charging for the learning cycle and I'm not seeing that happen here. This is why your learning cycle is failing. Why is your current and voltage on the charger jumping all the time during charging?

    Please use a standard 4200mV across all temp ranges and set your chg current across all ranges to C/2 which is about 1700mA.
  • 0 in reply to Batt
    Prodigy 240 points

    constant_charge_temp.rarHi Batt,

    thanks for reviewing the log.

    I did two testruns: At the first one I saw the current dropping to zero and then going back to "normal". I checked the log file and I saw a few temperatur spikes for some temp sensors but not for the internal sensor. However I see no tapered current. Am I expecting 250mA? This is the attached log "2cell_20181228".

    After this I did again a calibration and added a fan to cool the EVM. But I seems to be the same. I cannot see any CC/CV. When am I to expect the current to drop to a lower level? I stopped the charging process in this test. The log file is called: "2cell_20181228_new_calibrated_1700mA_charge_fan" 

    I know I've seen the current adjusting and also a tapered current of ~250mA with a different configuration. Did I adjust a a register wrong?

    I going to do some more test tomorrow.

    Thank you very much

    Best regards,

    Thomas

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    I would suggest flashing the default fw and then calibrating and programming your correct chem ID. That way you would have a reset and can start afresh.
  • 0 in reply to Batt
    Prodigy 240 points

    Hey Batt,

    it's getting strange. As suggested I programmed the default firmware "bq40z60_v0_15_build_21.srec".

    Then I calibrated, programmed the chem ID and changed following configs:

    - DA Configuration: CC1:cleared / CC0:set (2 cell configuration)

    - LED Configuration: LEDCHG:set

    - Advanged Charge Algorithm: Minimum Voltage Output: 4218mV / Voltage Resolution: 16 / Max Current Register: 241

    - Gas Gauging: Design Capacity mAh: 3350 / Design Capacity cWh: 2479 / Design Voltage: 7400

    When checking the log file I cannot see any tapering at all. When I reprogrammed the gauge shows 0%. As soon as I do the current calibration it's back to 100% and stays at 100%. I've added the log and config but you might wait for a second try.

    Strange thing is, that I saw the a tapered current before with the same configi believe. Do you think I should adjust the charging current according to the cell? Didnt want to change it yet. Can this be a hardware problem? I have a spare bq40z60 to change and I can also change the cells.

    Thank you very much,

    Best regards,

    Thomasdefault_firmware.rar

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    Please upload your log as well. I suggested that in adv chg you set all your currents and voltages to the same so that the charger control gives a constant supply and allows current to taper. Without seeing the log, I can't analyze this. I will load your srec and check it out sometime by Friday this week.
  • 0 in reply to Batt
    Prodigy 240 points

    default_firmware_2.rar

    Additional to the procedure before I changed all the charging currents to 1500mA. My problem is now, that the charging process stops way too early.

    I compared it to a setup where I can charge to a higher level. The only main difference I see is under "Gas Gauging"->"IT Cfg" -> Term Voltage: 9000mV. The setup which allows me to charge to a higher level the Term Voltage is set to 6000mV.

    I've attached the log and the settings.

    Regards,

    Thomas

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    Terminate voltage for a 3s pack should be set to 8200 or 9000mV. Setting term V artificially low does not aid in gauging as your cell voltage drops below the full discharge state voltage in your OCV.
  • 0 in reply to Batt
    Prodigy 240 points

    When does constant current changes into constant voltage? Are there any settings or adjustment you can do. I only see that the charging current during constant current can ber changed. Am I correct when I assume that for 2cell 8400mV should not exceed during charging?

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    CC changes to CV when the current begins to drop from set charging current. You are right about voltage. If your battery is rated 4.2V per cell, you should not exceed 8.4V.
  • 0 in reply to Batt
    Prodigy 240 points

    Hi Batt,

    in the meantime I've build up my own hardware, programmed the standard firmware and changed the relevant things. I tried to complete a learning cycle but charging stopped at 7622mV and the learning cycle aborted. Then I did a reset and it's charging again. I am logging this at the moment.

    I've added a log of the discharging and charging till it stopped and the memory configuration. Could you maybe take a look. I am seeing again the Over Charge Bit in the Safety Alert C+D.

    Thank you very much

    Best regards,

    Thomas

    20190129.rar

  • 0 in reply to Thomas Albrecht46
    Prodigy 240 points

    When I do a reset after everytime the charging stops I can go up to 8400mV but no tapering of the current can be seen. So that's definitely no solution.

    I've added the log file.

    log_file_reset_after_learning_cycle.log

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    Thanks for he logs, Thomas. I'll look into this and reply back to you on or before next week Monday.
  • 0 in reply to Batt
    TI__Mastermind 42535 points
    Thomas,

    Please do not change the advanced chg algorithm section. The preconfigured values in it will work for the 2s config.
    The only thing you need to change is the number of cells in DA config and your term voltage and gas gauging design parameters.

    With this you can cycle it for 2 cells without early taper. I believe the early taper was as a result of the charger voltage being low and therefore it not being able to push current into the cell.
  • 0 in reply to Batt
    Prodigy 240 points

    Hey Batt,

    thanks for your answer. I was adjusting the charger settings according to "slua750" which I've found here in the forum but I am going to try the defaults. Where do I find the term voltage? I just can find the "Charge Term Voltage" in "Termination Config" in the advanced chg algorithm. I am looking for something like "final pack" voltage (8400mV) or on cell base 4200mV.

    Thank you very much

    Best regards,

    Thomas

  • 0 in reply to Thomas Albrecht46
    TI__Mastermind 42535 points
    If you are looking for charge termination voltage it's the one that you find in termination config. Your thresholds for charging are set by the voltages specified in the temperature range.

    If you're looking for full discharged cell voltages to set 0% RSOC, that's in the gas gauging section under Term Voltage.