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Impedance Track Algorithm not working as expected ?

Hi, 

We are currently testing the BQ34Z110EVM and are facing difficulties ...

You can see from the screen bellow that the State of Charge is not being properly calculated, as there are discontinuities that are not to be expected (are they ?).

It seems the Remaining Capacity is being reset at times it shouldn't, as the gauge is not in relaxation state.

 On the first graph you can see the discharge current we are applying (in Amps), and on the second the SOC that the gauge displays.

Any help on the matter would be kindly appreciated !

  • The current was reduced, so the SOC could have increased. Can you provide a log file and gg file for analysis? 

  • Hi,

    Thank you for your quick response !

    Here are two log files from two different tests we did. You will notice that the same problem occurs in both cases.

    What exactly is a gg file and how do I get it ?

    Besides, why would the SOC be affected by a current change ? The only reason would be that the gauge takes Peukert's effect into account (right ?), but it seems it doesn't : we've used the @rate time to empty with different current and we've found that Q=I*t=constant no matter what...

    Your help is really appreciated.

    5633.Test SOC 10Ah Inom 2A.log

    3225.Test2 SOC 10Ah Inom 2A.log

  • Maxime,

    You have some really odd performance in the Passed Charge data. Can you export a senc file from the pack. Go to the I2C Pro screen. Use the Write I2C Data Block section (I2C Command 00, Data Block 000f) to place the device into ROM mode. Use the field at the bottom of the screen to save a senc file to your computer. Press the Read to 8.senc file button. Press the Execute button to return the pack to normal mode after the transfer has completed.


    Tom

  • Hi, 

    Thank you again for your time on our concern.

    I've managed to get the .senc file. I hope you can identify what is wrong (most likely what we did wrong).

    I couldn't upload it directly on this forum (extension not recognized) so here is a download link.

    http://www77.zippyshare.com/v/64712223/file.html

    Maxime

  • Maxime,

    I reviewed the senc file and found that you have not run the optimization cycle yet. You can download a document from the product website for some guidance in running the cycle. SLUA711

    I also updated some parameters in your senc file to to make it easier to pass the optimization cycle. You should also verify that you are using the proper ChemID before running the optimization cycle. You can collect log data and I can help to find a ChemID match. I will attach a document to help with this in the next post.

    Tom

    Data_modified.senc
  • Guideline to collect ChemID verification data.

    Chemistry selection.pdf
  • Hi, 

    Thank you very much for your help ! 

    In our case, we are testing the gauge with different batteries. For now, we are only changing the capacity in the data parameters. So we should run an optimization cycle every time we change the battery ? Is there a way to avoid doing that, and not having problems such as the one I previously described ?

    It seems the optimization cycle enables the gauge to measure Qmax and the Ra table. But can't we just change it manually to trick the gauge into thinking the optimization cycle is done (event setting update status = 6 ?)

    Thank you for your time and help on the matter.

    Maxime.

     

  • Maxime,

    You need to run an optimization cycle after you change to a different cell model (part number) or change the cell configuration. Otherwise, the Ra table and Qmax will be off and the gauge will not work properly. 

    Tom

  • Tom, 

    Thanks you very much for your help and time on the matter.

    We are going to adapt the way we are studying the gauge.

    Maxime.

  • Hi again, 

    We are now doing a learning cycle, but we are facing an other difficulty. The voltage of our battery is not high enough to set the VOK flag (approx 13.2V).

    We can't find the parameter that would allow us to change the VOK threshold...

    Maybe you know which one we should change ?

    Thank you very much for your help,

    Maxime. 

  • Maxime,

    Are you saying that the voltage is in the disqualified voltage range and this is preventing the VOK flag from setting or is there some other reason? Can you export a senc file from your pack and also provide a log file showing the problem?

    Tom

  • Hi Tom,

    Yes I think that's the problem. We could pass the first cycle to get update status = 5 be we can't finish it.

    Here is a link to the files you asked for. As you will see in the log file, we tried to overcharge the battery so that it's voltage would be high enough but weren't successful.

    http://www74.zippyshare.com/v/23095165/file.html

    But isn't there a parameter that we can change in the gauge data ? We tried to change Cell V at Charge Term but it didn't work ...

    Thank you very much for your help !

  • Maxime, 

    I reviewed the log file to determine why the Ra table update did not occur. The Ra table gets updated as the cells discharge and it gets saved to the flash when the second Qmax update occurs during the rest period. An 84 second long discharge occurred during the rest period after charge and this discharge pulled the cell voltages down inside the disqualified voltage range and cause VOK to clear. This disqualified the Qmax update. I think that the Ra table update would have completed, if this short discharge had not occurred. You can export gg files as the pack is discharging to see whether the table is updating. I usually export it every 60 seconds.

    Tom

  • Hi, 

    Thank you very much for your time and help on the matter. 

    The thing is that I stopped the discharge after 84 sec because I realized the OCVTAKEN hadn't been set. The PassedCharge was therefore negative (and not reset to 0) so I figured the cycle wouldn't work. 

    What shall I do now ? My update status is still 5, does it mean that if I complete a discharge where VOK is set, it will complete the learning cycle ? Or do I have to re enter the 21 command ?

    Sorry for bombarding you with questions ! We are grateful for your help.

    Maxime.

  • If the pack is fully charged and OCVTAKEN and VOK are set, then you should be okay. You can issue the IT Enable just to make certain. (This sets a DOD point and VOK.) I would export the gg files every 60 seconds during the discharge and we can see whether the Ra table is updating. You can find this tool under the Options menu on the Data Flash screen.