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BQ34Z100-G1: How to test SOH function is working

Jason Gurley61
Prodigy 160 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100, BQ34110, , BQ40Z80

Hi,

I am having trouble getting SOH to show anything more than 100%.  I found an app guide that talks about adding 100 to 200 mOhm between the gauge and battery leads in order to simulate an increased ESR. After a full charge/discharge cycle, It was said that adding this ESR would change the SOH value.  I have tried adding 45mOhm and 100mOhm ESR with no success.

We have 4S2P configuration of LiFePo4.  The gas gauging we have so far looks very accurate.

Q1. Cycle count in the "Gas Gauging/State/Cycle Count" is still at zero.  Is this an indication that Qmax is not updating and therefore SOH is not updating?

Q2. What else would keep the SOH from updating?

Q3.  Is there a better way to test that this function is working correctly?

our *.gg.csv file is attached.

4S2P_LIFEPO4_6200MAH_14V_Settings.gg.csv

  • 0
    TI__Genius 12215 points

    Hi, Jason

        You need to do another learning cycle so as to get Qmax and Ra Table updated, after this I believe you will be able to see a SOH change 

  • 0 in reply to Steven Yao
    Prodigy 160 points

    Hi Steven,

    A learning cycle requires the battery to completely drain down, relax and then completely charge and then relax.   During normal operation, our battery will never see those types of charge and discharge cycles.   The battery usage in our system keeps the battery charged, except for at night there is a 50mA constant draw.  The battery never truly gets a chance to relax.  It's either charging or discharging.  Does this mean that SOH will never update since it can never go through a full learning cycle out in the field?

    I have see RA table updates, and I have seen FCC change.  However, I cannot seem to get the battery to go through a learning cycle while in system.

    Are there parameters we can adjust to allow the GG to learn in our system during normal operation?

    Thoughts?

  • 0 in reply to Jason Gurley61
    TI__Genius 12215 points

    Jason

        Looks like bq34z100 is not the appropriated device for your application, you can check if bq34110 is more suitable for your applicaition

  • 0 in reply to Steven Yao
    Prodigy 160 points

    We started out with the BQ34110 and changed over to the BQ34Z100-G1 because it would not learn.  It didn't have impedance track.   Also, that device needed some large power resistors that had to stay on for several minutes in order to figure out the end of service with relaxation periods as well.  IOW, the battery had to be taken out of service for the determination to happen.  Sounds like the same is true of both gas gauges.

    What is it about the BQ43110 that makes it better suited for this application?  

  • 0 in reply to Jason Gurley61
    TI__Genius 12215 points

    I do not know how many cells are in series, if the series number is less than 8, than you can use bq40z80.

    We have implemented new algorithm for fast qmax learning, but this is only for the new generation gauges like bq40zxx.

    If you can use these devices, please refer the document via the link of http://www.ti.com/lit/an/slua997/slua997.pdf for details on how config this feature