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BQ2060A Bad FCC Update

Giovanni Marelli
Prodigy 160 points
Other Parts Discussed in Thread: BQ2060A, BQ20Z90

Hi !!!

At page 12 of bq2060A datasheet, I read "FCC becomes invalid if it is initialized or updated to a value less than 256mAH."

What does it happen into the BQ2060A if, using a damaged 400mAh Lead Acid Battery, FCC is updated to a (real) value less than 256mAH ???

At the first Qualified Discharge, FCC has been updated to a correct 250mAh value ... but, after a full charge (to the real 250mAH battery capacity) and a second Qualified Discharge, FCC was updated to 65530mAH value (equals to a 16 bits unsigned integer 250-256 !!!). After a third full charge and qualified discharge, FCC was updated to 65274mAH (65530-256 ...) and the gas gauge has become unusable !!!

Is it possible to avoid this problem in any way ???

 

Here is the .LOG file

2867.Bad FCC Update.LOG

 

Thanks a lot,

   Giovanni

  • 0
    TI__Genius 10235 points

    The gauge isn't going to be able to work with a capacity below 256mAh.  I believe the recommended capacity range for this gauge is  800mAh to 10,000mAh.

  • 0 in reply to Chase7071949597
    Prodigy 160 points

    Thanks Chase !!!

    ... but, what a limit for such a component !!!

     

    In such a situation, an error state could be acceptable: for instance ...

    if (FCC < 256mAh), then

        (FCC unchanged / no Qualified Discharge)

    or (FCC  = 0),

    or (FCC = 256mAh),

    or/and (set an error flag),

    or/and (gas gauge disabled),

    or/and (...)

     

    ... but an underflow (FCC = 250mAh -> FCC = 65530mAh after a Qualified Discharge), without any kind of gas gauge alarm is really hard to manage and will destroy any gas gauge performance !!!

     

    When will texas develop a new gas gauge component (such bq20z60) for Lead Acid or NiMH packs ???

    Because I succesfully used bq20z90 and bq20z60 with LiPo packs, but those components does'n work with Lead Acid and NiMH packs ...

     

    Have a nice day,

       Giovanni

  • 0 in reply to Giovanni Marelli
    TI__Genius 10235 points

    We are in the evaluation phase for creating a part that will be able to gauge Lead Acid and NiMH packs to replace the bq2060A, but we won't be able to give an update until sometime in Q2.

  • 0 in reply to Chase7071949597
    Prodigy 160 points

    Thanks, Chase ... I'll keep waiting for the new component !!!

    ... at the moment, I tried to "solve" the problem by multiplying the current with a 5x factor (I have a 50mOhm shunt, and I calibrate it with a 5x current, so I obtained a 10mOhm calibrated value). In this way, my 400mAh capacity becomes a 2000mAh, and the system seems to work fine also with a <200mAh damaged battery.

    Clearly, the problem still exist if the real battery capacity will fall to a <51mAh real capacity (<51x5 = 255mAh capacity for the gas gauge).

     

    Have a nice day !!!

       Giovanni

     

  • 0 in reply to Chase7071949597
    Prodigy 160 points

    ... the new component will be pin compatible with the bq2060A ????????????

    ... because I'm shifting from project to production phase ...

     

    Thanks,

       Giovanni

  • 0 in reply to Giovanni Marelli
    TI__Genius 10235 points

    We won't know for sure until the project is scoped out, but considering the bq2060A is really old hardware, I would assume no. They likely won't be pin compatible.

  • 0 in reply to Chase7071949597
    Prodigy 160 points

    OK ... I'll keep waiting !!!

    Thanks for all !!!

     

    Have a nice day,

       Giovanni