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bq78pl116 resetting RSOC value

Ran Aloni
Expert 2386 points
Other Parts Discussed in Thread: BQ78PL116, BQ76940, BQ78350, BQ77910A, BQ34Z100

Dear all,

we use BQ78PL116 for a 1KWh battery pack with IP scale 10.

we have set the design capacity to the right "absolute capacity" (39Ah).

but the RSOC is immediately set to a value much higher.

I thought a few cycles would fix this but it just won't go down...

I can see that FC and FD flags are set and we are waiting enough time at idle current.

is there any way to set the value of the FCC ? it is now ~100Ah...

best regards,

  • 0
    TI__Guru 73830 points

    Ran,

    Is Qmax also set to the proper value? This parameter gets set in the tmap file. If you can send me a log file, parameter dump and export a .dat file, then I will review them.
    Tom

  • 0 in reply to ThomasCosby
    Expert 2386 points
    Dear Tom,

    I'm preparing a log file for you, it is a huge pack so it takes time.
    basically I can see FD and FC flags rise meaning learning cycles are completed (+ enough idle time between them).
    one issue that can imply the problem is that this chip was used before on a different battery pack.
    at this point it is nearly impossible to create a new AUX file since the currents are too high (~30A charge).
    I noticed that the version of AUX file is 1 - meaning I'm using a different pack AUX file but with the right CHEM file.

    I fully discharged the pack, made a "relearn initialized", which reset the FCC value.
    but I can see Qmax of the cells in the area of 5500mAh instead of 39000mAh.

    is there a way to delete an AUX file to version 0? is this the cause?

    Ran
  • 0 in reply to Ran Aloni
    TI__Guru 73830 points
    If you have an AUX file, then you can edit it with a text editor and change Qmax and Qrem. You can then import this into the device. I meant to say that Qmax is set by the AUX file, instead of the tmap file. Is there a reason why you are using the PL116 device for this pack? It has been NRND for over 2 years and we have limited resources to support it.
  • 0 in reply to ThomasCosby
    Expert 2386 points
    Dear Tom,
    this is a soft spot you have just touched :-),
    we developed this circuit 3 years ago and produced a large number of circuits.
    we see why it is NRND, since it is very hard to bring it in to a stable production process, and many bad chips.
    but until very recently no vendor has made a better all in one chip for multi-cell BMS over 4 cells in series.
    your bq78350 + BQ76940 only came out very recently, and still soon to decide to move to it.
    BQ77910a + BQ34Z100 is very complicated above 10S battery packs, and doesn't have a cell by cell learning, but global for the pack.
    one thing for sure, when BQ78PL116 works - it's great!