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Original question:

BQ34Z100-G1: BQ34Z100-G1 reading learned Qmax

BQ34Z100-G1: "Qmax Cell 0" vs TrueFCC

Doug Baker
Genius 3420 points
Part Number: BQ34Z100-G1

I have done some testing where I charged to 60% SOC, relaxed for 20 min, discharged to 50% SOC and relaxed for 20 min and repeated tis over 3 days and the FCC is reporting around 2,000 but the qmax0 is still around the expected 7500.  I checked the Pack Config C and it is set to 0x37 so all three LSB bits are set for smoothing. 

Any idea why the Qmax and FCC would be so different and is this expected?  It appears the gauge is using the FCC for calculating and reporting SOC and not Qmax.

Thanks,

Doug

This is a follow up question to:

  • 0
    TI__Mastermind 25955 points
    Hi Doug,

    Is the device tapering at 60%? If so, it will learn. If not, need to investigate the log file. Please also send the gg.csv file and chemID #.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Genius 3420 points
    I have the taper current set to the max of 1 Amp and my test software was stopping the charge based on voltage so the battery was still charging just over 1 Amp when I stopped charging. I increased the voltage my test software used to terminate the charge a few millivolts higher so the current tapered back more. The battery is a 4S5P pack and it barley drops below 1 amp before the peak voltage is reached at the end of charge.

    After letting the battery charge just a bit more so the taper current dropped to 0.985 amps , the FCC jumped from 4626 to 7429 so it is back to where it's expected. Based on the gauge limit of 1A taper current and the battery pack we are using, the taper current is really close to not being reached.

    How do the FCC and Qmax differ and how does the gauge use them? It appears the gauge uses the FCC for SOC because when the FCC is off, the SOC is also off even though the Qmax is still accurate.

    Doug