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BQ34Z100-G1: BQ34Z100-G1. FCC Changes

Gorka Lorea
Expert 1620 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQSTUDIO

Hi,

I am using a BQ34z100-g1 with an 8s2p LiFePO4 batteries. The nominal capacity of the battery is 6400mAh.

I have obtained the golden image of the battery and load it in the bq24z100-g1. I have tested the bq34z100-g1 performance during two weeks in a laboratory functional prototype.

I was surprised to see the changes in FCC have been bigger than expected. Here I have a record of the evolution of different parameters.

First column is date of each record. 

Second column is SoC of the battery

Third column is voltage battery at the moment of the record.

Fourth column is current battery at the moment of the record.

Fifth column is nominal capacity of the battery.

Sixth column is FCC of the battery.

Seventh column is max error in SoC stimate. 

The temperature of the battery has been always between 20 and 27ºC.

As it can be seen, FCC values can vary in more than 5% (6458mAh on 13/7/2018 and 6081mAh on 24/07/2018) in only 2 weeks.

What  can be those high variations due to?

  • 0
    TI__Genius 14985 points
    Hi Gorka,
    5% variation is actually fairly reasonable since your conditions are probably not identical at each read point.
    The temperature is one factor that will cause FCC variation. Did you also capture the temperature at those read points?
    Also, depending on the setting you used for Load Select, the current or power you draw from the battery can also cause variations in FCC.
    Can you share your .gg.csv file from the pack so we can see the settings you used, please?
    It's also possible that the gauge is learning updated Qmax, Ra, and other values (especially in subclass 82 of the dataflash) which are causing the capacity to generally decrease.
    Ideally, to get the full picture of why it's going lower over time, if you can send us a .gg.csv file after each cycle then we could see what's being learned and updated each cycle. Also, if you can capture the full DataRAM register set, including debug registers as shown in bqStudio, for a few seconds each cycle, it would give us more details to work with.
  • 0 in reply to dMax
    TI__Mastermind 25955 points
    Hi Gorka,

    It has been a few days - I hope the issue has been resolved. If not, please send the gg.csv file after each cycle as well as capturing the full DataRAM register set including debug registers as shown in bqstudio for a few second each cycle, as requested by dMax, for further review.

    Sincerely,
    Bryan Kahler