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Original question:

BQ34110: Using the remaining charge capacity of my battery pack.

BQ34110: Trying to understand remaining capacity information when discharging battery

Elder Costa17
Expert 2825 points
Part Number: BQ34110
Other Parts Discussed in Thread: BQSTUDIO,

I am working with a NiMH pack, 10S so 12V nominal voltage.

I am charging the battery pack through its full capacity (4900mAh). I know the pack is fully charged because of the time it took for it to fully charge, and because of the dT/dt (temperature rise per minute) rate.

The Remaining Capacity (RC) reading shows 4900 as expected.

However, once I disconnect the charger and start discharging, RC immediately drops to some value around 150mAh.

I thought it could be related to my firmware doing something wrong when the state chaged from charging to discharging, so I stopped the firmware (on debugger) when full charge was reached (RC was at 4900) before disconnecting the charger and connecting the load; fuel gauge was being monitored with bqStudio.

What am I doing wrong? Is there some configuration that I may have forgotten to set?

FWIW I am using the gauge only for its measuring capacities (current, voltage, temperature, RC etc.); it is up to my firmware to determing the charging termination based on dT/dt or dV/dt or maximum temperature , whichever happens first.

  • 0
    TI__Mastermind 19195 points

    Hi Elder,

    Can you .gg and logs from bqstudio and we will take a look.

    Thanks,

  • 0 in reply to Nick Brylski
    Expert 2825 points

    Hello, Nick.

    First off, thank you very much for your quick response.

    While prepping to generate the files you requested, I think I found the cause of the behaviour I described above.

    I used the spreadsheet (0830.bq34110_dataflash_notes_rev03_20181002.xlsx) to create the configuration file for BQ34110. It turns out, the spreasheet set CEDV profile (EMF, C0, R0 etc.) to Li-Ion instead of NiMH, whereas for the fixed values it does perform some calculations based on the battery parameters supplied (first page of the spreadsheet). As the CEDV Configuration value is the default (0x102A), I suppose the fuel gauge calculated the remaining capacity based on Li-Ion defaults, giving (very) wrong RC data.

    I have changed the CEDV parameters to the NiMH example values on the spreadsheet and it is showing a more consistent RC now.

    I have not yet collected battery data to determine CEDV parameters, and on the short term I will not be able to do it (prioritizing firmware development items, still trying to figure out the behavior of the NiMH pack samples, still learning how to tame BQ34110).

    I suppose I should reset EDV_CMP until I have been able to colect the battery pack data, right? Or the example values could work for the time being?

    Any advice is welcome.

    BR.

    Elder.