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BQ2010: "learn" new battery capacity

bashkim racaj
Prodigy 10 points
Part Number: BQ2010

I'm not able to have the bq2010 gas gauge "learn" new battery capacity. This is an old gauge and I wouldn't use it now but having issues with battery packs in the field. 

Scenario: say CPI is 3 (three times charged without a qualified discharge), when I charge the battery the LMD seems to always get to PFC-1 (or perhaps as I put the battery to use and read registers one count goes down), then I discharge the battery to below EVD1, however, CPI does not reset to 0-stays at 3. This leads me to believe that re-calibration didn't take place.

Please advise. 

  • 0
    TI__Mastermind 42535 points
    The battery capacity can be learned by charging the battery until NAC = LMD (LMD = PFC on initialization) and then discharging the battery until the cell voltage reaches the End-of-Discharge Voltage (EDV1) threshold (1.05V for the bq2010). As discharge occurs, the bq2010 tracks the amount of charge removed from the battery in the DCR. The new battery capacity (DCR) is transferred to the LMD if no partial charges have occurred, the temperature is above 10°C, and selfdischarge accounts for less than 8 to 18% of the DCR when EDV1 was reached. The valid discharge flag (VDQ) in the bq2010 indicates whether the present discharge is valid for LMD update.

    I suspect that your LMD was not set up correctly.

    The LMD is susceptible to error on initialization or if no updates occur. On initialization, the LMD value includes the error between the programmed full capacity and the actual capacity. This error is present until a valid discharge occurs and LMD is updated (see the DCR description on page 7). The other cause of LMD error is battery wear-out. As the battery ages, the measured capacity must be adjusted to account for changes in actual battery capacity.

    A Capacity Inaccurate counter (CPI) is maintained and incremented each time a valid charge occurs (qualified by NAC; see the CPI register description) and is reset whenever LMD is updated from the DCR. The counter does not wrap around but stops counting at 255. The capacity inaccurate flag (CI) is set if LMD has not been updated following 64 valid charges.