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Linux/BQ27421-G1: SOC % seems to drop about 105 when we unplug then plug-in the same battery

michael schmid97644
Guru 10795 points
Part Number: BQ27421-G1

Tool/software: Linux

Attached is a spread sheet showing the values that the fuel gauge is showing before unplug then plug back in the battery.  It seems to occur only on the frits time but not the next few. Also we noticed the max. capacity also seems to jump , and in this case the max should be set at 2450, but the fuel gauge reports in access of 2500.

battery_SOC_plug-in.xlsx

  • 0
    TI__Guru* 76230 points
    Upon battery insertion, the gauge is prone to errors in SOC measurement because the cell votlage might not be relaxed, there might be current flowing into or out of the battery, or You might be in the flat region of the battery OCV curve. However, once the battery is charged to full or discharged to empty the gauge is able to accurately track the SOC of the battery.
    Also, have you configured the settings of the gauge as per the quick start guide document of the bq27421?
    thanks
    Onyx
  • 0
    TI__Expert 5640 points

    Michael,

    Do you monitor for battery removal and/or insertion, and re-configure the gauge at all when the battery is re-inserted?  This is a ROM gauge, and will default to a more general configuration when power is removed and re-applied.  You are using optimized configuration in the RAM registers.  When you disconnect the battery, it needs to be re-configured to your optimized configuration in order to accurately gauge your specific cell.  Are you following that procedure in SW?