摘要 |
Based on a plurality of valid data sets from a data set selection portion, an internal-resistance-during-charging calculation portion calculates the value Rc of internal resistance during charging from the slope of a voltage-current linear approximation during charging, and an internal-resistance-during-charging-and-discharging calculation portion calculates the value Rcd of internal resistance during charging and discharging from the slope of a voltage-current linear approximation during charging and discharging. A judgment portion compares the absolute value &Dgr;R of the difference between Rcd and Rc that has been calculated by a difference computation portion with a first predetermined value &Dgr;RT1, and when &Dgr;R≦̸&Dgr;RT1 is satisfied, the judgment portion outputs Rcd or Rc, whichever is smaller, as the value of internal resistance of a secondary battery.
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