摘要 |
A status of a battery is detected to determine whether an amount of residual charge is large or not. Detection of the status of the battery is performed on the basis of a change in the voltage level over a preliminary charge time. If the battery is determined to at low charge, then a sleep time is set. The full charge condition of the battery is, for example, detected when a second order differential of the voltage across the battery becomes negative. However, the computation of the second order differential is not performed during the sleep time. Further, to accurately determine the status of the battery, the duration of the preliminary charge time is prolonged if the battery is detected to have been deeply discharged.
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