US Patent 7391183 System for controlling charging of secondary battery

To provide a system for controlling the charging of a secondary battery (battery), which is capable of keeping an initial charging/discharging characteristic of the battery in consideration of a change in environmental temperature and deterioration of the battery with elapsed time. An ordinary charging portion for performing a first charging control specified to stop the charging at a charge level less than a full-charge level is used in combination with a refresh charging portion for performing a second charging control specified to stop the charging at a charge level more than the full charge level. After the charging by the ordinary charging portion is continuously repeated by a specific number of times, for example, ten times, the next charging is performed by the refresh charging portion. The cut-off voltage used for the ordinary charging portion and refresh charging portion is determined by correcting a reference voltage VO on the basis of an environmental temperature TAO detected by an environmental temperature detecting portion. The deterioration of the battery is corrected on the basis of a reference full-charge voltage, an initial full-charge voltage Vmax(1), a present full-charge voltage Vmax(n), an initial maximum battery temperature Tmax(1), and a present maximum battery temperature Tmax(n).