Importance

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Abstract

Charging and discharging of a battery are controlled while observing the state of the battery, thereby improving its efficiency and increasing battery service life. A program control circuit acquires vehicle speed from a vehicle speed sensor and the rotational speed of the internal combustion engine from a rotation sensor. The program control circuit controls an inverter which performs AC-to-DC or DC-to-AC conversion between a motor-generator coupled to the internal combustion engine and a battery mounted on the vehicle. At the same time, the program control circuit acquires the charging and discharging current (i) of the battery, which is detected by a current sensor, and calculates the time integral I of the charging and discharging current (i). The circuit controls the charging current to the battery during regenerative braking, and the discharge current when the vehicle is being driven, in accordance with a function of the time integral I. The overall life of the battery can be lengthened, and the energy lost by the brakes can be most effectively regenerated. Moreover, even if there is variability in the characteristics of the unit cells, its increase can be held in check. In addition, battery costs can be reduced and maintenance simplified.

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First Claim