Importance

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Abstract

In an electric vehicle battery charging system where the batteries of an electric vehicle are charged from an external power source including a battery energy management system which monitors the vehicle batteries and develops a current control command representing the current to be supplied to the vehicle batteries and a controllable charger having a design power limit supplies current under command of the current command at a voltage of the vehicle batteries, a charger power limiting circuit is provided and includes a voltage sensor, and a circuit for modifying the current control command to limit power to be low at least in approximation of the designed power limit of the charger. The current control command modifying circuit modifies the current control command from the BEMS to ensure that the controllable charger will not supply power to the batteries in excess of the controllable chargers design power. The charger power limiting circuit includes a power limiting characteristic defining circuit, a current limiting feedback circuit and a power limiting characteristic defining circuit. The voltage of the vehicle batteries is sensed and the current control command from the battery energy management system is used as the charging current. The current control command is then modified to limit power to below at least an approximation of the design power limit of the charger.

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