A battery charger comprising: a plurality of power converters (10_1, 10_2,..., 10_n) configured to convert power supplied from a power supply, and to supply converted power to a battery; and a charge controller configured to cause the plurality of power converters (10_1, 10_2,..., 10_n) to operate at least two charging operations selected from a constant current charging operation to keep a charging current constant, a constant power charging operation to keep a charging power constant, or a constant voltage charging operation to keep a charging voltage constant, to charge the battery, the at least two charging operations including at least the constant voltage charging operation, wherein the charge controller is configured to cause the plurality of power converters (10_1, 10_2,..., 10_n) to operate in parallel, in performing either one of the constant current charging operation or the constant power charging operation, wherein the charge controller is configured to cause any one of the plurality of power converters (10_1, 10_2,..., 10_n) to solely operate in the constant voltage charging operation, wherein the charge controller is configured to replace the one of the plurality of power converters (10_1, 10_2,..., 10_n) to solely operate with another one of the plurality of power converters (10_1, 10_2,..., 10_n) in turn for every predefined period of a plurality of predefined periods in which a period from a start to an end of the constant voltage charging operation is divided, wherein the plurality of power converters (10_1, 10_2,..., 10_n) includes at least three power converters, wherein the charge controller is configured to cause the plurality of power converters (10_1, 10_2,..., 10_n) to perform in an order of the constant current charging operation and the constant voltage charging operation, or in another order of the constant current charging operation, the constant power charging operation, and the constant voltage charging operation, to charge the battery, and wherein the charge controller is configured to cause the power converters of the plurality of power converters (10_1, 10_2,..., 10_n) to solely operate in a predefined order successively in the constant voltage charging operation, wherein until all the power converters of the plurality of power converters (10_1, 10_2,..., 10_n) have successively operated once, a successive order is set not to select again the power converter that has once operated solely. a plurality of power converters (10_1, 10_2,..., 10_n) configured to convert power supplied from a power supply, and to supply converted power to a battery; and a charge controller configured to cause the plurality of power converters (10_1, 10_2,..., 10_n) to operate at least two charging operations selected from a constant current charging operation to keep a charging current constant, a constant power charging operation to keep a charging power constant, or a constant voltage charging operation to keep a charging voltage constant, to charge the battery, the at least two charging operations including at least the constant voltage charging operation, wherein the charge controller is configured to cause the plurality of power converters (10_1, 10_2,..., 10_n) to operate in parallel, in performing either one of the constant current charging operation or the constant power charging operation, wherein the charge controller is configured to cause any one of the plurality of power converters (10_1, 10_2,..., 10_n) to solely operate in the constant voltage charging operation, wherein the charge controller is configured to replace the one of the plurality of power converters (10_1, 10_2,..., 10_n) to solely operate with another one of the plurality of power converters (10_1, 10_2,..., 10_n) in turn for every predefined period of a plurality of predefined periods in which a period from a start to an end of the constant voltage charging operation is divided, wherein the plurality of power converters (10_1, 10_2,..., 10_n) includes at least three power converters, wherein the charge controller is configured to cause the plurality of power converters (10_1, 10_2,..., 10_n) to perform in an order of the constant current charging operation and the constant voltage charging operation, or in another order of the constant current charging operation, the constant power charging operation, and the constant voltage charging operation, to charge the battery, and wherein the charge controller is configured to cause the power converters of the plurality of power converters (10_1, 10_2,..., 10_n) to solely operate in a predefined order successively in the constant voltage charging operation, wherein until all the power converters of the plurality of power converters (10_1, 10_2,..., 10_n) have successively operated once, a successive order is set not to select again the power converter that has once operated solely.