Patent ID: 8264199

Claim:
An interchangeable accumulator unit comprising a housing and at least one lithium accumulator cell arranged in the housing and a charging unit arranged in the housing for controlling the charging process of the lithium accumulator cell, wherein the housing encompasses at least a first charging contact unit and a second charging contact unit separate from the first charging contact unit, wherein each of the charging contact units comprises four charging contact surfaces, wherein each of the four charging contact surfaces of the first charging contact unit is electrically connected to a coupled charging contact surface of the second charging contact unit so that a charging of the accumulator unit can be performed over the first and alternatively over the second charging contact unit, wherein a first charging contact surface of the first and the second charging contact units provide an electrical ground, a second charging contact surface of the first and the second charging contact units provide a positive connection for connecting a charging voltage for the charging unit, and a third charging contact surface of the first and the second charging contact units provide a positive connection for connecting a supply voltage for the accumulator cell.