The present invention pertains to a method for charging a rechargeable battery (5) of a hearing aid (1). The proposed method comprises detecting a power supply (8) being connected to the hearing aid (1), estimating a state of charge of the battery (5), selecting one of at least a normal and a fast charging mode in dependence of the estimated state of charge, and charging the battery (5) according to the selected charging mode. Moreover, the present invention provides a hearing aid (1) including a battery charging unit (9) and adapted to support the proposed method.