Abstract: A battery charging unit for a medical appliance, preferably an inhalator, includes a transformer having a high-voltage side to be connected to a mains voltage and having a low-voltage side. A rectifier is connected to the low-voltage side of the transformer. A charge current circuit is connected to the rectifier for charging a battery. A timing control is connected to the charge current circuit for switching a charge current to a value being safe for long-term charging after a predetermined period of time at an initially higher value. A test key is connected to the charge current circuit for interrupting charging of the battery and loading the battery with a given maximum current requirement for a given period of time. The voltage of the battery under load is measured and compared with a predetermined reference voltage after the test key is actuated. A control light signals if the reference voltage is exceeded.