In a battery charger, the charging voltage is selectively supplied through a semiconducting rectifier circuit or a controllable semiconducting switch to the battery terminals. There is an electronic control box (32) for the switch, which comprises a half bridge (14) of back-to-back thyristors. The semiconducting switch is connected to two parallel half bridges (12,16) of diodes. There is also a smoothing circuit (26) with capacitor and load transistor. A zero-crossing detector (38) sends signals to the control box. The rectifier elements of the last half bridge (16) are designed for much lower electrical loads than the other elements. All the semiconducting elements are on a common circuit board with a cooling body. The charging current and voltage are continuously monitored (28).
