self-switching battery charger - for hibernating batteries

for hibernating batteries. This is a charger designed specially for batteries that are not used for long periods, e.g. those of motor- cycles that are laid up for the winter. You then take the battery from the vehicle and connect it permanently to the charger, which is switched on one or two times during a week. The battery is charged and when it has reached nominal voltage, the charger switches itself off. It remains on standby, however, and when the bat- tery voltage has dropped below the nominal value, it switches itself on again. Suppose that the battery in the cir- cuit diagram has a voltage below its nominal value. As soon as the charger is switched on, a current flows through D3 to the gate of silicon-controlled rectifier (SCR) Th1. The SCR conducts and a charging current flows through the battery that is indicated by ammeter M. The battery voltage increases gradually and with it the potential across R1/P1. Capacitor Cl then charges and at a given level of voltage across F1...