9 V battery charger

Nickel-cadmium battenes should normally be charged at 1/10 their eapacity in Ah. The capacity of a 9 V NiCd battery is usually 110 mAh and this type of battery should therefore be charged in about 10 h. However, the efficiency of the charger is only around 70%, so that the real charging period should be of the order of 14 hours. In the present charger, the charging time is measured by IC1, whose oscillator is set to a frequency of 1/6 Hz, ensuring that outpur Q13 goes high after 14 h.