overload protection for electric drills

elektor electronics november 1985 range, but, in addition, maintain an e.m.f. of over 3.5 V with normal loads (lithium manganese dioxide >2.7 V), and have a design (storage) life of 10 years. Lithium bat- teries also have disadvantages in that they are more expensive than alkaline types and, because of their different output voltage of 3.0 V nominal, cannot simply be used as a substitute for 1.5 V batteries in existing equipment. Silver oxide The nominal e.m.f. of silver oxide cells is 1.5 V. Storage life is about 2 years at +20 °C: at the end of one year, about 90 per cent of nominal capacity remains available. Bat- teries of this type also perform well at low temperatures. Zinc air In zinc air cells, the reaction of zinc with atmospheric oxygen in the presence of a catalyst is used to produce the elec- trochemical potential. The use of oxygen from the air means that the cell can be filled with nearly twice as much anode material, i.e., zinc, as, for instance, corresponding silv...