High speed NiCad charger - with temperature detection

7-44 — elektor july/august 1982 In the Elektor December "79 issue the 1 pros and cons of charging NiCads rapidly were discussed at length and two suitable circuits were put forward. The circuit here elaborates on the "old" idea in order to produce something new ... The graph in figure 1 shows what happens during a (fast) NiCad charge cycle. At first, the voltage rises very quickly from its initial 0% charge to attain as much as 1.42 V with a 25% charge level. After this point, the voltage will tend to rise more gradually. Just before the fully charged level is reached, the voltage surprisingly surges once more. In the first of the two fast charger circuits published in the December "79 issue, the rise in voltage was used as a parameter for monitoring the charge cycle. In the second circuit, however, a similar system was used to interrupt the charge cycle when the battery was "overcharged" by about 20%. The manufacturer assures us that this cannot damage the battery. As figure 1 ...