Fast Nicd Charger

EE September 1988 Most popular personal radios suffer from high current consumption, so that it is sensible to power them from rechargeable batteries. Unfortunately, with most battery chargers on the market it takes up to 15 hours to recharge batteries. The charger proposed here does it in under an hour. Most of the smaller NiCd batteries on the market today have sintered electrodes that can withstand fairly high currents. This makes it possible for such batteries with capacities up to about 500 mAh to be recharged to 80% of their capacity within an hour. The problem with fast charging of NiCd batteries is switching off the charge cur- rent at the right time. With these bat- teries, unlike, for instance, lead-acid bat- teries, it is not possible to determine this from the charging voltage. The circuit The circuit consists of four distinct sec- tions as shown in Fig. 3. In Fig. 3a are the supply section with rectifier, Bi, and 5-V voltage regulator, IC1 , and a Type 4060 timer, IC4...