Thermally Controlled Nicad Charger

Published:2013/3/20 1:31:00 Author:Ecco | Keyword: Thermally Controlled , Nicad Charger | From:SeekIC

One method to charge Nikel Cadmium (NiCad) batteries quickly with out abuse is generally to measure battery cell temperature and taper the charge accordingly. This nicad charger circuit works with a thermocouple for this function. Another thermocouple nulls out the effects of ambient temperature. The temperature difference between both thermocouples can determine the voltage, which will appears at the amplifier’s positive input. Since battery temperature rises, this small negative voltage (1 °C difference between the thermocouples equals 40 µV) gets larger. The amplifier, working at a gain of 4300, gradually reduces the current over the nicad battery to keep its inputs at balance. The nicad battery charges at a high rate until heating occurs and the circuit then tapers the charge. The values given in the circuit limit the battery-surface temperature rise over ambient to about 5°C.



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