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.
Do you sell a thermally controlled nicad charger?
The 18VDC battery charger for my portable drill causes the NiCad battery temperature to increase to 135 F, case temperature. Obviously, the interior temperature of the batteries would be much higher; most probably causing premature battery failure and/or potentially a fire hazard.
If you do sell such a charger, please advise price and delivery.
Thank you,
Michael F. Belgin