NiCd Charger for Mining Lamps

So I recently found this while clearing out the workshop of someone:


It is a charging indicator for mining lamp charger racks, in partcular for Oldham-Arras lamps. It still had the bus bar mounting clips attached to it. So of course with this sitting around, I decided to built my own mining light charger.

NiCd mining lights were charged using constant voltage, since they were used all ~20h with the charging requiring around 14-16h, so the time of the cells being charged and venting was kept fairly low.

I decided to use the same approach and simply put in a 5V/3A SMPS supply with a 3R3Ω 50W resistor in series in. The 3R3Ω resistor limits the current to around 1.5A, as to not overload the indicator, I went through some manuals for mining lamps and they usually have a not-to-exceed charging current of 1.75A. As such this fits perfectly.

Overview Overview

I would have liked to built this more old school by using a linear supply and regulating the voltage down. However since this thing has to run 16h+ at a time to charge a lamp, I decided to go with the way of the least resistance, as in the least amount of heat dissipation.