Nickle-Cadmium battery welder

by Brian
(North Central Florida)

Dad made a battery-powered welder, and constructed two trailers for homebuilt aircraft with it. The bottom two boxes contain surplus Nickle-Cadmium batteries intended for starting aircraft engines. The top box contains a choke and an amp meter. The open coil wire resistor on the side had a clamp-on tap to limit current. It got dull red in use. The remaining box contains spare batteries. All batteries together added to 48 OCV, and I believe they were designed to put out 1,000 Amps at half voltage for a few tens of seconds.

He could get something like 15 minutes of run time from it on a charge, and I suspect he used 1/8" rod. He was forever popping the circuit breaker for the patio trying to recharge it quicker. I remember a diode or a bridge on a heatsink about half the size of a lunchbox, and a porcelain wirewound dropping resistor about a foot long. The resistor sat on the concrete patio in an enameled pan full of water, which steamed at a simmer and made rusty foam. This was both electrically and thermally hot, and it was important to keep the dog from trying to drink from the water pan.