More on Battery Charging with a Welder
A little while ago I mentioned in a post that I charge my batteries with old welder from a generator. Let me give some more details about it.
Most welders that run of the mains power are called AC welders because the output is AC unless the welder is a ‘DC Welder’. Hence diodes are required. I also checked the open circuit voltage of the welder wouldn’t be too high. The output was approximately 40V as the lowest level. Since I am charging a 24 volt battery bank I thought it would be OK.
I’m not sure the exact current rating but I think by memory they are about 80A. These about 15 to 20 mm in diameter. One end of the diode is flat with a stud protuding so it can be bolted (with heat-sink compound coated on mating surfaces) on a heat-sink. The other end is a terminal. For a successful rectify, you need two heat-sinks with a pair of diodes mounted on each. Each pair however must have the opposite configuration, that is the terminal on one pair is the anode, while on the other pair the cathode (k) is the terminal. They can then be connected in a diode bridge fashion with the one heat-sink becoming the positive terminal and the other heat-sink being the negative terminal. Obviously the two heat-sinks must be mounted such that they electrically isolated from each other. Fans would complete the set-up so that maximum current could used that the batteries should be charged with.
Whatever diodes you use, ensure they are rated for the charging current. I’d also be careful when charging a 12 volt battery bank. You may get away with it if the welder voltage can be adjusted so that it isn’t too much beyond the 25 volt mark AC when open circuit.
