Diy On Board Welder

Over the past few years I have been tinkering with an alternator powered welder with mixed success. Recently, it’s gotten to a point that it seems to be working well enough that I thought I’d post up what I’ve learned.


Here is a pic of the overall system.



Close up of the control box



Close up of the box and switches on the alternator. The on/off switch on the alternator is redundant with the one on the control box and is not needed.



And some welds….not too bad when you consider that I am not a good welder. These are all stick welds. The ones on the 1/8” plate at the left were each done on a cold plate. It welds noticeably better when the work heats up a bit.




My goal was to have one alternator that was configurable for both conventional battery charging as well as welding. I also wanted to use the GM CS-144 alternator which can still be readily found at junk yards. I found them most often in northstar powered caddies. There are a couple versions of the CS-144 and I used the later model units.

You can find a bit on line about doing this, but I wasn’t able to find very much specific to the CS-144. I found some useful info I found at this site.

http://www.opensourcemachinetools.org/archive-manuals/TIG-Welder.pdf

This is a very good write up on modifying the CS-144 for welding, but 1) an external rectifier was used and 2) it was configured to just weld. This approach is viable if wanting to add a second alternator just for welding. I also took note of using non-avalanching diodes. As described in the write up, avalanching diodes are designed to fail over about 30 volts to protect other components. You need a rectifier with non-avalanching diodes.

I also found this site which looked like exactly what I wanted to do, but made to work with their control box

http://www.perfectswitch.com/downloads/DelcoCS-144-5030.pdf

The modifications shown are similar to the first write up, except an extra wire is run out so that the internal regulator can still be used. Also mentions using non-avalanching diodes and gives a part number for a rectifier.

With all of this info, I set out to give it a try. I ordered a bunch of parts from aspwholesale.com, including a regulator, brushes, bearings, non-avalanching rectifier, etc. Basically everything needed to rebuild the alternator and upgrade the rectifier.

I did the modifications described in the second write up. Split the connection from the regulator to the field of the rotor and ran wires for this connection out of the alternator case.

Now, theoretically, I have two potential conditions, 1) connect the two wires together and it should work as a normal alternator, 2) split the two connections and put power on the wire going to the rotor field and weld. In the second configuration, the output of the alternator should be proportional to the input voltage to the rotor, battery voltage (~12V) being max.

I wired up a sort of bread board test set up which included voltmeters and a rheostat in line with the rotor field and started welding. The intent of the rheostat was to vary the input voltage to control the output voltage.


Modifications inside the alternator



Running the new wires out of the alternator



The temporary test set up



Wiring diagram



It worked pretty well and I switched back and forth between charging and welding several times. Although it welded ok, I noticed that the open circuit voltage wasn’t as high as expected. I thought at maximum input, output voltage would be 100 volts or more. I did discover a strong relationship between the engines RPM and output voltage, but it was taking 2000 RPM to get to about 65 volts. Voltage is about 35 volts at 1000 RPM and 50 volts at 1500 RPM. These are all open circuit voltages. At this point I figured I didn’t need the rheostat since welding at about 1500 RPM worked fairly well.

I played around for a while that day and eventually broke something. I could still weld, but I could no longer charge. This was a couple years ago and I shelved the project at that point and swapped in another alternator I had laying around.

When I eventually got back to it, the rectifier seemed fine, (I could check the diodes with my DMM and compare to a known good unit), so I figured something happened to the regulator. I couldn’t figure out an easy way to test it, so I swapped in a new one and everything worked again.


All I could figure is that the higher voltage in weld mode on the input to the regulator was causing something in the regulator to fail. So, for version 2.0 I installed a switch to isolate the regulator inputs when in welding mode.


Here is the wiring diagram for version 2.0 and some photos of the extra wires installed. This is what is on my jeep now.




Added internal wiring. Yellow is the regulator output and rotor field input. Blue is the regulator input. I used ring connectors and non-metallic isolation washers to split the factory connection.



Orange wires are to split the regulator pulse input. Difficult to see in the photo, but one connection is below the nut in about the center of the photo. The other connection is on the right side at the end of the regulator just beyond the blue wire connections.



Orange wire connection to the regulator can be seen in this photo although you cannot see the wire. It is the on the tab just past the second blue wire. You can just see the contact and the connection is covered in shrink tube.



Although it looks like I have a working system at this point, I might approach things a little differently if I was starting over and would likely make the control and features of the system a little different. Also, although I have used the set up for charging for about 6 months, I have only done about 30 minutes of welding with it.

As for version 3.0 changes, first off, I might do something different with the stator pulse signal. This signal is one of the inputs to the regulator that I added to the switch. I think this is used to send a tach signal in some vehicles via the “P” pin on the alternator connector. An alternate approach to the switch might be to permanently disconnect this input since the tach signal is not needed in this application. Or maybe leave it connected all the time. I don’t know if the tach signal is needed to make the regulator function or if high voltage on that regulator input would damage the regulator. This would take some experimenting or more knowledge than I have on how the regulator works.

Another thing I’d consider is adding a household outlet. I originally was planning this, but decided not to incorporate it since the voltage was much lower than 110 volts. That said, it might be worth experimenting with a grinder at 60 volts and see if it works well enough for trail work. Also, a smaller alternator pulley might be able to raise the voltage enough to make this viable.

Third change would be to put the rheostat back. I didn’t think of this until later, but in a situation where the regulator fails one could use the rheostat to adjust the alternator field and output such that you could charge the battery continuously in weld mode. You can still do this without the rheostat, but you’ll be at full alternator output which would over charge the battery if left in this condition and this would likely damage the battery, possibly is spectacular fashion. Done intermittently though, it could work.

Other thought is trying to feed the alternator output into the rotor field input. This is how the alternator normally works. Theoretically, doing this you could send more that 12 volts to the rotor and therefore raise the output at a lower RPM. I think the dash light circuit would be needed for this and I am not sure how to try it. I think you'd also have to be careful about not stressing the rotor windings too much. This also seems to feel like some sort of a perpetual motion machine. I know there are some smart sparky's around here, maybe someone has some ideas about this.

Last item would be to add a fuse on the weld mode field supply.


All of these changes are incorporated in this diagram (except the alternator feeding the rotor input).




I don’t claim to even remotely be an expert of any of this, I took mostly a brute force approach.

 

Very cool but way to technical for me. I have seen the low tech stick welding with 2 batteries. That I could probably do.

 

It seems to me that Duffer, well known member, has some knowledge in this techno...

 

Awesome! And good on you for having the initiative to try it... and succeed!

I’ve had a plan to eventually do this with mine, but I’m too chicken. I’m afraid I’d do something wrong and it would fry my ECU.