See On Board Compressor/welder for a vehicle. Can 2nd alternator be eliminated?

This instructable relates to this question . I can see the need for a second air conditioning compressor for that part of the build. With the alternator however, there is one under the hood already. Why not hack it to do two jobs. Couldn't you just add back in the alternator parts you disabled in an external box and then with some wire and switches, alternate back and forth between welding and charging. The car can run off the battery for a while, so this should work. Part 2 of this question is, the alternator in my case is in a Toyota Corolla. Toyota makes pretty tough stuff, however will my alternator make nearly, or as much juice as the Ford unit the guy recommends for the hack. I could swap in a Ford alternator I suppose, however it would likely require significant work to adapt the mounting bits. Thanks for Listening, Zipperboy

Slowpoke8 years ago
You have asked a very interesting question.  As described in the Instructable the alternator is modified - severely. As modified it will produce nearly 90 volts and its outputs are isolated, going only to the welding leads.
 Whilst you could arrange a switchbox to alternated between vehicle charge and welding, you would be looking at some very serious switchgear owing to the possible high currents (>100Amps) that may be generated by the alternator, The main reason that I don't recommend using the one alternator is that welding is a very demanding application to ask an alternator to do. Device failure is highly likely. If it failed during welding, no big problem except your vehicle now has no alternator, big problem. I like the idea of this instructable and I want to do it, but it's the usual problem..How do you fit everything into the engine bay.

I also note a reference to a second battery in a latter post. You could weld at 12 Volts DC. I've done it. But it is very hard to strike an arc and maintain it. It is weak but usable. Weld penetration is poor so multiple runs of weld is needed. The 90 Volts from the modified alternator is to be preferred. 

If you wanted to run a single alternator you'd need something pretty beefy, one place to find really heavy duty electricals is army surplus, radio jeeps tend to be good places to look. If all depends on whether the electrical system in the car could handle it, which is doubtful though twin batteries might just provide the leeway to allow you to weld without an extra alternator...
zipperboy (author)  killerjackalope8 years ago
There is not much call for welding currently.  I may find time to light some wood on fire, however, not looking to melt steel or electrocute chemical rods.

Time will tell.  Maybe some time down the road, some steel will need to be fabricated.

Not now.  Later,  
zipperboy (author)  killerjackalope8 years ago
Thanks for the answer KillerJ, I had thought of the extra battery, and you are right, a good start to going one alternator. I also will do some research on HD voltage regulators to add to the downstream to the car mix. I have a voltage tester, so what I may do once I have a spare Toyota alternator is hack one not on the car and test the output to see what the hacked Corolla alternator can do. If it cannot make enough juice I will slice it up for the mounts and try and wedge the Ford alternator in there. I am very farmiliar with the Corolla under the hood and it would be possible to move the radiator down by replacing it with a shorter one from another model of compact. This would make a lot more room. More work, but it would be cool to have a travelling power fabrication workshop. Putting these HD mods on a Corolla makes it even cooler, as no one would expect these options to be on a compact car. Cheers, man, Phil aka Zipperboy aka adventureboyseven