How to Modify an Alternator for Charging AND Welding 

A couple thoughts that may help; 1) Most (not all) alternators have 'avalanche' diodes in their rectifiers. While they drop ~.5V in the forward direction when 'rectifying' the AC produced in the 3 stator windings, they have another function that conflicts with using an alternator as a welder that it seems you have experienced. Some background; When equipment in a vehicle is switched on and off, the magnetic field of the rotor grows and shrinks. Powering heavy loads results in creating a strong magnetic field in both rotor and stator that doesn't just disappear when the load is switched off. When the large magnetic field collapses, it produces a high voltage spike (often over 100V) that will travel throughout the vehicle's electrical system if not allowed to find a path to the ground. The 'avalanche' function of the diodes is to act as a 'pressure (voltage) relief'. While normal diodes have a very high reverse voltage tolerance (like your new bridge), if that tolerance is exceeded (even once), they will be destroyed. Avalanch diodes have a lower tolerance (~24V-50V) but are not damaged by repeated small reverse currents. Designers use this ground path to allow these spikes of voltage in excess of normal operation to flow to ground through the diode, without the spike flowing through the rest of the vehicle. If the avalanche diodes are overpowered (their reverse current capacity is less than 10% of their forward current capacity), they short permanently. I suspect this is what happened to your first alternator. When you full-fielded the alternator to weld, you created a voltage higher than the avalanche diodes were designed to contain, they went into reverse conduction and due to the sustained over-voltage, they failed/shorted. By switching to a high current and voltage 3-phase bridge, you have made the right choice for welding but not for 12V generation. You now have a high amperage, conventional diode bridge (which typically has a 1600V 'PIV' which means 'Peak Inverse Voltage'). There is now no path to ground for voltage spikes when operating the vehicle normally. 2) Adding spike protection is relatively easy. A device called a 'Transient Voltage Suppressor' (TVS) diode can be installed between the positive battery lead at the disconnect solenoid and ground. When the solenoid is off to protect the vehicle system from welding voltages, so will the TVS. When in battery charging mode, it is the nearest component to the alternator output to catch spikes. Littlefuse makes a family of large TVS under the part 5KPXXCA where 'XX' is the reverse breakdown voltage. For your 12V system which typically runs a max of ~14.2V, a 20-24V part would be appropriate. eBay is a good source for these. I would place 3 or so in parallel to increase their capacity (since you had 3 positive and 3 negative diodes in your bridge) to provide a ground path previously (not saying these are of identical capacity). 3) In addition to the 3 TVS in parallel, I would add an inline ATC fuse holder in series. Since the TVS fail by shorting, if they fail, they will conduct a lot of current till something burns up. Putting a 5-10A fuse in series with the TVS allows the small fuse to disconnect the short from the circuit. Fuze size doesn't matter a lot since transients happen so much faster than a fuse can function. It is sized appropriately to the capacity of the source (yours is large) connected to and the capacity of the wire in the TVS circuit. If the TVS are fried, you no longer have spike protection so checking the fuse periodically is needed. Having a fuse with an internal LED indicator is an easy way to check the status. 4) Your regulator hookup seems fishy. I don't deny it may work, just likely not the way intended. Voltage regulator terminal designations are typically; I = 'ignition'. Its purpose is to turn the regulator on/off with a 12V signal from the key. It also provides power for the regulator (as much as 8A) output so it should be from a relatively powerful supply. This is normally required. Without it, I wonder how your regulator is powered and suspect it is likely never turning off which will drain your battery. S='Sense' allows the voltage regulator to sense the output voltage at the battery which is where you need to be most concerned with its ability to charge. To insure this lead is not affected by voltage sag as a result of current drawn by other equipment, it should run from the regulator to the battery with no other load connected. This may not be required but if not used, sense comes through the 'I' lead which is often loaded with other equipment and may not sense correctly. This is one of the big advantages of using an external regulator, being able to choose where you measure the system voltage. F='Field'. This is the excitation lead to the positive side of the rotor coil. Its voltage will vary and is how the regulator alters the magnetic strength of the rotor which in turn varies output voltage. L='Lamp'. This lead operates the 'battery' light by grounding when abnormal. It is wired in series with a light that is connected to a 12V source. The regulator grounds this lead which turns the light on when the alternator fails to deliver adequate output. There is no terminal ID normally associated with the designation 'A' so I suspect this may be a lamp terminal which is nearly always available but you would need to check your documentation. I suspect this lead, being powered, is back-feeding the regulator to power it. Case ground; Of course, the regulator always needs a GOOD GROUND as well. 5) Welder ground seems poor. You have a great connection to the positive lead and need to have an equally great one to your negative or won't get good arc stability. As it is now, your negative path has to go through the engine block, the body grounding strap, and a number of other joints in the frame. Steel has ~12% the conductivity of copper and aluminum has 71%. I recommend another Dinse plug directly connected to the alternator case. Sometimes there is a tapped M8 hole on the back of the case. 6) I recommend you move your diode bridge to somewhere it can get good, fan-forced airflow. Use bare crimp terminals + heat shrink to connect your alternator windings (not solder) with either 105C rubber cable or 200C silicone wire (I use 8AWG for my 220A alternator). Your alternator fan can't really move air properly for it and it generates a lot of heat. I mount mine in the fan shroud. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-UBnKhqqsNNA.html

Cool project! Now take 10 minutes and fix that screaming idler pulley!! :)

I’m in my 60’s , and I’ve done mechanic work and welding all my life ; you really blew me away young man ! Thanks for sharing !

I see some very good advice in the comments. I would like to suggest you do a little research on welding rods. A very nice rod to use on dc is 7018 but they need to be kept in a well sealed container or an oven. For general purpose I use 6011 where I need deep penetration like fixing a crack. For shallower penetration such as on thin metal or buildup I go with 6013. There are many other rods but these are common ones. Some rods are best with reverse polarity so it would be good if you had a plug on your negative side in case you want or need to use these.

The Weldernator! Your diagram was really helpful and informative.

This is a cool project. My miller runs 75-80 volts OCV (open circuit voltage) when in stick mode just FYI. So rev up to that voltage and get the potentiometer working and youll be set

The rectifier connections are high temperature silver solder.

Diodes get hot so they sell bolt in type as I used to use press in type. We rebuilt everything so 60amp diodes went into plate where 30amp used to be. Remember the end case is were negative is produced, so proved a 04 wire with silver (3-5%) soldered eyelets. But use "Star Washers" that help cut thru paint, tar, grease, oil but get to the engine block and battery. Good video! DK, ASE Master Tech since 78, retired

You took everything that most other tutorials are lacking and masterfully included it in this video, great job! Master Auto Mechanic 1988-present.

I have a feeling this will be a massively popular video. It's extremely well done, informative but not sterile. I see a lot of comments from people overthinking it, perhaps not realizing it's only meant for trail repairs and emergencies. People have been doing that for decades with a couple of car batteries and jumper cables without destroying the universe. Your method is just an evolved way of doing the same thing, but better. I subscribed and look forward to seeing more of your videos.

Totally mindblown. I am a pipefitter/welder by trade and a home DIY mechanic yet this possibility has never crossed my mind. Thanks for sharing the detail info.

That aux idle control is something i did not know I needed in my life but seeing it I really do!

Made the alt Conversion process look a lot more simple that I have seen everyone else do. Thanks for that.

You are a really SMART man. Your comprehension of circuits is legend. Great job.

Very cool I have been playing with welding alternators for years its nice to have someone give a good explaination of how to set up.

This reminds me of an add-on my dad had attached to the alternator of the family station wagon to provide 110VAC@60Hz to power his electric drill, which he used to make side money mounting sign displays for local banks and assorted businesses. I later learned that it came available pre-fabricated and had been around for almost as long as alternators have been available on automobiles.

Get a good water tight container to keep your welding rods dry. Also I would throw as many desiccant pouches I could find in there also. If your rods get any moisture it will degrade the coating and they don’t weld good at all. I have always kept my rods in plastic containers in the shop. Great project thanks for sharing.

Stick welding was the very first type of welding that I had ever tried and I must say that i was drawn to it like a moth to a light bulb and it is a lot of fun! I adapted to it with nice clean welds with good penetration in no time at all! I was just tearing it up like nobody's business and liking it a whole lot! I was welding very close to being a pro because it came naturally to me! I already had the fundamentals down pat ahead of time with soldering metals and brazing, and so when it came to stick welding, it was like being downtown to me!!

Other commenters have noted some problems with your alternator/welder. As a welder, I should point out that you need some way to control the output voltage/current while you weld. Not all (if any) weld jobs will turn out well if the machine just blasts full power into the work piece. For every job, the person welding must select the proper rod to use, as well as the current rage it works best with, and take into account the thickness and alloy of the work piece that is to be welded. Besides the initial set point of current, the machine must be capable of automatically regulating that power thruout the weld process. You have a good start here, but your design could use some tweaking. Thanks for sharing.

Good project, technical difficulties notwithstanding. I have to agree with WorkingOnExploring there may be several issues you have not known or thought about. I only wanted to add your difficulty in trying to solder to the alternator windings is because there is an enamel insulation on them. They have chemical stripper specifically for removing it but you can just use 220 grit sandpaper and it will solder fine. You’ll want at least an 80w iron but one of the old Weller soldering guns are perfect for large wires.

Bro I'm from Oklahoma and that is just awesome! I've seen other people do this and try to do this but the way you did it is simpler and easier to understand and what people need to remember is it's just for emergencies it's not meant to be a full time welding rig truck so keeping all that in mind it works for what it is meant to be. Good job man. I've always wanted to do this and now I have a clear blue print to go off of. Thanks for making video.

That’s totally sweet! Jeep is rock solid too! I’ve got a 4Runner that’s itching to be a trail hog and the alternator/welder/120v source a necessity for that vehicle. What a super video! Thank you!

Great overview and detail really. Nice work! I like how WorkingOnExploring commented as well to detail the improvement design suggestion. That's totally awesome and great information to know. I've wondered about doing something like this for my Jeeps maybe a decade ago and almost invested in a larger alternator to move forward on. Never really needed and only now just started working with welding again. Oddly using the one type I never liked when I had welding in high school, the MIG and even worse seems, the FCAW. Handy however and rescued a few made in the USA welding machines while at it and I'll see how I can improve beyond the getting back into service. Have a good one and kind regards in Christ.

Great video man, watched it front to back. That ran better than some of the Amazon stick welders I’ve seen. I’m gonna go ahead and agree with the guy above me and say you could definitely sell those.

I think I blushed when you said rectify the rectifier 🥺

I am a certified welder repair technician/Industrial electronics repair technician by trade. I have build a welder from an extra welder and have build a wife feed welder using 2 batteries and an spool gun. I have been think about doing this exact thing to my JK alternator, but have been reluctant to do it due to not understanding exactly how to modify the alternator. THANK YOU so much for making a simple well explained video. I just watched it and have already purchase the components to complete the build.

Dude this is a game changer super smart!!! Thank you for the wiring diagram also, I’ll post pictures of mine when I’m done!

"...for somebody who doesn't know what they're doing..." Sincerely, this is an excellent video. It is excellent because it is tremendously thorough, well paced, & well filmed. Truly interesting, too. Appreciate this knowledge sharing so much! Prior to this, it was not known to me that you can do this, let alone how. Huge thanks!

The old baja 1000 guys were doing this back in the day very cool to see the idea coming back around

Absolutely fantastic video! Thank you very much for posting it.

These comments are 100% amazing. You never guessed you'd get such killer insights to power usage. MIND BLOWN!!! Much love man.. Keep up the good work! 🤩

Pretty cool the welder came out and helped. Cool guy.

You made it work Sir. Thanks for sharing. Keep improving.

Wowzers! I am impressed with your ingenuity and presentation Mr Sweeney!

Yeah, you can get some serious voltage out off that alternator unregulated, if you spin it up enough the voltage becomes deadly. Be careful with torching weld leads. Even the car cassy is grounded so it's a big Hadar torching the weld rod or lead if you run it up @ higher rpms, other ways, looks like a good idea and great job 👍 just know what your doing, be safe and don't lend it to your friends if they're not absolutely aware of the risks involved

If you'll revisit your project, you should leave the stock alternator as it is and install another alternator dedicated to welding, maybe get rid of the AC compressor to make room for the welding alternator instead. That way the system will be more reliable and simpler to wire.

I set up a second alternator(dodge/Jeep) externally regulated for my Jeep as a welder and to run grinders. I’ve used it on the trails. Once when my buddy sheared the bolts on one steering arm on his d60 knuckle, he needed to get the sheared bolts out of the knuckle to get new bolts in. Used the welder to weld on a nut to get the broken bolt out, another to weld ups ripped frame where the steering box ripped it, another to weld up a broken stub shaft and one time to weld up the front frame on a Sammy. All lots of fun.

Thx.for the thorough explanation, it's worth a new subscription and a huge like

Awesome idea and proof of concept. Probably not enough room in a jeep to run a second alt to isolate the charging and welding.

Very cool intriguing video and never knew that was possible to weld like that

That's better than I can weld. This is a great Idea. Thanks for the information.

thanks for sharing! this is bad ass to have on the trail!

Hey everyone, I'm impressed with this post and over half of the comments, they show what this channel is supposed to be , people helping people. Sharing your knowledge nowadays without trying to make money is getting rare, or sharing wrong knowledge so you can get a laugh. People wonder why this world is so f--ked up. To all you who left good comments you have a new subscriber and to (Sweeney off road) you sir are awesome you have my respect and my thanks, PLEACE keep on sharing

Thank you for showing us this and the work you did to make it for all of us. A huge amount of welders that drive around in these duallys with the old Lincoln on the back, have to have ACDC grinders and they use them every time they use the welder. I wonder what it's like where you're from but down here it seems like you're not cool if you don't have one of the old Lincoln 200 or 200a And the tiniest shortest bed you've ever seen on a pneumonia ton truck..

Awesome job Shalom..!

Love it. Me personally I’d have a dual alternator kit so that if I burn it up on a trail repair I still have charging capability

gem of a video...Thanks!

This is very cool. Thanks for putting together a video on it.

Never thought about doing it that way. Nicely done. My kid's live down there in out towns. Have to send this to my boy's, might help them out in fixing their problems with their Jerry rigging. Lol. Heck they might even know you. Good job on figuring that out.

Awesome on the trail welder. That's a Great idea that works. Cool Man.

Great presenttion! Thanks for the informaton. Happy trails.

Wow, mindblowing genius! 👏, I'd love to try this someday

This was super cool. Nice work.

I think you're a genius , it's too bad that you have to run and rev just to get the volts you need, but you are damn smart man. Hope you don't fry your wiring in your jeep. Keep up the great work, us do it yourselfers need people like you.

That's a good trick to know. Thanks for sharing.

Man that's super handy if you go trail riding, rock climbing ect...

I'm seriously impressed hella good job 👍🏿

Great job, thanks for the video 👍

That's cool you altered your alternator and rectified your issues with the rectifier.

That was pretty cool I’m into car audio systems and that alternator hack could help when for some people who don’t have the money to buy expensive alternators

Wow this is really cool! I never though of using an alternator to weld

Years ago I bought a device that allowed you to get 110 volts DC out of your vehicle alternator the unit had a voltage gauge and a switch when in charge mode your charging system worked normally to charge the battery and power the lights but when in 110 it disconnected the battery and regulator and you'd bring your revs up till the gauge read 110 and you could use your 110 power tools I used a drill and a circular saw quite a bit and they worked great one day I was power washing a oil rig mobile campsite and as it was getting dark I rigged up a cord to plug the lights in but only powering the lights in one unit about 8 hundred watts I had to rev my motor to the max around 11 PM the owner came by to see if I would finish up before I shut down for the night I said I still had the back side of the unit so would have to wait until the sun came up as it was too dark to see back there he informed me that it was fully lite up thats when I found out each unit had 5 150 Watt lights on the back and all 6 units were fully lite up so it was no wonder I had to rev up my motor to the max to get to 110 I was not just powering up 6 100 watt bulb inside the unit I was working on but the 5;150 watt bulbs on the back of all 6 units it was a wonder I didn't fry my alternator

If you ind someone with microcontroller experience, a nice upgrade would be a control box to adjust your throttle in response to welder settings. This is awesome information, thanks for sharing!

Ewan McGregor can alternate & weld… Pure dead awesome man ! Very cool ! 👍🏼👊🏼👌🏼

Amazing. Please share more!

Great Video, Thanks for sharing

Outstanding video worth all the views and more

I modified my Bosch 12v 90A alternator 15 years ago without changing the rectifier or regulator and it's still going strong. I'm an auto electrician in South Africa. I also use this to charge batteries of other vehicles on breakdowns. Even 24v systems on trucks. Training is required to use this without damaging the other vehicles electrical system.

i love DPDT switches! this is very cool awesome video man.

Interesting and impressive, thanks.

Great video and explanation!

THATS EFFING AWESOME BUDDY. 💯👍 👍👍👍👍👍THUMBS UP👍👍👍👍👍

Great Video ! Very informative ..

Great job..very cool!

Great job man

that was funny seeing a Trumpet with the three valves for a horn

Very useful! Thanks

Great idea

That is cool my friend.

That's awesome bro!!

So awesome!! Instant subscriber

I like how you said dont try this at home after showing and explaining to people how to do it themselves.

Great content , keep it up

A rectifier-based welder will weld much smoother and not generate much spatter if you put an inductor in series with the positive lead. I don't recall off the top of my head the inductance but a good design for this project is to sleeve or heat-shrink some 1/4" copper tubing and wrap 30 turns in contact with each other onto 1.5" PVC pipe. Remove the pipe form after welding.

Excellent explanation and engineering on this project! Just a heads up to anybody that wants to do this on OBS Ford (70's and 80's) and I think some of the square body Ford's (90's), you'll cook your alternator no matter what you do because the brush setups are very poorly designed, so badly designed in fact that if you jump a vehicle using your truck while your engine is running you will fry your alternator, if you're to do this on an older Ford I highly recommend converting it to a older style 2 wire GM.

Good job 👍

Great how-to and sick jeep you’ve built. Thanks for sharing, I’m following you now.

If this isn't sold as a safe working kit yet, it will be soon. Great work!

This is honestly really neat. Eventually going to world tour a w123 turbo diesel, this might be something to consider having.

Genius indeed!!! 👍👍

thats awesome man! I am planning to build like that in my Kei Susuki DA65t.

Thank you I’m gonna build me one . I do lowrider hydraulics and would be awesome for repairs when on the road or in hopping competition

excellent vid and good work and explaining it all out :) !!

thanks from ireland subbed

best vid ever. thanks

I'm not a Jeep guy but, nice Jeep. I like the horns too! Nice usable mod! 👍👍🏍

They used to market these way back, like before my time & I’m in my 40s. An old boss (my first proper job actually) talked about a small fleet of Renault light vans he had fitted with some sort of welding alternator for site work. Never seen or heard of them before or since, but when I was doing some boat electrical work I know you can get 200amp+ alternators that would fit most cars, so entirely possible.

Great vid I think it's the best one

Even if you don't want to do this to your vehicle , you could always make yourself a small portable engine driven welder with an alternator and a 5-10 horsepower engine . You can even use a vertical shaft engine as long as your alternator has enough airflow around it .

Using a car engine to weld. Never saw that before but it actually looks pretty cool :)