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!! :)

For DC welding, it's best to use electrode negative. Meaning the "ground" clamp woud actually go to the alternator and the stinger (rod holder) would go to your hood pin. It will help the rod burn smoothly and will prevent those balls forming close to the weld. But this was an amazing project and thanks for taking the time to share it with us.

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 !

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

Had to watch this video and one other worth while video on this subject, and honestly this guy makes it understandable for me, and thank god he put links in the description it’s a very dense subject, a lot to understand

The Weldernator! Your diagram was really helpful and informative.

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.

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.

"...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!

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

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

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.

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.

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

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

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

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.

The rectifier connections are high temperature silver solder.

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

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!!

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.

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

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.

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.

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.

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! 🤩

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.

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.

I think I blushed when you said rectify the rectifier 🥺

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.

Thank you. I've been trying to find out how to do this. A few years ago, I saw a RU-vid video of a guy that built a homemade welding block that would also rev up the motor as you start to weld.

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.

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

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

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

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!

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

I'm not a welder, nor am I an electrical engineer. It looks to me that if something goes wrong in your charging circuitry you will face a potential battery explosion causing a lot of damage to a very nice jeep that you have put a large amount of money into. With that said, I commend you for your ingenuity for creating a functioning welder "engine accessory" Good luck & be safe!

You are blowing minds, young man! 😮

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

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.

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.

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

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

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

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

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

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..

If you feed fresh solder into the joints it will penetrate the "old" solder thus breaking them loose, cool project, thanks for sharing!!

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!

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.

Thought I was a fairly intelligent guy, but after watching this I'm changing my name to Thak the Neanderthal🤣, awesome vid👍

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

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

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 .

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.

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

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

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

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

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.

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

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

My only suggestion is the ground should be direct to the alternator for the welder rather that the body . Body is grounding to the alternator via several lighter gauge wires body grounds are prone to failure . You may never know driving your car that 75-80% of your body grounds be broken but any weakness will show up at 40plus volts really fast and dramatic failure. Just a thought . Guys would use generators for welding in the olden days with simple modifications . When manufacturers began using alternators. Good luck I think I'll give it a try but I may run a separate generator specifically for a welder.

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

Ok for welding you need to make a reactor to smooth the weld. Basicly it is a coil of welding cable around a metal bar or pipe. This help to re establish the ark after it breaks.

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

GREAT IDEA.....YOU SHOULD SELL THEM........PEOPLE WILL BUY THEM.

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

Leece Neville alternators have external regulators, and have higher output, but are a space hog. Some have outputs in excess of 300 amps.

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

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

I here now acknowledge, Mr WorkingOnExploring dropped some know how knowledge.

Outstanding video worth all the views and more

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.

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

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

gem of a video...Thanks!

Having a reostat in the rotor circuit will allow you to adjust the field current, and so welding current. I have used instrument panel dimmers from 50's thru 70's or so American cars. My general procedure was to set the RPM to about 70 to 90 V for striking voltage and set the welding current down for a good weld/bead. If you have cause to use smaller rods, this works well. By the way, NAPA used to sell a conversion kit to do that conversion. It was very spendy! A friend of mine from South Africa used to make and sell some kits. They were popular with the farmers there. If you are running the rotor off the battery, you can use a running light bulb or a brake bulb in parallel to set a minimum welding current. Adding more in parallel ups the current and decreases the sensitivity of the reostat.

This was super cool. Nice work.

For a remote job with no electric grid available is cool but for a 100 you can get a cheap inverter welding machine, but is always cool to see project like this

Excellent DIY video. I like the idea and explanation. However, I have a couple concerns about the welding.1) Any chance this setup could fry the ECM making the car undriveable. 2) What about overheating the wires (especially the car ground wires)? You demonstrated that it works but possibly at higher RPM's there could be problems.

Awesome job Shalom..!

great video, Note on safety, D.C. voltages are generally safe, however there is a known voltage at which it has no problem penetrating your skin, it overcomes the resistance of the skin, then it can be lethal, i forgot what voltage that is, but if you exceed 48 volts assume you are fast approaching potential danger

If memory serves me correcty lead free solder, which anything mass-produced after about 2012 uses, melts at about 450-475 degrees farenheit. This high temp combined with the heat sinking action of the stator windings would certianly not be easy to de-solder without a nicer quality soldering iron or professional air gun desoldering equipment.

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

On the Lincoln Continentals 1976 Ford had 120 volt alternator to heat the glass.

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

I'm going to try this at home......😂 great video man!

Great video! Question. Haven't gotten through all the comments yet but I wonder, could you achieve similar results using an alternator + harbor freight engine on a mount?

Mind blown. What a cool project. And your aviation style mixture control for the throttle in the dash is amazing. Where did you get that?? Instant sub.

Well you can buy them, but you are a genius and built it yourself. I think that I would like to know how many amps it puts out full fielded and is the OCV just 14.5 from the regulator or does that vary with rpm?

Great job, thanks for the video 👍

Very precise, very comprehensive, clean to the point, Wonderful knowledge sharing. Thanks for the video. One question, can we put a solar charge controler and put a battery bank to have a Home on wheels RV get benefit from this.

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

Great presenttion! Thanks for the informaton. Happy trails.