How to Modify an Alternator for Charging AND Welding

Comments · 678

• WO

  @WorkingOnExploring · 3 years ago · pinned

  A couple thoughts that may help;<br>1) Most (not all) alternators have &apos;avalanche&apos; diodes in their rectifiers. While they drop ~.5V in the forward direction when &apos;rectifying&apos; 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&apos;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&apos;s electrical system if not allowed to find a path to the ground. &nbsp;The &apos;avalanche&apos; function of the diodes is to act as a &apos;pressure (voltage) relief&apos;. 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. &nbsp;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 &apos;PIV&apos; which means &apos;Peak Inverse Voltage&apos;). There is now no path to ground for voltage spikes when operating the vehicle normally. <br>2) Adding spike protection is relatively easy. A device called a &apos;Transient Voltage Suppressor&apos; (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 &apos;XX&apos; 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).<br>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&apos;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.<br>4) Your regulator hookup seems fishy. I don&apos;t deny it may work, just likely not the way intended. &nbsp;Voltage regulator terminal designations are typically; <br>I = &apos;ignition&apos;. 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.<br>S=&apos;Sense&apos; 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 &apos;I&apos; 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.<br>F=&apos;Field&apos;. 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.<br>L=&apos;Lamp&apos;. This lead operates the &apos;battery&apos; 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 &apos;A&apos; 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.<br>Case ground; Of course, the regulator always needs a GOOD GROUND as well.<br>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&apos;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%. &nbsp;I recommend another Dinse plug directly connected to the alternator case. Sometimes there is a tapped M8 hole on the back of the case.<br>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&apos;t really move air properly for it and it generates a lot of heat. I mount mine in the fan shroud.<br><a href="https://www.youtube.com/watch?v=UBnKhqqsNNA">https://youtu.be/UBnKhqqsNNA</a>

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• RU

  @rudeawakening3833 · 3 years ago

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

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• BR

  @BruceLyeg · 3 years ago

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

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• NO

  @normansabel1850 · 3 years ago

  The rectifier connections are high temperature silver solder.

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• GL

  @glumpy10 · 3 years ago

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

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• DE

  @deankay4434 · 3 years ago

  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 &quot;Star Washers&quot; that help cut thru paint, tar, grease, oil but get to the engine block and battery. <br>Good video! DK, ASE Master Tech since 78, retired

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• HA

  @hardcoretrout · 3 years ago

  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.

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• AL

  @Albatr0ss222 · 3 years ago

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

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• SW

  @swavacadoo · 3 years ago

  The Weldernator! Your diagram was really helpful and informative.

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• CR

  @craigtegeler4677 · 3 years ago

  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<br>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<br>just tearing it up like nobody&apos;s business and liking it a whole lot! I was welding very close to being a pro because it<br>came naturally to me! I already had the fundamentals down pat ahead of time with soldering metals and brazing, and <br>so when it came to stick welding, it was like being downtown to me!!

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• MO

  @moodberry · 3 years ago

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

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• RO

  @robertsturton8409 · 3 years ago

  I am a certified welder repair technician/Industrial electronics repair technician by trade. &nbsp;I have build a welder from an extra welder and have build a wife feed welder using 2 batteries and an spool gun. &nbsp;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. &nbsp;THANK YOU so much for making a simple well explained video. &nbsp;I just watched it and have already purchase the components to complete the build.

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