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Home made generator, mig/stick/tig welder, 48v battery charger, engine starter

Discussion in 'Back to Basics' started by oil pan 4, Jun 11, 2016.

  1. oil pan 4

    oil pan 4 Monkey+

    A little project I have designing and starting to collect parts for.
    Projected project start date is no later than September.
    The scope of this machine is to be able to provide remote high voltage AC power with 2,000 watts of inverter power, allow welding with stick, TIG and mig when I get a wire feeder. Recharge battery banks up to 48v and provide raw 12 volt power for engine starting.
    This will be powered by the engine I am looking at, a gasoline powered air cooled 25hp Subaru V-twin engine with 30 amp magneto charger and two butchered externally rectified, externally excited AD244 alternators. Exciter field current will be provided by a 10 amp field voltage regulator, for CV which is constant voltage, such as for battery charging, engine cranking and mig welding. CC or constant current will be provided by a rheostat or PWM.
    The little diagram I attached is just 1 alternator system. The 2 alternator system will pretty much be copies of each other and they have their outputs combined for higher power use, or the alternators can be split up for two people to weld at the same time or to use one alternator for welding and the second alternator for 12v power generation to power the inverter to run a run a power tool such as a grinder.
    To save fuel at lower power requirements I will unbelt one alternator. It takes about 3 horsepower just to free spin one alternator at full speed. So unhooking 1 alternator could save up to 1.5 pounds of gas per hour or 1 gallon of gas every 4 hours.
    Target speed on the alternators will be 9,000rpm at full speed, requiring a 1 to 2.5 engine over drive.

    Not shown: CEMF suppression diodes on all the coils and protecting the rectifier. MOVs placed on the alternator output power source for the mV shunt amp meter, Anderson connector on the output, the rheostat may be a PWM controller, a remote voltage sense, I may end up having more than 2 arc reactor choke coils and capacitors. Capacitors will have bleed down resistors and diode protection.
    All the fine details that keep things like voltage regulators, volt meters from frying and capacitors from exploding on welding applications. The 100ohm resistor my be a light bulb for a while if I don't have a 100 ohm 200 watt or larger resistor on hand.
  2. azrancher

    azrancher Monkey +++

    OK, nice design... why are you re-inventing the wheel?

  3. arleigh

    arleigh Goophy monkey

    Because it is a learning experience, and oft times one can do better than what's commercially a available.
    I might recommend using mag starters/controllers seeing switching usually takes the brunt of the load.
  4. oil pan 4

    oil pan 4 Monkey+

    The current "wheels" available don't meet my specifications and the ones that are kind of close cost as much as a new car and still don't do everything I am looking for.
    Then on top of that the commercially available units have individual circuit cards that have a replacement cost that is most of my budget to build this thing.
    The switches on the electrical side won't have to hand more than about 10 amps at the most.
    To combine alternator output I will use anderson SB175 connectors or miller welding lead plugs and receptacles.
    Last edited: Jun 12, 2016
    Homer Simpson likes this.
  5. oil pan 4

    oil pan 4 Monkey+

    After lots of reading and a little bit of experimenting with alternators I have found that unless I spend a lot of money it looks like a standard alternator with a 12 volt powered exciter field may not be enough. Plus the main engine 12 volt system may not be able to provide enough power to 2 alternator the exciter fields, a power inverter, recharge the battery after starting and provide power for other tools and still stay above 13 volts. I am sure it was never designed to do all that.
    Adding a stub shaft to the engine and a 50 to 70 amp 12SI alternator with a 24v voltage regulator should easily be able to power the exciter fields and run a power inverter.
    I have a feeling the "500 amp bridge rectifier" will really only handle 100 to 150 amps continuously. So I may run two bridge rectifiers per AD244 alternator. It all depends on how hot one gets. I will be watching it with my FLIR during testing.
    To procure the alternators I am going to get non functional "for parts only" standard 145 amp AC delco units for dirt cheap. Since I am going to rip out the original bridge rectifier, voltage regulator and replace the stator with a new 250 amp stator from "quick start" I don't need a working alternator. All the alternator needs to have is good bearings, exciter and brushes. The new 250 amp stators have nice long leads coming off the windings, I need those long leads to tie into a terminal board I am going to attach to the alternator.


    So far I have two 300dc amp meters with proper 75mv shunt. DC voltage gauges. The 12 amp 97 ohm rheostat. 10 amp PWM with remote. Samlex 12v 1000W pure sine wave inverter. Capacitors. Old 12v 12SI alternator that I can convert to 24 volt. A new 24v voltage regulator. Honda GX200 engine to do some initial testing with. 15A amp gauge. three of those "500 amp bridge rectifiers". I have all the wire aside from the magnet wire. I should have all the ring terminals, fuses, suppression diodes and MOVs I will need.
    For the 24v batteries I am going to buy a bunch of used 44ah optima AGM batteries from the scrap yard, charge them up and pick the best 2 for the 24v system. The local military base likes to throw them away with out even trying to charge them when they get low.
    For my fuel tank I am going to try and use a SHTF inspired 25 gallon capacity gas tank out of an 80s chevy truck, since these tanks are steel and have a very rectangular prism profile. If that's just not workable then I will get the biggest marine fuel tank I can afford or weld one up out of stainless steel if I can find enough stainless.
    DarkLight likes this.
  6. oil pan 4

    oil pan 4 Monkey+

    Here is the first working proto type of my welder generator. A Honda GX200 engine and my special blend of DR44G alternator with a "quickstart" 250 amp stator. If you are only going to use a 5 or 6 horsepower engine to make a welder generator you don't need a 250 amp stator, the stock 140 amp stator will work fine for you. But I actually plan on making around 200 amps with this alternator later on.
    Aside from needing new brushes and slip rings the alternator and rectifier is in its final configuration. The exciter field control is no where near the final configuration but this basic excitation setup and tiny 5.5hp engine will allow me to conduct some testing and see how it welds with stick and tig.
    It welds perfect with stick and I didn't even need an inductor, making up to 90 welding amps with 3 exciter amps before the engine boggs. This test only uses about half of what the alternator can make.
    With 12 volts and 6.7 amps going to the exciter I get 30 volts at engine idle no load and 77 volts at full speed and no load some where around 7,000 alternator rpm. So it will definitely charge some batteries.
    Exciter field draw 6.7 amps at 12 volts due to the very low resistance in the exciter field.
    Right now its just on a push cart. Final configuration will get a 25hp engine, 2 alternators and stuff.
    Its simple and will be EMP proof with no proprietary circuit cards. The automotive based voltage regulator for battery charging mode will be the only circuit board stuff and I will have a spare.

    Last edited: Aug 17, 2016
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