Just for fun: alternator as DIY generator

I have an old alternator off a 1981 Civic Wagon. The engine is kaput, but it still has lots of good parts. Like the alternator.

I made a note of each color wire was attached to the alternator before removing it, and also found a wiring diagram so I could identify the function of each connection:







F: field coil +
E: field coil -
B: power coil +
N: power coil -

For anyone who doesn't know, (I sure didn't) alternators don't have permanent magnets in them. So in order to generate a magnetic field, power must be applied to the field coil. This means you have to put power into the alternator to get power out. This took a while to wrap my brain around.

By the way, "field coil" and "power coil" may not be the proper terms for these components. I'm still learning this stuff. But at least they're descriptive, right? Also note, this alternator has no voltage regulator. Second Generation Civics have an external voltage regulator, which I won't be using.

So a 12V battery on the field coil terminals will generate the magnetic field, and a multimeter or light bulb on the power coil terminals will tell me if its working. Also, its seems like a good idea to ground everything to the alternator casing, since that's how it's done in the car. Here's a diagram of how I plan to wire it:




There's a couple features on this diagram that I haven't used yet. The switch to the battery, and the jumper from B (power coil +) to F (field coil +). Those I'll add later to try to make the field self-sustaining. For now I just want to see if I can make it work. Here's my actual wiring:




Well, the wiring is a mess, but I used a motorcycle battery for the field (which drew about 1.5A) and a hand drill to for rotation. It worked! The multimeter read around 15V, and when I hooked a light bulb up to it, nice and bright. Next is to clean it up better and put it on some kind of jig and replace the jumpers with proper wiring. Also, I need to find out at what RPM the alternator is meant to be used, and how many Amps can be safely drawn from it.

Tips: People do convert them to permanent magnet generators too. Then you dont need that battery to get it going. Done for wind-turbines if im not mistaken?

Yep, you take the stator (or is it rotor? the part that spins in the middle) out and remove it's windings and install permanent magnets in their place. This has the added benefit of making it truly brushless, too. Less parts to wear out. Altho, some alternators don't have brushes, but they use induction or something to move the magnetic field around. Just look on youtube for alternator generator conversion.

Also, note that if you do this, depending on the magnet will determine the amount of amps you will get in return. A ceramic magnet will not give you much amperage output. Though, they would be good for testing as they are super cheap.
If you go neodymium, which I highly suggest, you probably don't want any N grades less than 50. So an N50, N52, etc. I'd not bother with N35 or 36 or whatever it is. The higher the N number, the stronger the magnet, and hence the stronger the amperage output you'll be able to obtain (within reason of the coils gauge that is)

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btw, Really good use of extra parts just lying around

Permanent magnets is an interesting idea. The rotor is so tightly put together though, I'd have to make a new shaft to build the magnet on. My machining skills (and tools) are not quite there yet. Maybe someday...

rebelrider.mike said:

I have an old alternator...

Click to expand...

I stumbled across this video today and remembered your post. Thought you might find it very interesting (if you haven't already seen it).

watts-on said:

I stumbled across this video today and remembered your post. Thought you might find it very interesting (if you haven't already seen it).

Click to expand...

Cool. The rapid-fire description of how he connected the Arduino as a regulator was over my head, but yeah, I had not seen this video yet.

Speaking of regulators, I've decided to add the one from the same car that the alternator came from to get my regulation, rather than playing with switches and resistors manually. It took a while, but I finally figured out how the regulator works and how to wire it. Its an old-school electro-magnet actuated gizmo. And its actually still in really good shape. The inside looks like it was made yesterday!




The outside, and the bottom, were not in such great shape. But I was able to clean it up and gave it some paint.




Here's the diagram of the regulator that I had to work with. Nice and blurry!




Between the diagram, and actually looking at the parts, I was able to figure it out.




The outside wiring is pretty straight forward. But the car's wiring diagram got a little confusing in spots, and it took me a while to figure out the yellow and blue wires. Turns out Yellow is power in, and blue is for the charge warning light on the dashboard. I'm not sure it will have an application in this case.




Parts got cleaned and painted.




Assembly and wiring.




It works! I was only able to spin it up to about 1100 RPM, but that was enough to send a little power back into the battery.

Love this sort of stuff... pitty i don't understand it more

Got the alternator working on a bike.




At the moment I can generate 6 whole Watts of power! Its ugly, but everything but the spring and fan belt is stuff I found laying around. I plan to add an On/Off switch, V/A meter, and a variable resistor to the handlebar to see if I can get it to run a little more efficient. Eventually, a nicer platform and a battery mount would be nice too.

But in the meantime, electricity from fat, woo hoo!

rebelrider.mike said:

Got the alternator working on a bike.


At the moment I can generate 6 whole Watts of power! Its ugly, but everything but the spring and fan belt is stuff I found laying around. I plan to add an On/Off switch, V/A meter, and a variable resistor to the handlebar to see if I can get it to run a little more efficient. Eventually, a nicer platform and a battery mount would be nice too.

But in the meantime, electricity from fat, woo hoo!

Click to expand...

And a big ass flatscreen in front of the bike to watch YouTube while charging your batteries... could take some time to do
Not to forget lots ofsnacks to refill fat..

Love it !!!

Just awesome

What's the ratio between the wheel of the bike and the shaft of the alternator? You should build some sort of gearing to get more RPM

No idea what the gear ratios are. The wheel is larg-ish, and the alternator shaft is small-ish. I'm just jazzed it works, LOL.

Just for fun, here's a vid of me taking the alternator apart. Folks more familiar with modern alternators may find this old-school unit interesting.

Pulley ratios are easy. Just measure the diameter of each pulley. Then, it's Power:Load. So, if the motor (power) is 10", and the alternator (load) pulley is 2", then it's a 10:2, or 5:1 ratio

You could incorporate a variable adjustment pulley setup that would allow you to adjust the speed on the fly. Basically it's two cone shaped pulleys at 180degree rotation to each other (ones narrow end is at the others wide end). Then, the belt is adjusted along the pulleys to change the ratio.

There are different variations of the variable pulley set up. Some are just different pulleys stacked and you manually move the belt from one to the other. This is most common in Drill Presses to change the speed of the auger/chuck.
Another is you have a tapered pulley, but is smooth, no grooves. Then have a rubber wheel that rides along that and moves up/down the pulley to adjust the speed. This would be a one sided adjustable gearing. Kinda like your vehicle engine running at 2000rpms but the output speed can be different due to which gear is selected.