How To Rewind an Alternator

Step 8 Conclusions and Final Thoughts

Initially I wound the stator incorrectly for the standard 120 degree 3 phase output, which resulted in a rather dismal output of 12V open voltage at 500 rpm's  on a drill press under no load.
This was with an external 12V batt on the field connection to give a full field excitation.

Final testing has now yielded 17.6V open voltage and charging at 1A, giving a theoretical power output of 20W max.
However, the field coil required 11.45V @ 2.5A to achieve this, meaning the input power required is more than the output generated.

So, it will be rather futile to try this configuration as a windmill, unless you are able to modify the rotor with magnets of some sort. Even so this is a small output alternator and probably wont yield great power.

Feel free to experiment with the larger 65A  and greater type of alternators like the AC Delco 10DN or SI (internal regulator ), but don't be too disappointed  if the output isn't what you'd hoped for.

You can also use the Ametek range of DC treadmill motors which wont suffer from the parasitic power loss of the field coil on alternators.

When considering standard DC motors for use as a windmill generator, you need to divide the voltage into the working Rpm's of the motor in order to ascertain if it will be suitable.
For example a 220V  2850 rpm motor will have a volt to rpm ratio of 12.95. Multiply this ratio by your required voltage ie 12 and you discover that it will generate 12V at roughly 155rpm.
The lower the better. :)

Comments

[numberonebikeslover]

I think, removing the inner rotter coils and putting magnets from loud speakers would make the rotter a permanent magnet. This is something i saw on internet long ago, but never gave it a try. Best wishes.

[raviliyan]

Its really works, but I used magnets from microwave oven they are bit strong the speaker ones.

[skishore2]

hi everyone...i just went through the instructions..problem is how to opne the rotor coil further.i doubt while applying more force it might damage the poles of rotor.can somebody help me out how to open the rotor coil inside car alternator so dat i can place circular magnets of speakers inside.so that its strength will increase...thank you eveyrone

[caluire24]

Hello,
Did you find a solution I'm having just the same issue:
- removed the bearings (using a gear puller),
- removed the slip ring (unsoldering the coil wire links),
- cannot remove the two "fingers" parts: even with the use of the gear puller (begins to smash the axe).
Any solution may help, Thanks in advance,

[numberonebikeslover]

Well I have not done it my self so I am rather ignorant than you my friend. I believe in learning by doing. Wish you all the best.

[petercd]

You need a gear puller, the small 2 legged one will do. I found it easier to remove the rotor finger part closer to the slip rings, there seemed to be a collar of some sort at the back.
First I removed the bearing then the slip rings then the rotor finger part, the coil came off easy enough so I will be saving its wire.

[petercd]

I just recently came across someone who'd done this with microwave oven magnets but the results were rather dismal in the authors opinion. Needless to say I didnt even bother pulling apart the rotor to experiment with this method. Thanks all the same.

[Silence]

Permanent magnet alternators are far superior to standard alternators, they're far more efficient and require no external source for the field. They're the usually choice for marine, RV and performance vehicle applications.

[petercd]

Absolutely, couldn't agree more, however I discovered one for sale, a stainless steel 1kW low wind PMA and the price (10800 ZAR) gave me diarrhea for a week. Perhaps a modified bike alt, but they too are rather pricy at the 400W and up range.