>>367428You just need to rewind the car alternator so it will work at lower RPMs. However, the energy needed to magnetize the rotor may end up being more energy than what it generates. It really depends on how you've set things up, your RPMs, and mechanical input.
I prefer using permanent magnet motors/generators for this sort of thing. They are super simple to make. You can even just convert a car alternator into one by imbedding magnets into the rotor so it doesn't need to be electro-magnetized. That works well since you don't have to build a bunch of crap and worry about alignments of everything.
Here's what the stator will look like when you rewire it. Scroll down to the proper, corrected winding version. Note that this person's project was a failure due to the rotor needing more energy to magnetize than what it could generator normally,
http://www.instructables.com/id/How-To-Rewind-an-Alternator/?ALLSTEPSThe image I'm posting is where the rotor has magnets imbedded into it. This is what you need to do with a car alternator. Then again you could find a permanent magnet one intended for a motorbike,
http://www.dangerouslaboratories.org/altp1.htmlStill, a regular field-wound car alternator is still a great platform for winding your own stator and imbedding your own magnets.
