For your satisfaction Adriaan, here's the performance curve of my battery. My power meter isn't running right now on the windmill, so I have to base my power generation on the single cell li-ion cell voltage of the pack.
In other good news, it was very windy the last 3 days and the windmill was spinning for a good 24 hours of it. It put 51 Ah into the pack and successfully triggered my homemade max voltage circuit to turn in off at 4.089v. I'm hoping to record my first full kilowatt-hour this weekend.
Sparweb - I was thinking of a singular 1 x 2 x 1/2" magnet on each side. I think the steel case would be just fine, especially since it's not supporting any load with my new windmill.
Have you ever considered getting FEMM to model this stuff?
- After you mentioned this, I went looking for a student version through Autodesk and didn't see one. I probably have an ANSYS license for it if I looked elsewhere.... my brother has played with it before a few years ago.
So maybe I'm coming full circle here, but I decided to draw my own custom PM alternator that would fit in the space. The idea would be to 3D print out of plastic the stator and rotor (yes, I know there isn't any steel...) but I'm not looking to break any records. The main goal is to get the cut in down to 60 +/- 20 rpm at 5 volts.
Given my current setup, I'm thinking targeting 25 amps at 400 RPM and sustain 40 amps for a good wind gust while it transitions into full furling at 600 rpm. These numbers are based on what I've seen so far the last two months.
So what I have drawn is a 8 pole rotor with 16 magnets in a Halbach array. 8 main magnets of N48 4" x 1/2" x 1/2" + 8 magnets of N52 4" x 1/2" x 1/4" in between. 4" rotor diameter.
The stator is 12 coil, 3 phase, 24 slots. 16 gauge red enamel magnet wire with 43 turns per coil. The stator is 4 1/2" long. It's going to take just shy of 5 lbs of wire. I think it would be wired in star, but I was wondering if individually wiring each phase to it's own rectifier would help boost the voltage more. Or maybe star is the best I can do...?
I searched for other people's values for RPM / # of wraps / # of coils / diameter ... .to try and roughly estimate what my new design would do. I also bench marked a high quality hoverboard motor. Based on all of this, I'm thinking I would be at about 68 RPM cut it, with ~0.77 ohms/phase. At 200 RPM it would be about 10 amps and 24 amps at 400 RPM. I was hoping my long straight wires through the stator would help keep the magnetic flux passing by the copper in the most ideal way that might be a bit better than the wedge shaped coils of a axial flux generator. The magnets are also closer, but then again not as wide.
My hopes was that it would out perform these calculations and I could wire the 4 coils per phase in a 2 series-2 parallel fashion so it could actually do 20-30 amps continuously without getting too hot. I figured the 16 gauge would give me more flexibility for different configurations vs. going with 14 gauge.
I think I'm looking at about $175-$200 to build this.