Will it matter how I rewrap the coils? I mean like, should I feel free and do as many wraps as I want to? What should the voltage be?

 

This is a very tough problem.

If you have too many turns you will get maximum ouput power at too high a voltage, and the regulator will have to block voltage to keep the battery voltage at 13.5 to 14.5 volts DC. This is inefficient.

If you have too few turns you will not generate enough voltage to put out maximum power at a voltage high enough to charge a battery. This too is inefficient.

What you want is a coil turn configuration that puts out maximum power when the output voltage is around 12 volts AC. YOu're looking to optimize efficiency.

But I expect that the existing stock coil is already optimized. Why not just install a second stock coil in placeof the AC ignition power? I've never tried this. Will it even fit? I don't know. But if it does that is the way I would go. Of course rectifying and regulating this new setup is a whole new thread.

I responded in much greater detail earlier tonight, but by the time I hit the "post" button I had been logged off do to "taking too long" or something . It's all gone . I'm much too tired tonight to recreate that post again.

I really suspect that you don't realize how difficult this project is. There are so many issues down the road... But then again sometimes you surprise me .

 

I've done that too... I thought about it, and I realized that I could experiment! Make one wrap and measure the output and do the math and figure out how many wraps I should do!

 

But is there more than multiplying?

 

I am probably going to have to replace the R/R because the stator will not be grounded. Am I correct?

 

But that math is not so easy unfortunately. The output voltage changes with load. A heavier load makes more current and less voltage. The output power (in watts) is the output current multiplied times the output voltage.

You could also convert this to horsepower, since that power (in watts) is going to be subtracted from the engine's output power. One horsepower = 746 watts. They are just different units to measure the same thing - kind of like miles and meters are both used to measure distance.

Let's consider the extremes, and then what happens in the middle. With no load at all (with all else being equal) you get maximum voltage and zero current. The output power is the product of those two values. Zero current times any voltage = zero power. The other extreme is when the output of the stator is dead shorted. Here the output voltage is zero but the current is at maximum. But still zero volts times any current value is still zero power.

But in the middle range of possible loads you have some current flowing and some voltage. The product of these two values = real power. As you start out with small loads the voltage remains high and the current is low. You have low power. As the load increases you get more current and less voltage, but the output power still increases. As so on - untill you get to a point where you reach a maximum power output, and after the that the increasing current is negated by a rapidly falling voltage. At this point increasing loads cause a decrease in output power all the way down to zero output power for a dead short.

All the above is done with "all other things being equal". The engine speed is also involved, as is the size of the stator, the permeability of the core, the strength of the magnets in the flywheel, the gap between the magnets and the core, etc. This is not easy to model, not is it easy to extrapolate out from a few simple measurements. This is a big endeavor.

Remember that you want the maximum power point to be where the AC voltage is around 12 volts AC at some median engine speed (I would guesstimate this to be at around 3000 RPM). AT this point the regulator would be simply connecting the rectified output fully across the battery without any losses caused by reducing the output voltage, or failing to rally enough voltage to meet the battery requirements.

I repeat again that the existing battery charge coil has almost certainly been vetted out, and optimized for maximum efficiency for battery charging (for a single coil). A lot of work went into designing that coil, and I wouldn't attempt to reinvent their design unless you are really into research and development.

But if you simply add another battery charge coil they will be in parallel. That is not as good as having them in series, but it will probably work OK at maximum power output. Another possibility is to keep them completley independant, and put in two voltage regulators. And then sum the output of the regulators going to the battery. That would be better.

Or you could count the number of turns on the stock coil, then wind half that number on each coil and wire them in series. Also measure the gauge of the wire used and lower it by three wire gauges when you wind the new coil. The resistive losses go down by almost exactly 1 dB (decibel) per wire gauge, so a 3 gauge drop in wire size will result in a 3 dB drop in losses per coil (half power), but your adding another coil which will bring it back up the same as is was with one coil (but with twice the power out).

And yes, you definitely don't want to have one side of the stator output grounded. Leave both output wires disconnected from ground and use a four pin GY6 style style regulator/rectifier. That is another very complicated subject...

 

I'll bet you 50$ I can do this... (just Kidding) I can do this, I will proceed. Any recommendations for the type of epoxy I should use?

 

I wouldn't take that bet...

I assume this epoxy is to cement the windings in place? I don't know what current stator manufacturers use. I would suspect is is some sort of transformer varnish. With small gauge wires (like #30 or smaller you need to be really careful about differential coefficient of expansion between the wire and the epoxy or the wire will be ripped apart with extreme temperature excursions. But I don't think that is so much of an issue on heavy gauge coils you will be winding. Still if you can find an epoxy that is slightly pliable (and rated for) up to 200 degrees fahrenheit you'd be better off. But I don't have any brand and number at my fingertips...

 

I attached a photo showing the "new" stator without the epoxy. I customized the ignition coil core and wrapped the coil cores in electrical tape( I don't if it was a good idea, 176F ). I'm not that familiar with AC, but the coils are connected in series like this :_: this :=: is parallel right? Is it OK if I have some magnet wire going out a couple inches from the stator? I measured the resistance of the ground and the coil and I got ~300 ohms, is that OK because I'm afraid I grounded the stator on accident.

The ignition switch is a 5 pole magneto style switch. It has B (battery), G (ground), L (lights,output), S (solenoid), M (kill). When I twist the key to start it shuts off the output but it runs the starter. I might have to get a different switch or figure a alternative. Can I use my old R/R? I'm not sure if its going to work because I think its half wave. The "old" stator had a charging coil that was 2 coils in one (half coil for lights, half coil for battery) and one smaller coil for ignition of course. So this "new" stator is probably way better! The old coil had string wrapped with the magnet wire, and was kept into place with fabric and some kind of sealant.

All this is relevant to New CDI.... Right?

 

After rereading some of your posts, I might have made a big mistake. I used some sheet metal to customize the ignition coil. I got a sheet and twisted it around the core and made it taller by pounding it flat at the top. So the coil is bigger at bottom and gets smaller and thinner at top. Like this: lL, there is a little bit of a slope and space in the core. I'm not sure about the permeability of the sheet metal (off some carport pipes).