Re: electrical gurus need your help please
You don't need to step down the 45 volts. That is an unloaded voltage and the minute you connect the rectifier it will drop. Good heavens I did this on a 1971 Scorpion snowmobile when that sled was brand new. I really doubt that stator is capable of 20 - 30 amps. Build a full wave rectifier, epoxy the components into a pill bottle or other suitable container. Install a mating plug so it can accept the plug from whatever regulator you buy. My setup back then didn't even need a regulator as the battery took care of that job. If the stator on your sled was putting out 45 volts (loaded) the headlights would blow. The output on my sled was 38 volts unloaded. Turn the lights on and it dropped like a rock until engine revs got up higher. How old is this sled you are working on? For lights, unless the dim/bright thing bothers you, you can run lights directly from the stator. Other 12 volt stuff you add may benefit from the rectifier/regulator setup but even then, unless the 12 volt stuff is truly "electronic" and not just hand warmers, lights, etc, you don't even need the regulator or a battery.