Hello. I have a homebuilt alternator. It's not a fast one. Output is 12v 1a after rectifiers. Using a 12v led to test with, it lights up good, but blinks. It's dc input at the led. I know if it would spin faster the blink is faster until there isn't one, but I'm thinking a capacitor may work. I'm a bit ignorant on capacitors. What do I need?

 

If this is wired as a 3ph alternator there certainly should not be a 'blink'.
But an electrolytic on the DC output should fix it.
A 100μf should certainly cure it.
How fast is "not fast"?
I assume you used a full wave rectifier method?

 

BTW is this a 1ph or 3ph alternator?

 

9 coils, 3 phase. think of it as those diy windmill generator setups. charging a battery is the goal. 12v 1a with a multimeter. rectified.

 

So with rectified 3ph, the ripple will only be ~5% on average.

 

for reference, what would it be if single phase

 

100%.