From my experience there are three seperate issues that require solving. People everywhere struggle with this and theres a few (for example) on the moped page that keep sharing information thats slightly incorrect for most people.
Iv been over this a few times so sorry to bore everyone but im going to start again.
If you are going DC then we will assume you are also going 12v
1, you need to rectify your AC signal to DC
2, you need to regulate this to 12v
3, the resulting power supply is 12v dc (as far as we are all concerned) but its TERRIBLE in that it still varies from 0 to 12 (or 14v or whatever)
If you dont fix 3, voltage appears to vary as the frequency of the pulses changes, the only way of getting a decent voltage reading is to use a scope. LED lamps will work like shit, incandescent lamps take ages to warm and cool so seem to smooth the voltage out a bit. A stack of capacitors (as you know) makes things tons better.
Again, i have said this so many times but people dont get it.
The common "trail tech" units do NOT regulate and rectify.. they only perform one function (iv been drinking and cannot remember which one of the two it is).
They do have a more expensive model (about $140 delivered) which (with a capacitor) gives absolutely rock solid voltage and DC.
Come visit and see my rock solid DC plz.