I'm going to be getting a new wheelset for my commuter bike, and am mulling over the possibility of going for a generator hub. Although I don't mind recharging my battery pack in the evening, there is some attraction for never having to do that and for always having lighting available no matter how long the ride.
What I'm using today: My current bike headlight is an XM-L using a P60 drop-in module from nailbender. Rather than putting it in a flashlight, I have it in an old TurboCat (MR11 based) bike light head, powered by an external 4.8v (4200mAh) NiMH pack. It has 3 modes (100%, 40% and 5%), which gives it a lot of versatility for various cycling situations. This light is GREAT for mountain biking and puts out plenty of light (supposedly 600-700 OTF lumens) but the beam is pretty wide for onroad cycling. Not as bad as the MagicShine, but I can tell it's wasting a lot of light above and to the sides, and the throw is not great: too much of the light is hitting the ground 30' in front of me, and not enough 100' away. Even if I didn't switch to a generator, I might keep this light for mountain biking but get something with more throw (XP-E based, maybe) for commuting. By the way, I have taped a "hood" (shroud) on top of the light to provide a sharp cutoff and avoid "dazzling" people when I'm on the MUP.
My existing light is not perfect, but it IS bright. If I switch to a dynamo system with one of the better LED-based lights (such as the B&M IQ Cyo or the Philips Saferide 60), will it light up the pavement at least as well as my current system? It sounds like the answer to this question is probably "yes", but it's hard to get an objective opinion from someone who's actually compared them with mainstream battery lights that don't have a shaped beam. The response I always get is that these lights are awesome, but that's always coming from people who were used to the old halogen genlights, which of course sucked in comparison. I do understand that although the best genlights have less total output (250-300lm from what I can gather) than what I'm running, they do a better job containing the beam and concentrating it where it's needed, with the optics concentrating more of the light further away for better throw. So I suspect they're going to light the roadway as well or better than lights such as I have now, but it's really hard to get an answer.
Next question: if I go dynamo, should I just get a commercial gen light and be done with it, or consider going DIY? I've read about how gen hubs can actually kick out quite a lot more than their rated power at higher speeds (and I do ride at high speeds in the dark quite a bit, since I have to descend 500-800' out of Portland's West Hills on the way home, and the drain of powering this much light from a generator is not a concern). I'm comfortable with basic circuitry but not too much in the way of electronics -- maybe wiring up a bridge rectifier and a capacitor or resistor or two, but nothing much more advanced than that. If I had fairly simple circuit and an array of, say, 6 XP-Es (I understand the generator can only provide 500mA so you need more emitters to fully take advantage of it), could that potentially light up the pavement at higher speeds better than a B&M Cyo, or only maybe about the same? (If I did this, I would probably at least go to the trouble of wiring up a bar-mounted switch so I could shunt out 2 or 3 of the LEDs for better low-speed performance). Unless the DIY system would be substantially brighter on the pavement, I'd probably inclined to save myself the trouble and buy a commercial light.
I know that's a lot of complicated questioning there, but ... well, it's a somewhat complicated problem. Thanks in advance for any help you knowledgeable folks can provide.