I was going to go with Pedalites, a previous Cool Tool, but I didn’t want in-pedal generators that add resistance to your effort. These front/rear-mounted strobe lights add very little unsprung weight to both wheels and work via magnetic induction, so there’s very little additional weight and no added rolling resistance. The initial ride takes about a mile to bring the front (white) LED up to a full charge, while subsequent rides have me fully lit in about fifty feet of pedaling. The rear (red) LED gets flashing in about half the time and stays flashing longer during any stops (it also flashes more regularly). They both flash for at least two minutes after stopping, which is ideal for early AM rides and for any stopovers where you’re basically waiting for traffic.
I put about 400 miles on my SL120s last season. They worked terrific. After storing my bike for four months — no activity — they worked perfectly again on our first ride of the 2008 season, a “Midnight Madness” run at midnight, followed by a post-ride trip to the bar. The lights recharged within half a mile (white always takes longer than the red). 6.97 miles, 35 minutes, and the red kept flashing the whole time I was in the bar (15 minutes — we were tired!).
The caution here is they mount on your axles, so you’re not flashing “high” as you might with saddle lights or a headlamp. They do not effectively illuminate the road. These are not overnight travel lights. They’re safety lights, a smart pickup for any lowlight rides. A great investment for me: increased safety, no more batteries, and definitely the best “green” investment I’ve made for training. Short of breaking in a crash, these lights will last me decades. The LEDs are not likely to burn out for at least ten years and you can measure the magnets’ lifecycles on a geological scale.
Bonus tip: The instructions stink, so you might be tempted to mount it outside the fork, because it’s easier and does not involve removing the wheel (my buddy mounted his incorrectly). Don’t be tempted, you cannot move the bracket close enough to the pickup magnets unless it is mounted inside the fork — wheel has to come off. Not a big deal up front, but could be axle grease messy for the rear. Once it’s on, though, you’ll be within 3mm of the pickup magnets and generating nearly-free electricity.