Monday, January 22, 2007

Batteries, schmatteries.

Last spring or so, I picked up a set of Reelights— LED blinkie lights for your bike that don't use batteries.

Reelights instead employ a pair of magnets that fasten to the spokes and Faraday's law of induction to create an open-air generator that makes the small amount of juice required to get the attention of your fellow road users. This is the same technology found in shaker flashlights and hand-cranked radios.

They're very simple. A metal bracket with a hole at one end mounts between the quick release nut or axle nut and the outside of the dropout. At the other end, about 3 inches away, a pair of LEDs are mounted in a sealed plastic enclosure. A pair of strong magnets in plastic brackets attach to the spokes. There is no on/off switch. Apart from the magnets being attached to the wheels, there are no moving parts at all.

They're pretty easy to install. Attaching the bracket to the wheel is easy. Getting the two magnets attached to the spokes is a little trickier. The 28-spoke wheel on this particular bike required that the magnet brackets be turned at a bit of an angle (visible in the very first photo at the top of this post) but this has no perceptible effect on performance. Then the light is adjusted inboard or outboard on the bracket until it's within 1-3 mm of the magnets. You just have to make sure the magnets don't rub on the light.

Properly adjusted, you don't really even notice them. They just do their thing, day or night.

Here's the rear (sorry for the soft focus—I took these in the garage and I was starting to lose feeling in my fingers by the time I took this one.) Plenty of room yet for a fender stay, but not so compatible with larger panniers.

Here's one with the rear wheel spinning at about 40 rpm, frozen by the flash. The LEDs flash in sequence, each lighting once for each pass of the magnet. Only the left one is lit here. The net effect is a nice blink blink ... blink blink ... blink blink pattern, visible from quite some distance. The blinking varies in proportion to the speed of the bicycle. Their brightness comparable to most blinkies currently on the market, with the exception of the Planet Bike Superflash (dang, that thing is bright!).

Reviewed here are the SL-100 model. My wife used these all season on her '93 Bridgestone XO-4, and has been quite pleased with them. Why? No batteries! You don't have to buy them, store them, install them, worry about when they'll wear out, recharge them or send them to the landfill when they're dead. Sweet action. They're also ridiculously simple and seem impervious to foul weather. You don't have to think about turning them on or off—they just work.

There are two readily apparent drawbacks. The first is that they are constrained to a location near the axle, which might conflict with panniers or disk brakes. Second, the SL-100 version doesn't remain on when you stop. This might be fine if you're well-reflectored and using a headlight. It looks like Reelight has come out with a capacitor model that continues to blink for a while when stopped (the SL-120) but I'm not sure whether anyone has brought these to the US yet.

For another description, including where they're from, take a look at Hiawatha Cyclery's write-up. I bought both sets from them and have been quite satisfied with their mail-order service. Amazon carries them too, and more reviews are available there. Maybe someday we'll see them in regular bike shops...

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