Light & Motion ARC Li-ion
By James Sharp

Last year we had the opportunity to review the Light and Motion Arc High Intensity Discharge (HID) light. At that time we said, "[The ARC] is bright, burns for a long time and charges fast. Basically it is everything a light should be." Needless to say we were pretty excited to see what they had in store this year.

The only notable change is the addition of the Lithium-Ion (Li-Ion) battery. This type of battery has been around for a little while in consumer electronics like laptops and PDAs, but has only recently been used in bicycle lights. The reasons why consumer electronics manufactures like the battery is because it is light, small and packs a pretty good wallop power-wise. Like NiMH batteries, Li-Ion batteries don’t suffer from a charge "memory" like NiCads do. Unlike NiMH, however, Li-Ion batteries have a pretty good shelf life. Charge the battery in the spring, and in the fall, you still have some juice left. Try that with a NiMH and by mid-summer you have yourself one dead battery.

Usually when a bike light manufacturer goes the Li-Ion route, it is for one of two reasons; A) they want the lightest light on the market, or B) they want the longest running light on the market. Light and Motion chose route A with a little of B mixed in for good measure. The original Arc came in at 550 grams, or about 1.2 pounds, complete. Not too shabby in it’s own right. And, that is with an NiMH battery. This year, the Arc Li-Ion comes in at a very impressive 300 grams, or about 0.66 pounds, complete. That is what the Li-Ion battery technology can do.

Remember I said that Light and Motion mixed a little bit of B into the new Arc Li-Ion, the Arc’s original burn times were 3 hours on high and 3.5 hours on low beam. Though Light and Motion claim the same burn times in the spec’s, our test sample burned for nearly 4 hours on low beam and almost 3.5 hours on high.

Now if you are a 24-hour racer or just someone that rides year-round, this seems like the perfect light, right? It almost is. There are some interesting quirks that are associated with the battery technology. First, the discharge curve is almost flat. This means that the battery doesn’t give the circuitry very much warning before it goes out. The NiMH battery allowed for a 15-minute warning where the light goes into low beam before shutting off. The Li-Ion gives 5. That’s about enough of a warning to fire up the backup light, but not much else. The other problem with this technology is the cost. These batteries are very, very expensive. The battery alone is $200. Combine that with a light bulb that is very expensive, and, at $499, you have yourself a light that costs more than many beginner bikes.

Summary: Light and Motion took a very good light and managed to make it better. They kept the versatile mounting; the Arc Li-Ion comes with both helmet and handlebar mounts. They kept the breakaway mount with spare parts in the box. They kept the fast 3-hour charge. They kept the secure connectors. They kept the 3+ hours burn time. They added one of the lightest batteries out there, making this an amazing light. If, and this is a big if, you are serious about night riding/racing, this is your light, otherwise, L&M still sells the very good NiMH version for about $100 less.

James Sharp is a contributing editor for GearReview.com specializing in mountain biking.

For more information, contact:
Light & Motion
300 Cannery Row
Monterey, CA 93940
Phone: 831.645-1538
E-mail: bikelights@lmindustries.com
www.bikelights.com