The nightrider minewt is a small, compact light with a seperate rechargeable batter that mounts easily and unobtrusively to the handlebar of jsut about any bike.
The light: With a stated runtime of 3 hours it is more than adequate in my experience for a half hour or 45 minute commute in the evening. Used in conjunction with a second front light, such as a Cateye AAA model with a flashing mode, it presents a very visible light to other road users, as well as lighting the road ahead well enought o not only see where you are going but also to see potholes, rocks, and swaths of fine gravel. At night, within reason it is not possible to outrun your beam; I used it on a downhill stretch where I reached about 30 miles per hour and visibility remained constant. It is bright enough that an oncoming car waiting to make a left turn across my path waited for me as if I was a car or motorcycle!
Mounting: The light head is mounted to the handlebar with a stretchy rubber "o ring" that loops over one side of the light and is secured there; the other end has a pull tab, you thread this under the bar, with the light on top of the bar, then clip it to a natch on the back of the light. The rubber ring is entirely remable if you need to replace it, although the removal requires a phillips head screwdriver, and I have been told the rings are stronger than they look and probably will not need replacement. There are 3 size o rings included for use with different handlebar diameters, but I have used it on both narrow and oversize bars with one ring. It fits on the oversize mountainbike bars on the size, near the brake lever, where the bar diameter is thinner, and on the traditional road bars up by the stem.
The battery has a velcro strap with is secured to it by threading it through slits in the side; it allows you to cinch the battery pack to the handlebar stem or front part of the bike frame. I have used the cinch strap on both quill and threadless stems, both short mountainbike stems with a rise and longer road stems; it fits all of them securely. The battery pack itself is about the size of a deck of cards except only half as wide, a tremendous change from the enornous batteries of only a few years ago which were the size of a water bottle.
Charging: The battery charges quickly; NiteRider's information says 4.5 hours and this is about right. The light can be charged from a wall socket or your computer USB port, which is presumably useful for those who have desk jobs. The charge port is on the opposite end of the battery from the plug for the headlight cable, and covered by a flexible rubber shield.
The light is bright, both in terms of allowing you to see the road ahead, and in terms of allowing others to see you. I would hazard it is about as bright as a car's low beam light.
The light is entirely removable, meaning there is no seperate mounting bracket you have to leave on the handlebars. This allows you to take the whole thing off if you have to lock the bike outside, or switch it from one bike to another in a brief period of time. The light is small, compact, and fits virtually any bike.
The charging port: The charging port is covered by a soft flexible rubber shield, which may not by the best method for keeping out water. I would recommend anyone riding in the rain tape this over with electrical tape for safety, or perhaps put the battery in some kind of covering. It could be easily mounted in a small seatbag if the bag is of a sort with a velcro strap for securing it to the seat rails, this could go around the stem much in the way the battery's own strap attaches it.
Also, it would be nice if the light had a flashing mode or low setting, to allow for longer runtime or use in well lit downtowns where your primary concern is being seen by other road users, or during rainy or cloudy days. The light has only one setting; Bright constant beam.