Here, then, is my second contribution on the subject: some thoughts on lights for cycle commuting.
Front lightsCycle headlamps serve two purposes: both to be seen, and to see. The first so that oncoming or joining traffic can see the cyclist - many accidents happen when a car pulls out of a junction into the path of a cyclist without a front light. And the second so that the cyclist doesn't end up in a hedge they didn't see.
The type of cycling you do, or plan to do, will affect your choice of light. I cycled in towns for many years, never far from the orange glow of street lights, and needed a lamp that was visible to other road users more than I needed one to see by. When I took the same light on a ride along an unlit tow path, I quickly realised its deficiencies.
My current commute is on unlit country roads, so I have need of a light that will light my way as well as announce my presence to other road users. For the conditions particular to my daily ride, the latter is of secondary importance; I am well-equipped with reflectives, and high-visibility clothes, such that if a light is shone on me, I will be seen.
By contrast, the unfenced roads and deep ditches of the country lanes, combined with sweeping bends, means that I need a light that will enable me to find my way home safely. Even in the pale dawn at this time of year, before the full dark, it's often easy to miss bumps and dips in the road that will throw the bike and the steering if I ride them wrong. And the roadside ditches are deep enough to lose a small elephant in.
For the past 2 or 3 years, I've been using a NiteRider MiNewt, which has proven to be excellent. I bought it one morning after a particularly gruesome commute in misty darkness, using a halogen lamp that gave off so little light I quite scared myself. I went straight out and bought the best light my pocket would allow. It's not cheap, but I think it's quite reasonable compared to my safety.
The exact model is no longer available, but NiteRider now have a wide range from the Niterider Minewt Mini 2010 USB Light System [Evans, CRC] to the MiNext 700 Dual. I must admit, I love this little light, and would buy it again. It's powerfully bright, with a full and half-power option, and a burn time of around 1.5 hours at full whack (two commutes for me), double that on half-power. There's also a flashing mode that is technically illegal in the UK if fitted to the bike. It's no use to my commute, so I've not used it.
The NiteRider has an indicator light that glows blue in normal usage and red to indicate that there's 15% charge left, which in practice has proved to be around 20 minutes of light, depending on the temperature (remembering that colder weather affects batteries adversely).
I also have a Smart front light as a secondary backup. It's running on alkalines, which are less susceptible to the cold than rechargeables. It's not going to light my way, but it will help me be seen.
Rear lightsMy KnightRider rear light has last well over a decade. I don't think it's available any more, but when it was first sold, it was the only LED rear light that met the UK's legal requirements for rear cycle lights. Last year I treated it to replacement batteries.
I recently bought a Smart Rear Light [Wiggle, CRC, Evans] that I bought because it has spare brackets so I can move it quickly between my other bikes.
I also have a Skully Ultra Bright Mirco LED Bike Light (black body, red LEDs) mounted on my helmet. As it's on me, not on the bike, I can run it flashing, which is another point of attraction/attention to drivers approaching from behind. And it looks cool, which is a bonus.
Batteries - alkalines and rechargeablesMy NiteRider headlamp uses a rechargeable battery, and I prefer to charge them in the office so that they're fully-charged for my ride home; that's the ride heading into gathering darkness. The NiteRider's 4-6 hour charge time means I can be certain that my lamp is fully charged for the ride home (and ride to work the next morning). In the mornings, I know that it is getting progressively lighter and - at a pinch - I can reduce the output - perhaps through the lighted areas - and conserve power for the darker parts of the ride.
Other considerationsMy aim is to leave my lights that stay on the bike; so removing the excuse/chance of not using them. I'd much rather have them and not need them than need them and note have them. Both lights satisfy this requirement well, and I can charge the NiteRider without removing it from the bike (as long as I park it near a wall socket; later models can be charged using a USB cable).
At worst, to remove the battery pack is a single velcro band (and unplugging the cable to the lamp itself) and the lamp is secured using a rubber O-ring. I can move it to another bike in under a minute.
ReflectorsI should add that I have all legally required reflectors on my bike; at front and rear, and on the pedals (I have an insert into my SPDs). I'm not sure the police would necessarily stop a cyclist that didn't have the legally required reflectors, but if it ever came to an insurance claim, I don't want them to be able to wriggle out of settling the claim because of some trivial matter like a small reflector.
I've long thought that bike lights are a little like helmets in that it's a false economy to buy the cheapest one you can find. It's always a balance between spending the most you can and getting the best protection available. Equally, a good light removes a layer of worry, gives a certain confidence, in the same way that a good helmet does.