high - is there oncoming traffic that might be blinded and crash because of you?
if yes -> too much
if no -> light up the valley, no issues
strobe - are you bored with the current integrity of your bones? or did you mean you would use the strobe at daytime?
This suggests strobe in the daytime and, at night, either a steady burn or a flashing light and steady burn combination.
This is a popular question in the bicycling community, and the right answer depends on many factors. A study on snowplow safety found by Byron Ross on the Bicycles Stack Exchange
site explains that flashing lights appear brighter to the human eye than a steady light at the same output level. Flashing lights grab attention faster, but it's also much harder to estimate the distance and speed of a flashing light than a steady one.
Although you will find many differing opinions, and we've yet to see a bicycling-specific study on this (although I'm told one is in the works at an undisclosed university in the midwestern US), these are our recommended best practices for when to flash:
- Daytime riding: In broad daylight there is a lot of ambient light, so a steady burn light is unlikely to stand out. During daytime riding, it's a good idea to use your lights on the brightest, most attention-grabbing pattern they have, because it's easy for drivers to judge your position when your whole bike is visible, and you want to grab attention quickly.
- Riding at night: High-intensity forward-facing lights should not be flashed alone at night, especially if they put out over 200 lumens. You run the risk of disorienting oncoming traffic (be it on 4 or 2 wheels), and make it difficult to estimate your position and speed. Having one flashing light and one steady light is a good compromise — you can grab drivers' attention but the steady light helps improve distance estimates. Avoid extreme strobe patterns though, and opt for a pulsing light (like on the Light and Motion Urban 700) or a subtler flash like Cygolite's Metro and Expilion series.
Rear lights tend to be less bright, and are therefore more appropriate for flashing at night; however, the same principle of distance and speed estimates applies. If riding with just a single light, using it in a medium-speed pulse mode (like those available on the Cygolite Hotshot and the PDW Danger Zone) is a good compromise. Using two taillights is strongly suggested though, using one in flashing mode and the second in steady burn. If you're upgrading to a new light, consider one with a rechargeable battery to use in steady mode, and use your old light in flashing mode.
Generally speaking, lights should be positioned as far apart as possible. The further two points of light are away from each other, the further away the eye can distinguish them. Separating lights vertically also ensures that you will be seen by people in low and tall vehicles alike. For headlights a good setup is to have a primary handlebar mounted headlight, and a secondary light on the helmet. Good helmet lights should have a narrow beam and not be too bright - you want to be able to light up a specific area where you're looking without blinding everyone around you.
For taillights, a rack or seatpost mounted light in addition to a helmet light provides good coverage. More details on taillight placement are available on the recommended taillights page
The three primary brightness units are Candela (luminous intensity), Lux (luminous flux per area, aka illuminance), and Lumens (luminous flux).
Candela measures absolute brightness at a point. In other words, it measures the amount of brightness going in only one specific direction. This unit is sometimes used to define maximum brightness of a light. The value for candelas is the same regardless of distance from the light, but will be different depending on the angle from the light.
Lumens measure total luminous flux, in other words the total output of a light source in all directions that it points. If you were to integrate the candelas measured in every direction around a light source, you would get lumens. Lumens are measured using an integrating sphere, a scientific instrument that uses a reflective sphere to normalize the light beam and measure its intensity.
Lux is lumens per area. If you project a light onto a surface and add up the total amount of light hitting it and divide by the area of the surface, you get lux. The brightness in lux depends on the distance at which you measure it. Illuminance is inversely proportional to the square of the distance, so in order for lux to be a useful measurement you must know the distance at which it was measured.
Lumens are the most commonly reported value for bike light brightness. Many manufacturers use an "estimated" or "specified" brightness based on the LED's specifications at a certain power level, but the actual brightness will depend on the circuitry used, how efficient the light's optics are, the temperature the light operates at, and the quality of the LED. Many lights' claimed lumens are 10-40% higher than the actual brightness. The ANSI FL1 Standard specifies a specific, repeatable method for measuring the brightness of a flashlight or bike light. Lights certified by the manufacturer with the FL1 Standard are marked with an "FL1" logo on the Bike Light Database.
As explained above, many manufacturers overstate their lumen claims - especially no-name overseas manufacturers selling exclusively through online stores. While these lights rarely live up to their claims, they are always more than bright enough for most users. The primary disadvantage is in the build quality: these lights are typically designed to be as cheap as possible, and are not built with cycling convenience in mind. Battery quality in particular is often overlooked, and the battery packs are rarely waterproof and often the capacity drops significantly after minimal use. On the generic "Cree T6 LED light" available on Amazon that we reviewed
, the optics focused the beam into a small, over-bright circle of light. Even with an extra diffusing lens, the light still only illuminates a small area. That area is as bright as day, but it's too small to be useful. Additionally, the external battery pack is inconvenient, and the lights often don't have a quick-release in a useful position for removing the light when you leave your bike outside somewhere. Finally, with no warranty or even a real company to support the product, you're on your own if the light dies.
These types of no-name cheap bike lights are great for people looking to get a lot of light at a low cost, but they are not a replacement for the carefully designed optics, superior mounting hardware, and light-weight integrated systems offered from real bike light companies.
Most USB-rechargeable bike headlights these days use a single 18650 battery internally, which is recharged through a USB port on the light. In most lights the battery is not user accessible. A few lights have a removable battery but contain the 18650 cell in a proprietary casing. For example, the image above shows the proprietary battery packs for the Cateye Volt 700
, Cygolite Expilion
, and Serfas TSL
, along with a standard 18650 protected cell. If you want extras of these proprietary packaged batteries, you have to pay $30-50 for a single battery pack which can't be charged in a standard charger or used in any other lights. With a few lights like the Fenix BC30, BC21R, and the Lezyne Super Drive XL
), the batteries are directly accessible. This means you can get as many extra batteries as you want, swap them out any time, and charge them with any standard charger. For people doing really long rides, or who just don't want to worry about running out of charge on a ride, this setup is a great choice.
Bike taillights more commonly use lithium polymer battery packs (similar to those in cellphones) because they can be manufactured as smaller, flatter packs. Taillights usually don't draw as much power as headlights do, do these lower-capacity packs are possible. I have yet to see any bike taillight which takes a user-replaceable 18650 battery. If you see one, please let me know!
You always have to be careful when handling 18650 batteries. They have a very high energy density, so if they're overcharged, overdischarged, or shorted they can cause a fire. Some 18650 batteries are "bare cells". In certain lights they can give higher performance (although it shouldn't make a difference for the Fenix and Lezyne lights mentioned), but are more likely to become a hazard if not taken care of. Protected cells have a small circuit built into the top of the battery which prevents overdischarge, overcharging, and short circuits. The protection circuit adds a couple millimeters of length, so they won't fit in a few lights, but they do fit in every 18650 bike light I've tested. In general I would recommend protected cells – they cost a tiny bit more, but it's worth the extra peace of mind in my opinion.
Many low-quality super-cheap generic Chinese lights use 18650 batteries. Some are fine, but many of these batteries are extremely dangerous and most are low-quality. It's very common for the battery's actual capacity to be much less than its stated capacity. For example, 18650 batteries sold under the "UltraFire" brand often claim 4000+ mAh of capacity. In reality, the highest capacity 18650 available as of spring 2016 is 3600 mAh, and independent testing has found the UltraFire counterfeits to only be about 900 mAh cells in reality. These cheap cells are also less likely to have a protection circuit, and the construction quality is usually very poor. For safety reasons, most lighting enthusiasts strongly recommend only purchasing and using 18650 cells by reputable manufacturers and sold by authorized dealers.
The cheapest high-quality and high-capacity protected 18650 batteries available are the KeepPower 3400 mAh, sold by Illumn.com
. At $11 each, they're about half the price of most other 3400 mAh protected cells, and use the same Panasonic NCR18650B cell inside as name brands like Nitecore and Olight. These are the top choice of many flashlight addicts, and it's hard to find a better bargain.
You could check out a light that has a beam cutoff so you dont blind anyone. Maybe youre offroad and dont care though in which disregard. Im happy with this one.
Or go big and get a Lupine.
The Lumintop looks interesting.
I also learned that there is a German standard for bike lights. I did not know that until today.