When it comes to bicycle lights there is a huge selection to choose from.  Not only are there different designs, but different technologies that cater for different needs as well.  However, the majority converge on the same basic elements.  In this post we hope to explain the current state of technology to help you understand the benefits and application of today’s technology.

Bicycle lights can be divided  into 4 groups  and each of the groups have different requirements as explained below.

1. Commuters

Cycling to and from work can take you into the twilight zone and beyond, even more so during winter. Although having a good light will help to fill in the dark spots made by missing lamp posts and help you avoid that pothole or broken beer bottle, the main objective for a commuter is to be seen.  Safety from vehicles is paramount.  Flashlights typically have a narrow and more focused beam which is suitable for commuters who travel in a straight line.  A flashlight with a bike mount would work very well, but even more ideal is an integrated light (battery and light unit in one) that is USB rechargeable.  If you are riding on roads with streetlamps your light requirements will be quite low.  A real 100+ lumen flashlight would be adequate.  If it is USB rechargeable you can easily recharge the light once you reach your workplace or home.

Numen Cycle Light Mounted on Handlebar

The Numen Commuter Cycle Light works with 4 X AAA Batteries. It’s flashing function makes it very visible.

2. Road racers

The requirements of road racers, or roady requirements, are not that different from that of commuters, although they tend to travel faster and longer, and will most likely start in the early hours of the day.  A bicycle light should provide adequate light with sufficient reach to identify possible obstacles far in advance.  Therefore a small handheld flashlight might not be the best solution.  Some integrated lights are suitable, but due to the size constraints they suffer from a limited amount of available power.  Depending on the amount of ride time the needs of the cyclist would shift from being seen to being able to see.  Typically a flashlight that produces sufficient light will be visible to oncoming traffic as well.  It should be remembered that cycling in the dark on roads is very risky and rear lights is an absolute must.  A priority for any road cyclist is a light that has a very good throw, but also has some side spill. A USB rechargeable integrated light with 500 lumen or more is ideal.

3. Mountain bikers

There are two types of cyclists when it comes to MTB riding.  Those that stay on dirt and tar roads those that venture off onto single tracks.  Mountian bikers require the most light out of the 4 cycling groups.  A wider beam helps to compensate for movement of the handle bar without affecting the visibility of the road.  Multi-LED lights tend to be best for this type of rider, providing ample light with a wide beam. Technical rides that have winding single tracks or switch backs will benefit from a secondary helmet light or an exceptionally wide handle bar light.  When using a helmet mounted light care should be taken to avoid looking at items in close proximity, such as your handlebars or hands.  This will be too bright for the rider which will lead to night blindness, which in turn will reduce your ability to see in low light conditions.  For this reason it is recommended that a secondary helmet mounted light should not be brighter than your handle bar light.  It is also recommended that the secondary helmet mounted light only be used while riding on a singletrack, and should be switched off again on a normal surface.  The mounting of a light on a handle bar or helmet is a personal choice and may vary based on personal preference.

4. Endurance racers

An endurance racer is someone that will primarily use their lights for extended periods of time during darkness.  For example during a 24h race or during a multi day and night event.  Depending on the route conditions, the needs of a endurance racer may vary from that of a road racer to single track mountain bike rider.  The majority of endurance races are not that technically demanding and the runtime and weight of a light is of more importance than that of the light output.  If the race does not have too much technical mountain biking the beam pattern of light which is about the same as that of a road racer, where the reach of the beam is more important than the width, will be sufficient.  The reliability and weather proofing of a light is a very important requirement for endurance racers.

Beam Patterns

Depending on the type of cycling you prefer, you should first consider the beam pattern you will need before choosing a bicycle light.  The beam pattern can greatly affect the appearances of a light and its usability.  A small amount of light that is concentrated would appear much brighter than a light with significantly more output which is wider. Using a light with a small beam pattern is ideal when size is a concern.  Having more light just for the sake of more light adds unnecessary weight to your bike.

The above diagram shows 3 areas. It is interesting to note that the 3A diameter is only 41% bigger than the 1A, but its area is 3x that of the 1A. If you have a light that illuminates 1A at a specific brightness then you will need 3x more light to reach the same brightness of a 3A.

In general we would advise against Zoom lights for use as cycle lights due to the inefficiency of the optics.  We have done an in-depth article on Zoom lights vs Reflector lights. To fully understand please read the article.

Which LED? The Light Emitter

Over the last few years the bicycle light scene has changed quite dramatically. The first devices used incandescent (krypton, halogen-type bulbs), but it was soon replaced with the HID (High Intensity Discharge) types. As LED (Light Emitting Diodes) improved their efficiency (Power in Light out), their advantages soon started to outweigh their drawbacks of complexity.  Today LED dominates the mobile lighting market for the simple reason that LED can produce more light for less power than any of its competitors.  This is important for cycle lights due to the high weight requirements to store lots of power.  This, and the fact that they are very robust and impervious to vibrations and temperature fluctuation makes them the logical choice.

 Light Emitter  Efficiency Lumen Per Watt
Incadescent Krypton 2% 14
Incandescent Halogen 4% 24
HID 12% 83
LED Cree XM-L2(2014) 26% 182

With LED’s much higher power efficiency it is not surprising why LED have increased in popularity and dominates the mobile lighting market.

Not all LEDs are equal and care should be taken when selecting a cycle light to ensure that you don’t buy an old and inefficient LED.

Which LED is best?

This is not an easy question to answer.  There are many manufacturers of LED lights with strong competing products. The best known is Cree.  Other manufacturers include Luminous, Nichia, Seoul Semi Conductors and Osram, just to name a few.  At this stage the Cree LEDs top the notch when it comes to Lumen per watt.  The Cree XM-L2 U3 reaches over 165 Lumen per watt (@3W) and 116 Lumen per watt(@10W), compared to the older Cree XM-L T6 which is 129 Lumen per watt (@3W) and 91 Lumen per watt (@10W).

As with all LED manufacturers Cree has a wide range of LED models, but the low Voltage of the Cree XM-L design and high current (3A) has made them ideal for cycling lights.  The successor of the Cree XM-L is the XM-L2 which is 20% more efficient.  As with most LED models, the Cree models are sorted according to their Bin which is related to their efficiency.  The U3 Bin is the most efficient with the U2 and T6 Bins 7% less efficient.

The LED, however, is only a part of the complete light and its ability to convert energy to light is greatly affected by the driver and the housing of the light.  The exact same LED in a poorly designed housing with an inefficient driver will not perform as well.

Which Battery? The Power sources

The same happened with power sources as with LED lights.  The original alkaline based lights and Lead Acid batteries were heavy and large.  Over time rechargeable Ni-cad and Ni-MH batteries became more popular, but failed to address the needs of the mobile light market.  With the advent of cellphones the Li-ion rechargeable batteries became more and more affordable.  As with LEDs the required high complexity was a draw back, but their higher power density and longevity made them ideal for the mobile light market.  Today almost all mobile power sources are some form of Li-ion based batteries.

Battery Type Wh/kg Wh/liter
Lead-acid 41 100
Alkaline 110 320
Lithium(2)(3) 297 560
NiMH 95 300
NiCad 39 140
Lithium-ion (Low grade) 128 230
Lithium-ion Panisonic 18650B (4) 260 739

Li-polimare is a subset of Li-ion

When it comes to energy per weight (Watt Hour/kg) there are two types: the Primary Lithium and the new Secondary Li-ion (Lithium-ion) battery packs.  Primary batteries cannot recharge, whereas secondary batteries can.

Lithium batteries should not be confused with Li-ion batteries.  Lithium is not rechargeable but do come in the standard AA and AAA sizes. On the other hand, Li-ion batteries are rechargeable, but do not come in the standard battery sizes.  The reason for this is that Li-ion batteries have a cell voltage of 3.6V or 3.7V and if installed into devices that are designed for 1.5V it will result in permanent damage.

The benefits of having a rechargeable battery pack for cycling lights outweighs the little advantages the primary Lithium has.

As with LEDs not all Li-ion batteries are equal. The highest quality types are very expensive but will extend both the runtime and lifetime of the light.  The actual cost of a high quality light is not the LEDs or the light itself, but it’s the battery.  The cheaper the light, the lower the performance and quality of the battery pack that is supplied. We have done a battery comparison which shows this clearly in “Cycle Light Battery Pack Comparison


It is not surprising that the combination of the two, LED lights and Li-ion batteries, have been incorporated so quickly into the bicycle light industry.  But not all Li-ion and LED technologies are equal.  It is highly likely that most customers already know that Li-ions and LEDs are the best choice for cycling lights.  But very few people are able to identify which is best. We hope that the above information will be helpful when choosing your next cycle light.

If you are looking for a comparison between lights hop over to our bicycle light buyer’s guide.

Technical Jargon

Light output ratings

When it comes to comparing lights it is convenient to settle on one unit. Unfortunately the choice of which unit to use is somewhat disputed.  The four units that are most popular are:

  1. Watt
  2. Candelas
  3. Lumen
  4. Lux or Illumination

Although manufacturers use watt it is not the most appropriate figure. Wattage alone is a poor measure since (a) it reports the consumption of power rather than the output of light, and (b) lamp optics will significantly impact the portion of the light which is delivered where it is needed, for example concentrated in a spot beam or dispersed as with flood lights.  The last three units are used to measure light output.  Candelas, measuring the intensity of a beam, are more appropriate when the aim is to brightly illuminate a small spot.  Lumens measures the entire production of light and are more relevant to the purpose of broad beams or non-directional flood lights.  Lux is an indication of how bright a spot is at a certain distance.

1.  Watt

Read more at Wiki Watt

Watt (W) is the unit of power, and not the light power output, that is usually quoted for the electrical power input. Electrical power is the product of voltage and current (watts = volts × amperes). Input power is only useful when comparing lights of similar technologies.

Watt would be very handy if one talks about radiated energy but in most cases it is used to state the maximum input of power. If all LEDs were equal then this would be a very convenient way to compare the brightness of lights, but it is hardly the case.

2.  Candelas

Read more at Wiki see Candela.

Candela (cd) is the SI unit of luminous intensity. It is the power per unit solid angle, weighed according to the sensitivity of the human eye to various colours of light.  A typical candle produces light with about 1 candela of luminous intensity.  A lamp can produce higher luminous intensity either by producing more light, or by focusing it more condensed.  The luminous intensity of a light depends on many factors, including the colour of the light and the eye’s sensitivity to that colour, the optics involved, the reflector and lens.  Despite its complexity, it is a more useful measure than watts, because it defines how much usable light is shed in a given place.

3.  Lumens

Read more at WIKI Lumen (unit).

Lumen (lm) is the SI unit for luminous flux, the total amount of light emitted by a source, weighed according to the sensitivity of the human eye to various colours of light. The luminous flux is of less value for bicycle lighting due to the importance of directionality.  Lumen per watt is a common measure of the efficiency of a light source.  Luminous intensity is much more useful, but lumen per watt is a handy way to compare the output of otherwise similar lights.

4.  Lux or Illuminance

Read more at WIKI LUX

Illuminance is a measure of how much luminous flux is spread over a given area.  One can think of luminous flux (measured in lumens) as a measure of the total “amount” of visible light present, and the illuminance (Lux) as a measure of the intensity of illumination on a surface.  A given amount of light will illuminate a surface more dimly if it is spread over a larger are.  Illuminance (Lux) is thus inversely proportional to an area when the luminous flux (lumens) is held constant.