The problem of choosing LEDs is acute due to their wide range and unlimited price range. The production technology and parameters of LED lamps are accelerating very quickly. It is difficult to keep up with new products, and it is even more difficult to figure out which diode is better, which is newer, and what should be bought in this or that case.
Of course, you should choose a light source based on your needs. If you're a fanatic of new products and love to test the length and width of the beam in the company of like-minded people, naturally you need the latest super-bright new products. For hunters, fishermen, divers and other lovers of active pastime, the brightness, focusing or scattering of the beam, and its color tint are important.
Decoding bin codes of LEDs
When producing LEDs, they are assigned bin codes. At first glance, this abracadabra does not mean anything. Only knowing the classification, it becomes completely clear which diode is in front of you. The LED bin includes data about the housing design, color subgroup, color shade, brightness code. There are additional digits related to the internal production code; they are of no value to the user.
For example:
XPGWHT-L1-1C0-R5 is a diode with an XPG housing, color - WHT (white), subgroup L1 - white, 1C0 - shade according to the ANSI table, R5 - brightness code (139-148 lumens at 350 mA).
Cree XLAMP XR-E
A common but rather outdated LED. It is a small crystal with a protective glass lens mounted on a substrate, which acts as a heat sink and serves as the basis for contacts.
The luminous output depends on the brightness code and ranges from Q2 (87.4 to 93.9 lumens) to R2 (114 to 122 lumens) at 350 mA. As a rule, a diode of this class is used in inexpensive flashlights. The maximum temperature of the light-emitting crystal is up to 150 °C, when operating with a maximum current of no more than 1 A and a voltage of no more than 3.9 V.
Available in colors:
warm white - 2700-3600°K;
neutral white - 3700-5000°K;
cold white -5000-10000°K.
Cree XLAMP XP
- XPE. This series is especially popular due to the combination of reliable design, increased light output characteristics and reasonable cost. Externally, the crystal has big sizes than previous series, the reflector is shallow. Maximum temperature 150 °C, current 1 A, voltage 3.4 V. Cree XPE has a wider temperature color scale, the “Outdoor white” shade has been added to the scale with a range of 4000-5300°K. It's more natural cold White color. Luminance bins: N4, P2, P3, P4, Q2, Q3, Q4, Q5, R2, R3, this is 144-280 lm. Luminous efficacy 19-34 lm/W.
- XPC. This series is a modification of the XP-E with a current of 0.5 A and a voltage of 3.5 V. Color shades and luminous flux power are in the same range as the prototype. The luminous efficiency is higher (35-59 lm/W), so we can talk about a clear advantage in this parameter. XPE and XPC are used in small-sized hand-held flashlights.
- XPG. A new generation LED that is super bright and efficient. Has comparatively large area crystal, can withstand up to 1.5 A. The luminous efficiency leaves far behind its predecessors and ranges from 90 to 139 lm/W. Maximum luminous flux 346-534 Lm. Color shade is divided into 4 groups. Luminance bin classification: Q4, Q5, R2, R3, R4, R5, S2, S3 - determined at a current of 700 mA. Diodes of this class are used for powerful hand-held and sports flashlights. For long-range, super-bright flashlights should be used the latest system XP-G2, which has greater light output with standard characteristics.
Cree XM-L
Very powerful LED (10 W), used in professional flashlights and stationary lighting sources. The crystal has dimensions 2.5 times larger than XPG, which provides a wide beam of light. If you use a shallow reflector, you get a large flood spot from the flashlight. The luminous flux at a current of 3 A can reach 900 Lm. The maximum luminous flux, depending on the brightness bin, is 1008 lm. The classification of brightness bins is determined at a current of 700 mA, using: S6, T2-T6, U2, U3 (analogous to Cree J-A5).
Which diode to choose?
If light characteristics are important to you, then you don’t have to look at the LED brand, since it only determines design features. There is no need to buy a powerful Cree XM-L diode for a keychain flashlight; XPE is sufficient here. For powerful and reliable light sources, XP-G, XP-G2, XM-L, XM-L2 are better suited.
The color group is a matter of taste. Optimal options is neutral or natural white. The exception is professionals who use LEDs in their optics and the spectral shade is important to them.
The power of the flashlight depends on the power source, but the brightness directly depends on the bins. At a current of 350 mA, the brightest will be Q5 and R2, at a current of 700 mA - T6, S3 or U2, U3. When choosing brightness bins, keep in mind that some of them, for example, U, can only work in the cold spectrum, so for flashlights with soft, warm light it is better to choose something with T coding.
When selecting or assembling a new LED flashlight Be sure to pay attention to the LED used. If the only task of the future flashlight is to illuminate a dark entrance, then almost any bright white LED will cope with this task. Another thing is the desire to get a portable lighting device with parameters for a more complex task. In this case special meaning has a luminous flux, that is, the ability of the flashlight to produce a sufficiently powerful beam and illuminate a wide area of space.
Which LED brands are in the top positions, and what characteristics do their light-emitting diodes used in flashlights have?
Main characteristics
The quality of light emitted by the flashlight is controlled by the LED, which can be called, without exaggeration, the heart of the device. The stability of a flashlight's heart rate depends on many parameters, the main ones being current consumption, luminous flux and color temperature. The trendsetter is considered to be the Cree company, which produces a wide line of super-bright and powerful LEDs, including for flashlights. Modern flashlights are designed with a single LED with a power of 1, 2, or 3 W. In the one-watt version, the forward current is about 350 mA with a voltage drop of 2.8-2.9 V.
The current and voltage of a two-watt LED is about 700 mA and 3.0 V, respectively, and a similar 3 W crystal consumes about 1000 mA and 3.2 V. Given electrical indicators typical for LED models of the world's leading brands.
The intensity of radiation, also called luminous flux, depends on the manufacturer and family of the LED. The rated value of the luminous flux of high-power LEDs is usually measured at the maximum permissible operating current. The manufacturer of branded flashlights, along with the type of LED installed, indicates the number of lumens produced by the product.
Unfortunately, flashlight packaging often indicates inflated characteristics, including luminous flux. The reason for this is simple - any manufacturer wants to sell as much product as possible.
Luminous flux is inextricably linked with light. Modern light-emitting diodes are capable of emitting a luminous flux of up to 200 lumens per 1 watt and can be produced with any glow temperature: from yellowish warm to cool white. Lanterns with a warm white emission color (T≤3500°K) are the most pleasing to the eye, but less bright. Lighting with a neutral color temperature (T=4000-5500°K) allows you to view fine details more effectively. Cold white beam (T≥6500°K) in powerful flashlights with a long illumination range, but within long work irritates the eyesight. 
Due to the impossibility of carrying out accurate calculations, the lifespan of LEDs is calculated by extrapolation. At a temperature of 25-50 °C, their crystal service life can exceed 200 thousand hours, but this is not economically justified. Therefore, manufacturers allow an increase operating temperature up to 85°C, thus saving on cooling costs. Exceeding the threshold of 150°C leads to irreversible processes of crystal burnout and loss of brightness.
Color Rendering Index (CRI) – qualitative indicator, characterizing the ability of an LED to illuminate objects without distorting them real color. For LED lighting sources, including flashlights, a color rendering index of 75 CRI or higher is considered good.
An important element of an LED is the lens. It sets the angle of dispersion of the light flux, and therefore determines the range of the beam. The technical characteristics of LEDs must indicate the value of the radiation angle. For each model, this parameter is individual and can vary from 20 to 240 degrees. Powerful LEDs for flashlights have an angle of 90-120° and, as a rule, are equipped with a reflector with an additional lens in the housing.
Despite the sharp leap in the development of high-power multi-chip LEDs, world leaders continue to produce less powerful LEDs. They are produced in cases small size not exceeding 10 mm in width or diameter. The typical current value of such light-emitting diodes does not exceed 70 mA, and the luminous flux is 50 lm. Powerful flashlights based on them are gradually disappearing from store shelves due to worse technical characteristics and the need for series-parallel connection to increase brightness. Compared to one powerful crystal, the reliability of the circuit and the dispersion angle of several such elements in one package are much worse.
Separately, it is worth noting the four-pin LEDs in the P4 “SuperFlux” or “Piranha” package, which have improved technical characteristics. Piranha LEDs have two important advantages, thanks to which they are in demand:
- distribute the light flux more evenly;
- do not require heat removal;
- have low cost.
5 largest manufacturers
A portable flashlight should not only be ergonomic, but also equipped with a reliable LED source with a high working life without loss of brightness. In order not to make a mistake with your choice, preference should be given to world-class manufacturers of LED products.
Division of the Japanese company Nichia for a long time held a leading position in the production of LEDs of all types. Due to the high cost of products and increasing competition from China and Taiwan, today it is becoming increasingly rare to find their LEDs in flashlights on the European market. However, the world needs Nichia as an engine of progress. After all, the developments of Japanese companies are taken as a basis by their Chinese and Taiwanese colleagues. 
Powerful LEDs for flashlights from the world-famous company Cree hold the lead not only on the American continent. Standing out due to their lower cost and high quality, LEDs from Cree are available to everyone on the European continent. A rechargeable flashlight with a powerful crystal from an American brand is a reliable friend on a hike, night fishing, etc. 
Philips Lumileds is a European manufacturer of wide-spectrum light-emitting diodes. The company has achieved certain progress in the construction of outdoor lighting systems of functional and architectural significance. Philips Lumileds developers implement A complex approach in the construction of LED systems, taking into account their design, degree of protection and ease of use. 
The South Korean corporation Samsung, well known in Russia, promptly financed its division to search for new LED solutions and now has a full production cycle of emitting diodes. Samsung is not limited to producing LED backlights for its own displays. Their successes have spread to other market segments: high-power LEDs (including for flashlights), ultra-bright flash elements, as well as indoor and outdoor lighting modules. 
Osram Opto Semiconductors has become famous for the excellent characteristics of LEDs from the Duris series, which are distinguished by their high luminous efficiency and color rendering index. German company relied on the introduction of LED technologies in industrial sectors, focusing on the production of ready-made specialized lamps and fixtures. Osram laboratories improve the performance of light-emitting diodes not only in the visible spectrum, but also make discoveries in the IR, UV and laser directions. 
Reports from scientists along with development news artificial lighting indicate continued healthy competition between large corporations. We see positive trends in the development of LED technologies in the constantly updated model range lanterns that surprise with their long-range beam, high degree protection, charging ability from solar energy and other know-how.
Read also
LED operation is based on semiconductor knowledge and practice. They have been known to mankind for almost half a century. At the same time, everything starting materials for the production of such lighting fixtures We've known each other for more than 20 years. However, it was only recently that we succeeded in connecting them correctly and obtaining impressive LED characteristics. This lighting represents an innovative breakthrough, making diodes quite efficient and environmentally friendly. It is believed that such accessories are much more economical than classic incandescent lamps. They can be used in various fields human life not only because of ease of use, but also due to the desired glow temperature.
Characteristics
In order to understand the principle of operation of the devices, you need to know the following characteristics of LEDs:
1. Luminous flux. This parameter is measured in lumens (Lm) and shows the amount of light that the lamp produces. The higher this indicator is, the brighter it will shine.
2. Power consumption is measured in Watts (W). The smaller this parameter, the more economical the energy consumption.
3. Light output, its unit of measurement is considered to be Lm/W. It is central to the operation and efficiency of the entire lighting device.
4. Radiation direction diagram. Parameter of the luminous intensity curve, due to which the fluxes emitted by the diodes are distributed.
5. Color temperature (shades of white light). It is measured in degrees Kelvin in the permissible range from 2700 to 7000 K. The shade of a warm color is considered the most favorable for the eyes, which varies up to 4000 K, and all indicators that are higher are usually referred to as “cool white”. Most often, lamps with warm light are much more expensive than those with cold light, since this is directly related to the features of their production.
6.Color rendering index. This value shows how truthfully the color of an object illuminated by the selected lamps will be displayed. The higher this parameter, the more truthfully the shade of the original object is conveyed.
7. Performance of lighting devices. The most correct decision is to choose branded manufacturers, since such companies can provide more accurate technical characteristics of LEDs, thanks to which the device will last the stated operating time. Also, such lamps provide protection against voltage surges and overheating.
8. Device size. There is no need to judge the advantages and disadvantages based on the size of the crystal. It does not matter whether the LED is large or small, the most important thing is its power.
Considering these characteristics of LEDs, you can choose exactly the device that will give the maximum effect from its intended use.
Quality indicators
The quality indicators of an LED product can be judged based on the following criteria:
- manufacturer (preferably products from well-known companies that publish open data on the reliability of their devices);
- use of a specially designed structure and shape for the fastest possible heat removal, regulating temperature regime when the chip is working;
- optical (lighting) specifications of the LED lamp, which can be obtained from an independent laboratory or manufacturer;
- high-quality guarantees;
- results of long-term tests of the functioning of devices.
White varieties
Most often in everyday life, for decoration and lighting, white LEDs are used, the characteristics of which depend on their tone.
- Warm white light: its color temperature is 2700 K and it has a slight yellowish tint, similar to the flame that a candle emits. This shade is typical for incandescent lamps; it calms and relaxes. It is important to note that using a matte or transparent shade will change the shade to a softer or richer one. This type of light is not the main one, but it is perfect for additional and decorative lighting, will be ideal for installation in bedrooms. Thanks to it, you can create harmony and homely warmth in the room.
- Natural white light: Its color temperature is 4200K, it is the most popular and most commonly used. Suitable for use as the main source of lighting for both commercial and domestic premises. Can be used on all types of surfaces such as kitchen countertop or a desk in the office. Like warm light, natural has several shades. Fixtures and lamps with matte dispersion will have a completely different saturation spectrum than devices with a transparent bulb. It helps produce more accurate and directional light than matte, through which soft highlights of an unobtrusive shade are emitted.
- Cool white light: its color temperature is 6000 K. It has a peculiar bluish tint. This tone is very bright and is most often used for offices and also as local lighting. It has become quite widespread in parking lots, entrances, local area, as well as in parks, alleys and squares. Often installed to illuminate street advertisements, commercial signs, and more.
Types of LEDs
There are the most different LEDs, the parameters and characteristics of which completely depend on their types:
1.Blinking: used in indicators to attract attention. This type is practically no different from the usual ones, however, for its production a built-in multivibrator circuit is used, which flickers with a break of 1 second. The main types of such diodes distribute single-color light rays; more complex ones in their characteristics can flash in several shades alternately or simultaneously, thanks to the RGB parameter.
2. Multi-color blinking LEDs, the characteristics of which are quite diverse and can be represented in two different crystals, working one towards the other, therefore, when the first one lights up, the second one goes out completely. With the help of a current that moves in the initial direction, one color appears, and in the opposite direction another color appears. Thanks to this type of work, a third color is formed, since the two main ones are mixed.
3.Tri-color LEDs, the parameters and characteristics of which consist in the presence of several light-emitting diodes, not connected to each other, but combined in one housing. They work separately, they can light up at the same time, but their controls remain completely different.
4. RGB light emitting diodes with blue, red and green elements that use a four-wire connection and a single common cathode or an anode.
5. Monochrome displays with seven segments, as well as using starburst format. Such screens show all the numbers, and some even a certain set of letters. Using Starburst allows all symbols to be displayed.
Alphanumeric and numeric displays, which were quite common in the 80s, became less popular after the advent of LCD monitors.
Advantages of LED lighting
Being relatively new technology, LEDs are in most cases superior to many lighting sources in terms of light quality, energy efficiency, environmental friendliness and cost-effectiveness. The characteristics of LEDs are superior to those of high-incandescent lamps in almost all areas of application, but such lighting cannot yet solve all the tasks. White diodes have already proven themselves to be an excellent alternative to fluorescent tubular and high-pressure lamps. But it still has to pass a large number of time until such technologies begin to be used in the public system.
What does the SMD marking mean?
The decoding of this indicator sounds like Surface Mounted Device, which translated into Russian means “a device that is mounted on a surface.” Such a device is a diode, and the surface in our case is the base of the tape.
Any SMD LEDs, the characteristics of which are similar to those of all other similar lamps, consist of several crystals placed in a housing with contact leads, as well as lenses that form the luminous flux. It is emitted by semiconductors and directed into a miniature optical system, which is formed by spherical reflectors, as well as the transparent body of the diode itself.
What other characteristics do SMD LEDs have? The marking, which is represented by numbers on the tape, shows the dimensions of the crystal in millimeters. The SMD-based strip bends very well in the longitudinal direction.
What does the DIP LED marking mean?
There are also LEDs on sale, the characteristics of which are very similar to SMD. According to their own technical parameters they are a cylindrical body, which is placed on the end strip. This type has good silicone protection. The numbers that are present in the marking, as well as for SMD, indicate the diameter of the diode.
Such crystals can be used to illuminate furniture, only for glass shelves. Unlike the previous tape, this type bends very well in the transverse direction.
Parameters of a high-quality LED flashlight
Today, you can buy a large number of conventional flashlights on the market, but they are being actively replaced by LED ones. This happened primarily due to the fact that the latter give much brighter light.
In order to choose the right LEDs for flashlights, the characteristics of which are very diverse, it is necessary to take into account all the basic requirements of the buyer when choosing. What you need to pay attention to is the type of beam, it can be wide or narrow. Which type to choose depends on the future application. For example, in order to be able to see objects at a distance of 30 meters, it is better to choose a flashlight with a wide beam, while models with a narrow beam can illuminate distant objects well. Most often, such lighting is provided by tactical devices used by tourists, hunters and cyclists.
Another important factor affecting the operation of the flashlight is the type of power supply. For the simplest household appliances ordinary AA or AAA batteries are used, but for strong and powerful devices this volume will not be enough. In this case, it is necessary to use lithium-ion batteries, which can operate continuously for 5 hours.
It is worth paying attention to LEDs for flashlights, the brightness characteristics of which differ from each other by no more than 40%. The quality of the selected devices is guaranteed by the presence of markings. In cases where it is absent, we can talk about an uncertified product, most often made in China.
LEDs from CREE
This company specializes in the manufacture of high-quality and bright diodes. She was one of the first to develop new white light bulbs, thereby setting a new milestone in the industry.
CREE LEDs, the characteristics of which are presented, remain competitive in their industry:
They have record luminous flux values reaching 345 lumens at a current of 1000 mA;
- thermal resistance at a low level;
- relatively wide angle of study;
- miniature, evenly distributed crystal;
- maximum current reception up to 1500 mA;
- improved silicone lens instead of glass;
- maximum crystal operating temperature 150 °C.
As you can see, such technologies are just coming into force and bring exceptional benefits from their use. Every day new discoveries are made, LED lamps become more economical and brighter, thanks to which they rightfully begin to occupy a leading place in the lighting arena.
Features of SMD 5050 tapes
LEDs in this series have a size of 5x5 mm and a luminous flux depending on color, which ranges from 2 to 8 lumens. They can also be divided according to the degree of moisture protection - IP20 and IP65, since they have two different types coatings, namely polyurethane and silicone. The former can only be placed indoors, while the latter, accordingly, are suitable for the street, since they are not afraid of excessive humidity.
5050 LEDs, whose characteristics and properties help create bright light, consist of three crystals with different or identical diodes in one package. Multi-colored lamps are called RGB (red-green-blue), after connecting controllers, you can get a variety of colors in them.
Main technical characteristics are:
Transparent and rigid polyurethane coating;
- high-quality soldering;
- the number of LEDs per 1 meter is 60 pieces;
- cutting ratio - 3 crystals, which is 50 mm;
- width, length, height in mm 10 x 5000 x 3;
- the power supply is connected to 12V or 24V DC.
Features of SMD5730 tapes
Adopting high-efficiency 5730 LEDs, the characteristics and properties of high thermal conductivity and low resistance ensure a long service life of the device. They are vibration resistant high humidity environment and temperature changes. They are small enough, have a wide beam angle and are perfect for any surfaces during installation. They can be purchased in reels and tapes.
Many people like to use 5730 LEDs, whose characteristics are suitable for use in various devices, which is very convenient for both ordinary users and designers. They are indispensable for lighting retail and office premises, where not only high energy efficiency is considered important, but also comfortable light transmission.
For those who use LEDs, markings, characteristics and properties are of no small importance. They have a number of advantages over their predecessors, namely:
Phosphor white LEDs with a nominal power of 0.5 W are distinguished by a significant service life, stable performance and high-quality performance;
- high resistance to temperature changes, vibrations and high environmental humidity;
- degradation of the luminous flux - no more than 1% for 3000 hours of operation;
- the body is made of high-quality heat-resistant polymer that can withstand up to +250 °C;
- LEDs are fully suitable for reflow soldering.
To move or work in the dark, you need a flashlight. They are different types ranging from small pocket ones to large military or search ones. The design and power of a flashlight depends on its purpose, for example, in order to illuminate a keyhole in a dark entrance, a flashlight is enough low power, and for backpackers, you need a camping lantern that can shine in all directions, like a kerosene lamp, and a waterproof, impact-resistant lantern to move around in low visibility conditions. In this article, we'll look at how to choose a powerful LED rechargeable flashlight for your needs.
Criterias of choice
To do right choice LED flashlight needs to take into account a number of factors, including:
- Type and power of LEDs. Brightness and energy consumption depend on them.
- Colorful temperature. Comfort during use depends on it.
- Capacity and type of batteries. Affects the duration of work.
- Reflector and optical system. It depends on them how focused the light flux will be.
- Design features. They affect impact resistance, resistance to water and dust, ease of use, carrying and holding in hands.
Types of LEDs
Flashlights can use various LEDs, and every year more and more powerful and brighter models are released. However, this does not prevent us from dividing them into the main types used:
- 5 mm LEDs. Previously used in all LED lights, now it's obsolete type LEDs, the reason for this is their low brightness and significant energy consumption. To get a strong luminous flux from a flashlight, you have to install many of these LEDs, which is not always possible, since such a flashlight will not fit in your pocket.
The photo below shows an example of flashlights with 5 mm LEDs 5 mm LEDs in flashlights
- SMD LEDs.
Can be used various types– 5050, 3528, 5730 and others. They have two advantages - high power and small dimensions. This allows you to achieve good luminous flux for small lanterns. Matrixes of such LEDs are installed on camping lanterns and other types of lanterns with a diffused light mode function. It allows you to illuminate a large area from one flashlight with a diffused stream, albeit with losses of illumination, rather than a focused bright beam. 
Panel with diffused light on the flashlight
- Powerful LEDs 1, 3, 5 Watt. Two groups can be distinguished here:
- Noname LEDs.
- Branded LEDs, for example, the CREE brand and its popular XM-l models and others.
Flashlight with powerful LEDs Accordingly, cheap Chinese LEDs are installed in budget products price segment, and branded ones - into more expensive flashlight models. The differences lie in the specific luminous flux - the number of Lumens per 1 Watt of power, in other words, the efficiency. This determines not only how brightly the flashlight will shine, but also how long it will operate on a single battery charge. It is also observed that cheap high-power LEDs fail faster, like any noname products.
What kind of LEDs are installed in high-power flashlights?
As already mentioned, the most common LEDs are from CREE; we have prepared a summary table with the characteristics of popular LED models for flashlights.
| Name | Cree XM-L T6 | Cree XM-L2 | Cree XP-G2 | Cree XR-E |
| Photo | 
| 
| 
|  |
| U, V | 2,9 | 2,85 | 2,8 | 3,3 |
| I, mA | 700 | 700 | 350 | 350 |
| P, W | 2 | 2 | 1 | 1 |
| Operating temperature, °C | <150 | <85 | <85 | <85 |
| Luminous flux, Lm | 280 | 320 | 145 | 100 |
| Illumination angle, ° | 125 | 125 | 115 | 90 |
| Color rendering index, Ra | 80-90 | 70-90 | 80-90 | 70-90 |
And more powerful.
| Name | Cree MT-G2 | Cree MK-R | Luminus SST-50 | Luminus SBT-90 |
| Photo | 
| 
| 
| 
|
| U, V | 5,7; 8,55; 34,2; | 6; 12; | 3,6 | 3,5 |
| I, mA | 1100; 735; 185; | 2500; 1250 | 5000 | 9000…13500 |
| P, W | 6,3 | 8,5 | 18 | 20…40 |
| Operating temperature, °C | <85 | <150 | <85 | <85 |
| Luminous flux, Lm | 440 | 510 | 1250 | 2000…2500 |
| Illumination angle, ° | 115 | 120 | 100 | 90 |
| Color rendering index, Ra | <70 | 70-90 | 80-90 | 80-90 |
But LEDs can be designated in a different way, with a more concise marking, for example:
- XM-L: T5, T6, U2.
- XP-G: R4, R5, S2.
- XP-E: Q5, R2, R.
- XR-E: P4, Q3, Q5.
This video shows the process of replacing such an LED.
Colorful temperature
For flashlights, color temperature is not as important as color temperature for indoor lighting. However, it is worth paying attention to it. is perceived as softer to the eye, and neutral and cool shades make you more alert and focused. 
Color temperature of flashlights
Batteries
Now the leading place in sales is occupied by Li-ion batteries. The reason for this is their large capacity with small dimensions, good current output, and almost complete absence of memory effect. There are also disadvantages that should be remembered - in the cold, lithium-ion batteries discharge faster than in the heat, and if a lithium can is short-circuited without protection, a reaction will occur with a large release of heat, even leading to an explosion. 
18650 battery
Powerful LED flashlights are most often equipped with lithium batteries; in addition to them, there are also other types of batteries:
- Ni-Cd – nickel-cadmium.
- Ni-Mh – nickel metal hydride.
- Pb – lead.
But recently they are used in flashlights less and less.
Reflector and optical system
The design of the reflector and the presence of lenses affect the shape of the light spot. Some models have the ability to move the lens, which allows you to focus the light beam. The lenses collect the light flux, as a result you get a more illuminated space, but a smaller area than without focusing. 
Focusing the light beam
But different tasks require a light beam of different sizes. For example, if the flashlight will be used to repair a car, then in most cases, a model with the ability to focus will be better suited to illuminate a large area when searching for a problem, and then narrow the beam of light to a small but bright point when eliminating it or studying it in detail. At the same time, a focused spot is not needed to move in the dark; flashlights that widely illuminate the space in front of you are better suited.
Types by purpose
In addition to the elements used and their features, when choosing flashlights, they are also distinguished by their purpose. To choose the right LED flashlight for specific tasks, you need to clearly understand what you will use it for, because there are no universal models as such.
Military and special devices
The main feature of military flashlights and special-purpose lighting devices is, first of all, the high strength of the body and its resistance to moisture. Such devices also include search lights that shine brightly and far away, which allows you to find something in difficult conditions, for example, in a forest or in large rooms. 
Military lantern
Models for technical personnel
Flashlights for technical personnel should be compact and have a long operating time. Their size and weight should not complicate the movement of the worker, who already carries tools and parts with him. An excellent addition to such a device would be the ability to focus the light beam and a head mount. 
Headlamp
For outdoor recreation and tourism
Search and camping lanterns, as well as those used for military purposes, are suitable for tourists, since the conditions in which they will work are similar - humidity, the possibility of bumps and falls, etc. A camping lantern resembles a kerosene lamp and is a broad-directional or all-directional lighting fixture. It is convenient to use, for example, when preparing for an overnight stay and dinner. You should also pay attention to flashlights with a built-in generator. They can either operate without batteries or be recharged by operating the generator lever (rotation or rhythmic pressing of the handle, depending on the design). 
Camping lantern
How to convert an ordinary flashlight into an LED one
Let's look at how to make an LED flashlight with your own hands. To do this you will need the following set of parts and tools:
- Frame. You can take it from an old lantern or make it yourself, or print it on a 3D printer.
- LEDs. Selected individually.
- or resistors to limit their current.
- Battery.
- A charge controller for batteries or a charger suitable for the type of battery used.
- Power button or toggle switch.
If you use high-power LEDs, you will need a circuit board on an aluminum substrate. 
LED substrate
To improve heat dissipation, you need to use a radiator, you can take it from the motherboard. Small radiators are installed on chipsets, northbridge, power switches and other board elements. 
LEDs on the heatsink from the motherboard. Don't forget to coat everything with thermal paste!
To charge and protect the 18650 battery, you can use the TP4056 board with protection, it can be ordered on Aliexpress or bought at a radio store, it costs 20-50 rubles. 
Lithium battery charging board based on tp4056
Interesting: This board can be used to replace disposable batteries in a flashlight or to convert any device to batteries.
We pack this in the flashlight housing, if it is iron, as in the photo, do not forget to provide insulation for all boards.
To power the LEDs, you can use a specialized driver or a switching boost converter, for example, MT3608. The output voltage is set using a multi-turn potentiometer; in the photo below it can be recognized by its blue housing.
Expert opinion
Alexey Bartosh
Specialist in repair and maintenance of electrical equipment and industrial electronics.
Ask a question to an expertIf you use a driver for power, its main characteristics are the output current and power; it determines how many LEDs you can connect in series.
It is necessary to select a voltage such that the current is 10-30% lower than the rated current. For 1 W LEDs, the rated current is in the range of 300-350 mA. 
Boost converter in a flashlight
A less complicated way is to select the operating mode for heating the LEDs. That is, gradually increase the voltage, testing the radiator by touch; it should not heat up, or its temperature should be less than 50 degrees Celsius, this is the temperature when your hand still tolerates it when you touch it and you don’t want to pull it back. This is an imprecise method, so it is better to focus on both current and heating. 
Homemade flashlight assembly
The American company CREE is a leading manufacturer of solid-state light sources. The LEDs of the XLamp family of the XR, XP, MC series developed and produced by it are highly efficient and economical, which makes it possible to create modern technologically advanced and environmentally friendly lighting devices on their basis.
So let's decipher the notation a little.
For example, the flashlight says: LED CREE XP-E R2
CREE is naturally the name of the diode manufacturer
XR-E, CREE has XP-E, XP-G, other companies have P4, P7, etc. - this is the designation of the diode itself.
R2 - brightness bin. Bin shows how many lumens the LED produces when consuming 1 watt of energy, for an LED this is a current of 350 mA. In English this parameter is called flux bin. Currently there are Q2, Q3, Q4, Q5, R2, R3, R4, R5, S2. The table below shows how many lumens can be obtained from which diode.
Q2-Q5 and R2 are available for XR-E diodes, R2, R3 are available for XP-E, R4-R5 and S2 are only available for XP-G.
What is the main difference other than brightness?
XR-E is the oldest and is found only in flashlight models that have been on the market for quite some time. XR-E is externally very easy to identify, it has a large hemisphere covered by a diode, the crystal itself is larger than that of subsequent series (for comparison, on the XP series it is just a droplet, the size of the XP-E compared to the XR-E was reduced by 80%. XP -E differs from XP-G in that the E has three stripes on the diode, the G series has four, it turns out that the area of the XP-G is larger.
Consequently, in reflectors of the same size and structure, the longest-range one is XP-E, since it has the smallest crystal, and the smallest light source, since it is easy to focus into a narrow beam, then XR-E, and the widest beam is XP-G, not because of the crystal size, but because of the difficulty of focusing, more on that below.
If the diodes are arranged according to energy efficiency from weakest to brightest, we get XR-E - XP-E - XP-G, where the latter is the most energy efficient, see the table below.
It would seem that if there is the brightest and newest and most efficient XP-G diode, then why are all the well-known and respected flashlight manufacturers in no hurry to switch to this diode. The reason is simple. Each diode requires a specially designed reflector to produce an acceptable light beam.
Let's look at all the series. If you shine a flashlight on a flat wall, you will see the following artifacts:
U XP-E- an ideal picture without any flaws: a well and evenly focused central beam and smooth side illumination without dips.
U XP-G When focusing using a reflector, a so-called donut hole can be observed, when the central beam of light looks like a donut with a noticeable darkening inside. This is not the fault of the flashlight manufacturers, but a feature of the diode. Therefore, companies such as Fenix, Jetbeam, Nitecore, Zebra, 4sevens were in no hurry to update their lineup, while others, in the race for new products, either installed a highly textured reflector, or simply used reflectors for other types of diodes. All this negatively affects the focusing of the beam and the range of the flashlights. According to many experts, flashlights using this type of diode are inferior in range to older models using XP-E and XR-E.
XM-L- is a real masterpiece of this company! This is the latest development of 2011! Since the invention of this LED, 95% of powerful flashlights are built on it! This diode has outstanding characteristics. Its brightness reaches up to 1000 lumens at a current of 3A!