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Basic Flashlight Tutorial
An Introduction to High-Performance Flashlights

  1. Overview
  2. Flashlight Basics
  3. Popular Brands
  4. Flashlight Prices
  5. Light Sources
  6. Runtime
  7. User Interface
  8. Batteries
  9. Headlamps
  10. Battery Charging and Battery Chargers
  11. Light Output and Beam Patterns
  12. LED Manufacturers
  13. Special Considerations
  14. Flashlight Modifications
  15. Accessories Included with Flashlights
  16. Trusted Sellers
  17. Some of the Flashlights and Spotlights I Currently Own
  18. Troubleshooting

I know what you're thinking to yourself.... What is there to know about a flashlight, switch it on and it lights up, switch it off and the light goes out. That's true for the most basic flashlights. When looking for a new flashlight, I discovered that there is a huge community of people that are interested in (or obsessed with) flashlights. They typically refer to themselves as 'flashaholics'. Initially, it was difficult to understand some of the discussions on the various forums because there were so many new terms. This page is a primer. After you understand the basics you'll better understand the discussions on the various flashlight forums (like the Candlepower forum).

There will be products that I recommend on this page. I receive no compensation for this. These are simply products that I have used and would recommend to my friends.

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Flashlight Basics

Until recently, virtually all flashlights were simple on/off devices (like the one below) with very limited output. Flashlights like the 4D-cell Maglite were considered to be some of the best, in terms of light output. Those flashlights used an incandescent lamp (hot wire filament producing light). Except for the cheapest flashlights, incandescent lamps are being phased out. The newer flashlights using LEDs produce much more light than most of the flashlights using incandescent lamps. Most people have never seen a flashlight that has anything other than a simple on/off switch. The newer LED flashlights have many modes and various output levels. This makes them much more versatile. If the only options for a flashlight are off and full-on and the flashlight produces an intense output, it makes it almost useless for close-up use (reading a map while someone is driving, etc...) because it's simply too bright. With multiple output levels, the light becomes much more versatile. The various output modes will be described in more detail later.

A quick note... Most people think it's normal to have to beat on a flashlight to make it work. We do it without thinking. It's almost as if it's coded into our DNA. Having to beat on a flashlight is normal for older, budget lights but not for high quality lights. High quality lights switch on flawlessly EVERY time.

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Popular Brands

There are dozens of popular manufacturers of high performance flashlights. Names like 4Sevens, Fenix (pronounced like Phoenix), Nitecore, Surefire, Streamlight are considered some of the best. Most of these lights remain on the cutting edge and, at any point in time, produce lights that produce the most intense output possible. Maglite (a familiar example below) is another very common brand but they're not typically considered to be at the cutting edge of technology (although the new XL100 may be an exception). That doesn't mean that they're not good quality lights but if you're looking for bragging rights (brightest light, smallest size...), Maglite isn't generally in the running. However, if you want a light that's going to be reliable and will last nearly forever, Maglite is still a very good choice.

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Flashlight Prices

When you initially get into flashlight collecting, you may be shocked by the prices. Many people are used to buying a two D-cell Rayovac flashlight for $2 at Wal-Mart (really, $2.00, batteries included). Some spend $30 on a two or three D-cell LED Maglite. For most people, these will do everything they need them to do. If you want higher performance flashlights, you'll have to pay significantly more. For example, there are LED flashlights that operate off of one AA or one CR123A battery that produce significantly more light than a 2D-cell Maglite but you can expect to pay at least twice as much for those tiny, high performance lights. For example, the Nitecore EX11 below sells for approximately $60. On average, small single cell high performance LED flashlights cost approximately $50. Small high performance two cell flashlights (those that use two AA or 2 CR123A batteries) can cost $100 or more. The second image below (Maelstrom G5) is one example. It's powered by two CR123A cells or one 18650 lithium-ion cell. It sells for $100-150 and is about 6" long. Custom lights (custom machined housings with high performance emitters and custom reflectors) can cost $500 or more. High performance handheld HID search lights can cost well over $2000.

In the two photos above, you can see that there is a chrome bezel on the end of the flashlight. In some instances, this is cosmetic only and serves no special purpose. In other lights, the ring is used to maintain force against the reflector which maintains force against the LED which keeps it tightly against the internal heatsink. If the bezel is loose, the LED may not remain tightly against the heatsink and that could cause it to fail prematurely. If the bezel gets so loose that it falls off of the light, the lens and reflector may fall out and become lost or damaged. Check the tightness of the bezel on your flashlights. They don't often get loose but if they do, it could lead to the flashlight becoming unusable and un-repairable because not all parts are available for all lights.

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Light Sources

Incandescent Lamps:
Incandescent lamps have been around since the 1800s. They are nothing more than a wire that's heated (by driving current through it) until it glows. It's simple and has served us well. It's not, however, very efficient. High power lamps produce a lot of heat and use a lot of energy. Incandescent lamps are also fragile. This isn't a big problem with most stationary lights (in the home, installed into a table lamp or in a light fixture) but in a flashlight, it can be a significant problem. Dropping a flashlight often causes the filament to break (especially if it's lit when dropped). If you're in a situation where you rely on the light for your safety and it uses an incandescent lamp, it's important that you carry a spare lamp. Many of the Maglite flashlights have a spare lamp in the tailcap. Most others don't.

Incandescent lamps have a filament in the glass envelope. The wire that makes up the filament is generally tungsten. In the most common incandescent lamps the glass envelope has the air evacuated, leaving a vacuum. This prevents the tungsten filament from burning (as it would if oxygen were present). This is why an incandescent light bulb instantly burns out when the glass envelope is broken. Other types of incandescent lamps are filled with an inert gas (vs having a vacuum - no gas). Halogen lamps will typically be filled with argon, krypton or xenon gas. Halogen lamps are typically brighter than standard incandescents for a given wattage. That's why many people replace standard lamps with xenon or krypton lamps.

The image below is an incandescent lamp with the filament lit. As you can imagine, the wire is VERY hot. When the filament is hot, the tungsten is constantly evaporating. In time, the wire becomes thinner and thinner until it opens (burns out).

LED Emitters:
Most of the newer, more advanced flashlights use LED (Light Emitting Diode) emitters in place of incandescent lamps. They're typically much more efficient (more light output for a given amount of energy used) and last a very long time. They're generally rated for 50,000 hours or more when operated according to the manufacturer's specifications (i.e., not over-driven to produce more output). LEDs are also much more durable. Dropping them generally causes no damage to the emitter. There were a few early LED flashlights that were easily damaged if dropped but that's no longer an issue. The LED emitter below is shown at approximately 50x the actual height/width (depending on your monitor and the display resolution). The actual device is 3.45mm wide.

In general, common flashlights don't heat up when used. It's surprising to some that high performance LED flashlights heat up when used at or near the highest output level. The ridges or cooling fins around the head of a flashlight aren't cosmetic, they are there to promote cooling. The ridges increase the surface area of the head and therefore make it easier to dissipate the heat produced by the LED. Without the ridges, the light would get significantly hotter which would mean that the LED would run hotter which could cause the LED to fail prematurely.

Power dissipation in the LED causes it to heat up. The LED dissipates heat because there is current flowing through it and there is a voltage drop across it. The voltage drop will generally be between 3.25 and 3.8v and varies depending on the current flowing through it. The voltage drop is the greatest when the LED is being driven the hardest (most current flowing through it). Higher current must flow to make it brighter. If you look at the Ohm's law formula P=I*E (power dissipation equals current flow multiplied by voltage) you can see that increasing either the voltage or the current cause the power dissipation to increase. Since increasing the current flow also forces an increase in the voltage drop, you can see that when you get more output, you produce more heat. This is why the larger flashlights with higher output must have larger heads (which have more surface area). It's also true that, many times, they have larger heads because they have larger reflectors but even if they didn't need larger reflectors, they would still have to have larger heads to keep the operating temperatures low. If you want/need a refresher on Ohm's law, go back to the Ohm's law page of the site.

The image below is from a Dorcy flashlight. The LED is the square device in the center. The outer ring is a reflection. THIS is a photo of the LED with no power applied. The blue tint in the photo is due to the polarizers I used. This is a white LED.

HID Tubes:
HID (High Intensity Discharge) flashlights are a bit more complex than the previous two types of flashlights. HID lights use a tube filled with metal halide gases. On each end of the tube, there is an electrode. The lamp uses a 'ballast' to drive the tube. Initially, a higher voltage is required to produce an arc between the electrodes. After the arc is produced, the ballast reduces the voltage to whatever the tube requires to sustain the arc. These are typically VERY bright lights. The best bang for the buck in this type of light is probably the Stanley HID spotlight. It's VERY bright. Similar lights cost $300+ while the Stanley costs only $60-70.

Below is a photo of the HID tube with the arc formed between the electrodes. This arc is incredibly hot. It took less than 2 minutes to get the photo I wanted but if it would have taken any longer I would have needed gloves to keep the light from burning me.

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Runtime vs Output Level:
A lot of people look only at the output level of a flashlight to determine it's worth. I have several 1AA and 2AA flashlights that produce more output than a 2D Maglite (especially out at 10-20 yards). Some would consider those lights better and they may be better under some circumstances. If you're never far from a fresh set of batteries, the smaller light may be a good choice. If you're going to be out in the woods or somewhere that won't allow you to get replacement batteries, the 2D Maglite may be better. The smaller light may not be able to operate for more than 1 hour on a set of batteries at the highest output level. The Maglite may be able to go for 12 hours on a single set of batteries. Maglite is being used again as an example because so many people know the lights and because I've seen so many people criticize Maglite products. Not everyone needs high performance lights (which can be a bit more finicky). Maglites are extremely reliable and still a very good choice for emergencies.

Many of the small high-performance flashlights only run about an hour at the maximum output level. In most instances, using the light at 40-50% of full brightness provides more than enough light and can greatly increase the runtime. This will also reduce the cost of replacement batteries. Generally, rechargeable batteries are available for most lights but that's not always the case. For example, lights that produce intense output and use the CR123A batteries may have no option. They have to use the CR123A primary battery. The RCR123 is a rechargeable lithium-ion battery but it can't produce the current required by some of the high performance lights. If you have a light that must use the CR123A batteries, buy them online. They're about 1/3 the cost compared to local retailers.

Most of the inexpensive flashlights use 'direct drive'. This means that they're driven directly from the batteries. This is simple and reliable but it means that the light output varies with the battery voltage. As the batteries discharge, the light output drops. This can begin almost immediately. This isn't always a bad thing. For instance, the old directly driven incandescent lights would give you plenty of warning before the light output dropped to a point where it was unusable (this is especially true when using alkaline or carbon-zinc batteries). Unregulated (directly driven) LED flashlights operate in a similar way but LEDs require a minimum voltage (typically 3-3.5v) to operate and as soon as the voltage drops to that point, they will no longer produce any usable output.

Lights that are not directly driven use a 'driver'. There are several types of drivers. For flashlights that use a voltage source that doesn't have enough voltage to drive the LED directly (i.e. a flashlight with a single 1.5 volt AA battery driving an LED that requires 3+ volts to operate), the driver will have to be a boost regulator/converter. For flashlights that easily have enough (or too much) voltage to drive the LED directly, the regulator/driver will be a 'buck regulator'. There are driver ICs that are buck/boost drivers but I don't know if they're used in any flashlights. For most driver/regulators, they use 'current' regulation instead of 'voltage' regulation. This is because the output of the LED is determined by the current flowing through it. For regulated flashlights, the output will generally be absolutely constant until the battery is drained. The output could go from full to almost no output within just a few minutes. When looking at runtime graphs for regulated lights, it's common for small, high performance lights to operate for about an hour and a half at 100% brightness and within approximately 10 minutes go from 100% to VERY low output (some simply shut off).

You'll see the term PWM (Pulse Width Modulation). Pulse width modulation is an efficient method of controlling current or voltage. In general, there are two types of regulators, 'linear' and 'switching'. Linear regulators provide good regulation and are very simple but they're very inefficient. Inefficiency is not good for battery powered devices. Switching regulators are much more efficient. Switching regulators are more complex but circuit design is becoming simpler due to the availability of integrated circuits (chips) that can perform as well as discrete components. The input/control circuit and the switching transistors are all in one tiny package.

A regulator that uses pulse width modulation is a type of switching regulator. In a switching power supply with no regulation, the pulse width is constant. In a PWM switching regulator, the pulse width varies to control the voltage or current in a circuit. In the following image, you can see that there are three different switching waveforms. The top one is only 'on' 20% of the time which means it's 'off' 80% of the time. If this were driving an LED, the LED would be relatively dim at 20% duty cycle. Bear in mind that the switching is so fast that it's not visible. The second waveform shows a square wave that's on 50% of the time. This would make the LED moderately bright. The last one has a 90% duty cycle (on 90% of the time). This would make an LED almost as bright as it could possibly be with the available voltage. Driving it directly (100% duty cycle) would make it only slightly brighter. Some flashlight manufacturers may choose to never drive an LED at the equivalent of a 100% duty cycle until the battery voltage drops a bit. In effect, this would allow a longer runtime with no drop in brightness. Directly driven LEDs start to dim almost immediately and continue to get dimmer as the batteries become discharged. Starting at 80-90% gives the regulator a bit of 'headroom' to work with. As the batteries become discharged, the pulse width gradually increases to keep the current through the LED constant. The LED brightness will remain constant until the batteries become discharged to a point that the 100% duty cycle (fully on) cannot maintain the current. At this point, the LED will start to become dimmer (it's brightness will follow the battery voltage). Boost regulators work in much the same way but they must boost the voltage. They use the pulse width to boost it just to the voltage or current required.

The following light (Proton Pro) uses an LTC3401 (<<--click to view the datasheet for the IC) synchronous boost converter/regulator IC to produce the voltage required to drive the LED. In a synchronous boost converter, one transistor (a transistor is a fast electronic switch) grounds an inductor (a coil of wire) and then releases it. The coil acts much like a spring when the transistor switches off. Since the other end of the coil is connected to the positive terminal of the power supply (the positive terminal of the battery here), the voltage on the released end of the coil springs up and over the power supply voltage. This 'higher-than-battery' voltage is passed through another transistor which passes the voltage to the LED. The output voltage is monitored by the IC and is regulated. The regulated voltage is determined by the value of two resistors (which form a voltage divider). A fraction of the output voltage is fed back to a comparator which determines if the voltage is too high or too low by comparing it to a reference voltage. The output of the first comparator and a sawtooth waveform are fed into another comparator. The point where the voltage from the first comparator matches the instantaneous sawtooth waveform voltage, determines the pulse width.

In the images below, you can see all of the components. The small IC with 10 legs is the LTC3401. There is another IC under the switch. That's the microcontroller that determines the modes for the flashlight. On the bottom of the board, there is an inductor (green component) and a diode. The diode helps take some of the load off of the IC and protects it from over-voltage. The brown components below are ceramic capacitors. The components with the numbers on them are resistors.

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User Interface

The UI (User Interface) is the way the user controls the flashlight's output. Most flashlights have a single way (either clicking or twisting) of accessing all modes. To access the various modes, you have to click/twist in a specific sequence. This allows you to select the various modes and brightness. For example, the UI for the Preon 2 light from 4Sevens requires that you click the rear switch 3 times in succession to step through the 3 brightness levels (low, medium, high). The Preon 1 is a twisty and has the same basic interface but instead of clicking, you twist the bezel 3 times in succession. Most high-end flashlights have controllers that can remember the last mode used and will return to it when it's switched back on. For example, if you generally need the output to be only 25% of the maximum output, you can program most high-end flashlights to turn on at that level. If there is no memory, you'll have to re-adjust the output each time you switch the flashlight on. Memory isn't important if you only need to use a light occasionally but if you have an EDC (Every Day Carry) light that you use daily for the same types of tasks, you need a light with a memory (especially if the light produces significantly more light than you need for those common tasks).

As of now, Maglite has the most unique user interface. The XL100 uses a position sensor to control/adjust the output level, strobe flash rate and lockout. A demo can be seen on YouTube. Click HERE to view it (please email me if the link goes dead).

Twisty vs Clicky:
In virtually all flashlights, you either twist the bezel of click a switch to switch it on or change modes. A 'twisty' is a flashlight that you twist the bezel to operate it. A 'clicky' is a flashlight that you push a button to turn it on or change modes. The switches can be on the side or on the rear tailcap. Lights with the switch on the tailcap are generally referred to as 'tactical' flashlights. There are other features that make them 'tactical' lights. Some of those features will be covered later. There are a few flashlights that use both twisting and clicking to operate. For example, you may have to click a button to turn it on and then twist the bezel to change modes.

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Flashlights that you'll commonly see in retail outlets are generally designed to operate off of the most common cell types (AAA, AA, C and D-cells). It's generally assumed that the average user will use alkaline cells in them. These flashlights will operate off of batteries with other types of chemistries (lithium, NiMH, NiCd...) but most people won't use anything but alkaline batteries (although, this may be changing as rechargeable batteries continue to improve). For most users (those who don't collect flashlights as a hobby), alkalines are a good choice. This is because they'll use the flashlight only a few times a year for a few minutes at a time. Alkaline batteries can maintain a charge for many years and are likely to be charged when the flashlight is needed (assuming that they weren't discharged when the flashlight was previously used). For flashlights that are rarely used, lithium batteries are another good choice. Lithium, batteries can remain charged for 10 years or more. Neither alkaline or standard lithium batteries are rechargeable (although, they do make rechargeable lithium batteries- lithium-ion and lithium polymer are two examples). Don't try to recharge a non-rechargeable battery, it will overheat and may explode.

When 'lithium' batteries are mentioned on this page, this refers to non-rechargeable lithium 'primary' batteries. Other 'primary' batteries are non-rechargeable alkaline or carbon-zinc batteries. Carbon-zinc batteries are rarely used and typically only found in budget devices that were sold with the batteries included.

People who buy/use high performance flashlights often need something other than alkalines. One reason is that they use their flashlights a lot more than the average person. Using rechargeable batteries over alkalines saves a lot of money. The initial cost is greater but the savings over time is worth it. The most popular types of batteries for high-performance flashlights are NiMH (Nickel Metal-Hydride). These are readily available and relatively inexpensive. This is a good battery if you use your flashlight a lot. It's not so great, however, if you only use the flashlight occasionally. Most NiMH batteries self-discharge to some degree and won't be fully charged if the flashlight is rarely used.

In the following photo, you can see 4 types of batteries that can be used in flashlights that are designed to operate off of AA-cell batteries. They are, from left to right, alkaline, hybrid low self-discharge NiMH, lithium and standard NiMH. If you've ever paid attention to the fine print on a battery, you likely noticed that alkaline batteries are 1.5v batteries. Lithium primary batteries like the one here are also 1.5v. The re-chargeables are 1.2v batteries. In general, most devices that can operate off of 1.5v primary batteries can run off of NiMH batteries. There was one instance where they would not, however. I use a lighted magnifying glass to read very tiny markings on electronic components. The light source is an LED directly driven from two AAA cells. Since the forward voltage of the LED is greater than the 2.4v from the batteries (two 1.2v cells in series), the LED would not illuminate with the re-chargeables.

High-performance flashlights often draw a significant amount of current from the batteries. NiMH and lithium batteries are a good choice for high-current applications. Standard lithium batteries are not rechargeable but store more energy than most other types of batteries. NiMH have the advantage of being rechargeable.

Earlier, it was stated that NiMH batteries self-discharge. There is a newer NiMH that self discharges at a much lower rate. They're called hybrid NiMH batteries. They typically have a lower capacity (they store less energy) than the standard NiMH batteries but are better for flashlights (or other electrical devices) that aren't used very often. The Sanyo Eneloop is a very popular hybrid NiMH battery.

Standard flashlights draw no current when off. Some of the high-performance flashlights draw a very small current from the batteries when they're off. If you have a flashlight that draws current when off, or if you don't know if it draws current when it's off and the flashlight is mainly to be used in emergencies, store the batteries with the flashlight but not in the flashlight.

Some flashlights give a range of voltages that it can operate on (often with no difference in brightness). For example, the 4Sevens Maelstrom G5 has an operating range of 2.7v to 12v. It's primarily designed to use two CR123A batteries. These are 3v each and in series produce 6v. The light will also work well on one rechargeable 18650 lithium-ion battery. The 18650 cell is only 3.7v but the light's performance is essentially the same.

In the photo above, you see two sets of CR123A batteries. The ones on the left are individual batteries. The ones on the right are shrink-wrapped together. This ensures that you don't mix old and new batteries and makes it a bit easier to replace batteries. It's important that you don't mix old and new batteries. If you install a dead battery with a new battery, the polarity of the dead battery could be forced to reverse. At the very least, this could cause the battery to swell and leak inside your flashlight. Leakage could cause damage to the light. Swelling could make it very difficult to remove the battery. This isn't a big problem in many other devices because the batteries are not typically pushed to their limits. In high performance lights, the current draw can be excessive which makes it more critical that the batteries match as closely as possible.

Below there are 3 batteries of approximately the same size. Two are 3.0v and one is 3.6v. As above, the orange battery is a lithium primary battery. The other two are rechargeable lithium-ion batteries. In many lights, these are all interchangeable but that's not always the case. In some lights, the longer 16340 (16mm x 34mm approximately) may be too long. In some lights, the added voltage could cause the light to fail or malfunction.

A couple of examples... The EX11 that was shown previously on this page uses a cylinder that extends from the back of the light to the control board. The cylinder is used to make contact with the circuit board. The RCR123 and the CR123 are identical in length but the shoulder on the button end of the battery of the RCR123 is 1mm longer and won't allow the light to function/switch properly. The added length of the 16340 (which is actually 16.5mm x 36mm) won't allow the EX11 to function at all. The battery is longer than the cylinder. In the JetBeam PC10 (below), all 3 batteries will work but the light functions differently with the higher voltage 16340 battery. The light is supposed to have turbo mode when the head is fully tight. When it's loosened a bit, the light should have 5 modes (two flash modes and 3 modes of varying brightness below turbo mode - high, medium and low). When either of the 3v batteries (or a slightly discharged 3.6v battery) is used, the light works in all modes. When used with a 3.6v battery, the high mode (which is supposed to be below the turbo mode) produces turbo level output. One of the similar lights (the PA10) is even more hanicapped. With a 14500 lithium-ion battery (3.6v), the light will only function in turbo mode. If you use a lithium primary battery, an alkaline battery or a rechargeable AA battery, it has the turbo plus 5 modes like the PC10. The drawback to that is that the output is MUCH less with anything other than the 3.6v lithium-ion battery. It's still a good light but it's hard for some of us to use a light with batteries that produce a maximum of 200 lumens when it's capable of a maximum of 650 lumens (lumens from specs, not measured or verified).

The 18650 cell above has a 'button top'. On some lithium-ion rechargeable batteries, the top terminal is as flat as the bottom terminal on this cell. This makes it very difficult to produce a mechanical protection feature that prevents the batteries from being installed with reverse polarity. Applying voltage to a circuit with reverse polarity (installing the batteries backwards in the case of battery powered devices) generally causes the circuit to fail catastrophically. With the button, the flashlight manufacturer can recess the positive terminal in the light slightly and if the battery is installed backwards, the flat terminal can't make contact with the light's terminal. The image below shows how the guard ring is preventing the straight edge from making contact with the terminal. Some of the lithium-ion cells have no button and therefore won't work with some lights. So that cells without the buttons can make contact with each other when used in series, they (AW batteries, for example) sometimes have bumps on the negative terminals. When the preferred cell is a flat-top cell but the device requires that you use a button cell, you can use a small cylindrical magnet (like THIS) on the positive terminal. The pop-up image is only for illustrative purposes. This was actually placed on the negative terminal for the photo.

Protected vs Unprotected Lithium-Ion Cells:
Lithium-ion cells can be dangerous if precautions are not taken to prevent them from overheating. There are 'protected' lithium-ion cells and lithium-ion cells that are not protected. Good quality cells have protection against over-current and protection against overheating. Cells without protection (possibly what people buy when they try to buy cheap cell phone and computer batteries) are unsafe and can cause fires (remember the laptop computers that had their batteries burn through their case and into the surface the computers were on?). When purchasing lithium-ion batteries, ALWAYS purchase batteries with protection. THIS page has more information if you are interested.

The newer high-tech batteries in LED based flashlights can require a bit more knowledge than the old incandescent based flashlights with alkaline or carbon-zinc batteries. With the old types of flashlights, you ran them until the batteries were so dead that the flashlight could no longer produce light at a usable level. Of course, those were disposable batteries. The newer battery types can't be used in the same way. Earlier, it was stated that the output of an LED flashlight could drop off quickly as the batteries became discharged. This was because the batteries no longer had enough voltage to overcome the forward voltage of the diode. There is sometimes another reason that the light output will drop abruptly. The 'protected' lithium-ion cells will, in effect, disconnect the terminals from the actual lithium-ion cell. This prevents them from becoming damaged from deep discharging.

Know Your Flashlight:
The line above may seem strange but it's very important. Most of us won't be in danger of losing our lives if the batteries in our flashlights go dead but that's not true for those who are a bit more adventurous. Various flashlight/battery combinations will function differently. If you really need to have a reliable light, you should do a few tests. I don't test extensively but was getting, what I thought, was poor runtime from my PC10 so I did some basic tests.

I had the Tenergy 3.0v RCR123A, the UltraFire 16340 3.7v and Titanium Innovations CR123A batteries. The first two of these are rechargeable. The CR123A is not. The Ultra-Fire lasted about 29 minutes before the light went out. The Tenergy RCR123A lasted only 13 minutes before the light went out. A second one went about 15 minutes. I tested two different RCR123As to confirm that it wasn't just one bad/weak battery. The Titanium Innovations lasted much longer and the light gradually fell off. The two rechargeable batteries abruptly switched off. One second, the light was nearly full bright. The next, it was completely off. The primary lithium battery was producing a usable light output at just over 1 hour of runtime. It wasn't full bright but would be enough to allow you to safely walk through a room that was pitch dark without the flashlight.

Something else that was interesting was that the PC10 would not switch back on after the CR123 battery had been nearly completely drained. Something like this is important to know if you're in a situation where you really need the light to work. I tried the drained battery in a Thrunite 1C and and a Nitecore EX11. Both of these lights worked with the weak battery and would switch on and off. This means that the last two lights would allow you to switch the light off to save the batteries for when they are really needed. Of course, there is some point where the battery will become so discharged that no light will be able to switch back on.

Of course, if you know that you're going into a situation where you will rely on your light for your personal safety (or the safety of others), you would carry extra batteries. Since the lithium-ion batteries have a 10+ year shelf life and cost only about $1 each, keep several in your vehicle, in your home and office in case there is an emergency. Rechargeables are better for most of us for normal use but primary batteries are a good, safe backup.

This was mentioned previously but bears repeating. If you need a flashlight that's reliable, it's very hard to beat a Maglite. Many of the small, high-tech lights are very complex and can be prone to fail, especially those pushed to the limits to produce the most output possible from the emitter (LED) that they use. The standard LED Maglite is conservatively designed so it's not so prone to failure. When keeping a flashlight around for emergencies, don't store the batteries in the light. If the light accidentally gets switched on or if the light has parasitic drain (like the EX11), it can drain the batteries and the light will be useless when you need it most. Also don't forget to keep extra batteries on-hand. Lithium-Ion batteries and high quality alkaline batteries have a very long shelf-life. This doesn't mean that they last forever. If you need to buy new batteries, rotate out the older ones and leave the newest ones for emergencies.

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Many times, you'll need a light that will allow you to use both hands to perform a specific task (working under the hood of a car, working on an electrical panel with the main breaker switched off, setting up a tent...). A good headlamp is preferable to a normal flashlight. Headlamps (AKA headlights) vary in price and quality as much as normal flashlights. Below are two examples. The first is an inexpensive (Wal-Mart special). When you absolutely need a headlamp, these are better than nothing but the quality isn't great. There are two main problems, in my opinion. The first is that the light patterns are uneven and 'ringy'. The second problem is that the light spectrum that's produced isn't very good. Ideally, you generally want a neutral white light. This renders colors properly. The cheaper lights tend to produce a bluish-white light. The one below produces a combination of bluish white and nearly pure white.

This next headlamp (Fenix HP11) is much better in virtually all aspects. The light output is greater and much whiter. The pattern is very smooth, especially with the diffuser over the lens. Some prefer a smaller lighter headlamp. I don't mind a heavier headlamp if it gives me more runtime and/or more output. This headlamp has a battery pack that clips onto the back of the headband. When looking for a headlamp with extended runtime and fairly good output, I narrowed the search to those using 4 AA batteries because I had plenty that I use in my cameras. There are other headlamps that use other batteries (single AA, 3 AAA, CR123A, 18650...). You have to decide what's important to you (light weight, output, features, runtime) when looking for a headlamp.

Other features available on various headlamps include different color LEDs, focusing beams and special output LEDs. Headlamps used for tracking game when they didn't drop when shot. The special LEDs highlight blood drops and make them stand out. I no longer hunt but the reviews on some of the tracking lights are pretty favorable.

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Battery Charging and Battery Chargers

One of the most important things that you need to know about charging batteries is that you should not leave them on charge when no one is around to monitor them. The following image shows a very minor incident where a battery overheated. Even though I was in the room, it got this far before I noticed that there was a problem (alerted by the smell of burning plastic). Many times, the damage is far worse. It could have started a fire or exploded. When charging batteries, place the charger on a hard, flat surface. A kitchen counter-top or a similar surface is preferable. If you place it on a table, the table should not have a tablecloth and there should be no decorative cloth or paper material under the charger. If you place the charger on a chair or a bed and there is a problem that causes a battery to overheat, it's much more likely to start a fire. It's also important that the charger is on a hard flat surface so that it can remain cool. Some chargers (particularly those that can charge batteries quickly) rely on convection cooling to keep the electronic components in the charger cool. If it's on a soft surface, convection currents cannot flow, the components cannot cool and are therefore more likely to fail prematurely.

There are several different types of battery chargers. 'Dumb chargers' simply apply a voltage to the batteries and they charge until the batteries reach the applied voltage or until the circuit 'times out'. The charger below is one such charger. This charger applies 2.4v to the batteries (two 1.2v batteries in series). It will drive as much as 165mA (0.165A) into the batteries. The actual current flow will depend on the condition of the batteries. If you look closely at THIS image, you can see that the contacts put the batteries in series. There's no way to properly charge batteries properly when you're charging one battery through another battery. When batteries are identical, it can be done when there is no other option but batteries are rarely identical, especially after they've been charged and discharged repeatedly.

Better, more sophisticated, chargers use microprocessors to control the charging cycle. These chargers (referred to as smart chargers) often use the 'delta-V' charging method. When NiMH batteries are charged with a constant current, the battery voltage will drop just a bit as the batteries become fully charged. In general, this is generally considered to be the best way to charge a NiMH battery. As a safety measure, some chargers will stop charging at a preset (safe) voltage for times when the delta-V dip isn't significant enough for the charger to detect. The following is an MH-C808M. It's a relatively good charger. It uses the delta-V charging method. It can 'soft' charge (slow charge) batteries which is often better than fast charging because it doesn't produce as much heating. This charger can also recondition batteries. It reconditions them by charging, discharging them and then recharging them. This helps remove any 'memory' the battery may have developed. To learn more about the memory effect (AKA voltage depletion or voltage depression), click HERE.

If you intend to recondition batteries, understand that it's not a quick process, especially for high capacity batteries. Sometimes, reconditioning takes more than 24 hours. 8 hours isn't uncommon for AA batteries.

Charge/Discharge Rate:
Although it may be desirable to recharge batteries as quickly as possible, it may not be good for the batteries. Charging or discharging too quickly can cause undue heating. At the very least, the useful service life of the batteries will be reduced. At worst, you could damage the batteries (they could explode if they overheat too much) and would have to replace them. When buying a charger, try to find one that has selectable charging rates. This will allow you to charge quickly when absolutely necessary and charge more slowly when there's no urgent need for the batteries. If you have to charge quickly because you can't wait for them to charge, buy one or two extra sets of batteries. This will give you a fully charged set when you drain the ones in your flashlight (or camera or any other device).

When reading through the various forums, you'll see charge/discharge rates like 1C or C/2. The C refers to the mAh rating of the battery. If you have a NiMH battery rated at 2500mAh (equal to 2.5Ah) and the maximum recommended charge (or discharge) rate is 1C, you can charge it at no more than 2.5 amps. For a charge rate of C/2, you could charge with no more than 1.25 amps of current. The previous charger (MH-C808M) is a relatively sophisticated charger but newer chargers can do even more. The MH-C9000 (and others) allow you to control the charge/discharge rates. They will even analyze the batteries and give the true mAh ratings of the batteries. Many manufacturers exaggerate their ratings. Even good batteries that originally met spec will deteriorate as they get older. There have been instances where one battery of a group (group of 4 batteries in my case) has failed. The batteries seemed that they were not holding a charge. In a digital camera, there would be a message to replace the batteries after taking only a few photos. It was difficult to determine if one or all were defective. The analyzer found the defective battery. Since I had others that were purchased at the same time as the one that failed, I simply used one of those with the three remaining batteries. Remember, you shouldn't mix batteries that aren't virtually identical. If four batteries would have been needed and there wasn't another battery from the original batch, the other three would not have been usable in the camera.

Recharging Lithium-Ion Batteries:
It was mentioned previously that there are protected and un-protected lithium-ion batteries. These must be charged in a charger specifically designed for lithium-ion batteries. Lithium-ion batteries are available in both 3.0v and 3.6/3.7v types. If you have both types, you must have the correct charger for each one. Some of the chargers have a switch to allow you to charge either type. The protected cells are more user friendly and safer than un-protected cells. Protected cells have circuitry to disconnect the internal cell from one of the external terminals when it senses that there is a problem (too much heat of too high charge/discharge current). Unprotected cells don't have this. When discharging unprotected lithium-ion cells, you have to be more careful. If you discharge them too far, you will reduce their useful service life as well as their capacity. If you discharge them at too high of a rate, the sells could explode or catch fire. This isn't generally a problem when using them in flashlights that are designed to use them because the current draw is within their safe output capacity. In devices that were not specifically designed to use lithium-ion batteries, the risk of a fire or explosion when discharged they are quickly is significant.

When using a charger specifically designed to re-charge lithium-ion batteries, there is little risk of fire or explosion (but you should not leave the charging batteries un-attended).

If you're using a charger that was not specifically designed to recharge the lithium-ion cells that you have, you stand a real risk of fire. A lithium-ion battery fire is very dangerous. It burns hotter than many other fires and can be difficult to put out. If you have a device with lithium-ion battery packs (multiple batteries connected together), there can be multiple explosions and flare-ups. If you're using a charger that doesn't have all of the safety features built in (many people like to try to make their own chargers to save a bit of money), charge them on a steel table, preferably with a cover or shield to prevent flames or shrapnel from escaping.

Used properly, lithium-ion batteries are safe but you must understand that they're not as idiot proof as other battery types.

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Light Output and Beam Patterns

There are some flashlights that have no reflector at all (bare LED, like the one below). They simply flood an area with light. Of course, something like this (Photon Light - Photon II keychain light) can't illuminate a large area intensely but this one lights a very wide area immediately in front of the light out to about 20 feet well enough that you can walk safely through poorly lit areas. If you need a very small light, the ones sold by Photon Light are a good choice. Cheaper ones work but not nearly as well. The light distribution is often poor and badly tinted (generally purple) due to poor quality LEDs.

Flood vs Spot:
When deciding what type of light you want/need, you have to determine whether you need to light a large area relatively closely or if you need a light that can light up objects in the distance. Lights that light up a wide area but don't light up much in the distance are considered to be floody (flood lights). Lights that primarily light up objects in the distance are considered to be 'throwers' or spot lights. Most of the 'throwers' do a reasonable job of lighting up the area around the central spot but the light level is generally significantly less than that of the central spot. If you're buying a light to allow you to safely walk your dog at night, you don't want a light that is primarily designed to illuminate an object 200 yards away. What you'd likely want instead is a flashlight with a more floody beam that can brightly illuminate a relatively wide area out to about 50 feet.

You may hear the terms 'task light' and 'search light'. A task light is typically a light with reasonably good output with a floody beam pattern that illuminates the general area where you're working. A search light is typically a light with very strong output and beam pattern that's fairly concentrated. They are typically used in search and rescue operations. I tend to buy lights that have a good throw but they're only good to compare to my friends' newest thrower. For example, I purchased a Maelstrom G5 (6" long). It's a nice light but for most of my needs, it's utterly useless. I RARELY need to find something 100 yards away. A light like the tiny EX11 (3" long) I have is much better for lighting objects within 10-15 feet. It will light a much larger are but, again, that's not generally needed. Buy the light that best suits the task.

Light Output Specifications:
There are several ways that the light output is specified. Candlepower is the least useful and the one that leads to the most exaggerated ratings. Candlepower ratings should generally be ignored. Lux is a more accurate way of specifying the output of a flashlight but the distance from the front of the flashlight where the light level is measured greatly affects the lux rating. Lumens is the most reliable but can be misleading. A manufacturer may simply give the specifications from the LEDs datasheet. This isn't very accurate because not 100% of the light is going to get out the front of the flashlight. As of now, the best way to state the light output is with out-the-front lumens. This is the light that exits the front of the flashlight. Even using the OTF lumens, it doesn't tell the whole story. The beam pattern determines the way the light is distributed. For throwers, most of the light is through the center of the beam pattern. For floodier lights, the output is more evenly distributed. I've been dealing with audio amplifiers for more than 20 years and thought car amp manufacturers were the worst at over-rating their products. It appears that flashlight manufacturers are, in some instances, just as dishonest.

To measure the light output accurately (it's doubtful that many manufacturers bother to do so), an integrating sphere or a goniometer is used. The integrating sphere is a reflective sphere that allows a light meter to measure all of the light produced. The goniometer is another light-measuring device but has a bit more flexibility than the integrating sphere. To read more on these, click HERE. This link is from the Lawrence Berkeley National Laboratory.

Reflector Types:
There are various types of reflectors. The differences are related to the desired beam pattern. For throwers, the reflectors are very smooth so that the light can be precisely focused. If a flashlight is to have a floody pattern, it will have a stippled (roughened) surface. A mildly stippled surface can produce a relatively tightly focused beam but will diffuse the light enough to remove any artifacts produced by the light source. Heavier stippling will make the light more floody. There are various abbreviations for the various type. Most refer to the surface stippling as orange peel.

  • SMO = Smooth reflector
  • LOP = Light orange peel
  • MOP = Medium orange peel
  • HOP = Heavy orange peel

Lense Types:
In most flashlights, there is simply a flat plastic or glass lens in front of the reflector and light source but that's not always the case. In more advanced flashlights, the glass is not as common as it may appear. Some are specially hardened to make them less prone to breakage. They may also have coatings on the glass. In an effort to get as much light as possible out of the front of the light, some manufacturers apply an anti-reflective coating so that very little light reflects off of the lens.

There is another type of lens called an aspheric lens. It's curved (see below), not flat like a standard lens. These lenses are designed to focus the light. Some are so effective that they can actually project an image of the LED on a surface 100+ yards away.

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LED Manufacturers

There are many different flashlight manufacturers. As far as I know, none of them make their own emitters (LEDs). They rely on a handful of LED producers. The following are a few of the one that produce the brightest, most efficient LEDs.

At this time (January 2011), Cree is making some of the brightest, most efficient LEDs. The XP-G is being used in flashlights like the Nitecore EX11 and the 4Sevens Maelstrom G5. Both of these lights are very bright for their size. The EX11 is rated at 200 lumens and operates off of 1 CR123A battery. The Maelstrom is rated at 350 lumens and operates off of either two CR123As or one 18650 lithium-ion battery. The Cree XR-E LED can be seen below. This is in an Photon Light Proton Pro flashlight.

At this time, as far as I know, the SST-90 LED, produced by Luminus, has the highest output of any commercially available LED. It's being used in the Olight SR90 flashlight. As always, the highest performing products command the highest price. The SR90 sells for nearly $500.

Philips LumiLEDs:
Maglite uses the Philips Luxeon Rebel LEDs in many of their LED flashlights. The following LED is in a 2D Maglite. The number can be difficult to read but I think it's a 090. In the 3D, you'll find a 091 in the ones with the Luxeon Rebel LEDs. The earlier Maglite LED flashlights used a different LED and it wasn't as good as this one.

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Special Considerations

Intrinsically Safe Flashlights:
Intrinsically safe devices are those who can operate in an explosive atmosphere (mines, chemical plants, grain silos, etc.) with no risk of setting off an explosion or starting a fire. Intrinsically safe lights will generally be air-tight so that none of the flammable gasses can enter the light. This ensures that any sparks created by switching the light on or off won't be able to touch off an explosion. IS lights are also generally made of plastic. This prevents them from creating a spark if they're dropped. For those who work in areas where intrinsically safe electronic devices are a requirement, ONLY flashlights designated to be intrinsically safe should be used. This includes the flashlights that you carry on your keyring or in your pocket (EDC lights). Virtually none of the keychain lights that use button cells are intrinsically safe. If you work in areas where there is a risk of fire or explosion, you should not carry one. For other lights, you should contact the manufacturer to see if it's designated as being intrinsically safe.

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Flashlight Modifications

Many of the collectors flashlights like to make modifications to make the better suit their needs. This can include changing the light source, modifying or replacing the reflector to work with different light sources, modifying the case to accept a different type of power source, etc. The list below will grow as I find more examples.

Replacing the Light Source:
This can be one of the simplest mods and can turn a useless light into a light that you enjoy using. One of the most modified lights is the Maglite. It's probably because they're inexpensive and so many people own one. If you compare an older Maglite 2D light to the newer LED version of the light, the LED light is better in almost every way, especially in the light output. This is why many Maglites are unused. There are drop-in LED modules that can make them as good as or better than the newer LED lights. One such module can be seen below. Its base is shaped like the original incandescent lamp and it's installed as easily as replacing a bulb. This is a 1 watt LED and not as bright as a new Maglite LED but is probably as bright as the original incandescent lamp in a 2D Maglite. This module is the TerraLUX TLE-1F and costs about $12. This module will also fit in other (inexpensive) flashlights but it probably doesn't make sense to install a $12 module in a $2.00 flashlight.

The drop-in module below is a 3 watt module with the same LED (if I'm not mistaken) that's used in the new LED Maglite. The output of the 2D LED Maglite and this LED module in a Maglite that originally had an incandescent lamp are about the same. This module is the TerraLUX TLE-6EXB and costs about $17. it's probably worth the cost to bring an old Maglite up to date. If you don't own a Maglite, it's probably better to buy a new LED Maglite.

These are the simplest and least expensive of the mods you can perform on Maglites. There are more expensive modules that can be purchased. Some drop in, some require that you replace or modify the reflector. For higher powered, brighter drop-ins, visit the Malkoff site.

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Accessories Included with Flashlights

This is the looped cord that you attach to the flashlight. Short ones are generally used to go around your wrist. Longer ones go around your neck.

Extra O-Rings:
These are typically included because the ones used for most flashlights are a very odd size and very difficult to find locally.

Pocket Clips:

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Trusted Sellers

I've purchased items from the following sellers/sites and have had no problems.


Battery Junction


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Some of the Flashlights and Spotlights I Currently Own

If you have any questions about any of the following lights, email me.

  • ThruNite Catapult V2 XM-L
  • ThruNite Neutron 1C
  • JetBeam PC10
  • Fenix TK35
  • Stanley Waterproof Spotlight FL5W10
  • Stanley HID spotlight
  • Black and Decker spotlight FL3WBD
  • Dorcy 41-4750
  • Photon Proton Pro
  • Nitecore EX11
  • Nitecore EZAA
  • UltraFire WF-502B
  • Lumapower IncinDio V3+ with/without upgrade kit
  • Lumapower D-Mini VX Ultra with/without Turbo Force kit
  • 4Sevens Maelstrom G5

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Above, on this page, you read where various batteries caused some of the lights to malfunction. That's one example where you may need to do a bit of troubleshooting if the light appears to be malfunctioning. Another common problem is bad connections. For older lights, it's simply a matter of cleaning the various contacts for the switch. For more advanced/newer light, there are other problems that you should be aware of. In the three following images, you can see the internals of various lights. In all photos, you see two indentations near the outer perimeter. These are used to turn the internal nut. In all three lights, these have become loose and the lights failed to operate properly. In the first image (JetBeam PC10) and the last image (Olight T10), this area becomes accessible when you remove the end of the light (as you do when replacing the batteries). The middle light (IncenDio V3+), the back bezel ring and button cap has to be removed to access this area. The IncenDio supplied a set of tweezers to turn the nut. You can use tweezers or snap-ring pliers if nothing is supplied with your light. In all three lights, the lights operated intermittently and then would not switch on at all. Tightening the nuts (some of which had left-hand threads -- tightened by turning counter-clockwise instead of clockwise) returned all of these lights to proper working order.

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Perry Babin All rights reserved

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