The selection of the best light-emitting diode (LED) flashlight bulb will be determined based on what the user of the flashlight is seeking to do. Sometimes, all a user is seeking to do is obtain a direct replacement for the bulb in his or her flashlight. In such instances, considerations include bulb voltage, luminous intensity, wattage and color. In other cases, the user may want a more powerful bulb or a different type of LED bulb than the one being replaced.
One of the most significant aspects of any LED flashlight bulb replacement is the voltage at which the LED will be operated. This is normally based on the number and type of batteries the flashlight takes. It is important not to push more voltage through the LED than it is rated to handle; while the bulb will be brighter with more voltage, heat dissipation becomes a problem. This can lead to a situation known as “thermal runaway," in which the heat causes the bulb to continually draw more current, leading to more heat and, eventually, a ruined LED.
Another important criterion for selection of the right LED flashlight bulb will be the physical fit of the bulb. If a drop-in, or direct replacement, bulb is desired — with no modification to the flashlight or bulb needed — the best bet is to see if the manufacturer of the flashlight offers such a bulb. The bulb must be able to physically fit the socket in the flashlight, and it must do so with the correct polarity. Even if both of these criteria are satisfied, it is worth noting that the type of bulb selected may affect the flashlight’s ability to focus the beam to a spot or a flood.
Aside from the correct fit and required voltage, other features are worth examining when selecting an LED flashlight bulb. The luminous intensity, or overall brightness, of a bulb is one such characteristic. Brightness ratings for flashlights are usually measured in lumens and can range from 10 lumens or so for the smallest models to many hundreds of lumens for tactical flashlights. The luminosity of a bulb is the largest factor in how far it can throw a beam of light, and the brightest LED flashlight bulbs can illuminate objects at least one-eighth of a mile (around 200 meters) away. Multiple LEDs are sometimes utilized on one bulb assembly to achieve maximum illumination and, depending on the flashlight, it may be possible to vary the number of bulbs or wattage to create varying brightness levels.
The luminous intensity of an LED flashlight bulb tends to correlate to the bulb’s specified wattage, which is the rating of how much energy an LED flashlight bulb will consume over time. Typically, the brightest LED flashlight bulbs are rated at 5 to 8 watts or more and, as a result, are the brightest available; however, the battery life will be lowered. Conversely, a bulb rated at only 1 watt is likely to offer long battery life but less brightness.
Color is yet another distinction in the selection of an LED flashlight bulb. The bulbs are available in a great variety of colors, but white is often preferred for its brightness and because it offers the user the ability to see the true colors of the objects being illuminated. White LED flashlight bulbs tend to have less yellow and be a purer white than their incandescent counterparts.
If the type of LED flashlight bulb to be acquired is an ultraviolet (UV) or black light bulb, there is at least one more consideration when selecting a UV LED bulb. While UV bulbs are rated in terms of wattage and luminous intensity like other LEDs, the more important specification for UV LED flashlight bulbs is the wavelength. This is usually given in nanometers (nm) with the usual range being between 365 nm and 410 nm; the lower the rating, the more brightly a UV light will cause objects to glow. UV flashlight bulbs intended for professional use will have a rating between 365 nm and 380 nm but will cost more. In contrast, UV flashlight bulbs rated closer to 400 nm will not make objects glow as brightly but are available at a lower cost.