Originally Posted By: mikemacHey guys I have a nother question for you. I see a lot of the larger lights we are using for shooting lights are very similar in all aspects except the output rating. When you see one listed at 500 lumens and the voltage range is 3-9 volts would it be 500lumens at 9 volts. I have seen quite a few listed higher than my hs-802 but are actually the same brightness or less. They all seem to run the same 18650 battery so what is the deal Thanks
LEDs only want a certain voltage (called the LED forward voltage) to run properly. For Cree LEDs that produce white light, the forward voltage needed is in the range of 3.5 to 3.9 volts. For Cree LEDs that produce red or amber light, the forward voltage needed is around 2.5 volts.
The unloaded, fully-charged 18650 battery has a voltage of 4.2 volts. When it is under load, its actual voltage ranges from 3.2 to 3.9 volts, with 3.7 volts being typical.
Flashlight LED modules will often contain a voltage (and amperage)regulator called a driver. Some driver designs are called "buck" drivers. The buck drivers regulate the voltage from the flashlight batteries so that the proper forward voltage (3.5 to 3.9 volts) is delivered to the LED. Therefore, even if you have a flashlight that has multiple batteries in series (for example, two 18650 batteries in series has up to 8.4 volts), the LED driver regulates the voltage supplied to the LED to still be in the range of 3.5 to 3.9 volts. The LED driver is not 100% efficient, so there is some wasted battery energy when the driver is doing its job of regulating voltage.
Some driver designs are called direct drive (and they are more efficient). Basically, the direct driver provides the single 18650 battery voltage directly to the LED forward voltage. The light output varies directly as the battery depletes its charge. Flashlights designed with direct drivers CANNOT handle multiple batteries, or else "poof". So these flashlights design are not advertised to work with voltages up to 9 volts.
The are other designs of drivers. One is called the boost driver. It's job works opposite to the buck driver. The boost driver regulates by increasing the forward voltage (for example, LED flashlights using a single alkaline battery - the LED still requires its proper forward voltage to work).
Then there are the combined drivers (boost and buck).
Getting to your question about lumens. Many of the Chinese manufacturers "fib" about their lumens. Depending on the LED type (for example, XR-E or XP-G or XM-L, etc) only a certain amount of lumens is possible. The hard driven XR-E can produce up to about 270 lumens; the hard driven XP-G can produce up to about 450 lumens; the hard driven XM-L can produce up to about 900 lumens.
The XR-E type is a smaller size LED, so its design is great for light "throw" (even at lower lumens as compared to other LED types).