Over break, a friend and I decided to build the brightest flashlight we could, just for fun. The business end of the light uses nine 100-watt LED elements mounted to a heat sink and cooled by three server fans.
The system, which altogether draws almost a kilowatt, is powered by six three-cell lithium batteries. The 36-volt light circuit is fused and independently switched for safety. The battery status is continuously monitored by an Arduino and estimated time remaining is displayed on the control panel. Once the batteries reach a safe discharge level, the lights are disabled.
The control panel also includes a software enable switch, a rotary switch mode selector, a keyswitch, and a potentiometer for adjusting strobe frequency and other mode characteristics. The LED elements are tied together into four groups, which can be controlled individually by the Arduino.
We designed and built it in about a week and a half entirely on our own time and mostly in my dorm room.
Our light puts out about 81,000 lumens. The brightest handheld spotlights on the market are around 6000-8000 lumens, and 40-50 million candela. After doing some algebra, this works out to a beam angle of approximately .8 degrees. Our beam angle is almost 180 degrees, but we plan to add some lenses. If we are able to focus the beam this much it would be a 500 million candela spotlight. That means we could light up a 40 foot diameter circle half a mile away to the brightness of an overcast day.