I modified a Coast brand LED flashlight to wire into the airplane electrical system for a Cockpit Spot Light. The flashlight is small and is cotroled by a white and red button on the side of the case. No need to cycle thru colors or anoying flasher mode. The battery operated light has three AAA batteries in series for a nominal voltage of 1.6 X 3 = 4.8 volts. Under load (white light) the voltage drops to 3.8 to 3.45 volts or 4.45 volts (red light). The white light draws .83 amps which is too high the light gets hot. I am going to use a 5.2 volt 1.2 amp USB power supply to drive the light. After testing I've determined to get the same voltage under load as the battery pack was supplying I need to add a 2 ohm resister in the system. This drops the 5V power supply to 3.8 volts under white light (5 v red). The light was warm to the touch without it. With the resistors (2x 1 ohm each) the light stays at room temperature just like when it was powered by 3 AAA batteries.
Cut down the flashlight to fit
replaced batteries with sodered low voltage conection