This flashlight was built on 0,5W 35lm LED. It is powered from a li-ion accumulator in size 18650. The flashlight does not have any driver, LEDs' current is limited by 12ohm resistors connected in parallel. 45 degrees collimator is put on a LED. Housing was made of connector tubing and Cu plug from the CO installation, painted with matt black lacquer.
The device is eqiupped with a accumulator voltage indicator on TL431, when the voltage drops below 3V, LED goes off. That prevents the accumulator from discharging below the safe limit.
The flashlight gives a lot of light and should withstand some time. Current in the LED is approximately 140mA and the capacity of the accumulator is 2200mAh.