Convert the flashlight to a 18650 Li-ion battery
Converting a flashlight from batteries to a Li-ion 18650 battery. A simple way to switch from power from large R20 batteries to a Li-ion 18650 battery. Do-it-yourself universal charge module for Li-ion batteries. Replacing the diode in a flashlight at home. Assemble the long-lasting lantern yourself. Emergency flashlight with diode, take it and do it.