How much is the working voltage of 5W's bright flashlight LED?
The 18650 common market mostly fake copycat lithium-ion batteries, the quality is poor, mostly for the flashlight, may not have the best internal protection plate, for better quality of the goods, the battery should use lithium battery charger. Charging with 5V is not appropriate.
The single charge should be between 3.7V---4.2V. There is a protection circuit in the charger. It can charge at 3.7V, and the 4.2V will stop automatically. The charge voltage should not exceed 4.2V, exceeding the battery will damage or shorten the life.
The 18650 is a standard lithium ion battery type lithium ion battery originator - Japan SONY company in order to save cost and set, where 18 represents a diameter of 18mm, 65 65mm length, 0 for cylindrical battery. Common 18650 batteries are divided into lithium ion batteries, lithium iron phosphate and nickel hydrogen batteries. Voltage and capacity specifications for nickel metal hydride battery, voltage is 1.2V, common capacity is 2500MAH, lithium-ion battery voltage is 3.6V, LiFePO4 battery voltage is 3.2V, the common capacity is 1500MAH-3100MAH.
