Flashlight battery 1AA (v. 1 No. 5 batteries), 2AA (2 batteries of 5), 3AA (3 5 batteries), 5 batteries and alkaline batteries is usually said can not charge the dry battery (4.5V) and can charge the nickel metal hydride battery (1.2V)
There is a lithium battery, voltage 2.45-4.20V, type 14500, 16340, 18650 and so on, these figures some faint many friends, that how to distinguish ah, actually very simple, specific model numbers are reasons, such as the 14500 cell diameter 14 mm, length is 50 mm; 16340 cell diameter is 16 mm, length is 34 mm, and so on, the 18650 battery is diameter 18 mm, length 65 mm. Ha, see.
The battery can be direct drive (that is, directly to the battery positive and negative joint in the two ends of the wire links to LED on most LED), but the current instability, large and small, easy to cause the LED to shorten the life span of the light, flashlight dedicated circuit so that the control voltage and current was born.
1, boost circuit. Mainly used for 1AA, 2AA battery flashlight, because most of the working voltage of LED 3.6, AA battery voltage 1.2-1.5, the voltage is not enough, need the voltage to rise to 3.6 in order to make the LED work, also produced the circuit.
2, the step-down circuit. Generally used in the double lithium flashlight on, such as the use of 2 16340 flashlight, LED operation in 3.6, 2 and 16340 series voltage is about 7.5V, you need to put the circuit output voltages down to 3.6 LED power supply.
3, automatic lifting pressure circuit. As the name suggests is that when the voltage of the battery voltage is above LED of the output voltage to the working voltage of LED, when the battery voltage is lower than the working voltage of LED to the output voltage to the working voltage of LED, resulting in a constant voltage and current, which is the ideal circuit.