18650 is a lithium-ion battery. Its real name is "18650 cells". The 18650 cell has a voltage of 3.7V and is between 1800 mAh and 3500 mAh (milliampere-hour).
The 18650 can have a voltage range between 2.5 volts and 4.2 volts or a charge voltage of 4.2 volts, but the standard voltage of 18650 is 3.7 volts. You can also get more information about the 18650 restore cell via the web.
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18650 battery that has protected electronic circuits. The circuit is built into the cell pack (battery housing), which protects the cell from "charging", heating or "overcharging", from currents and from short circuits.
The battery can say the protection mode of 3.7V 18650 3000 mAh low self-discharge. What does all that mean?
"Protected mode", as mentioned above, means that there is built-in protection against overcharge and overload.
"3.7V" – is the optimal voltage or peak voltage. It will drop when the battery is used.
"3000 mAh" measures the amplifier that can be produced by the battery. The higher the value the better. The highest realistic availability of the current 18650 is around 4000 mAh, all that goes beyond that is marketing advertising.
"Low self-discharge" is a good thing. That means you keep paying. The less the memory leak, the more power you have left to work with the flashlight or other device.