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What is 18650 battery
- Dec 25, 2018 -

A battery has a chemistry and every chemistry comes with a set of characteristics. The most basic feature of any chemistry is the voltage. For lithium, it is around 3.6 volts, and an alkaline battery, for example, AA or AAA cell, is 1.5 volts. 

A good battery must be more than just lightweight and large capacity. For any heavy load use, it also has to be rechargeable. An electric car lacks a fast charge port so there is no easy way to replenish the range, on the road. Charging is critical in cars, but less so in ebikes. 

Battery capacity is based on what goes in, and what can them come out, charge and discharge. So a battery has a maximum capacity, and a capacity as it sits, right now. One of the great features of Lithium cells is that almost everything you put in a pack can be used when you start to discharge the pack. It is very efficient. If you want to know the precise capacity of your pack, you need an amp hour or watt hour meter. You can do the measurement when the battery is on the bike, or do it when the battery is on the charger. Your battery has a voltage rating and an amp hour rating, in general. Since Watts = (Volts X Amps), the watt hours are the Volts times the amp hours.

Most 18650 lithium cells charge to 4.2 Volts maximum, and the charge current is about 0.5 times the capacity. A 3000 mah battery would be charged at 1500 mA maximum, using this rule. Cells have data sheets that specify precise numbers for charging.