The world is shifting away from fossil fuels and will one day become fully electric. In the present world, Lithium-ion is the most promising chemistry of all batteries. Most of the battery packs used in Laptops, RC Toys, Drones, Medical devices, Power tools, e-bikes, and electric cars (EV) are based on 18650 batteries. It is one of the most mature Li-ion formats available, is produced in high volume, and enjoys a low cost per Wh.
The 18650 (18mm diameter and 65mm length ) battery is a size classification of lithium-ion batteries. It is the same shape, but a bit larger than a AA battery. AA batteries, by comparison, are sometimes called 14500 batteries because they have a 14mm diameter and 50mm height.
Step 1:Prepare parts and tools required
Step 2：Selecting the Right 18650 Cells for the Battery Pack(http://apowergroup.en.alibaba.com)
You will find many types of 18650 cells in the market in the price range of $1 to $10, but which are the best? I will highly recommend buying 18650 cells from branded companies like Panasonic, Samsung, Sanyo, and LG. These cells that have well-documented performance characteristics and excellent quality control. Reputed brand 18650 cells are generally costly, but if you consider for long time use then they are worth having it.
Don’t buy any cells with the word FIRE in the name like Ultrafire, Surefire, and Trustfire. In reality, these cells are just factory rejects, purchased by companies like Ultrafire and repackaged in their own branded cover. Many used batteries are rewrapped as new and white-labeled. They sell the battery by marking capacity up to 5000mAh, but in actual their capacity is between 1000 to 2000 mAh. Another major problem with these cheap 18650 cells is the high risk of explosion when overheated during the charging or discharging.