Cells are now very sturdy and most people never have problems. Lithium-ion battery chemistry is getting safer every year. The battery’s protective circuitry has important functions like overcharge protection and load balancing. Nearly all 18650 cells are sold for assembly into a battery or battery pack. A battery is then defined as the larger whole: a battery pack composed of many cells with a central PCB (protective circuit) like a BMS (battery management system). A cell becomes a loose, individual 18650 without protection. When talking specifically about lithium-ion battery packs, it’s important depending on industry to distinguish between a cell and a battery. As cost per kilowatt hour continues to drop, new applications are able to use the technology - fueling demand and economies of scale. The cost to manufacture an 18650 has dropped from $10 for ~1500mAh (twenty years ago) to $2 for ~ 3000mAh (today).

The 18650 battery is one of the most widely produced lithium-ion battery types as it is found in laptops, power-tools, robots, electric vehicles, vaporizers, solar grids, and almost any application you can think of that desires to store electrical energy more efficiently. Over 40% of the world’s batteries are lithium-ion. Anti-counterfeiting measures like quality control, and supply-chain inspections are very important for retailers or manufacturers to ensure safety for end-users. Many used batteries are rewrapped as new and white-labeled. These batteries often are dangerous and marked with exaggerated specifications. CounterfeitsĬounterfeit cells are a growing problem, especially prevalent are those from Mainland China and Malaysia where the methods and markets for fake batteries have matured. Typical highest-capacity batteries in 2015 are ~3500mAh, and highest-amp batteries are 30A. continuous discharge and high-amp batteries have a low capacity. When selecting a battery type you must favor one over the other. The two most important specs for 18650 cells are capacity measured in mAh (milliamp hours) and maximum continuous discharge measured in A (amperes). Cylindrical lithium-ion batteries all follow the same nomenclature, their name being determined by their size (diameter, followed by height). AA batteries by comparison are sometimes called 14500 batteries, because they have a 14mm diameter and 50mm height. If you have ever held one in your hand, you probably noticed it is the same shape, but a bit larger than a AA battery. The 18650 (18mm by 65mm) battery is a size classification of lithium-ion batteries. Lithium polymer, or li-po cells on the other hand can be different shapes and are soft and shapeable. The tight roll of anodes and cathodes is then jammed into a hard steel cylinder with an open top, and finally capped with the positive pole and sealed. Lithium ions move between these layers, in one direction when the battery is charging, and in the opposite direction when it is discharging. Thin, flat sheets of metals comprising the anodes and cathodes of the cell are stacked one on the other, and rolled very tightly together like a jelly-roll.