What is a 21700 battery?
The 21700 battery is a rechargeable lithium-ion (Li-ion) cylindrical cell that can come with or without protection circuitry, and has either flat top or button top terminals. Like other Li-ion cells, this battery is identified and named 21700 for its dimensions. For example, a 21700 cell is 21mm in diameter and 70mm in length just as an 18650 battery is 18mm in diameter and 65mm in length. These cells are slightly bigger in size than standard 18650s and can often times hold twice the power. This family of batteries are usually considered high-drain and are becoming more and more popular in the LED flashlight, custom project and vaping industries for the higher capacities and discharge rates that they can provide while keeping the cell at a low, safe operating temperature. 21700 cells are required in a variety of electric vehicles ranging from skateboards to scooters (including medical mobility scooters), battery packs, cordless power tools and more! To learn more about 21700 batteries, click here!
Are 21700 batteries safe?
High capacity lithium batteries usually require a PCB (Protection Circuit Board) or other kinds of protection (like a PTC aka Resettable Fuse, and a CID Pressure Valve) to limit over charging, discharging, high temperatures and internal pressure. Protected cells are great for high performance devices and electronics, and are commonly recommended or designed for specific compatible models to get the most consistent efficiency while keeping your device and battery safe with the on-board protection. While PCBs are needed in some batteries and uses, the more advanced Li-ion chemistries (IMR and INR Lithium-ion) are considered to be safer and do not require protection circuitry. Unprotected cells can be found in custom DIY projects and specialty electronic devices.
Battery Junction offers a wide selection of unprotected lithium and 21700 batteries, all of which come with a very specific warning about improper and proper usage. If you are planning on purchasing an unprotected battery, we highly recommend that you read this warning thoroughly.
How long does a 21700 battery last?
Most 21700 batteries can be recharged between 300 and 500 times before their capacity is depleted to a point where they are no longer operating efficiently. They also have a safe, stable shelf life of 3 to 5 years! Rechargeable lithium batteries may cost a little more up front, but they save you money in the long run! Recharging your drained cells not only saves you money by not continuously buying new batteries, but it also helps the environment by reusing them again and again! By following manufacturer recommendations on charging and discharging, you can keep your battery running strong and sometimes even extend the lifetime. To keep your 21700 battery charged, we offer a large selection of smart chargers with various features and numbers of channels. Choose which charger is best for your Li-ion battery here!