Understanding the 21700 Battery and Its
The 21700 battery is a cylindrical lithium-ion battery with a diameter of 21mm and a length of 70mm. It offers a nominal voltage of
2170s may have a voltage range between 2.5 volts and 4.2 volts, or a charging voltage of 4.2 volts, but the nominal voltage of a standard 21700 is 3.7 volts, just like the 18650s batteries. There are two types; protected and unprotected. We absolutely recommend protected 21700 batteries. Protected 21700 batteries generally have a button top.
The 21700 is physically larger than an 18650 battery, and AA/AAA batteries. 2170s may have a voltage range between 2.5 volts and 4.2 volts, or a charging voltage of 4.2 volts, but the nominal voltage of a standard 21700 is 3.7 volts, just like the 18650s batteries. There are two types; protected and unprotected.
However, most 21700 cells are based on lithium-ion (Li-ion) technology, which is widely used across many types of rechargeable batteries due to its excellent energy density and long lifespan. There are several types of lithium-ion chemistries that could be used within the 21700 format:
21700 protected batteries have an electronic circuit. The circuit is embedded in the cell packaging (battery casing) that protects the cell from “over charge”, heat or “over discharge”, over current and short circuit. A 21700 protected battery is safer than an 21700 unprotected battery (less likely to overheat, burst or start on fire).
PDF version includes complete article with source references.
Get technical specifications, ROI analysis tools, and pricing information for our BESS integration and energy storage solutions.
Av. de la Innovación 15
28042 Madrid, Spain
+34 91 133 2769
Monday - Friday: 9:00 AM - 6:00 PM CET