Most Inspired Energy batteries contain ‘18650’ size cells, however demand for increased battery run time means that ‘21700’ cells are gaining in popularity. As a leading manufacturer of standard smart battery packs, Inspired Energy have incorporated 21700 cells into a new range of batteries for the new decade; which includes the company’s first 18V battery.
So, what's the difference between 18650 & 21700 cells?
The terms ‘18650’ and ‘21700’ refer to the physical size of the lithium-ion cell; 18650 means the cell has a diameter of 18mm by a length of 65mm. 21700 therefore represents 21mm x 70mm. This seemingly minor difference in outward appearance becomes more striking when we calculate the volume.
18650
π r² h / 1000
π 9mm² x 65mm / 1000 = 16.5mm³
21700
π r² h / 1000
π 10.5mm² x 70mm / 1000 = 24.2mm³
An extra 5mm of length and 3mm of diameter gives us 47% more volume. This extra density allows the 21700 cell to have a longer running time than an 18650 cell.
What 21700 based batteries are available?
There are currently four batteries that utilise the 21700 cells. The key specifications are:
| Product | Cell Configuration | Nominal Voltage | Nominal Capacity | Nominal Energy |
| NB4037HD50 | 2 Cell | 7.2V | 5.0Ah | 36.0Wh |
| NC4040HD50 | 3 Cell | 10.8V | 54.0Wh | |
| ND4054HD50 | 4 Cell | 14.4V | 72.0Wh | |
| NE4068HD50 | 5 Cell | 18.0V | 90.0Wh |
There will also be new single and dual bay chargers that accept the 21700 based batteries, whilst being fully backwards compatible with the 18750 based models.
Introducing, the first Inspired Energy 18V battery
Many power tools and other portable electronic equipment use 18V as it offers an excellent power to weight ratio, particularly important for handheld devices.
Inspired Energy’s first 18V Lithium ion smart battery, the NE4068HD50, offers 5.0Ah (90.0Wh) and is composed of five 3.6V 21700 cells in a 5-series, 1-parallel array (delivering up to 8A of discharge current).
*Actual product may differ from image shown
As with all Inspired Energy Lithium ion smart batteries, the four new additions have an energy rating below 100Wh, which avoids complex and costly shipping regulation.
Inspired Energy batteries are available from Accutronics in the UK and Europe. Accutronics serve as Inspired Energy’s sole distributor for their range of smart batteries, chargers and accessories and offer online purchasing, local stock holding, technical support and multi-currency pricing.
