Lithium-Ion Cell Size Fuels Cordless Advancement
Around here, we primarily focus on the tools and gear surrounding the construction industry. That makes the 21700 vs 18650 conversation incredibly relevant to us, but these lithium-ion power sources reach far beyond the latest cordless tools. They’re driving innovation in Teslas, hoverboards, the vaping community, and so much more.
21700 vs 18650: What do the Numbers Mean?
21700, 18650, 20700, and others simply refer to the physical size of the lithium-ion cell. For 18650, it’s an 18 mm diameter x 65 mm length. 21700 is 21 mm x 70 mm. While the explanation is simple, the difference is profound. It’s easy to see with a quick volume calculation.
18650
3.14(9 x 9)(65) = 16,532 cubic mm
21700
3.14(10.5 x 10.5)(70) = 24,233 cubic mm
An extra 5 mm of length and 3 mm of diameter gives us 47% more volume. That’s a little more than 7,700 cubic mm of space to pack with energy-delivering anode, cathode, and electrolyte material.
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