21700 vs 18650 Is there really that much difference.
21700 vs 18650 Choice Fuels E-Bike Advancement
Around here, we primarily focus on the gear surrounding the e bike industry. That makes the 21700 vs 18650 lithium-ion battery cell conversations incredibly relevant to us. After all, these lithium-ion power sources reach far beyond the e bikes. 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.
3.14(9 x 9)(65) = 16,532 cubic mm
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.
MORE CAPACITY = MORE RUNTIME
The most obvious benefit of going with 21700 vs 18650 is that the extra density means there’s more available energy in them to run your electric bike or scooter longer. Batteries that we see using 18650 cells for ebikes and e-scooter’s range from 1.5Ah (1500mAh) to 3.0Ah (3000mAh) in each cell. 18650 cells on the higher end of that scale have reported issues and 2.5Ah (2500mAh) cells seem to be where most manufacturers settle at the top.
On the other hand, 21700 cells start around 3.0Ah (3000mAh) and go up to 5.0Ah (5000mAh).
From the perspective of comparing 21700 vs 18650, you’re looking at a 50%–100% runtime gain over today’s standard 18650 packs.
Current Standard E-Bike Battery
18650 LI-ION BATTERY CELLS
- Compact 52V Battery: 9Ah (468Wh)
- General Purpose 52V Battery: 12Ah (624Wh)
- High Capacity 52V Battery: 15Ah (780Wh)
21700 LI-ION BATTERY CELLS
- Compact 52V Battery: 15Ah (780Wh)
- General Purpose 52V Battery: 20Ah (1040Wh)
- High Capacity 52V Battery: 25.2Ah (1310Wh)
21700 CELLS PROVIDE MORE POWER
Battery packs like our Tesla and Molicel do more than just take advantage of longer runtime. They improve their packs’ cooling abilities and build them with better materials that reduce resistance (ohms). The result is a battery with much greater power available.
Take Molicel, for example. Their standard 4.2V batteries can produce up to 189 watt hours of power output. When we build an ebike battery with capacity of 52V 16.8Ah, it goes up to 900 watt hours output.—that’s enough to run your 52v1000W @ full throttle no peddling for 1 full hour and reach a distance of 60km. If you ride a little less aggressive and more conservative there is no reason why you wouldn’t see 100km on one charge. Now that’s amazing. It gives us the ability to produce electric bikes that we didn’t think we’d ever see