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The gap is not closing. Look again. Capacity of the 26650 is also growing. The 21700 is just a bigger version of the 18650. The battery chemistry and energy density is pretty much the same as an 18650. Development actually seems slow.

The reason the 18650 and 21700 have such high capacity for their physical size is because the big battery companies make them with their special mixes. This gives them high energy density. Unfortunately only smaller battery companies make the 26650. Their chemical mixes and energy density are not quite as good, but they are getting closer to the big companies all the time.

When you see the Samsung 48G with 4800mAh and a Littokala 26650 with 5000mah you can’t just assume they are the same. The 48G is only rated at 8A to 10A continous. The Littokala is rated at 20A continous. If you want 20A continous from a 21700 you have to move to a lower capacity version. I think the Samsung 40T 4000mah can do 15A continous. This is close, but you have to go another step down in capacity to the 30T 3000mah to reach 20A continous (The 30T can actually do 30A continous, btw). Maybe if Samsung did a chemical mix that gave 3500mah capacity it could match the Liitokala 26650 in continous output.

So you see, if you need 20A continous, you can use a 5000mah 26650 or a 3500mah 21700. There is quite a gap in their capacities.

If you need 15A continous, a Samsung 40T 4000mah can be used. In 26650 there is the 5000mah Liitokala or the 5500mah Shockli. I don’t think the 6000mah KeepPower has been tested, but surely it can do 15A continous. So you still have a decent gap, 4000mah to 5500mah.

Only if you need 10A or less continous output do the 21700 high capacity cells start to equal the power of the 26650. At these lower power levels is where we need the big battery companies like Samsung, Sony, LG and Sanyo/Panasonic do make a high capacity 26650. If they put their same high energy density mix in a 26650 container we would see 7000mah 26650.

At the moment, anything needing between 10A to 20A continous is advantage 26650.

Edit: Even at the 10A range, the 26650 has a lot of advantages such as less voltage sag plus a bit more capacity as well.


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