im not saying its 125% larger than 100…
125 is 125% of 100
you said it yourself 125/100 = 1.25
so now we’re not diving by the smaller number are we?
Sure sure.its all in how you word it i guess. 125% of 100 or 25 percent larger than 100.
Or 100 is 80% of 125… which is 100÷125… just depends on what info you want.
yea im just a bit annoyed at this thread. Im pretty sure the 30q packs more punch for its size than the 21700 mentioned here but theres no way im doing that math for that just to prove a point.
Ya the tesla 2170 needs to be tested as this will prob beat out the 18650 but we just dont know yet, at least not that i have read.
Wait a second. I think I just might have solved this;
18650/21700 = 86%, so the 18650 is 86% as good as the 21700. 21700 clearly wins!
Or wait, is it 2170? Then the 2170 is (2170/18650) only 11,6% as good as the 18650. 18650 is superior!
4 Likes
samsung 21700 40t
70.15 mm height 21.10 mm diameter 1.49686 cubic inches volume 4000mAh capacity 3.6v x 4ah = 14.4 kWh 14.4 kWh / 1.49686 cu in = 9.62 kwh per cubic inch 14.4 kWh / 69g = 0.208 kwh per gram
samsung 30q
64.85 mm height 18.33 mm diameter 1.044296 cubic inches volume 3000mAh capacity 3.6v * 3ah = 10.8 kWh 10.8 kWh / 1.044296 cu in = 10.34 kwh per cubic inch 10.8 kWh / 45.6g = 0.236 kwh per gram
Jesus christ i need a life
6 Likes
Yo7 said you werent gonna do the math…
So, assuming we’re paying per cubic inch (using imrbatteries prices),
buying 40T will cost 13,35 USD per cubic inch, which will give us 9,62 kWh, = 1,39 usd/ci/kWh
buying 30Q will on the other hand cost 5,74 USD per cubic inch, which will give us 10,34 kWh, = 0,56 usd/ci/kWh
Does a possible discharge of 25-30A per cell compared to 15-20A motivate a buy of this cell at 2,5 times the price of a 30Q (volume and capacity equaled out)?
Or does one just like bulkier cells?
1 Like
so did everyone else here. This is a forum for nerds, remember? you don’t need calc to have a basic understanding of how proportions work.
1 Like
Ugh, this thread enjoys annoys me too, but for the other reasons. Now I know this certainly doesn’t matter AT ALL, but if y’all really are gonna get technical about the energy densities and amount of space these both take up, perhaps recognize that your not using rectangular cells. No one bothered with a simple ((pi*r^2) * height)= area. Granted, it would still result with the same percentages… Just a little thing to point out since apperantly that was the point of the thread, not to discuss these new cells beyond anything but their relative size to one another.
FWIW, I also don’t see why it’s such a huge deal when bringing up it’s energy densities compared to a 30Q, UNLESS (and this is capitalized, so pay attention) size restrictions AND price are more important than over all battery size and power and capacity, etc… I’ve proposed this same argument a few times to get the same negative feedback, but each time I said that space, and money were not an issue! Yet that’s all that was focused on. If I have the money and space to build a 12s6p out of insanely expensive Samsung 40T’s, can anyone at all tell me how that is stupid and a worst battery than I’d get if I had just used the 30Q instead, and you have to make the argument WITHOUT (important again) bringing up size or cost.
Ok… 
GO!!!
LOL, love you all 
3 Likes
Everyone else took calc a yr. and a half ago? I agree, thus why I said it was middle school math. My proportions have always been correct.
I thought we were comparing the 4900mah 10A 21700 to the 3500mah 10A 18650. But if we are comparing the 30q to the 40t and we have a length of 295mm to cover with batteries the 40t would give me 56000 combined mah and 420 combined A while the 30q would give me 48000 combined mah and 240 combined A. Obviously the 21700 is 5mm longer but 2 strips side by side set up like the battery pack in the Raptor 2 adds just 10mm in width to your battery pack and 3mm in height.
They are obviously perfectly fine to use. Nobody ever said otherwise. People also use 26650 lifepo and they can if they want to. But in general a top of the line 18650 is the better compromise.
Also we did use the cylinder formula so I don’t know what your point was there.
3 Likes
but arent efest bogus or at least over-rated compared to real testing?
Please accept that you are wrong and move on. Percentages and ratios can be calculated either way and the context matters. If you don’t accept that then there is nothing we can do.
1 Like
A proportional percentage is only calculated one way buddy
Efests just relabel big brand cells so as long as the OEM one is a good they are ok - you could just by the OEM one then but that’s a different story
No it’s not
1 Like
Oh was it used… My fault, I didn’t see it in the first few mathematical posts, lol. Maybe skipped over it when I saw that was the argument in every post then. And yes LiFePO4 26650 cells are great too. They all have their ups and downs 
Efests are rewraps, but actually not significantly over rated.
Yes it is, a percentage proportion by definition can not be more than 100%