> Are you comparing the Tesla 21700s with all the commercially available 18650s, or with the specific 18650s Tesla uses? It's possible Tesla doesn't use the mos

> Are you comparing the Tesla 21700s with all the commercially available 18650s, or with the specific 18650s Tesla uses? It's possible Tesla doesn't use the most energy dense 18650s available, so their 21700s could be an improvement for them. For reference, Tesla's current cells are about 215 to 225 Wh/kg; they are not the most energy dense cells you can get. What I'm comparing are Tesla's new cells to the best cells out there. The reason why I do this is because that's what Tesla fans - and Elon Musk - repeatedly do. Also, I'm almost certain that Tesla's new cells will have a higher energy density than 215-225 Wh/kg; if they didn't, they'd be on par with batteries from a decade and a half ago, which would be pretty pathetic. > Also, are they currently limited by the heat dissipation? If not, increasing the volume per cell might not be as much of a problem. The linked article mentions that they doubled the number of cooling loops per module, which might already be anticipating an increase in heat to be removed. It's complicated. Technically, at the rate of discharge that Tesla uses right now, they shouldn't be. Teslas right now discharge their 65-100kWh pack in 3.5 to 5 hours. That's about 20 kW power continuous. There are roughly 6000 to 9000 cells per pack, so very roughly you discharge, while driving, between 2 and 3.5 watts per cell, so around 0.2C discharge. However, Teslas have their packs in an enormous, insulated, heavily managed sealed blob of batteries. This confines the heat to the pack, which requires their water cooling system. Another complicating factor is that heat dissipation matters in a few different contexts. First, there's the important matter of getting the heat from the inside of the battery to the battery surface; this is a matter of battery design and solved by the people that make the batteries. Then, there's the matter of what you do with the heat once it's at the battery surface (Tesla water-cools their cells); this is a problem for whoever makes the battery pack. Then there's the problem of what to do with the heat in general; now that you've drawn the heat away from the batteries and into the heatsinks or water, how do you cool your hot water/hot heatsinks? Switching to 21700s 'only' changes the first part of the equation - heat dissipation within the cell - but this is one of the trickiest parts to deal with. You can put a water cooling system on the outside of your battery, but you can't put a water cooler in individual cells. You can change the chemistry of the battery to better dissipate heat, but changing the chemistry of course also changes the battery's characteristics: energy/power density, cycle life, weight, cost, etc.