Conventional EV packs are typically built around stacks of 2170 cells – 21 mm in diameter, 70 mm in length (0.83 x 2.8 inches). The 4680 cells, as the name suggests, are much fatter and a tad longer at 46 x 80 mm (1.8 x 3.1 inches).

So what's the big deal here? Well, these fatter 4680 cells pack in five times as much energy as their smaller cousins. That doesn't mean you can expect a 500% range boost when you stick them in an EV, but at the system level they do require less supporting material, so they're both lighter and more compact for a given energy capacity.

According to EV Lithium, they should also be able to handle higher instant power levels, meaning better peak power to the wheels and potentially faster charging. They should also deal with heat better, meaning improved efficiency as well as higher sustained power outputs. And finally, they should come out cheaper, helping to reduce the green premium facing car buyers looking to go electric.

This is the same size of cell Tesla announced at its 2020 Battery Day, promising around a 16% boost in range, and 600% boost in peak output power at lower cost. After some serious difficulties, these are now in production – indeed, Tesla has recently moved to a second-generation 4680 'Cybercell' design for the Cybertruck that slashes weight from 70 g down to an impressive 49 g (2.5 oz to 1.7 oz).

Panasonic is yet to publish specs on its 4680 batteries, so we can't yet compare them side by side to see how they stack up – but it's gutted its entire 60,907-square-meter (655,600-sq-ft) factory in Wakayama, Japan and re-fitted it exclusively for 4680 production, which will begin after final evaluations, with as many as 400 staff expected on the lines by March next year.