Last month, when Tesla Motors announced new, even larger battery packs for its Model S sedan and Model X crossover utility vehicle, reaction was less than ecstatic.
While even faster, even longer-range electric cars are nice and all, commentators said, shouldn't Tesla be sticking to its knitting?
Specifically, shouldn't it be focusing every last resource on the $35,000, 215-mile Model 3 sedan it says it will launch before the end of next year?
But suppose, as some have quietly pointed out, those two things aren't in opposition to each other?
Suppose, in fact, that the battery pack and module structure used in the Model S P100D and Model X P100D are, in fact, a result of the Model 3 development?
Could these two models be the first Teslas to use battery technology that will appear at much higher volume in the Model 3?
Tesla Model 3 spotted at service center
That's the line of reasoning suggested by a post three weeks ago on Electrek, which calls the 100D batteries "a test bed for Tesla's third-generation battery-pack technology."
The changes all come in the architecture of the modules and the pack into which they fit, as indicated by statements from Tesla CEO Elon Musk during a conference call on the latest models.
“The cell is the same [as in previous versions]," Musk said.
"But the module and pack architecture is changed significantly in order to achieve adequate cooling of the cells in a more energy dense pack and to make sure we don’t have cell to cell combustion propagation.”
The 100D packs, which have the same form factor as all earlier Model S packs (which have variously offered capacities of 60, 70, 75, 85, 90, and now 100 kwh).
And Tesla continues to use the modified version of a standard 18650 lithium-ion cell it developed with its battery partner Panasonic.
Tesla Model 3 design prototype - reveal event - March 2016
The new pack, however, offers 11 percent more energy capacity but gains only 4 percent in weight, indicating some rearrangements to its internals and circuitry.
That said, Musk indicated that 100 kwh may be the practical limit on energy capacity using the current cells in the battery's existing form factor.
Tesla is committed to retaining that packaging so that Model S cars can be upgraded with new battery packs (presumably at a profit) in future years.
But the importance of the new battery internals for the Model 3 program were underscored by Tesla's chief technology officer, JB Straubel.
The Model 3, he said, will have entirely new cells (coming from the Nevada gigafactory) as well as the new module architecture.
It is a pretty big change on the battery module and pack technology. It’s a complete redo of the cooling system, which is quite unique to Tesla and that we have been improving on for many years. This new pack is the next version of that.
The Tesla Model 3 is thought to use slightly larger 2170 cells, which are only slightly bigger in height (70 mm vs 65 mm) and diameter (21 mm vs 18 mm), while holding 46 percent more volume.
Rough math would indicate, then, that the Model 3 could use as many as one-third fewer cells for the same energy capacity as the previous 18650 format.