Slashdot Mirror
Is Elon Musk Greatly Exaggerating Tesla's Battery Technology? (bloomberg.com)
"Tesla's newest promises break the laws of batteries," writes Bloomberg. Long-time Slashdot reader rudy_wayne summarizes their report.
"Elon Musk knows how to make promises. Even by his own standards, the promises made last week while introducing two new Tesla vehicles...are monuments of envelope pushing. To deliver, according to close observers of battery technology, Tesla would have to far exceed what is currently thought possible." The Tesla Semi, which Musk claims can haul 80,000 pounds at highway speeds for 500 miles, then recharge 400 miles of range in 30 minutes, would require "a charging system that's 10 times more powerful than one of the fastest battery-charging networks on the road today -- Tesla's own Superchargers."
The Tesla Roadster is promised to be the quickest production car ever built. But that achievement would mean squeezing into its tiny frame a battery twice as powerful as the largest battery currently available in any electric car. These claims are so far beyond current industry standards for electric vehicles that they would require either advances in battery technology or a new understanding of how batteries are put to use, said Sam Jaffe, battery analyst for Cairn Energy Research in Boulder, Colorado.
But Jaffe reaches an interesting conclusion. "I don't think they're lying. I just think they left something out of the public reveal that would have explained how these numbers work."
The Tesla Roadster is promised to be the quickest production car ever built. But that achievement would mean squeezing into its tiny frame a battery twice as powerful as the largest battery currently available in any electric car. These claims are so far beyond current industry standards for electric vehicles that they would require either advances in battery technology or a new understanding of how batteries are put to use, said Sam Jaffe, battery analyst for Cairn Energy Research in Boulder, Colorado.
But Jaffe reaches an interesting conclusion. "I don't think they're lying. I just think they left something out of the public reveal that would have explained how these numbers work."
With a title like that, you know the article is going to be good for a laugh. Sort of like people who say "physics says..." who wouldn't even recognize the formulae that apply to the problem in question if you wrote them out in front of them.
1) Passengers in the Roadster noted how high its floor is. Aka: it's a double-high pack. Tesla already makes 100kWh packs for the S and X that are single-high. They may need to extend a bit further forward and back because the Roadster is a bit smaller of a footprint (on S and X they only slightly overlap the wheelbase, and on Model 3 they're inside the wheelbase entirely), but there's nothing at all implausible about 200kWh in such a form factor.
2) The megacharger charge port has been filmed by KMan. It has 8 giant pins in what appear to be a 2x4 arrangement, with ground and control pins likely clustered in a side slot on the right. These pins are much larger than those on the supercharger port, and there's a lot more of them. Also note the 2x4 arrangement: there appear to be four separate battery packs, and there 4 separate drive units. It appears that bloody everything on this vehicle is redundant (one assumes that there's at least a charge balancing system between the packs).
3) The means to provide the power to the megachargers is very, very simple: they're battery buffered. Tesla has always been clear on this; they're not drawing that power straight from the grid. More to the point, Semi uses the same battery chemistry as Tesla's grid-battery buffers (NMC). It's an extremely durable chemistry.
4) The article is very reasonable in its assessment of the battery capacity on the 500mi semi - they say 600-1000kWh (I've been working on the assumption of 900kWh, but it could be a bit less). Their estimate on the price, however, assumes that batteries cost $100-$170/kWh retail. Yet the raw material costs for said cells is only about $50/kWh - and that's currently at "spiked" prices which can be expected to drop as the mining industry readjusts to the new demand curve (historic prices would be more like $35/kWh). The whole point of the Gigafactory was to make li-ion batteries - finally - get closer to the cost of the raw materials that go into them. These numbers simply suggest that the Gigafactory has done exactly what it was designed to do.
5) Their estimate of the weight of the battery pack is probably correct (around 5 tonnes). However, in addition to the weight savings from using electric drive units vs. a big diesel / transmission / pollution controls / etc, Tesla always builds light. Don't expect the primary structure to be made of mild steel on this one; expect UHS steel, with 4-5 times the tensile strength, for example. Guillen stated in Europe that it has the same payload capacity as a diesel semi (aka, the tractor is no heavier), and that's probably correct.
Or, to put it another way: none of the "experts" expected the Model 3 SR to come in at almost exactly the same weight as the BMW 330i, with the same performance, more standard features, and a cheaper price. It did. And the LR isn't much heavier than a 330i, and well faster (can't wait to see the specs on the performance package!)
6) Charge rates of 7 cents per kWh: First off, their estimate that charging should cost 40 cents per kWh is just absurd. Pure nonsense. Even Tesla's current generation of superchargers is half that ($0,20/kWh), and they have to pay demand charges. That said, 7 cents per kWh comes across as extremely ambitious... until you start looking into it. And then you realize how much of a game changer it is that Tesla is doing here.
We gotta go to a crappy town where I'm a hero.
I'm betting the eight "pins" on the port aren't pins. They are sockets with two contact surfaces.
Eight 120 kWH batteries (five in the 300-mile version) made using the newer 2170 cells wouldn't be much of a stretch of the current technology. This would provide 960 kWH total which is within the range of estimated needs.
Tesla reuses the same AC/DC converter in their superchargers that they use in their vehicles. Current superchargers use 12 of these 11kW AC/DC modules to provide about 130kW (after losses).
If you go with the same theme but update it to use 12 of the 20kW AC/DC modules now used in the model S, the existing supercharger design could be trivially increased to about 216kW after losses.
Eight 216kW superchargers operating simultaneously could deliver 1,728kW - more than enough to provide a 400-mile charge in 30 minutes.
Well, they did have a working prototype doing max acceleration 0-70 mph runs all night long without recharging. The numbers they quoted appeared to be real numbers for that prototype.
Unlike Porsche and others who display a stationary model and claim that it will be able to almost match the performance of current production Teslas, some day, when they actually manage to make it work.
I think Tesla did figure out something new, aren't quite able to mass produce it yet, but already did make it in very small volume and are now testing it. They may not make the 2020 deadline (it's still Tesla, after all) but I doubt it will be much later than that. They are getting a lot better at actually producing things, delays on Model 3 are only a couple of months and that's after accelerating the development by a whole year. I expect them to deliver the first token roadsters in december 2020 and start producing them for real in the second half of 2021.