As in they “break the laws of batteries.”
By any metric, the proposed numbers delivered by the Tesla Semi are impressive. Over 500 miles of range per charge even with 80,000 pounds in tow, best in class acceleration, and even 400 extra miles of range added per 30-minute top-off. All of these numbers help make the Tesla Semi a viable competitor to diesel trucks as long as they can be improved upon over time. The problem with these claims, at least for now, is that the proposed numbers are exactly that: proposed.
The big question is whether or not Tesla can actually achieve them in real life. Bloomberg comes to us with a dissenting opinion, citing the fact that Tesla’s proposed numbers for the Semi defy the laws of battery physics that the current technology is capable of. It also questions the feasibility of building this technology in a cost-effective manner. According to Bloomberg’s estimates, there are four inconsistencies with Tesla’s claims and the current reality of battery technology. The first has to do with range. To attain 500 miles of range, the Semi needs between 600 kWh to 1,000 kWh batteries, with fluctuations depending on variables like wind resistance and weather.
Assuming the middle ground, an 800 kWh unit, the battery itself would weigh 10,000 pounds and cost over $100,000. Tesla experts to sell the Semi for $180,000 meaning $80,000 will go towards building the rest of the truck—electric motors included. The automaker plans to cut costs by using screens and motors from the Model 3, but even so the price of the batteries would have to drop significantly in order for Tesla to profit off of the truck. Another limiting factor is the Tesla Megacharger. In order to meet Musk’s claims of 400 miles of range added to the Semi with a 30-minute top-off, the Megachargers would have to have an output of 1,200 kW—about ten times what a Tesla Supercharger can supply today.
And this doesn’t even come close to the third inconsistency between Tesla claims and reality: the price of such a charging feat. At $180,000, the Semi will compete with trucks that cost as little as $100,000. Tesla hopes the trucks will pay for themselves over time by cutting the cost of recharging the batteries to 7 cents per kWh—resulting in fuel savings of over $30,000 per year for some truckers. Salim Morsy, an electric vehicle analyst for Bloomberg, thinks that price is impossible. “There’s no way you can reconcile 7 cents a kilowatt hour with anything on the grid that puts a megawatt hour of energy into a battery,” Morsy said. “That simply does not exist.”
If Tesla wants to achieve this price, it’ll have to heavily subsidize its Megacharger operation, though it already does that for Model S and Model X owners with its network of Supercharger stations. The fourth and final battery challenge that Tesla must overcome is with the Roadster. With a proposed range of 620 miles, the Roadster will have the longest battery range of any production electric car in the world. To achieve that kind of performance, Tesla needs to use 200 kWh battery packs, which could be happen simply by stacking two 100 kWh batteries from Model S and Model X 100D models on top of one another. Still, the Roadster’s small frame makes it tough to fit even a single pack within its small frame.
To meet that challenge, Morsy thinks that Tesla will bank on improvements in battery density over the years, with the expectation that such a pack will fit into the roadster come 2020. So no, it's not like Tesla's battery performance claims are totally out of the realm of possibility. It's just that achieving them means rapidly improving on current battery tech to improve performance drastically while costs are cut deeply. Until then, Tesla sure has its work cut out for it.