Tesla Semi pack details

A battery pack is the heavy box of cells under an electric vehicle, and in a truck it has to store energy, stay warm enough to work, survive fast charging, and not eat into cargo weight. Tesla says the Semi now uses a different pack layout to do all four jobs at once. (tesla.com, youtube.com) On Tesla’s current Semi page, the company lists deliveries starting in 2026, a 500-mile estimated range for the long-range version, energy use of 1.7 kilowatt-hours per mile, and charging that can recover up to 60 percent of range in 30 minutes. Tesla also says the truck is 1.2 megawatt charge-capable and rated up to 82,000 pounds gross combination weight. (tesla.com) The new detail came from Semi engineering lead Dan Priestley in a March 2026 episode of *Jay Leno’s Garage*, where Tesla walked through the production-intent truck ahead of a volume ramp. Reporting from that episode said the Semi uses Tesla’s 4680-format cells in a “cube” pack rather than the flatter layouts used in passenger cars. (youtube.com, electrek.co, driveteslacanada.ca) That shape matters because a flatter pack exposes more surface area to cold air, while a denser block holds heat longer, like a loaf cooling more slowly than a thin sheet. Multiple reports on Priestley’s comments said Tesla expects that thermal advantage to cut winter range loss by roughly 20 to 40 percent. (electrek.co, teslarati.com, ilovetesla.com) Priestley also said the pack is structural, meaning it is part of the truck’s frame instead of cargo bolted onto it. Electrek reported that Tesla cut about 1,000 pounds from the production-spec truck, a change Priestley tied to redesign work aimed at getting the 500-mile Semi to payload parity with diesel rivals. (electrek.co, autoblog.com) Tesla said in the same media push that the Semi battery is designed for 1 million miles, a number aimed at fleet buyers who keep tractors in service far longer than consumer cars. The company has been pitching lower fuel and maintenance costs for several years, but the new battery details are more specific about how Tesla plans to protect range on cold routes and preserve payload. (electrek.co, finance.yahoo.com, tesla.com) The charging side matters too, because long-haul electric trucks need very high power and often need stationary batteries at depots to smooth demand from the grid. Tesla’s official Semi page confirms megawatt-class charging, while recent community posts and follow-on coverage discussed larger on-site energy-storage units paired with truck charging. (tesla.com, electrek.co) Tesla has not published a detailed engineering paper on the “cube” pack, cell orientation, or the exact winter test cycle behind the 20 to 40 percent figure, so most of the public description still comes from Priestley’s remarks and secondary reporting. That leaves open questions on pack size, serviceability, and how the design performs across different trailer weights and climates. (youtube.com, electrek.co) Community discussion also raised electromagnetic-field concerns, which come up regularly around electric vehicles and chargers. The National Cancer Institute and the World Health Organization both say extremely low frequency electric and magnetic fields have been studied for decades, with evidence still limited and mixed rather than establishing a clear everyday-vehicle health hazard. (cancer.gov, who.int, niehs.nih.gov) For now, the clearest takeaway is practical: Tesla is telling fleets that the Semi’s battery is no longer just an energy tank under the cab. It is now part heater, part frame, and part economics pitch for a truck Tesla says will begin broader deliveries in 2026. (tesla.com, electrek.co)