the battery eats the cargo space

Problem statement

Long-haul heavy-duty trucks (Class 8) face a fundamental weight constraint. Battery pack weights described by commercial battery-electric vehicle OEMs run 14–25 lb per kWh — a 1,200 kWh pack "optimistically" weighs about 16,800 lbs (~7,600 kg) — and NACFE/NREL's analysis found that doubling range from 250 to 500 miles by doubling the pack from 550 to 1,100 kWh may add roughly 7,700 lbs of tare weight, cutting maximum payload to about 37,300 lbs; a 750-mile pack could cut it to about 29,600 lbs (Mihelic and Kotz, EVS33, 2020). The US federal Interstate gross vehicle weight limit is 80,000 lbs (23 U.S.C. § 127), so every added pound of battery is a pound of freight not carried. For payload-sensitive freight (dense goods, bulk materials), this requires more trips, eroding both economics and the emissions benefit. At current pack-level energy densities this is a physics limitation, not merely an engineering optimization.

Why this matters

Road travel accounts for about three-quarters of transport CO2 emissions, and trucks carrying freight account for about 29% of global transport emissions (2018 IEA data via Our World in Data). Long-haul routes are the hardest trucking segment to electrify precisely because of the range-weight coupling. If battery-electric trucks cannot match diesel payload capacity, the business case collapses for freight operators working on thin margins where every ton of cargo matters.

What’s been tried and why it hasn’t worked

Tesla Semi production specs (announced February 2026) offer 325-mile standard and 500-mile long-range variants, with the long-range tractor at 23,000 lbs tare weight (battery capacity undisclosed; industry estimates near 900 kWh). The Mercedes-Benz eActros 600 carries a 621 kWh pack for a 500 km (~310-mile) range. Hydrogen fuel cell trucks (e.g., Hyundai XCIENT Fuel Cell: 180 kW fuel cell system, 72 kWh battery, ~31 kg of hydrogen, ~400 km range) carry far less onboard energy-storage weight but face the fueling infrastructure chicken-and-egg problem. Federal law grants trucks powered primarily by electric battery (or natural gas) a 2,000 lb allowance, to a maximum of 82,000 lbs (23 U.S.C. § 127(s)) — small against the multi-thousand-pound battery weight penalty NACFE estimates for 500+ mile packs. The Megawatt Charging System (MCS, up to 1,250 V / 3,000 A) now has initial standards documents published (IEC TS 63379; SAE J3271 technical information report, 2025), and shorter-range batteries with en-route fast charging could reduce weight — but MCS hardware remains at prototype/early-deployment stage and corridor charging infrastructure is not yet built out (CharIN). Trailer-based battery swapping has been proposed but adds complexity and requires standardization across manufacturers.

What would unlock progress

Pack-level energy density substantially above today's deployed truck packs (OEM-described pack weights of 14–25 lb/kWh correspond to roughly 90–160 Wh/kg at pack level) — for example via solid-state or lithium-sulfur chemistries — would shrink battery weight for the same range. Deployed MCS charging infrastructure along freight corridors enabling shorter-range batteries with fast en-route top-ups, reducing the required onboard energy and weight. Weight limit policy harmonization across states/countries for zero-emission vehicles.

Entry points for student teams

A team could model the freight economics of battery-electric trucks across different route profiles (length, terrain, cargo density) at current and projected battery energy densities, identifying the crossover points where battery weight no longer destroys the business case. Alternatively, a team could design an optimal charging network placement model for MCS stations along major freight corridors. Transport engineering, energy systems, and operations research skills apply.