As International Mining‘s article on the latest in open-pit haulers is prepared for the June issue, we hear the technology underpinning the Tesla Roadster, a high-performance electric sports car is showing up in a truck. The Silicon Valley automaker is providing the batteries Freightliner Custom Chassis is putting in the electric trucks it will have on the road next year. Freightliner has offered CNG (compressed natural gas) and hybrid electric trucks for years and it’s about to start selling a hydraulic hybrid. It says electrics are the logical next step.

A hydraulic hybrid combines a diesel engine with a hydraulic propulsion system. In most hydraulic hybrids, according to Design News, the diesel engine powers a pump that charges an accumulator, which drives pump motors connected to the wheels. Without a conventional drivetrain and transmission, the engine can run at maximum efficiency at all times. During braking, the pump motors are reversed and can recapture at least 70% of braking energy – nearly three times the amount that can be recaptured in the regenerative braking systems found in electric hybrids.

“We’re trying to drive some of the revolution within the commercial sector,” says Jonathan Randall, Freightliner’s Director of Sales and Marketing. “This is one more arrow in our quiver to make sure we’re following the technology and providing what our customers want.” Freightliner says its electric rig will save $15,000 a year in fuel and maintenance costs. Ford recognises this as well, which is one reason it’s rolling out the light-duty Transit Connect Electric van at the end of the year.

Freightliner already builds a lot of the delivery trucks – called walk-in vans – you see around US towns. It essentially took the chassis from one of those trucks, the MT-45, and swapped the engine and transmission for a motor and a really big battery.

Enova provided the motor, which produces 120 kW peak power and 45 kW continuous. The controller and charger also came from Enova. The power comes from batteries made by Tesla Motors. The pack is comprised of three 18.5 kWh modules for a total of 55.5 kWh. That’s good for something above 160 km range. Mike Stark, who leads Freightliner’s alternative fuel efforts is not sure of the exact range because the truck is still being tested. If more range is needed, simply add more modules to the pack. Stark says the truck can handle as many as five, which would provide 92.5 kWh.

The battery is essentially the same as the Roadster’s 53 kWh pack. Each module contains 2,000 cells and weighs 136 kg. The cells are the same kind you’ll find in your laptop – 18650 lithium cobalt oxide. Plug the truck into a 220-V line and it’s good to go in six to eight hours.

All of the components fit between the frame rails and what would be the engine compartment in a conventional truck, so there’s no loss in cargo space or capacity. The electric van will have a more than 2 t payload. Although the battery pack weighs 408 kg, Stark says the electric drivetrain is lighter than the engine and transmission it replaced.

Freightliner Custom Chassis is a subsidiary of Daimler, which bought a stake in Tesla Motors almost a year ago. “We talked to Tesla because of the relationship with Daimler,” Stark said. “But we also found they offered the best energy density for the price and the packaging. We believe they provide the best product for our application.”