Mercedes-Benz is scrapping extended-range EV powertrains after tests of prototypes, according to an Autocar report citing an anonymous source with knowledge of the matter.

Mercedes built and tested some prototypes based on existing models, “concluded that the range-extender drivetrain is a transitional technology with a relatively short-term benefit in terms of sales and comparatively high production costs,” the source told Autocar.

One of the prototypes was reportedly an EQS with a front-mounted 1.0-liter turbo-2, reported to be essentially half of the M254 2.0-liter turbo-4 currently used throughout the Mercedes lineup. This engine reportedly acted purely as a generator, supplying power to an electric motor rather than directly driving the wheels.

The engine ran on the Miller cycle to improve efficiency at the near-constant-rpm operation a range extender is likely to experience, as well as a front-mounted exhaust system for packaging efficiency, according to the report.

Propulsion was reportedly provided by a 268-hp rear-mounted electric motor, drawing power from a lithium-ion battery pack roughly half the size of a production EQS pack. As in other range-extended EVs, the battery could be replenished either by the internal-combustion engine/generator or via conventional AC or DC charging, per the report.

Autocar reports that combined range from both battery and fossil-fuel power was estimated by Mercedes to be beyond that of the EQS 450+ model. That’s the longest-range version of the production EQS, currently EPA-rated at 352 miles.

2024 Mercedes-Benz EQS 580 4Matic

Ram apparently knows some engineering tricks that Mercedes doesn’t. It says that it can pull this off in the Ram 1500 REV, while allowing the towing prowess of Ram’s non-electrified trucks. But other automakers have had less success with range extenders.

BMW used a range extender with its i3 REx, and at the end of the life cycle essentially said that the batteries had improved enough to push the idea to extinction. One of the few other vehicles to have used such a system is the Karma Revero—also called the GS-6 and, originally, the Fisker Karma.

2024 Mercedes-Benz EQS 580 4Matic

Several years ago Infiniti envisioned its entire future around series hybrids with range extenders and downsized engines, such as this, with complementary full EVs sharing some of the components. But in 2021 it aborted that plan. In that case, the small combustion engine was set to be a 1.5-liter turbo-3 with special encapsulating noise insulation.

Mercedes has instead been shifting toward more plug-in hybrids, with DC fast-charging capability and larger batteries—but it hasn’t downsized the engines substantially yet on those.