BMW is moving forward with plans to bring back its range-extender (REx) technology, with engineering work already underway in collaboration with long-time partner ZF. According to senior sources within BMW, this decision comes as global demand for REx models rises sharply—especially in China, the automaker’s largest market.
Range-Extender SUVs in the Works
BMW intends to integrate its new range-extender drivetrain into popular SUV models, including the X5, the new sixth-generation X3, and the upcoming second-generation X7, due in 2026. These models all ride on BMW’s 10-year-old Cluster Architecture (CLAR) platform.
The new drivetrain is aimed at markets where electric vehicle (EV) charging infrastructure is still limited. It targets buyers who are still hesitant to adopt fully electric cars. BMW expects the new REx systems to deliver electric driving ranges exceeding 600 miles between refuelling stops.
A Return to Familiar Technology
BMW has experience with range-extenders. In 2013, it launched the i3 REx—a version of its electric city car equipped with a small two-cylinder petrol engine that recharged the battery when needed. However, BMW discontinued the i3 REx in 2018 and has not used the technology in any other model since.
That is set to change. BMW’s board is expected to review the final specifications with engineers this week before giving the green light for production, sources told Autocar.
CEO Reconsiders Earlier Position
The move marks a notable shift for BMW CEO Oliver Zipse. Last year, he had dismissed range-extenders as too costly. “To have a very large battery plus a combustion engine in there—there is a limit to the financial logic,” he told investors. Zipse had instead favored plug-in hybrids, suggesting their 100-kilometer electric range struck a better balance between performance and price.
X5 to Host Multiple Powertrain Options
The X5 is already BMW’s most versatile model in terms of powertrains. It is currently offered with petrol, diesel, plug-in hybrid, and hydrogen fuel cell systems. While the hydrogen model is produced in small numbers, it plays a key role in BMW’s zero-emissions development efforts.
It remains unclear whether the new range-extender will be sold alongside or replace the current plug-in hybrid drivetrain used in the X5 xDrive45e.
ZF’s Role in the New Powertrain
BMW’s range-extender will be based in part on ZF’s new eRE and eRE+ systems. The eRE includes an electric motor, planetary gearset, and integrated converter. The more advanced eRE+ adds a clutch and differential, allowing it to act both as a generator and as an auxiliary drive unit.
The combustion engine used in these systems delivers between 148 and 201 horsepower. ZF’s system runs the engine only in its most efficient rev range. This reduces fuel consumption and emissions while simplifying the vehicle’s design. It also speeds up development and lowers production costs compared to traditional hybrid systems.
Inspired by Hydrogen Tech
BMW plans to combine the ZF system with its sixth-generation electric drivetrain, which uses 800V architecture. The company has also drawn on its experience with the iX5 Hydrogen project, which uses a hydrogen fuel cell to generate electricity for a buffer battery that powers the motor. Like the planned range-extender, the iX5 Hydrogen has no mechanical connection between the engine and the wheels.
BMW engineers note that adapting a combustion engine for use in a range-extender system poses unique challenges. “It’s not a simple case of taking the battery we use for our plug-in hybrids or pure-electric models and applying them to a range-extender,” one engineer said. The energy cycling and heat loads are different. As a result, the battery and energy management system must be specifically designed for continuous charging during engine operation.
Pure-Electric X5 Coming Too
BMW is also preparing a fully electric version of the X5, set to launch in 2026. A prototype of this model has already been seen in testing with M performance enhancements. This version will feature BMW’s sixth-generation electric drivetrain and new cylindrical-cell battery technology. It will debut on the second-generation iX3 later this year as part of BMW’s Neue Klasse electric vehicle lineup.
The new battery uses nickel-manganese-cobalt (NMC) chemistry and cylindrical cells. Compared to current Gen5 lithium-iron-phosphate (LFP) batteries, it is 20% more energy-dense and easier to package. BMW claims this will result in a 30% increase in range, 20% higher efficiency, and 30% faster charging. The new cells are also 50% cheaper to produce, which could help lower prices for customers.
Following Li Auto’s Lead
One of the reasons BMW is revisiting range-extender technology is the success of China’s Li Auto. Founded in 2015, the Beijing-based automaker has become a leader in the range-extender market. It currently sells four such models—the L6, L7, L8, and L9.
Li Auto’s global sales passed 500,000 units in 2024, and the company has set a goal of reaching 700,000 units in 2025. All four models offer driving ranges of more than 600 miles. The flagship L9, equipped with a 52.3kWh battery, can travel up to 731 miles under China’s CLTC testing standard.
BMW is believed to be working with Chinese battery supplier CATL—the same company that supplies Li Auto—to develop the NMC battery technology for its new range-extender vehicles.
