Currently reading: BMW plots range-extender revival with 2026 X5

BMW is set to reintroduce REx to its line-up to boost the global appeal of its electric SUVs

BMW is preparing to reintroduce a range-extender (REx) drivetrain to its line-up as part of a renewed push to offer pure-electric driving without the constraints of charging infrastructure – and its first REx model will be the upcoming sixth-generation X5.

Engineering work is claimed to be already well under way in partnership with long-time component supplier ZF and high-ranking BMW sources say the decision to revisit the range-boosting technology comes as global sales of REx models are gaining strong momentum – particularly in China, BMW’s largest market by sales volume.

BMW plans to deploy its new range-extender drivetrain in some of its most popular SUV models for markets where charging networks remain under-developed and buyer hesitation around pure-electric drivetrains persists. REx tech is expected to provide potential electric ranges of well over 600 miles between refuelling.

In addition to the X5, a REx drivetrain is also being considered for the recently introduced sixth-generation BMW X3 and the second-generation X7, due out in 2026. All three models are based on BMW’s 10-year-old CLAR (Cluster Architecture) platform.

BMW is no stranger to range-extenders. It first offered the technology in a production model in 2013 with the i3 REx (pictured), which offered an optional two-cylinder petrol engine to maintain battery charge, but the firm has not rolled the tech out to any other models following the i3 REx's retirement in 2018.

BMW board members were this week due to review the final specification with engineers, prior to signing the range-extender off for production, Autocar has been told.

The decision would mark a change of heart for CEO Oliver Zipse, who told investors last year that the technology was too expensive. “To have a very large battery plus a combustion engine in there - there is a limit to the financial logic,” he said. “Our PHEVs are currently around the 100-kilometre [range] which I think is the perfect point where the customer says ‘This is what I would like to pay for.’”

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The X5 is currently the only BMW to be sold with four different drivetrain technologies, including petrol, diesel, plug-in hybrid and hydrogen fuel cell. The last of those is a low-volume model but has played a prominent role in the company’s recent zero-emissions research and development activities.

At this stage, it is not known whether the new petrol-electric range-extender will be offered as an alternative to the existing plug-in hybrid drivetrain used by the X5 xDrive45e or whether it will supplant it.

ZF’s newly developed range-extender architecture consists of two variants: the eRE and eRE+. The former combines an electric motor, planetary gearset and integrated converter. The latter adds a clutch and differential, enabling it to serve as both a generator and a secondary drive source. Output of the combustion engine ranges from 148bhp to 201bhp.

ZF's eRE and eRE+ units can operate at peak efficiency, running the combustion engine only within its optimal rev range. This not only improves fuel economy but also reduces emissions and complexity, offering shorter development cycles and more affordable production than traditional hybrid set-ups.

BMW is expected to combine elements of the ZF system with its sixth-generation electric drivetrain, which uses an 800V electric architecture. A key part of the development has involved leveraging experience from the experimental iX5 Hydrogen programme.

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Although hydrogen-powered, the iX5 employs a system that mirrors the REx format: a fuel cell acts as an on-board generator, producing electricity to charge a buffer battery that then powers the electric motor. The vehicle has no mechanical link between the power unit and driven wheels – a layout that BMW aims to replicate with its combustion-equipped range-extender.

BMW engineers working on the project told Autocar that adapting a combustion engine for this new application is not as straightforward as it might appear.

"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," said one source. "The cycling efficiency is different, as is the thermal load. In a range-extender, you have a continuous charging effect while the engine is running. The entire energy management strategy must be tailored for that."

However, the REx is not the only new drivetrain set to be brought to the X5. A new pure-electric version of the US-built SUV (seen here testing in sporting M-tuned guise) is planned for sale in 2026. It will use the same sixth-generation electric drivetrain and cylindrical cell battery technology that is set to be launched on the first of its Neue Klasse models, the second-generation iX3, later this year.

BMW says its upcoming Neue Klasse EVs, including the i3, iX3 and iX5, will represent a “quantum leap forward” in terms of technology compared with its current EVs. Chief among the upgrades for this next generation is a new type of nickel-manganese-cobalt (NMC) battery with cylindrical cells, which is said to be 20% denser and easier to package than modules (made up of square cells) found in today’s 'Gen5' lithium-iron-phosphate (LFP) packs.

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The results, BMW claims, are a 30% increase in range, a 20% uptick in efficiency and 30% faster charging. Production costs are also 50% less, it has said, suggesting potential for lower prices in the showroom too.

Munich looks to Li

Among the key drivers behind BMW’s decision to revisit the range-extender is the meteoric rise of Chinese car maker Li Auto. Founded in Beijing in 2015, it has taken a leading role in the technology and currently offers four models with a range-extender drivetrain: the L6, L7, L8 and L9 (below).

Li Auto’s global sales surged past 500,000 in 2024 and the company has set an initial target of 700,000 for 2025.

NMC battery technology for BMW's new range-extender drivetrain is said to be under development in partnership with CATL – the same Chinese-based automotive battery specialist used by Li Auto.

All of Li Auto’s existing range-extender models offer a range beyond 600 miles. The L9, which comes with the option of a 52.3kWh battery, manages up to 731 miles on the CLTC test cycle. 

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