BMW plots range-extender revival with 2026 X5

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.

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.