Range-extenders have been in the mix of possible alternatives to pure-petrol and pure-diesel powertrains for nearly three decades, and with new eRE and eRE+ powertrain products from ZF Friedrichshafen arriving in 2026, we could start seeing more of them.
It’s a technology that appears to be enduring. Citroën produced versions of the Saxo, Xsara and Berlingo back in the 1990s and there have been plenty of working concepts from various manufacturers since. For instance, GM launched the Chevrolet Volt in 2016 and the Mazda MX-30 R-EV is on sale today.
ZF is one of the world’s largest automotive tier one suppliers and it’s investing big in range-extender technology. Its aim is to make it easier for manufacturers to slot the technology into production cars in a modular way rather than evolve it from scratch.
Such an approach is not unusual. Often, a new technology we see in a car is a product that has been developed by a tier one supplier and sold to the car manufacturer.
ZF developed a range-extender for London black cabs in 2018 and in November 2023 it began work on its latest products, the eRE (electric Range Extender) and eRE+, which gives the option of four-wheel drive. Work first started on the eRE at ZF’s technical centre in Shanghai, reflecting the increasing appetite for range-extenders in China.
What exactly is a range-extender? In its purest form, it’s simply an EV but with a much smaller battery and a generator to top the battery up when needed.
Unlike a full parallel hybrid, in which the engine and electric motor can drive the wheels in whichever configuration the manufacturer chooses, the combustion engine in a true range-extender doesn’t drive the wheels: the electric motor does, powered by the battery, which is charged by the generator.
The battery can usually also be charged via a socket like a plug-in hybrid. The technical name for a range-extender is a series hybrid, because the energy is passed in series, from generator to battery to motor.
The ZF eRE does that and a typical configuration is for a generator powered by a combustion engine, with a motor driving the rear wheels. The eRE+ develops that by adding a planetary gearset, a bi-directional clutch and a differential.
This enables the motor-generator to drive the front wheels, which, with the main motor driving the rear wheels as before, gives four-wheel drive. Alternatively, the motor-generator is able to work in generator mode, de-clutched from the axle, to charge the battery while the car travels in rear-drive.