The only hybrid that embodies logic, sustainability, redundancy, and long-term reliability is the REEV or REX system, the Range Extender. In this system, the primary drive is electric, with a smaller (or larger) battery, while the ICE (Internal Combustion Engine) serves as a generator to assist under heavy loads, protect the battery from high currents, and reduce the overall number of charging and discharging cycles. It sounds simple and looks simple.
The image shows a masterpiece, an unfulfilled pioneer, the Fisker Karma Plug-in Range-Extender with a 20 kWh battery in the central tunnel. At the rear, it features two axial electric motors on the differential, and at the front, a GM/Opel 2.0 Turbo gasoline engine with side exhaust pipes and no axles or connection to a drivetrain toward the wheels. It functions solely as a generator, charging as needed and acting as a power-assist generator. It operates very quietly and is almost imperceptible during driving.
This particular vehicle, with 200,000 km, is still in perfect working condition without a single screw being touched on either motor. The small battery, which in a typical substandard hybrid would have long since failed, still performs well in the REX system. What’s even more interesting is that the REX system doesn’t rely on the battery being fully functional or how much it has degraded, as high currents are still managed by the generator. Even if the ICE engine is non-functional, you can drive on electricity and charge via a socket, or if the battery is faulty, you can drive using the generator.
The REX hybrid system is everything that conventional hybrids are not: reliable and redundant. Besides having a generator, you never have to turn it on; you can charge it daily using a home charger and drive 100 km. This particular vehicle arrived with a fault in the OBCM module due to water entering the connector, damaging the module, making socket charging impossible, but it still runs on the front generator. We haven’t been able to repair the OBCM module yet, but another is on its way from eBay.
The company went bankrupt in 2013 due to a series of unfortunate events, as their battery module supplier, A123, went bankrupt, halting their entire production and leading them to bankruptcy. Today, this model is still produced under new management under the name Revero, by Karma Automotive.
In person, this car is a true road renaissance. Its design, crafted by Fisker, who is also the artist behind the Aston Martin DB9, Artega GT, BMW Z8, and had a hand in the Tesla Model S and Model 3, is stunning.
The Fisker Karma is a textbook example of a perfect hybrid, where the EV drive is primary. Even after 12 years, it still drives with original parts and without authorized service or support—something 99% of EU conventional hybrid junk couldn’t endure for six months. Stay away from hybrids that are not REX. This is one I would even buy myself, and we’ve included a complete aftermarket support specialization in our plans.
MHEV (Mild Hybrids) are the teletubbies of hybrids—barely deserving the hybrid label. Some rare models are decent, but many are prone to failure and very expensive to maintain. REX is the only sustainable hybrid, sometimes even better than EVs. The list of true REX systems is very short:
- Fisker Karma
- Karma Revero
- BMW i3
- BMW i8 (Almost EREV, but not same)
- Opel Ampera
- Cadillac ELR
