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UK company launches new optimized single-cylinder range-extender engine

UK-based hybrid & electric vehicle powertrain specialist Hyperdrive Innovation Ltd. has developed and built a technical demonstration electric vehicle using its range-extender engine. The range extender is based on a single-cylinder, water-cooled four-stroke engine that builds on proven, low-cost technologies in a design optimized for this application.

Hyperdrive’s new range extender engine. Click to enlarge.

Based on a standard D-segment family car, the Hyperdrive CUE-V uses the range extender to reduce powertrain weight by 50 kg (110 lbs) while also eliminating range anxiety. The vehicle also demonstrates Hyperdrive’s latest battery pack and battery management system (BMS). In the CUE-V, the 60 kg unit delivers 15 kW at 5,000 rpm—sufficient to allow the vehicle to cruise at 60 mph without depleting the batteries.

This allows a substantial reduction in the size and weight of the battery pack and of associated systems such as cooling and power electronics. Further improvements in power density are expected and the system is designed to allow an efficient design path to future generations.

The new range extender engine is the result of a detailed review of the many technologies available for this application; its development was supported by supported by the Newcastle University Centre for Advanced Electrical Drives.

We started with an open mind and considered many quite radical ideas—including two-strokes, rotaries and gas turbine—as well as more traditional solutions. Each one was evaluated against a pragmatic list of requirements that include cost, refinement, weight, emissions and risk. It became clear that the most attractive solution for the coming generation of range-extender EVs is to build on established expertise.

The cleverness is in the combination of proven and bespoke components that allow the system to exceed the design targets with minimal cost and risk. This approach, combined with our proprietary electronic control system, allows us to fully exploit the potential of near constant-speed operation to deliver greatly improved power density without the cost and risk of significant new technologies.

—Hyperdrive director Chris Baylis

The rationale for range-extension. Hyperdrive managing director Stephen Irish suggests that most electric vehicles are fitted with too many batteries, simply to reduce the driver’s range anxiety.

Research has shown that 80 percent of journeys in Europe are less than 30km. Our experience of city trials in the UK shows average journeys as low as 20km. If batteries could be sized for the majority of journeys, the cost and weight of electric vehicles would fall sharply. Batteries also have other issues, such as the environmental impact of mining some of their constituent materials, the challenges of end-of-life recycling and the cooling and control systems that add packaging volume and weight.

—Hyperdrive managing director Stephen Irish

Liquid fuels have an energy density around 100 times that of today’s automotive traction batteries. Even the most optimistic projections suggest that this ratio will not improve much beyond 30 times within the next five years, notes Irish.

That means that the most convenient way of travelling long distances remains an internal combustion engine, while the most environmentally responsible way of travelling average distances is using low-emission, night-time generated electricity. With a range extender electric vehicle, you can do both.

—Stephen Irish



"In the CUE-V, the 60 kg unit delivers 15 kW at 5,000 rpm—sufficient to allow the vehicle to cruise at 60 mph without depleting the batteries."

Could the answer to 'range anxiety' be a 132 lb. ~lawn tractor engine/generator?

Nick Lyons

I would be very interested in a car with such a powertrain. My driving alternates between daily short trips around town (< 5 miles/day), weekly trips to a nearby small city (~50 miles round trip) and occasional trips to the big city (~500 miles round trip). Can a car with a pure serial hybrid drive give good fuel economy on the highway portions of the latter two drive cycles? Also, I realistically need to cruise at 70 mph to avoid being run off the road on the California freeways.


Could be a great product, but....

"Batteries also have other issues, such as the environmental impact of mining some of their constituent materials, the challenges of end-of-life recycling"

Can't these MORONS just be happy to tout the features of their product and stop with the Fear, Uncertainty and Doubt BS for 5 minutes? Geez, I get tired of seeing idiots who are trying to get involved in green tech slamming other parts of the industry.

Now we'll have Republican EV/HEV haters quoting this line as a reason not to support the damn things.


This may turn out to be the first common sense genset for small PHEVs. People who want a larger/heavier/faster PHEV could always buy the 30 KW turbo equipped unit.




If this is an existing and proven technology, it begs the question, why haven't the auto manufacturers fitted ALL cars and trucks with a small IC engine like this and mated them to electric drive trains?

It clearly works better than a straight IC drive car...uses far less gas and would have cut dependency on foreign oil ages ago.

My feeling is that range extended electric and other alternative fuel range extenders are going to be the death of the gas guzzler.


You're right, this has been feasible for decades.  There was even an amateur conversion of an Opel which made it into Mother Earth News in the 1970's.

Auto makers are concerned about cost and warranty issues; the deeper the battery is cycled, the more it is stressed and the shorter its lifespan will be.  The obvious solution is to make the battery cheap and treat it as a wear item, like tires.  It's a pity that Firefly Energy's vitreous carbon lead-acid technology seems to have been abandoned, it looks like it would have been a very good fit.


Honda's motor cycles ICE are very quiet. Many Moped ICE are also very quiet. Making small light weight quiet ICE is a very well know technology that could be further improved.

It is doubtful if major car makers are really interested in the mass production of simpler, lighter, more efficient PHEVs. The Volt is not a very good example to follow.

Tata-India may be the first firm to be interested. More may follow?

Trevor Carlson

The article does not address the emissions impact of using a small engine. It seems the concept vehicle that is described would have to adhere to Enhanced AT-PZEV standards.
Lawnmower, moped and motorcycles do not have as strict of standards when it comes to emissions. I think the reasoning being that they are low volume and not used as much. Since any vehicles using this type of powertrain solution will likely be low volume maybe they can get CARB/EPA waivers. Maybe that's not feasible for large automakers and why the haven't gone this route.


If anything, it should be easier to meet emissions with a small sustainer engine.  There is not going to be any period of low-power idling operation after startup (catalyst gets hot and lights off faster), and there won't be any throttle transients with the associated mixture excursions to worry about.  If you are going to modulate the power level you can ramp it smoothly with full closed-loop control all the way for the sake of catalyst efficiency.


Very small turbochargers don't work very well (too much leakage), but I wonder if this isn't the regime where a Comprex pressure-wave supercharger might not shine.  It could even use close-fitting pistons on springs to isolate the intake air from the exhaust (with a bit of EGR thrown in).  Harvesting the exhaust-pulse energy for supercharging would both quiet the exhaust and reduce compression work, so the engine could shift to an Atkinson cycle for greater efficiency with no loss of specific power.

william g irwin

As I posted elswhere:
"I look forward to the PEV and PHEV shift toward more electric and less ICE power in a vehicle. I like this trend! All you really need is just enough ICE power to maintain high speed cruise plus a bit of charge for the larger battery to keep the E-motor useful for passing and hills etc. How large an Ice is needed for a 20kw or so alternator?"
Assuming ~30% O/A efficiency, thats ~75hp! I would also prefer a twin for smoother running though.


20 kW = about 27 horsepower.

The Lotus 15/35 kW sustainer would be a step up from this, both in performance and price.

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