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AVL Introduces New Modular Range Extender Technologies and Engineering Services

A Range Extender Module based on a rotary engine. Click to enlarge.

AVL has introduced new range extender system technology and engineering services targeted at OEMS for short-term market introduction of range-extended electric vehicles.

The Range Extender is an autonomous auxiliary power unit added to pure electric drive vehicles to extend the operational range beyond that obtainable in the pure electric mode. AVL took a modular approach; depending on the specific customer production background and product needs, the internal combustion engine (ICE) component can be designed as a 2- or 4-stroke piston engine, or for lowest NVH and best compactness, as a rotary engine.

Because of the specific drive train system layout, the electric system and the ICE can be optimized for single point operation. Design requirements that AVL brought to the development task included:

  • Lowest NVH, compact design and high power/weight ratio;
  • Dependable system—i.e. available after long period of inactivity;
  • Reduced system life time and load response requirements compared to standard ICEs;
  • Single load point optimization for low system cost and good efficiency;
  • Thermal management to protect heat sensitive e-components; and
  • Low raw emissions to meet most stringent emission legislation targets at affordable cost.
Range Extender Core Module: Rotary Engine, Generator and Power Electronics. Click to enlarge.

All Range Extender functions are integrated in the module for to enable minimum interfaces with vehicle. The ICE, generator and power electronics are highly integrated in the single drive unit for best compactness, low weight and system cost.

The modularity also enables low part numbers and high part commonality for different performance ratings and applications.

For a demonstrator of the Range Extender system, AVL coupled a 250cc rotary engine running at 5,000 rpm with a permanent magnet synchronous machine. Electric output is 15 kW @ 320-420V, and fuel consumption is 260 g/kWh.

Dimension of the Range Extender box are 490mm x 400mm x 980, and the unit weights 65 kg. System to vehicle interfaces are high- and low-voltage, CAN bus, fuel supply, mounts and cooling.

AVL is also offering a suite of range-extender development services, including:

  • Concept development and simulation
  • Technical specification development
  • ICE and electronic system integration
  • Model-based component optimization (ICE, generator, power electronics, controller and software)
  • Continuous methodology and toolchain for simulation and verification
  • Operation strategies and control
  • System calibration development
  • Definition of testing requirements
  • Prototype and production development



The compactness of the rotary genset is interesting to keep the vehicle size and weight as low as possible and reduce energy consumption.

However, the fuel consumption of 260 g/Kwh is high and pollution may also be higher than more efficient gensets such as:

a) Mapamanpu AD16-3C @ 177 g/Kwh

b) Volvo's @ 206 g/Kwh

Can the current fuel consumption increase of about 46% be compensated by it's smaller size and lower weight?


i didn't find your gensets;

but i did some math and i found out that with 260gr/km you will consume ~ 2l / 100km, i think this is very good;

Put this and a electric drivetrain of about 150kgr (with battery) in my car and i am happy

i don't think the volt will consume less then that ....


The question is how much you will use it.
If you use the range extender very little (say < 1000 miles / year), the efficiency doesn't matter much, having a range extender just allows you to sleep better at night.

If you are using it a lot, say >5K miles / year on range extender, perhaps you need another vehicle.

We are only starting out with range extenders. It may well be that you end up with several points along a curve where you trade volume (or NVH) for efficiency.

As Harvey has pointed out, there are other, more efficient range extenders, but they might be larger or worse in other ways.

But it is very early days in EV range extenders.


Price hint?



One of the most efficient small genset, such as the AD30-3C, uses a VAMO-D3900TG engine with an ECO32-3S/4 generator for an amazing 173 g/KWh. Other combinations do almost as well with published fuel consumptions of 175, 177, 183, 186 and 189 g/KWh.

Deutz WAD31 is also doing very well with 189 g/KWh. The WAD40 does even a bit better with 186 g/KWh.

However, the above sets are no lightweights and would be more of an on-board handicap where size and weight is very important.

The 260 g/KWh of this rotary genset will be difficcult to improve unless rotaries become more fuel efficient. However, they will have a place where size an weight is at a premium.


"250cc rotary engine running at 5,000 rpm"

You want about 400cc producing 30kw at 2000 rpm. The speed, vibration and noise will be big factors in range extenders. You should not even hear them when they turn on and off.


"You want about 400cc producing 30kw at 2000 rpm."

No no, that would make it a hybrid. This is just meant to be a back up for an BEV. You don't need the RE to pump out enough juice to hum alone the highway, you only need enough to limp slowly home if you're stupid enough to let the batteries run flat.

Get the right car for the right job, if you DO need your car to travel hundreds of miles at highway speeds you should buy a hybrid - not a BEV. An EV is for making short commutes and a RE of this size should only be thought of as insurance.


ai vin:

Shouldn't BEV buyers have the choice to select various size and type of range extenders to suit their needs, such as;

1) none, but more modular batteries to extend e-range.

2) lightweight low power rotary type to crawl to the next charge station.

3) more rugged flex-fuel ICE genset for extended highway drives.

4) future fuel cell in place of 2) or 3) above.

By 2020/2025, with affordable modular high energy density (400 to 500 Wh/Kg) quick charge batteries, range extenders may no longer be required, no more than a second gas tank today.


Because batteries are so heavy, it seems to me that the ideal BEV would be one that carries just enough battery energy to meet one's mileage need plus a little for safety. However, there is a point where the battery becomes overwhelming in size and weight, so one must think of using a PHEV/EHEV. In the case of the Volt, the battery size is set for 40 miles of use before the on-board extender comes on-line. The problem with the Volt is it has to also carry the weight of the range extender,including the fuel, coolantand oil, eeven when it isn't being used, thus reducing the efficiency of the battery only mode. There appears to be three main paths for extending the range of BEVs: swapping out the battery, such as suggested by "Better Place;" Quick charging the batteries, if you have the more expensive batteries; and lastly, the range extender genset. All have their pros and cons; but, what if you could rent a genset for those times when you intent to journey beyond your BEV's normal range? Perhaps the genset could come in the form of a small chassis mounted, one wheel trailer that plugs into the control electronics of the car. I like this idea because you only carry the extra weight of the genset when you must.


"Shouldn't BEV buyers have the choice to select various size and type of range extenders to suit their needs?"

Of course they should! However, given that this article is about a 250cc engine, I stand by my statement that "This is just meant to be a back up for an BEV"

OTOH given that this engine also has an output of 15kW it could still be used to keep a small BEV going along the highway.


@Lad "The problem with the Volt is it has to also carry the weight of the range extender,including the fuel, coolantand oil, eeven when it isn't being used, thus reducing the efficiency of the battery only mode."

Which is why I favor an engine that's only big enough for a 'limp home device.'

"Perhaps the genset could come in the form of a small chassis mounted, one wheel trailer that plugs into the control electronics of the car."

As I suggested in http://www.greencarcongress.com/2009/05/better-place-demo-20090513.html#comments


"No no, that would make it a hybrid..."

Now take your BEV and climb a 10% grade with four people and luggage for an hour and see how much utility you have. Cars are about utility, how much usefulness you can get from it, not how it fits ONE person's idea of what it should be.

Fred H

Hi SJC, assuming you drove a leisurely 40 mph up a 10% grade for one hour, starting at sea level, you would reach an elevation of 21,120 feet. That is higher than the highest mountain in North America. No such road exists in the entire world.

I estimate that a BEV with a 15 kW range extender would be adequate for more than 99.9% of all trips. For that one in a thousand trip where you must get to the top of a 2100 foot mountain within an hour, I would recommend chartering an aircraft.


Chevy Volt owns 50 kW range extender. That is too much redundancy for running at 100 mph speed to the mount of Everest or similar with four passengers and conditioner turned on once per entire life. With 15 kW range extender it would be possible as well but it would take 10 minutes more to charge batteries at the bottom. (Average sedan power consumption not more than 10 kW at 70 mps speed.)


Great to see this focused engineering done on RE technology. This will push the auto co's. The more ideas kicking around the better.

Bill Max

Pretty smart, but not genious. Soon somebody will show how to build cheaper, better ER-EVs and hybrids.
For the now there are enough executives who don't really understand technology, so we will see many guys like Bob Lutz, Elon Musk and so on.

Thomas Pedersen

Fred H:

Funny! And true. Why is somebody using a BEV to haul 4 passengers with luggage anyway? How many 4 person families in the US only have one car with a BEV being the only option? The first generations of BEVs will most likely be cummuter cars with space for picking up some groceries or one or two small children. That's what I think. That's also what displaces the greatest number of miles.

For every commuter that switches his/hers F2500 truck with a BEV, a lot of gas gets saved! Family trips with luggage don't count nearly as much and, besides, when there's a whole family in the car, higher fuel usage in a larger vehicle is certainly justified!

I'm not too impressed with the specific fuel consumption of this particular RE but for sporadic use, the low weight and volume may be more important. I wonder how the rotary engines fares with the criteria of coping with long periods without usage?


The basic fail with bev is it cant replace all that large a percentage of cars because not only can most people not afford one they dont have room for a second or third car with those drivability metrics AND costs.

It simply most times wont replace a current used car and instead will add anouther car to the pool of cars someone owns. And then only for wealthy people and for bev fanantics and no one else.

To get any real traction at all it will have to fully replace a car someone already owns.


Onboard genset: RadMax™ engine (generates 1hp/0.75 lb with multifuel capability)
Have just enough bi-polar lead acid battery with Supercapacitor for a 10 mile range.
Lower total weight & improve drag coefficient. (Don’t move mass or push air you don’t need to.)
Inexpensive, outstanding fuel economy and can be built now!
Engineers and automotive workers are available to start now!
Dealer showrooms, manufacturing plants, suppliers are waiting…
You build it and we’ll buy ‘em….


Um no alot of people wont buy because they dont trust all that many of these companies to still be here 5 years down the road when thier car starts breaking down.


"Um no alot of people wont buy because they dont trust all that many of these companies to still be here 5 years down the road when thier car starts breaking down."

I just bought a Chevy, I wonder what I'll do when GM goes out of business? ;^)
It's actually NOT a big problem. Even if GM were to close its doors tomorrow most of the parts on my car were supplied to GM by other companies, companies that supplied the very same parts to at least a dozen other car manufacturers.

OTOH an ev is a really mechanically simple car, it has a lot fewer moving parts to wear out. That was one of the reasons GM flattened the EV1; their service department complained they wouldn't make any money on a car that didn't need fixing. :-(


ai the problem is that small car company likely as not doesnt have many if any spare parts stocked up and so if it goes under your toast. Its VERY different if a car company makes 5 million of a car you KNOW someone will continue to make parts.. 10000... not so likely.

This has happened before with small car companies and im sure it will happen this time as frankly many of them have realy crapy cars while others are far better.

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