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ebuggy concept promises "unlimited range" for EVs


September 19, 2012

The ebuggy project is developing range-extending battery trailers, that could be towed behind electric vehicles on long highway trips

The ebuggy project is developing range-extending battery trailers, that could be towed behind electric vehicles on long highway trips

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Until there’s some huge revolution in battery technology, electric vehicles are destined to remain as urban runabouts, never going out on long highway trips ... right? Well, not if Germany’s ebuggy project has anything to say about it. The group is developing little range-extending battery trailers that could be towed behind electric cars, providing power to the vehicles on longer trips. When a user’s trailer started getting low on juice, they could just pull over at a roadside exchange station and swap it for one that was fully charged.

In more detail, the plan is that users would start by hitching an ebuggy to their car when leaving their home city. They would pick that trailer up at an exchange station, on their way out of town. It would only take about two minutes to hitch up and plug into their vehicle’s electrical system. They could then swap it out if needed while en route, depositing the final ebuggy at a station outside of their destination city. For driving within either city, they would just use their car’s existing battery.

Users would pay for the trailers on a per-use basis, via an ebuggy card which they would receive when signing up for the service. Fees would be automatically calculated and billed, and would reportedly “always be lower than driving a gas or diesel car.” Those users would also initially have to get an ebuggy kit installed on their vehicle, which would include a standard trailer hitch, a power socket, and a dashboard user interface.

A prototype trailer has been built and tested, thanks to the involvement of Germany’s Ministry of Economics and Technology, and project partners including the Fraunhofer Institut IPA and Stuttgart University. That prototype is claimed to work perfectly – its battery capacity hasn’t been stated. The group is now optimizing the design for large-scale production, and is looking into establishing a network of the exchange stations across Germany and ultimately in other countries.

While the system may indeed make long-distance EV travel possible, it could conceivably also cause electric vehicles to become more affordable. “ebuggy allows the automotive industry to build reasonably priced electric vehicles with a smaller battery, because ebuggy is available for longer distances,” said the group’s managing director, Dr. Manfred Baumgärtner. “As a result, electric cars will become cheaper than vehicles with a combustion engine and e-mobility will be able to assert itself rapidly and dynamically.”

Should the ebuggy system become a commercial reality, it may have some competition. Germany’s Rinspeed is developing a similar concept, Dock+Go, in which two-wheeled range-extending modules are actually attached to the back of an existing EV – essentially temporarily turning it into a six-wheeled car.

The ebuggy prototype can be seen in use in the video below.

Source: ebuggy

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

For quite long trips a gas/diesel generator would currently be a better option giving longer range and utilizing the current infrastructure. Battery trailers would be good for moderate trips but not long trips with current technology.

Max Kennedy

"Long trip" in Europe is different than "long trip" in the US. A long trip here could be 2K or 3K miles with lots of nothing between buggy locations. I'm with you that a diesel genset would make more sense here.


Sorry, but I predict doom and failure for this idea.

Firstly, no-one can drive with a trailer attached. Backing, parking, going round corners, changing lanes on the freeway are just going to result in a lot of accidents.

Secondly, the added weight of dragging that thing around is going to kill your efficiency.


This is actually a really good idea. People that own electric cars own them as second vehicles only and something like this would enable them to be used as a primary vehicle because it would extend their range.

One of the biggest problems with using an electric car on long drives isn't just their shorter range but because they can't quickly be refueled. Being able to replace the main battery pack in the vehicle requires a bunch of difficult problems to be solved first but this would be compatible with anything.

and @Max, if you owned only an EV and needed to take it somewhere where only gasoline would be available you could always trailer a gas/diesel generator the same way.

It seems kind of stupid to trailer a gas powered generator behind an EV but the point is you would only need to do this a couple times a year (like on a camping trip or something) and you would still be EV only the rest of the year.


Why not set up the trailer as a generator, driven by the trailers tires, that could provide a continous flow of energy to the prime mover while travelling at highway speeds? Could also be made so that the trailer would go into neutral at lower speeds with the energy provided by the battery pack in the prime mover (in and around town situations).

I'm not an engineer of such things so there may be something fundamentally wrong with the idea but it seems this would be easier to implement than an infrastructure to provide trailer replacement support with sufficient saturation to where people would feel comfortable making long trips with an all electric car.


Why not just fit cars with a replaceable battery pack like a forklift?

Ian McIntosh

Better than the Dock Go but still not as good as an ICE driven vehicle.

If I am going to deal with the hassles of pulling a trailer I want more than a gas tank. And what's with that wing?


You're basically proposing a perpetual motion machine -- or free energy. It doesn't work that way. You can't get more energy out of the moving wheels than the energy you put in to move the wheels.


@Rt1583 the fundamental problem with your idea is that where does the energy come from that is driving the wheels of the trailer?

On the flat etc, it comes from the car.... so you'd just be using the car battery to charge the trailer battery via the generator / wheels / road / wheels / engine.

If it only worked as a brake (e.g. hooked up to your brake system) as an energy recovery system, that would be different, but these are generally built into the car anyway.


So that's "unlimited range" as long as you stop to refuel every now and then? I'm no expert but I'm fairly certain my non-electric car works in a similar way.


I've been waiting for solutions like this to emerge. For the electric purists I understand the sense in towing a batterypack but I personally would also see the benefits of a trailer with a petrol/diesel engine and a generator that would feed the car (possibly a sterling engine that can burn just about anything). The trailer with an engine ought to be smaller and lighter than one with batterypacks.

Conny Söre

You could put an ICE powered generator (preferable diesel) on a short narrow 1 wheel trailer preventing the worst of the trailer driving problems and far lighter than the battery pack. But I don't understand why anybody would buy an overpriced EV in the first place.


I suggest you guys take a peek on BP's solution (not that BP, BetterPlace:) It's much more plausible compared to this buggy. Swap batteries every 200 or so km. in less than it takes to fill a tank.

Or fast charge them in 20 min. (better yet, where there are wind and solar power ready)

The whole issue is to stop with fossils. If there is a tail-pipe (even plug-in Hybrid) then we are not talking about EV.


A great idea for the one tenth percent of the rolling stock. Internal combustion engines push pistons, compressed air can do the same for the rolling stock without any burning to keep the air flowing. A trailer with more capacity until we make the regeneration system capable of compressing the air faster than the engine can use it, solar generation. Best example a 777 powered by compressed air stored in the vast storage of the fuel tanks and solar panels on the flying surface to keep the takes full and buoyant. What is the weight of the fuel in a 777?

Can you imagine an electric 777? the engines are called turbines because that is what they are, its all in the spin.

Patrick McGean

The problem with replacement battery packs is that battery packs come in different shapes, sizes, and technologies. They are difficult to get to, expensive, and when you buy an EV car from a manufacturer, your warranty with that manufacturer extends to that battery pack.

If you buy a $40,000 plug in Lexus do you want to just blindly swap your main battery pack at a gas station with someones random Junk? No way.

A crappy battery pack would cripple the cars performance and why would Lexus want to be on the hook to fix it under warranty?

This makes so much more sense because you just rent a charged trailer from the rental company and give back the same equipment when you are done.


It reminds of the Clever Trailer in shape. http://www.clevertrailer.ch/ They have a fuel cell trailer at the site.

Logo Boats have a trailer with a solar panel. http://www.logoboat.com/PULMOR/PULMOR%20TRAILER%20AND%20PULMOR%20POWER%20TRAILER%20HOME%20PAGE.htm

Here is a trailer with a diesel powered generator. http://www.plugincars.com/company-launches-electric-car-range-extending-diesel-powered-trailer-101953.html it can also be used for storage. This is what the eBuggy should be. http://www.emavco.com/


The biggest problem is that the electric motors and controllers in most EV's are designed to operate up to a certain load. Ask any EV manufacturer if you can add a towball and tow a trailer and they will tell you that doing that will void the warranty. The only way to get around this will be to have the trailer driving and braking it's own wheels based on signals from the onboard EV control (or a more clunky solution would be a TPS sensor on the accelerator) then there would be no extra load placed on the EV itself. Then add a biodiesel turbine generator to the trailer and you have unlimited range.

People shouldnt bag ideas like this - come up with a solution or an improvement - any fool can tell you why it can't be done.

Ben Stanton


Ask any EV manufacturer if you can add a towball and tow a trailer and they will tell you that doing that will void the warranty.

Automobiles have a GVWR (gross vehicle weight rating) and a GCWR (gross combination weight rating) set by the manufacturer.

As long as the trailer is within the weight of those specifications it would not void the warranty. The GCWR (that counts a trailer) is typically higher than the GVWR because trailer weight isn't required to be supported fully by the automobiles chassis and suspension.

The delta between a Chevy volt curb weight and GVWR is about 1000 lbs. The curb/GVWR delta for an SUV is ~2000 lbs for comparison.

You wouldn't anything too heavy but it should be able to pull a small trailer (~1,000 lbs) without too much stress. The term "void the warranty" is also a little ambiguous because the manufacturer has prove the mod you made is the reason for the failure they are refusing to cover and even then the warranty would still continue to cover other things.


re; Diachi

You had better make sure you read the fine print. If it says that adding a tow bar voids the warranty it voids the warranty whether you have towed anything or not.


the trailer wheels could have a generator hook up there, whenever the brake pedal is applied the Gen can start producing juice. then normal driving there is no extra drag from the trailer wheels.

Jimbo Jim

re; Jimbo Jim

You forgot about the regular extra drag from trailers The additional rolling friction, inertial mass, and aerodynamic drag.


To all those that think this is a good idea put your own money up. Yeh I thought so.

Matthew Jacobs

Try this on for size: 2008 Dodge Dakota (Spec'ed at 9.8 Litres per 100 Kms for Highway) Towing my Electric Firefly from an EV Show - since it is still Lead Acid Powered and has short range - which - as a Gas version was rated at 45 Mpg Highway in the USA [ 1989 Pontiac Firefly 3 cyl, 1.0 L, Manual 5-spd, Regular Gasoline and using a conversion site says that is 5.2 l/100 km.

Added together - that equals 15 L/100 km - but while towing the car - with my aerocap on the truck delivered a Highway result of just 10.8 L/100 km, or a penalty of just one (1) litre more per 100 Kms to tow a 2,000 lbs Firefly!

Basically - if the eBuggy is aerodynamically clean - it could even improve the efficiency - by cleaning up the drag bubble behind the towing vehicle - like the Smart ED must surely have!

Robert Weekley

RT1583.. you are either trolling, or had better NOT become an engineer...

Powering a generator from the drive wheels of the trailer (bad idea).... The energy must come from the battery pack in the car (through the drive motor).. You don't get anything for nothing.. So this idea will run the car's battery flat even quicker, due to loses in the system... (Nothing is 100% efficient....)

We all dream of perpetual motion performing some useful work.. Most of us don't say such things out loud.... (Who wouldn't want a car that never needed filling up or recharging...)

As said above, a better idea is a diesel generator in the trailer, rather than a battery pack which will only give you another 100km travelling distance... Remember that the energy density of petrol or diesel is something like 40 times that of the best current battery technology, so for 1kg (a bit over a litre) of diesel, you would need at least 40 kg of battery.... that will make a huge difference in the efficiency of the system. once you have enough extra range to negate the mass of the generator ( 10kW genset weighs say, 250kg). 250 kg of Lipoly batteries ~= 6kg petrol (approx energy density), which is about 100 km for most cars, ok it is electric, magic happens, make that 200 km... (optimistic) add 6kg of petrol and your car can go 100-200 km... add another 6kg and you can now go up to 400 km (total mass = 262 kg).... For the same advantage you would need 500 kg of batteries... that is a huge load to be towing around... For 250kg of diesel/petrol, and an efficient electric car/ generator (500 kg total), you should be able to get over 4000 km....

All of these ideas are so stupidly obvious, that they cannot be patented, except in some broken patent system such as most countries seem to possess these days...

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