Video: EP Tender is a Hitch-Mounted Range Extender


EP Tender is a hitch-mounted range extender that its developer, Jean-Baptiste Segard, says is the solution for the EV range issue.

Zoe Hitched to EP tender

Zoe Hitched to EP tender

Segard’s EP Tender is an engine on a trailer.  It’s a simple solution for those who occasionally travel long distances, but who still wish to own only an EV.

Apparently, Segard has already pitched the EP Tender to Renault and plans to speak with BMW, Volkswagen and Ford, too.

Quoting Segard:

“I’m hopeful that, at the end of the day, [the automaker] will say market research demonstrates we could sell more car if we allow these cars to use EP Tender.”

Though we suspect OEMs will show no interest in Segard’s EP Tender, there’s something else in the works that perhaps makes sense.

Segard hopes to rent out EP Tenders to EV owners for use on occasional long trips.  There’s no word on what the daily rental rate would be though.  Segard says EP Tender can extend an EVs range  to up to 500 miles.

As Coexist explains:

EP Tender Guts

EP Tender Guts

Segard claims his devices solve the most obvious technical problems. He patented a mechanical method that makes backing up a cinch (which you can watch him demonstrate). Electric vehicles can’t typically be charged while driving, but Segard says his devices get around this issue by essentially operating in parallel to the battery, connecting between the battery and the inverter in a way that he says is compatible with all the EVs on the market. “They would fit very nicely on a Tesla Model S or a Nissan LEAF,” he says.

We see no reason why a Model S owner would use such a device though, especially with the growing network of free Superchargers.

Segard says there’s one major hurdle though: EVs don’t come factory equipped with hitches.  That’s a problem, but of course there are aftermarket hitches that fit EVs, but then again towing with an EV voids most warranties.

Can Segard find a work-around solution?

Time will tell.

Source: Coexist

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35 Comments on "Video: EP Tender is a Hitch-Mounted Range Extender"

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I don’t think it will ever be utilised widely, but boy there is some clever engineering in there!
The way it handles reversing is so simple, but so effective!

The added weight, additional length and poor aero would mean you’d want to leave this thing parked unless you planned a long trip. Maybe it would have a use in cross country rentals?

That’s the idea.

This is an old idea but, if well implemented, a good one. Yes, it does not make sense for 250+ EPA rated EV’s (Model S 85 being the only current model with this range) but it can make sense for the rest. It has to offered as a rental and for sale with built in capabilty to power a house during a power outage. Being in Florida and being a Model S owner, I would be happy to purchase a 15kw unit for $8k + emergency transfer relay. This is what a whole house generator would cost anyway.

it looks like the early part of the video shows pop down casters when backing and not the guidance rods. If it was tightly coupled when backing, (lock the ball) you could get away with just casters. Looks like a great idea for a range extender on rental with 24hr access needed of course.

How big is the gas tank?
What is the MPG for a *typical* EV?
How loud is it, dB?

Here’s a PP presentation

Looks like it has a 9.25 gal tank and is rated for 35kW (or that is the goal, not sure)

I don’t know if it has this option, but it should have an inverter to put out AC voltage. That way you could go camping/whatever and use it as a power source. Could also be used to power your home if the power goes out. Brings up another question, how many kW is it rated for?

Dr. Kenneth Noisewater

Neat idea, though it would be more useful built into a larger, aerodynamic trailer (for more cargo capacity). I assume such an accessory wouldn’t be subject to emissions inspections, which would be convenient. I reckon a 50kW motorcycle engine would also be a better way to go to maintain performance at highway speeds.

How about towing more batteries instead of an ICE?

That is impractical due to the weight of enough batteries to make a difference.
Electric cars which were not designed to tow anything at all couldn’t even manage to tow that much extra weight at reasonable speed.

Not necessarily, as you would probably have single-use (but recyclable) air batteries in such a scheme, like those that Phinergy is working on. They’re claiming up to 1000 miles with only 25kg of Al plates.

Even if it weighed twice that, it’d be a negligible towing load. You could even pop that into an EV’s frunk when needed.

You shouldn’t use a phrase that something will “void a manufacturer’s warranty”. It’s highly dubious, and unless a manufacturer can demonstrate that a hitch and/or towing an object caused a problem for which a repair is sought under warranty, they can’t deny warranty coverage.

Reminds me of the RAV4 EV trailer some guy built:

However, one major issue is that the J1772 spec does not allow the car to start up/move while plugged in (iirc).

It looks like a nice idea to have in a power outage or if you have to drive to grandmas house 300 miles away. I could picture something like this being a rental idea if someone only makes two to three major trips in a year.

The only thing I picture happening to this system is it could become outdated if 300 mile EV’s with supercharging abilities become mass marketed do to falling battery costs and battery break though. But for the next few years this trailer system could do really well.

Dr. Kenneth Noisewater

You’re not gonna want to use a J1772 charger with such an engine, you’ll want to send DC power directly to the battery. I have to wonder how you’d go about getting the battery controller to not freak out.

The AC Propulsion was not built by “some guy”. It was some guys with PhDs and IIRC, a federal contract!

Why not make on that goes on the top of the car??

Where are the purists??? Is the Leaf still a BEV if it has this RX?
When GM made the Volt, they leapfrog the competition by including the RX IN THE CAR, not in a trailer. And since its in the car, why not put it to use in very specific circumstances like heating the cabin or going up a hill?!?
Of course, we.could not call the Volt an electric car then? Right?
Of course not…….
Huge leapfrog.
In time, neysayers will see the genius of the Volt.
i love my amphibian car…;)

I agree – This trailer is not an elegant solution to the range problem. I do prefer the range extender being built in like the Volt or i3. However, I think the Volt’s range extender is a bit oversized. I’d rather see a smaller 2 cylinder engine at half the size and weight of the current one. Right now, I believe the Volt’s range extender produces 55kw. But with the size of the main battery on the Volt, I believe it could easily function properly with a 35kw unit, keeping a larger buffer in the battery when using the range extender.

Agree, but GM built the current Volt using off the shelf parts, and in my mind, that is stellar acheivement.
Is it perfectible? Yes, of course.
smaller engine, 12kw out of the 16 (like the ELR) of usable energy, a few adjustments and you get a 50AER for Volt 2.0
AND plugless, of course.
So…What do you call a plugin that you dont plugin but still recharge then???
an IRBEV (Induction Rechargable Battery Electric Vehicule)?
A plugless Volt would be a ERIREV???
OK, i’ll go take a nap for now……

From what I hear, the way the rex is hooked into to the Volt is different than it is in the i3. The Volt’s ICE is connected to the wheels. When you run out of juice and the ICE kicks in, you don’t notice much, if any, difference in the feel of the pedal. I think with a smaller motor you would be able to feel a significant difference in the transition, especially at highway speeds where more power is needed. I don’t think you can get away with driving a depleted i3 like an idiot, like I regularly do in the Volt. I think it will punish you for over-asking by capping your max speed for a while, to 40 mph or so.

They’re just different machines. So much so that I rarely see anyone refer to the Volt’s ICE as a rex.

I just wish the ICE was lighter. Hauling it around brings miles-per-kilowatt down to 3 or less, where BEV’s are typically 4+ mpkw. But I am sure they also wanted it to be lighter when they designed it, but had a bunch of variables to balance.

As David says, with a large enough buffer, performance should not suffer with a tiny engine. Even driving like an idiot, you shouldn’t be using more than 30kW except on steep hills at high speed.

The i3 REx is very compromised in its (largely failed) attempt to still be classified as a pure EV by regulatory agencies. That’s why it can’t be manually engaged and has such a tiny gas tank. Stupid decision by BMW, IMO.

I think cheap range extenders are just around the corner. You have companies like Tata making a whole car around a 38hp engine for ~$2500. I can totally see a company like that cranking out range extenders at $1500 each (or less!) for any automaker that wants to build an EREV. Renault-Nissan is looking to make an 800cc engine for a cheap Pulse/Micra in India, and I hope they’re also making a range extender out of it.

You can find a 15 kw generator for 800$ at Walmart so 1500 $ should be feaseable. For what the power level is concerned, why not let the people chose for themselve just like for a convential gas car. For me i would be more then satisfied with 15 kw since it would fit my rx needs. I just want a Leaf to be able to do 400 miles in one go when i go in vacation and that’s ok if i drive at 90 mph on that particular trip. Now of course if someone want to have a 1000 kw rx for whatever reason, so be it. In the end choice must become the norm.

@Driverguy01: unlike an on-board REx, that mini-trailer is detachable, and the idea is that people would only use/rent it for the few times a year it’s needed.

For those who only rarely travel long distances in areas not covered with quick-chargers, it makes a lot of sense IMHO to not drag around that ICE, gas tank etc etc every single day, nor have to worry about its depreciation and maintenance.

The beauty of electric cars is their simplicity. I see this as adding so many more possible failure points. If you need to rent a gas engine, hook it up to an EV that wasn’t designed to have a range extender or tow anything…wouldn’t it make more sense to just rent a compact car?

The economics compared to renting are probably what will make or break this idea. Existing car makers can use off-lease cars in their dealerships as a rental network for EV owners, and the EP Tender will have to beat that in net cost.

It’s obviously cheaper than a full car in theory, but compact cars are produced in 100x the volume that this trailer can even dream of achieving in the short and medium term.

Indeed, the rental price will be lower than renting a full ICE car. Other benefits: you get the tender en route to your destination and travel door to door with your own car; when going for vacation you rent only on the way out and on the way in, not for the whole period.

Handy contraption of you HAVE to move your BEV a long distance. But if you have to move your BUTT a long distance, park the BEV and rent. A van. Or fly. The break-even on a towable power plant – via-a-vis renting a nice van and pouring gas into it – has to be many, many vacations into the future.

Maybe dealers can use these to move BEV’s from one city to another.

Since I saw my first picture of a towable, I have wondered if there was a way to make a one-wheel version that actually drove its own wheel, running only at >=50mph, just to assist with (or take over) the pushing at highway speeds. It would have a sensor on the hitch to ensure it only ran when it was aligned straight. Have it disengage and/or turn off when the brake lights came on. Put an accelerometer on it so it could know how much if should bear down on that poor hitch ball. Tongue weight would have to be zero or slightly negative.

If not already illegal for safety reasons, would probably be made illegal very quickly on general what-the-hell-is-this-guy-doing principle.


Okay maybe two narrow wheels.

Then there is the obvious fact that it makes more sense to just rent a car for the infrequent long road trips, if all you have is a sub 100 mile EV.

Pretty cute and yes it could work but the short answer is: Tesla Motors has a different idea.

Aiding an EV with a combustion engine is valid as an interim solution but it will very quickly be replaced by fastcharge.
And he would need support or hack the cars. And I’m not sure you can always assume you can just wire it in parallel. A car might have systems that monitor anomalous signals and freak out.

I would buy one, as all my family are scattered all over the USA.. I want one..Moni

Will this work with a Rav4 EV? How much will it cost? Is it ez to hook up and remove? How does this differ from Dual Carbon Battery ?