By on November 2, 2010

OK, so the EMAV PRU (Electric Motors and Vehicle Company Power Regeneration Unit) isn’t expected to go on sale until sometime next year, but it’s one curious approach to the “range anxiety” problem that caused GM to develop the Volt as a range-extended EV rather than a pure battery-only EV. The PRU takes a simple concept, a trailer that can both store goods and generate 25kWh of electricity from a 750cc diesel engine in order to extend range, and makes it considerably more complicated than it needs to be. For one thing, it’s self-propelled, necessitating on-board lithium-ion batteries, as well as an electric drive unit.

As a result, the projected pricetag comes to a prohibitive $15,000, and the weight reaches an EV range-sapping 1,220 lbs. And for all that, wouldn’t a $15k hatchback make a better “range extender” than this cumbersome trailer? On the other hand, a trailer like this just might work as a rental item, offering a portable generator as well as range extension that its makers say will work with any electric car. But would something like this be more appealing as a simplified, lighter unit (non-self-propelled), or will add-on range extension always struggle to offer more for money than having a gas car as a compliment to an electric car? Given that American families typically have several cars anyway, the answer would appear to be yes… [via]

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35 Comments on “For $15k, Voltify Your EV With A Range-Extending Trailer...”

  • avatar
    bumpy ii

    This is all old hat for EV types. Skip the range-extender concept completely and chop off the front end of some FWD subcompact to use as a pusher trailer.

    And to be nitpicky, kilowatt-hours (kwh) is an amount, and kilowatts (kw) is a rate.

  • avatar

    Only $15,000 you say…That’s about 10 years worth of gasoline for my old Toyota.

  • avatar

    These people ever heard of Hertz?

    • 0 avatar
      Darth Lefty

      Rent a job-site generator built into a trailer, and plug the car in as you roll down the road.  Problem solvinated!

    • 0 avatar
      SVX pearlie

      Let’s start with Honda Generator is 6500W, which produces 27A at 240V. That’s perfectly compatible with the Leaf’s Level 2 charging (240V <30A). The Generator itself is $3k, and a cheap trailer with an extension cord can be fabbed for $1k to $2k, for a total price of under $5k. The problem is that Level 2 charging takes 8 hours! So you can go 70-100 miles, but then you have to stop for 6 or 7 hours while the Leaf recharges. Not really practical.

      So let's now look at what it *really* takes to put the Leaf in to ER CS mode…

      According to Nissan, a Leaf driving at 55 mph has a 70 mile range, so it exhausts the battery in 1.25 hours.

      That means, you need a generator which can fully charge the Leaf in an hour or so.

      To do that, the Leaf will require a rolling Level 3 charger (charges 80% in 30 minutes, per Nissan). Full charge is probably an hour to taper up the last 20%. The problem is that a Level 3 charger is 480V / 125A!

      Also: "Nissan warns that if fast charging is the primary way of recharging, then the normal and gradual battery capacity loss is about 10 percent more than regular 220 volt charging over a 10 year period." Not good.

      I think this entire concept is a non-starter.

    • 0 avatar
      SVX pearlie

      Looking at it, when you recognize that the EMAV PRU is a rolling Level 3 Charger system producing 120A for only $15, it’s actually very fairly priced.

      I think it’s a good solution to a problem that doesn’t exist in the real world.

    • 0 avatar

      Level3 charging is more power than it takes to sustain cruising speed so it is overkill for a range extender.  You won’t be able to put a normal generator on the trailer because they aren’t certified emissions-wise to be an engine that runs while moving over a public road (whatever the EPA calls that).  Best / worst case scenario will be if they are regulated like motorcycles (i.e. barely) and you can get a trailer with a hayabusa engine and velocity stacks poking through the lid.  On the bright side, maybe some new companies will be able to use this market to develop low cost, light weight exhaust treatment systems.

    • 0 avatar
      SVX pearlie

      Yes, Level 3 charging is somewhat more than consumed at 55 mph, but running 55 mph consumes far more than what a Level 2 provides.

      It’s the difference between having 120-mile range for a 100-mile trip, versus a 25-mile range. Having 20 miles spare beats coming up short by 75.

  • avatar

    Oh please… I was joking!!!!
    I posted this on another article…
    The poorman range extender.
    Certainly the extender trailer would kill the range anxiety

  • avatar

    From a strictly nerd perspective, it’s a neat technology exercise. From a perspective of practicality, it’s ridiculous. $15k will go a long way toward gas, car/truck rentals (hookers, booze…).

  • avatar

    isn’t that almost like the price difference between Volt and Leaf? So, GM should be able to have done that cheaper.
    Especially since the Leaf has larger (presumably more expensive) batteries.

    • 0 avatar
      SVX pearlie

      Chevy Volt lists for $41k

      Nissan Leaf lists for $33k
      ER trailer is $15k

      So Leaf + ER trailer = $48k, or $7k *more* than the Volt.

      Buying the combination of Leaf + ER trailer, you’re paying more than the Volt, but getting a less-sophisticated ER system that requires more space, more axles, more weight, and more overall complexity.

      Anybody who’d buy one of these would do better to simply buy a Volt.

      Of course, if somebody could simplify the ER trailer and get the price down under $5k, then that’d be a very different proposition which might make sense for some larger number of people. In that case, you’d save a little money, and only carry the generator for those rare times when you think you’ll actually needed. The problem is that, as above, if you’re trailering an ER bolt-on any appreciable amount of time, then it’d be a lot easier to get a Volt and be done.

      In the end, it appears that GM did a pretty good job with the integrated generator / series-parallel hybrid system for the $8k premium you pay over the Leaf.

    • 0 avatar

      How much to get a really small engine and really small gas tank into a Leaf?  It can’t be $9,000.

  • avatar

    When I was an undergrad engineering student I recall volunteering to help out on some senior-level design projects, one of which was called the Hybrid Electric vehicle team (this was 98/99 time frame).  They competed in national competitions sponsored by PNGV or DoE or something like that.  They were trying to outfit a Chevy Lumina with a series hybrid Hydrogen fuel cell, but the cell stacks were late due to manufacturing delays and the fact that this team wasn’t the only group waiting on one.
    They ended up getting around the cell stack delay by building the car as a pure electric vehicle.  I don’t recall if they were using lead-acid or NiMH batteries, but the car didn’t get very high range.  So they cannibalized their prior-year Lumina series hybrid and used it’s 3cyl Metro engine (that ran on CNG) and put it on a small utility trailer with it’s propane tank to recharge the batteries.  After competition the department would host tailgates at the football games using the range-extender trailer and gas tank to run their grill.  As I recall, the trailer didn’t weigh more than 400-500 lbs even with the grill on it.

  • avatar

    Utterly insane.
    Most EVs will be purchased by multi-car households, so you simply use the gas car for long trips, not hook up your $15000 long range trailer.
    Even if you are one car household and you occasionally need a long distance trip. RENT a CAR!, Swap with a friend who would probably love to try an EV.
    This is a completely loony solution to a problem that doesn’t exist in reality.

  • avatar

    Wow!  What a great idea!  Maybe in the future we could build it right into the car itself!

    Oh, wait….

  • avatar
    Tree Trunk

    I love the trailer the size and the shape would be perfect for a luggage trailer for my Prius.
    Wonder what the trailer shell alone would run for?

  • avatar

    I have a great idea: How about we take the electric car, shrink it down, and supplement it with a gasoline-powered engine. Then we could just use the electrical bits to start the car, the rely on internal combustion to take us 300-500 miles before stopping, and we’d have the ability to refuel at tens of thousands of locations? I think that’s where electric car evolution is going.

  • avatar

    Can I just get the trailer without the range-extending stuff? It looks so cute being towed by that Fiat 500C.

  • avatar

    i think the point of the “self propelled” trailer was to reduce the rolling resistance and load placed on the electric motor. I could see Nissan over engineering a portable power station so that it wont inhibit the joy of driving an EV

    • 0 avatar
      SVX pearlie

      The trailer is self-propelled because that 120A generator weights a lot, and the load is too much for a Leaf or other EV to pull by itself without tearing its drivetrain apart.

  • avatar
    Brian P

    I have a trailer that weighs around that amount when loaded, and I know that fuel consumption increases by about 50% when I have it in tow. So, this will increase the energy usage of whatever powertrain you choose, by probably around the same amount. Better to just chuck the whole thing and just drive a regular small car. FAIL …
    This brings up the interesting possibility of circumventing the EPA / CARB emission rules. The trailer isn’t part of the car, so it’s not subject to the emission testing program. I doubt if that diesel engine they chose is fully compliant with US EPA Tier 2 bin 5 the way the diesel engine in, say, a regular VW Golf TDI is …

    • 0 avatar


      I know somebody who actually built their own range extender for their EV and tested it.  He found the same thing, the increased load (aerodynamic drag was, well, a real drag) of towing the trailer hardly made the small bit of net power from the generator even worth having.

      We’d be better off having high-capacity charging stations, or developing quick-change battery packs (could drop out the bottom, pull into battery station, lift comes up, lowers empty pack, raises up charged pack, you swipe your card, and you’re back on the road), I think the first of these ideas is more likely to happen than the second.

      And don’t poo-poo the FWD front clip pusher concept, it has been done by many, usually using a diesel VW rabbit:

    • 0 avatar
      SVX pearlie

      What generator did they use for their ER system?

    • 0 avatar

      Better Place has quick-change facilities running in a few places, but general consumers don’t have access to them. Which seems about appropriate for early adopters.

  • avatar

    This is obvioiusly a wedge entry into Formula Steam.

  • avatar

    Since the trailer is self propelled, does it have a maximum speed that it can hit?

    • 0 avatar
      SVX pearlie

      Ohh… now that would be amusing. Pop the cover and add a tiller-steered front wheel, and you’d get a trike that could move at 35+ mph, or more, depending on gearing and one’s nerves.

    • 0 avatar

      Pop the cover and add a tiller-steered front wheel
      Add the capability to recharge the battery by plugging it in and it might qualify for the government EV subsidy.

  • avatar

    Calling Rube Goldberg…

  • avatar

    I know grown men that can’t back up a trailer. It’s harder than it looks. Now picture teen drivers and the elderly…

  • avatar

    I have a 1963 catalina with a 421s and a 2bbl carb anyone ever seen one??? I can not find one anywhere on the web sany help would be apprecitated I can be reached at [email protected]

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