By on August 21, 2011

We’ve heard about range-extending trailers which could allow EVs to become range-extended plug-in hybrids, but how about this: a trailer with its own battery storage, regenerative braking and even electric-drive assist. That’s the idea behind German camper trailer firm Knaus Tabbert’s concept, on display this summer at Düsseldorf’s Caravan Salon. And besides adding hybrid capabilities to the car that happens to be towing the trailer, the trailer itself can use the energy gained through regenerative braking for its climate control, refrigerator, lights and more. Autobild reports:

Here’s how it works: Two AC generators, each with 850 watts of power are connected to each wheel of the caravan. The energy generated during the drive is stored in lead-acid batteries, which add an extra weightof 70 to 80 kilos. Starting at a speed of about ten km/h the generators begin feeding electricity to the batteries, and the maximum charge power is available by about 35 km/h. If the Caravan’s electricity use is limited to seven hours per day (total power 100 watts), campers can take advantage of up to four days of independence from an external power supply.

Even if you don’t understand German, you might enjoy the video above, which demonstrates many of the promised functions of this system. Outside of videos though, the system still is not ripe for public sale, according to its developer. There’s still no word on when it will be ready or how much it will cost, but it’s one of many small ways that hybrid technology is seeping into nearly every form of transportation.

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14 Comments on “Are You Ready For: The Hybrid Camper Trailer?...”

  • avatar

    I’m surprised no one has thought of it before now. Another bonus, with the heavy battery pack the centre of gravity is lowered which is all to the good when it comes to caravans.

    • 0 avatar

      Yup this a potential great use of EV technology. Depending on where and how far you are going it would be useful to have different modes. If you are going to a campground with 240v service put it in charge depleting mode where the motor provides assist all the time it isn’t doing regen braking. If you are going to be dry camping a charge replacement mode where the motor provides no assist and it’s only used for regen braking. If you are traveling long distances a charge sustaining mode that provides only the amount of assistance that can be recovered in regen braking and hill decent control.

    • 0 avatar

      Excellent observation.

  • avatar

    I’ve always understood that there is no free lunch in this kind of situation. In other words, having the rotating wheels of the trailer drive a generator while the vehicle is cruising imposes additional drag on the wheels, increasing the fuel consumption of the tow vehicle. Regenerative braking on the trailer wheels, in and of itself, is converting to electricity some energy that would otherwise be dissipated in the braking system as heat. However, does the regen braking by itself produce enough energy to offset the burden of the weight of the batteries and generator?

    If it does work, would it make sense also to install solar panels on the roof of the RV? The roof is a 20-20 foot long mostly flat surface that is usually fully exposed to the sun while the rig is on the road. And the solar system can continue producing juice when the RV is parked at the destination.

    • 0 avatar

      Solar panels on the roof of the RV are unlikely to provide enough power to be useful in moving the vehicle at highway speeds.

      However, people do replace the generator+battery system in RVs with photovoltaic+battery systems for things like lighting and the refrigerator. They’re much quieter, and RVs tend to be fairly efficient when it comes to electrical use even before this kind of a conversion.

    • 0 avatar

      An extra-cost option for those wanting or needing the extra “juice”?


      Perhaps a model without the regen but having the solar panel.

      On or the other or both.

  • avatar

    Unless I am missing something, other than any generation done during braking or downhill, charging the batteries has to add drag to the the trailer, meaning the charging is not for free, as the pulling car has to expend extra energy to pull the trailer (not to mention the extra weight). So other than being able to charge the batteries while you drive for later use as a power supply, what is the purpose?

    • 0 avatar

      Yes you are missing the fact that the batteries drive the trailer, it’s a self powered trailer. In the video they show that the batteries get charged when the brakes are applied in the tow vehicle. Not sure how it determines when to provide electric assist for accelerating and climbing hills. The “stability” control function could be a little tricky too. What I really like the idea of is using it to hitch/un-hitch and park the trailer.

      So the purpose it to reduce the MPG penalty associated with towing a trailer, provide some convenience features, and IF needed serve as a dry camping power supply at the loss of the MPG savings on at least part of the way home.

      • 0 avatar

        A self powered trailer also allows for a much smaller, and more fuel efficient, car to be used the 90% of the time you are not towing; instead of being stuck commuting in that diesel dually all year around, just so you can tow the camper for summer vacation.

  • avatar

    This is interesting.. but, the key for me would be how much it adds to the cost of the trailer vs. what it saves on fuel.

    Most RVer’s (I have a 40ft that sucks fuel like a battleship :-)))
    don’t drive that many miles per year.

    My personal setup is at a lake near I-40. The motorhome stays there year round and I use the RV like a cabin to enjoy the lake.. Then 2-3 times per year I fire it up and head out on a trip with the family.

    So maybe a 2000 miles a year.. maybe…

  • avatar

    I think the economics/physics here are being overlooked, so to speak. It might be better to have a powered trailer, but the extra weight will wear the tires quicker and require a heavier frame,and the batteries have to be manufactured. I think this is actually a clever way to disguise the fact that most “green” technology actually uses more resources to manufacture and maintain. Oh, and the price difference? I wonder how many lifetimes it will take to recoup the price of even the first set of batteries.

  • avatar

    Another consideration may be related to the advice regarding using cruise/speed control during rain or other possible “slick road” conditions.

    Do you want those trailer wheels to provide propulsion whenever they are designed to do so with no regards to road conditions?

    At the least, a handy on/off switch so the driver who knows or should know friction factors can maintain maximum control of his vehicle and attached units.

    • 0 avatar

      It does show int the video how it could be used as a stability or sway control system too, so if it was programed right it shouldn’t be a problem. Particularly if it was connected to the tow vehicles CAN bus so it knew what the tow vehicles stability and ABS systems were doing. You’d probably want it to be connected to the can bus anyway if the trailer is going to provide that assist. IE that way it knows the driver is requesting full throttle so the trailer should too.

  • avatar

    So, we leave the flatlands for some camping in the mountains. Since most of the drive is uphill, there will be very little regenerative braking benefit on the way up, and the hybrid car will need to run on gasoline most or all of the trip. Coming back down the hill, there will be some minor benefit, but then, any car, coasting down a hill, doesn’t use much fuel. Then we get home and park the trailer on the side of the house with it’s fully regeneratively charged batteries, where it will gradually discharge until we pull it out again next summer. Handy in a power outage, but so is a generator and a standard camper trailer, and for a lot less money. But, we do get the benefit of feeling superior to those other campers who don’t have regenerative braking on their overpriced trailer. Color me skeptical.

    A difference, to BE a difference, has to MAKE a difference…

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