Regenerative braking is great and all for electric and hybrid cars, but for those of use with old beaters another approach can be had via a trailer hitch. The beauty of this is that it requires no modifications to the host car, save for the trailer hitch.

Attach the signal wires for the trailer brakes to switch an electric motor that is linked to the trailer wheels. The motor would be used only as a braking-assist, powering some arrangement of trailer mounted batteries. Upon arriving home, plug the trailer into your wall socket to power the house or to sell back to the electric company.

This would be even more useful when arriving at a destination without electricity, such as a campsite, Florida after a hurricane, or Baghdad most of the time. Your mileage may vary depending on the weight of the batteries, cost of fuel, and cost of electricity. Do take care to make the trailer fit aerodynamically within in the wake of the auto, and if possible try to plan out a route that runs mostly down hill.
-- Laughs Last, May 16 2005

PopSci article on using a trailer to add mileage/charging to electric cars http://www.popsci.c...range-electric-cars
[theircompetitor, Nov 02 2010]

Somebody patented my idea in 2008 https://www.google....tents/US20080169144
not cool: US 20080169144 A1 [Laughs Last, Apr 11 2016]

Bicycle version Bicycle_20Flywheel_20Trailer
[Vernon, Apr 12 2016]

I once saw a bicycle that had a 2 wheeled trailer that could push. There was a universal joint between bike and trailer.

It is relatively easy to make a trailer that can drive as well as brake. I never thought about applying it to a car before, so +.

Batteries/trailer could be changed instead of recharged, or the unit could be continuously recharged by the IC engine using regenerative braking mode. But parking might be a problem (and in town is where I would expect it to be of most use).
-- Ling, May 16 2005


I don't think it's worth the cost to pull the extra weight around.
-- BJS, Feb 10 2006


The problem comes in getting enough braking force out of the trailer. Force=mu*n where mu is the coeffecient of static friction, and n is the normal force acting through the braking surface. mu is about .8 for an ideal rubber/asphalt interaction. n approximately equals weight, in this case of the trailer.

Thus the trailer cannot provide more braking force than it's own weight, and the energy recovered will be less than the energy used to accelerate its mass. Regenerative braking is useful on cars only because the accleration and braking are happening anyway. You benefit more by lightening the vehicle in the first place.
-- MechE, Nov 02 2010


<Gravelly Voice> In a car, on a road to nowhere....

<tumbleweeds tumble across desolate road, a car comes up over the horizon>

<Gravelly Voice> One man, on a road to destiny...

<Man Talks on Phone> I'm sorry honey, I'll be home for thanksgiving, tell Timmy I'll be there...

<Gravelly Voice> One night, he would ever forget...

<Zombie Jumps into Screen - sounds of screetching wheels on tarmac - thud of impact accompanied by Zombie moan...silence>

<Gravelly Voice> ....all he needed was to survive...

<Taught, outstretched hand, possibly zombified, reaches out from ugly car-wreckage...fade to black>

<Gravelly Voice> Regenerative Braking, coming Summer 2011 - rated 18.
-- zen_tom, Nov 02 2010



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