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Concept: Through-the-Road PHEV Conversion Kit

The Poulsen Hybrid system attached to a Jetta. Click to enlarge.

Poulsen Hybrid is developing a conversion kit that will add through-the-road plug-in hybrid capability to conventional vehicles by externally mounting electric motors onto 2 of the wheels. The motors are normally applied to the rear wheels, in the process converting a FWD car to all-wheel drive, but the system works with rear- and all wheel drive vehicles as well, according to Poulsen.

The system will be available in kit form and could be installed by individuals (do-it-yourself, DIY) in a day, although Poulsen says that it has not decided whether or not to offer the kit that way, due to potential liability issues. Poulsen, which is competing for the Progressive Insurance Automotive X-Prize, plans to offer the system through a network of authorized installers.

The Poulsen PHEV conversion system. Click to enlarge.

The system is based on the premise that 10-15 hp is required to propel a compact or mid-size automobile along a level road at a steady 60-70 mph, and that a relatively small amount of electric power would be able to cope with 70-85% of normal driving, only aided by the combustion engine during start up and when extra energy is required for acceleration and hill climbing.

The Poulsen system, which supports regenerative braking, uses two 5 kW (7 hp) Permanent Magnet, Axial Field (PMAF) motors developed by Alpha-Core, Inc. The disk-shaped on-wheel motors are installed onto the original wheels by means of adapter plates, which are bolted onto the back of special wheel lug nuts.

The stator is prevented from turning by means of a torque bar, which extends from the outside center of the motor to connection fixture situated directly behind the rear wheel and attached to the fender or rear quarter panel. Power supply takes place via power cables extending through a channel in the bar/conduit to the motor controllers and battery pack located in the trunk.  Addition of the Poulsen Hybrid system does not touch existing brake, steering and suspension systems.

The controllers in first generation systems are programmed for torque control and are not connected with the original accelerator pedal. The armature current and thus amount of superimposed torque and the brake torque are controlled by potentiometers located in a pot box which is connected with the power supply in the trunk by a 10 ft. cable. A toggle switch turns the system on and off.

Poulsen is currently using a lead/acid deep cycle battery pack comprising six 12V 120 Ah batteries with a 72V/10A on-board charger. The company expects to have a 4.3–4.5 kWh lithium-ion battery pack available this year.

The company has not yet tackled the issue of Department of Transportation (DOT) approvals. Poulsen says that it will post third-party  performance data for the hybrid system when it becomes available.

In June, Poulsen announced that it was proceeding to build a pilot series of 500 motors (250 kits), based on the performance of its prototypes. Part of the current effort is focused on the development of manufacturing equipment for the motors, torque arms and model-specific components.

The company said that it hopes to reach a capacity of 100-150 systems per day late in 2008. Although the initial motor design was for light vehicles, the company is working on two more powerful versions suited for SUVs and pickup trucks.


John Taylor

This is a conversion to hybrid for under 4 G.
Sounds good!


They do realize that this will kill any warranty on the vehicle.


Interesting....looks odd, but interesting....


A good effort. It probably achieves moderate regeneration in the BAS (battery-alternator-starter) range. Providing cruise power (like achieving 30 MPH w/o the ICE in a Prius) is not the issue. Reclaiming the brake energy and re-using it before the next brake application is what’s needed. It needs some niche, like 4WD for snow country or …. Otherwise it’s probably costly and/or awkward to control.
But I don’t know why it would affect the warrantee.


It has to pull a lot of weight. I'd like to see
some numbers. Better a car designed from the
ground up that has batteries & Genset. If you
have a lot of weight, let it be the batteries,
not a huge ICE under the bonnet. I'm happy to
see all of the innovations that people are
dreaming up, though. It seems that the inventive
aspect peculiar to Americans is still alive and


Won't kill the warrenty (aftermarket parts allowed), but there will be no warrenty for any part damaged by the kit.

So what would happen if I put this on an existing hybrid? It sounds a bit like crossing the beams.


I went to the website to see
if the system is still offered
to just FWD autos. Now they
say all FWD, RWD and 4WD. My
commute vehicle, a small 1989
Toyota RWD pickup would be a perfect
candidate for Poulsen's drive. A
bed with plenty of space for the
batteries and room for 2-3 passengers.
Japan should start exporting small
pickups again.


I have to wonder how well this plays along with things such as anti-lock brakes, stability control, and the like. Still, a neat idea, even though almost certainly not cost-effective.


Perfect for my 96 Tercel and short urban commute.


You could use hub motors, but they might be more expensive. A BAS+ type system might be more cost effective. You could probably do one for under $4000 installed and it might improve mileage 20-30%.

Mad Max

I drive an eight year old diesel Lancia: guarantee is not an issue for me.

It would be great if I were able to uninstall the kit once a year, when I drive for very long highway trips where the benefit would be minimal.

During the rest of the year I drive mainly in town, for no more than 10 miles a day.

Would the kit be able to move a 1,6 metric to car?


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Brian P

So the torque arm is attached (with what appears to be rather wimpy fasteners) to the plastic bumper cover on the outside?

And the controls don't interface with the vehicle's original controls?

Niiiiiiice. My check is in the mail.


and will it give you car a boost?!!

exelerating much faster??

Ryan B

Maybe I'm just being dim, but...how do you change your tire on the side of the road?


I'm sorry but $5000 (with installation) is waaaay to expensive at today's prices to get back a return on investment (ROI) in any meaningful amount of time for this system - which, by the way, looks like it could be stolen pretty easily by a motivated thug. Guilt and enviro-scorn won't work either!


@ ejj ... I guess this system is just not meant for New York ... Especially Harlem. $5g in 5 minutes is way too much temptation.

This could be made to interface with the throttle by a simple OBD2 connector. Any time throttle=0, it can do full regen.


"$5000 (with installation) is waaaay to expensive"
Well let see. If you have you one year SUV that you pay $60 000 and you like to sell it right now (because of fuel consumption ) and they offer you $30 000. What you will do?
Take the $30 000, drive that thing despite fuel cost, or buy conversion kit for $5000?

On the other note
I will add couple suggestions:
The conversion kit have to be connected to internal system in order to take full advantage. You need one management system for ICE and the kit.
Also you could upgrade you alternator to something like 20KW so the system could work like series hybrid on the highway.
Another thing that I will also do, is to change the differential to have lover ration. The car will have lower acceleration but improve millage.
We do not need acceleration of 6 or 8 second to 62 miles. 12s or more could be good enough if you use this car to get to work.

By the way that last approach could be apply to any existing car (specially the older one that do not have CVT or 6 speed box) and could improve milage10-20%.

Henry Gibson

A. Convert all pumps, including air-conditioner, to electric drive.

B. Put in a battery big enough to run all electric demands for your entire commute.

C. Put in alternator disable circuit that turns alternator back on when braking or battery is only 20% charged. Have the biggest alternator possible for car.

D. Recharge battery at work and home to save on gasoline use.

E. Ignore the above and buy good working "clunkers" and use the money you save to buy expensive gasoline.

F. Ignore the above and pay me to tell you how to build a cheap variant of this method. ..HG..

John Taylor

The system here has two advantages .
1 it is simple enough that anyone can install it.
2 it is reasonably cheap.

Actually, for a retrofit for hybrid, it would make more sense to bolt an electric motor/generator to the front of the differential, (or the back of the transmission) and shorten the drive shaft.

Adding wheel motors to the non-powered wheels would also work. (and give you 4 wheeling capability)

but ... if retrofitting, why not just toss out the ICE altogether and install an electric motor. Lots have done this already, and it works just fine.


The great idea here is that it's relates to something to
be added to existent vehicles.
Additionally, for the set of batteries required could be provided a leasing supported (with incentives) by government. Just an idea


"buy good working "clunkers""
Next year at this time you will see on streets many abandon "clunkers" - SUV.


Not being an "Otto Motive Engineer" (or whatever they will be called in the future after demise of the ICE paradigm) it is difficult to assess how this "through-the-road hybrid" does interface with the existent propulsion and control systems. I certainly would hope that the torque arm attaches to the frame.

Additional coolness factor would be attachment of aerodynamic skirts to the torque arm to cover the rear wheels and improve performance a la l' Aerocivic

I would like to see how someone just "changes" a differential gearing willy nilly if the auto manufacturer does not offer the same tranny with different ratios. Will you have a machine shop custom cnc you a differential? I hope you have several thousand dollars ready for that (especially if you own a front wheel drive car)!

I would also like to see how someone just bolts on a motor/generator to the front of a differential or back of the driveshaft(s) in a front wheel drive car...

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