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MIRA Introduces Plug-in Hybrid Retrofit System with Removable Li-ion Pack

The H4V on the test track.

MIRA (Motor Industry Research Association), a UK-based automotive design, development and certification consultancy, has unveiled a plug-in hybrid retrofit system with the potential to reduce fuel consumption and tailpipe emissions by 39%, and applied it in a demonstrator vehicle.

The ‘H4V’ (Hybrid 4 wheel drive Vehicle) features a novel removable lithium-ion phosphate battery pack. MIRA built the technology demonstrator around a Skoda Fabia with funding from the Energy Saving Trust’s Low Carbon R&D program.

With this project we’ve removed the primary limitation of the “plug-in hybrid” concept by allowing the battery pack to come to the mains, rather than having to park right next to a socket ... which is more than a little difficult if you live in a terraced house or flat.

—Derek Charters, MIRA’s Advanced Powertrain Manager

The hybrid derives power jointly from the Fabia’s 60 kW (80 hp) gasoline engine and two 35 kW inboard motors powering the front-wheel drive car’s rear wheels though MIRA’s ‘e-differential’. The control system provides for pure electric driving in the city, moving to series hybrid operation ‘in the suburbs’ and parallel hybrid operation in cruising conditions.

MIRA plans to apply the lessons learned in the development of this concept demonstrator to other, more commercially-oriented hybrid projects which will lead to new hybrid models in the next year or two.

Overall, the H4V returns 4.4 L/100km (64 mpg UK, 53 mpg US), as measured on the EU drive cycle, a 39% reduction compared to the standard gasoline model’s 7.24 L/100km. Top speed and acceleration are similar to the standard gasoline model. The Skoda Fabia 70hp 1.4-liter diesel version does a combined cycle 4.8 L/100km, while the 1.4-liter Fabia Greenline version achieves nearly 4.1 L/100km, better than the H4V prototype.

The removable cassettes. Click to enlarge.

The H4V’s battery pack is built from portable cassettes, each with 1.5 kWh capacity. MIRA designed and made the battery packs, using Li-Ion Phosphate cells “sourced from an American supplier.” They take about 30 minutes to take a full charge, and in combination can power the H4V in electric-only mode for up to about 15 miles. The pack’s 22 kg weight (for a double cassette pack) is expected to reduce when readied for series production.

The battery units could also power external devices, which could include camping equipment, or to power electric jet skis or quad bikes.

MIRA retuned the engine and created a custom calibration that works in harmony with the electrically driven axle to deliver additional synergies beyond the simple fuel savings possible via ‘torque-neutral' hybridization schemes.

The MIRA hybrid uses regenerative braking, which can deliver enough energy recovery potential to outweigh its mass penalty. An aerodynamics pack reduces drag by 8% to achieve a Cd of 0.299.



two 35kw motors?.. that is a lot.. still a very good idea, you also get a 4wd vehicle from the conversion. This is not optimum but it is low hanging fruit.

If they used in-wheel motors then the conversion would be simpler.. you could do it yourself in your garage.

Another option would be a belt driven generator to top off the battery.


The tech stock people keep talking about hybrid retrofits. I would like to believe that is possible, but I have my doubts.


PHEV retrofit in most cars is tricky due to belt-driven power steering and brake pumps, plus A/C compressors. Converting all this to electric is expensive.

Removability is a two-edged sword. These packs are worth $1000 each, tempting for theives. Lugging a couple 11 kg casettes up to your flat for recharging would build your biceps, though.


once the chinese start pumping out appropiate batteries and in-wheel motors plus the controllers these conversions will be common. The gas engine will have to keep idling to drive the compressor/steering/AC etc


The chines will have to wait for someone else
to discover and then steal it


I think Herm has just pointed out why conversions won't become common - there are too many cross links in a car.

Better to use the batteries in new cars designed to be hybrids or EVs from the start.

It seems a bit like the idea that you could add a "CCD back" to a 35mm SLR camera - it never happened.

It seemed like a good idea, but the digital camera needed to be built as such from the ground up.

Same with digital cars.

The removable battery pack is is interesting - but as ddw points out, heavy and worth stealing. Once the word got out, it would increase the risk of owning such a car.

It might be easier (and civic minded) to run lockable power outlets down to the kerbside.

It is the sort of thing that a prospective mayor for London might propose (next time around).

Better MPG NOW....Green Tech Later



Conversions seem like a good idea to me and apparently they do work. Obviously not as good as a car like volt designed from the ground up for electric propulsion. Check out


kevin wrote: The chines will have to wait for someone else to discover and then steal it

I hate to burst your racist bubble, but Chinese R&D is moving up fast. The old rules no longer apply.


"The old rules no longer apply."

Good. Maybe they'll overthrow their totalitarian, religion hating, world polluting CCP! Free Tibet!


If car thieves break into a vehicle to steal parts like air bags, you have to wonder about PHEVs in general. If the car has a $10,000 battery pack of any kind, I would not leave it parked on the street.


It's getting closer to a pure EV that could have been solving the range problem all along.

Using roboticlly swappable batteries, in standard size formats, you would exchange them at the station a bit like how we exchange propane bottles. But easier and faster because the process would be automated.


One of the benefits of using batteries for power is that you can charge them at home, or at least at any socket.

The infrastructure is already in place for this kind of charging.

If you go to robotically swapped batteries, you lose all that.

A better idea would be a fast charge at a "gas" station or a slow charge at home or in your work car park.

Plus, you have fewer constraints as to where you can put the batteries in a car (like under the rear seat) - leaving the boot (trunk) available for luggage.


I just checked the Hymotion web to see whether their promised PHEV conversions ‘early 2008’ had arrived. They have! All new website and they take orders for a $10000 conversion of the Prius into a 100 mile per gallon PHEV. See for yourselves

Funny they have not yet announced it at the A123 website. It is kind of important. Maybe they are afraid of annoying GM that they are selling something that make Toyota look that they are first with a PHEV on the US market. Time will tell how well they will sell. I guess Hymotion pray for higher oil prices these days and it seems their prayers are getting heard ;-)


I've been saying for years that PHEV retrofit of existing vehicles is what we should be doing, although with an E-tek 10 kW pancake motor or similar blending power in at the crank.

Removable LiIon storage for PHEVs has been suggested many times before for flat owners etc but was considered only feasible once the batteries are above 300 Wh/kg (such as Electrovaya manganese series).

This pack is at 100 Wh/kg and consumers will likely find the benefit to their commute costs is "outweighed" by the heavy weight of the pack as they lug it up and down the stairs every day.


The ETEK brushed motor has led the way to a newer MARS brushless 3 phase design that replaces it. One of the guys that used to do engineering for ETEK started MARS electric.

Harvey D

Would like to see PHEVs using scalable/modular battery pack. A storage system made up of two to six lightweight plug-in (330+ Wh/Kg) 3 to 4 KWh ($750 to $1000 each) modules or removable battery packs would be more convenient.

A PHEV with variable size storage unit could be reconfigured (by the owner) from a PHEV-10 to a PHEV-60 by adding more battery modules.

People living in flats could carry two of the lower cost lightweight modules for overnight charging. This may get to be more practical as weight is progressively reduced, from 330 Wh/Kg to 660 Wh/Kg.

Of course, PHEV buyers should be able to select various sizes of on-board range extender gensets to suit their needs. The smallest, lightest genset required to keep the vehicle going at 100 Kmh should be sufficient for many. With the proper size battery pack, a very small genset (10 Kwh to 20 KWh) should be enough for most small and/or compact vehicles. People livng in hilly places would plug-in one or two extra battery modules or select the larger genset.

One PHEV model with enough built-in energy storage and generation flexibility could satisfy the needs of many more users.



Don't see any reason why robotically swapped batteries couldn't also be charged at home or from any normal outlet. This would complicate the rental aspect.

Freedom to cram batteries in nooks and carnies is nice and would be lost in a swappable system, but everything has a price.

Way easier to implement then hydrogen and it solves the BEV range issue. But developing and agreeing on standards would take this current government and auto industry at least until hell froze over two or three times.


The industry can set standards. As soon as they see that it is their best interests, they get real cooperative.

"while the 1.4-liter Fabia Greenline version achieves nearly 4.1 L/100km, better than the H4V prototype"

4.1 L/100km is 69mpg, so what's the point in this prototype again?


I guess to prove that it could be done. They power the rear wheels with hub motors, so conceivably the car could run in EV mode. This is one of the advantages of 3 wheelers and rear drive like Aptera. There is no differential, mechanical or electrical to worry about.


Taking your battery with you would be a great security system. . .


After a rash of car stereo thefts the stereos that you can pull out and take in the house with you become popular, but then people get tired of taking them out and putting them back in every day. A heavy battery pack would grow old in a hurry.


"They take about 30 minutes to take a full charge..."
Instead of lugging batteries into your house or insisting on fast changes at a gas (charge) station, why not charge them at the parking lot of any larger store while you're inside shopping?

You are parked for about 30 minutes minimum;

You're already buying something, and the store/ shopping center wants to make sure you can both afford to get there AND leave;

Installing chargers (with pull-out clips, credit card activation, etc) at each individual slip in a parking lot would turn the store's parking lot into a sales area, instead of a cost-center.

It could also be a competitive advantage for the store, since it could be a crucial reason for shoppers in high-density neighborhoods (no garage at home) to choose that shopping center over others without the option.

It MAY also be easier on electric utilities to run extra power lines to shopping centers to handle the load than handling changing load patterns directly within residential neighborhoods, even if only to trickle-charge overnight.

The major retailers (with the help of local electric utilities or independent power producers) are one of the few groups who already have the sizable footprint and the distribution of locations necessary to present a totally post-petrol alternative to the oil companies' obsession with hydrogen or anything else they can continue to sell and control from their corner stations.


In the early 90s, Fry's electronics had charging stations for EVs in the parking lots in Sunnyvale, California, the SFO Bay area Silicon Valley. There were lots of techno geek engineers with money to but the EVs, so it was a pretty safe bet.

They have pay pass transponders for toll roads. The same thing could be done for charging stations. With inductive pads you do not even need to plug it in, just park it. The car and station communicate, transact and charge. When you get back you have enough energy for the rest of your errands.

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