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Bosch Developing Modular KERS Systems for Range of Motorsport Applications

The KERS flywheel energy storage device can store up to 750 kilojoules of energy. Click to enlarge.

Bosch Motorsport is developing a Kinetic Energy Recovery System (KERS) for use in motor racing. The modular KERS kit covers racing requirements from Formula 1 to series such as the DTM or 24-hour races. Bosch presented the variable, modular KERS kit at the Professional MotorSport World Expo 2008 (11-13 November) in Cologne, Germany.

Hybrid systems by Bosch Motorsport comprise an energy storage system, the electric motor, and the KERS controller, containing the power electronic, battery management, and management system for hybrid and engine functions.

KERS control unit and 60 kW motor. Click to enlarge.

A lithium-ion battery with scalable capacity or a flywheel energy storage device is used for storing energy. The latter can store up to 750 kilojoules (0.208 kWh) of energy. The electric motors weigh between four and eight kilograms with a maximum power level of 60 kW.

Due to its modular structure, KERS from Bosch can be put together individually in terms of weight, robustness, and performance to suit the requirements of the respective race series.

In comparison with the hybrid technology of production vehicles, the concepts for motor racing are considerably more powerful, and at the same time more compact. We are already holding discussions with many teams from various racing series.

—Klaus Böttcher, director Bosch Motorsport

Depending on the specific design, the systems are intended to allow for more overtaking maneuvers using additional power that can be called upon temporarily or even to reduce the number of refueling stops by cutting consumption.

Bosch Motorsport Service is part of the subsidiary Bosch Engineering GmbH, which specializes in engineering services.

The Bosch Group offers a range of electri and hydraulic hybrid systems for commercial and light-duty applications. (Earlier post.)



60 kW (81 hp) from an 8 kg electric motor isn't bad, especially when you realise a typical car's 60 kW gasoline engine weighs over 120 kg!


a 80 hp gas engine would weigh more like 45kg not 120


This is a case where we might get something useful from racing - if they go hell for leather for kinetic energy recovery by whatever means possible, they may well come up with something new.

Hopefully not something unaffordable, or which can only be used in 1 race.



After adding the weight of all essential accessories such as pumps, oil, radiator & liquid, starter, charger, battery, belts, transmission, exhaust system etc the average 80 hp automobile ICE package weights over 250 kg.

An 80 hp e-motor can be wheel mounted (2 x 40 hp) and wouldn't required most of those accessories.

No ICE can drive the wheel with the same power to weight ratio as light weight high performace e-motors and certainly not with the same efficiency.

Healthy Breeze

What about the gyroscope effect of fly wheels? Wouldn't it add weird forces when turning, or (depending on the axis) going up or down hill?

Chrysler had an endurance racer (Patriot?) for the 24 hours of Le Mans a long time ago that was supposed to use some new ultra-high tensile strength fly wheel, but as I recall, they did not finish the race 2 years in a row.

To me it's just a question of the mass of the flywheel to the mass of the car. Let's say a fly wheel weighs 30 Kg and the car weighs 1500 KG. That's a 50:1 ratio. Now let's say the fly wheel spins at an average momentum of 1,000 meters per second. If the car converts all the fly wheel energy into linear momentum, it would at best build up to 20 m/s. It might be better than a supercap for regenerative braking, dunno. I also don't know which is safer in a crash, because they both seem tricky. Even if fly wheels can be made with amorphous iron and spin at 40,000 RPM, when exactly does this get good? When does it store more than a minute or two of acceleration?


If you flip from Le Mans to everyday driving, you get a much simpler problem - the ability to decelerate a 2Tonne car from say 40 mph to 0 and back again, 1 minute later.

Occasionally, you might want to decelerate form 60 mph, but nothing like braking coming into a corner in a race.

Should be easily solvable for normal driving if they make a half decent attempt at a racing situation.

Stan Lass

Re "To me it's just a question of the mass of the flywheel to the mass of the car. Let's say a fly wheel weighs 30 Kg and the car weighs 1500 KG. That's a 50:1 ratio. Now let's say the fly wheel spins at an average momentum of 1,000 meters per second. If the car converts all the fly wheel energy into linear momentum, it would at best build up to 20 m/s. I believe that energy is proportional to speed squared, e.g. it takes 4 times the braking distance to stop from 60 mph as from 30 mph. So, in the example, seems that it should be square root of 50 times 1000 meters/second, or about 130 mph. Stan


To me, Ultracaps make more sense for racing.

All of the vehicles have a minimum weight that they have to meet. Getting them to be lighter than that isn't a problem. Thus, you make the chassis as light as possible and then add ultracaps in to bring the weight up to spec. The ultracaps can also be placed wherever you need them to act as a ballast, something you can't do with a flywheel.

The specific power of that motor seems pretty phenomenal. IMO, the best use would be two of them arranged in such a way to take up the space currently occupied by the differential. That helps isolate them from shock while still doing away with the driveshaft.

Two of them would be 162hp from a 17lb package. That's awesome! Now if we could only get those batteries lighter...


@ Stan Lass

The units for angular momentum of a fly wheel using the MKS System are Kilogram-Meter squared/second.

Please get the units right at least before writing other remarkable nonsense.

Healthy Breeze

I don't think the inverse square law applies to the energy stored in a vaccuum sealed flywheel does it? There's precious little gas to push out of the way, no matter how fast it spins...right?

Henry Gibson

Where money is no object as in racing cars, flywheels made with high performance graphite fiber can produce higher power and store more energy per unit weight than Ultra capacitors and with a much more simple system. High power semiconductors have made both systems possible. Flywheels have an undeserved reputation for being dangerous because of several that have failed when overtaxed. Every automobile engine has a flywheel and few if any have burst because they are operated well within the design specifications. Automobile racing or even ordinary driving is, in and of itself, far more dangerous than any flywheel danger; Cell phone use especially text-messaging will and has caused more man hours lost than any possible use of flywheels.

The balance of a vehicle is not altered by small flywheels, and two operated with reverse rotation have no external effect. One kilogram of car going 100 km per hour has less than 400 joules of kinetic energy, and a one tonne (1000KG) car would have less than 400 kilojoules. The proposed system would store enough energy to get a two tonne car to 100 Kilometers per hour.

Bosch Rexroth has bought the automobile rights to the electric valve hydraulic hybrid technology of Artemis and the question becomes whether it is a more efficient use of the Graphite fibers to build the high pressure air storage tanks for that system than for electric flywheels. In spite of being a Diplom Electro-Engineer, I favor the hydraulic system; it does have electric valves after all. The INNAS floating cup devices have high efficiency without the complications of electric valves.

The Flydrid highspeed wheel and gears might be able to connect to the Artemis fast electric valve technology if someone insists upon hydraulic-flywheel-hybrid tecnology.

The Prius should be converted immediatly to the Bosch flywheels or something similar, and a small ZEBRA battery could give 10 to twenty full electric miles if fully charged and hot, but if cold, it can be ignored for a while. Electro-converters allow the ZEBRA battery to be any voltage, and it should always have a single chain of cells; any number of which can fail and only decrease the performance by a small percentage each.

Two large steel flywheels were used in several Electroloks on the third rail electrified systems of southern England to take freight trains through the necessary gaps in the third rail at full speed or even to pull the whole train out of such a gap after being stopped at a semiphore. These Electroloks ran for many years until being replaced by electro-diesels when they became available. Electro-diesels should have retained the flywheels for better performance.

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