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Volvo Group Introduces Heavy-Duty Hybrids

Volvo’s heavy hybrids.

The Volvo Group has unveiled a prototype hybrid system for heavy-duty vehicles (buses and trucks) which promises fuel savings of up to 35%, depending upon usage. The company is targeting series production of the hybrid vehicles by 2009.

Designated I-SAM (Integrated Starter, Alternator, Motor), the parallel hybrid system comprises a combined starter motor, drive motor and alternator fit between the clutch and the I-Shift automatic transmission. Effpower bi-polar lead-acid batteries are recharged by the diesel engine and via regenerative braking.

I think hybrid technology is an important step in the long-term vision of becoming oil independent, and with that have sustainable transport in society. We can see hybrids taking off a big part of fuel consumption. Hybrids also lend themselves well for the incoming use of biofuels or alternative fuels to diesel.

I think we see now quite the enhanced interest in reducing fuel consumption. Obviously that is driven by fiscal availability of oil, it is driven by political availability of oil, and it is perhaps above all driven by climate change issues.

—Leif Johansson, President and CEO of Volvo

Volvo’s I-SAM system.

The Powertrain Management Unit (PMU) contains the key logics on gear shifting strategies and power split between diesel engine and electric motor. The high power and torque output from the permanent magnet motor enables the downsizing of the diesel engine.

The electric traction motor provides all-electric acceleration from stop as well as power assist to the diesel engine, as well as stop-start and idle-stop functionality. Auxiliary functions such as the servo pump and AC compressor are driven electrically in the hybrid truck instead of by the diesel engine.

The battery system for the hybrid uses bi-polar lead acid technology from Effpower, a Swedish company in which Volvo has a 45.8% interest.

Monopolar versus bi-polar.

Many lead-acid batteries today are monopolar—a configuration in which a large number of plates can be stacked in every cell, increasing the capacity of the battery, with cells serially coupled to increase voltage.

Since the current in a monopolar battery is introduced in one post in the upper end of the battery and leaving via another post adjacent to the first one, high currents will be unevenly distributed over the electrodes with maximum current flowing close to the posts.

The bipolar lead-acid battery uses a stack of serially coupled bipolar electrodes. Each such electrode, except the ones at the ends, has one side of a conducting partitioning wall covered with porous lead, which is the negative side of the bipolar electrode, and the other side (the positive), covered with porous lead dioxide.

Because current can pass only through the end electrodes, it flows perpendicular to all electrode surfaces, efficiently utilizing all active materials with a minimum of internal resistance.

Effpower designed its bi-polar batteries specifically for use in hybrid electric vehicles. The system are characterized by:

  • 800 W/kg discharge—about double that of advanced lead-acid batteries, and approaching the low-end of NiMH systems, but at a much lower cost

  • A cost of about US$10/kW in high volume, compared to $8/kW for conventional lead acid systems and about $50/kW for NiMH

  • Very high cycling ability: more than 500,000 shallow cycles

Bi-polar lead-acid technology has been under investigation for more than a decade by different researchers and companies. The European Union had funded a specific research project on the subject: Bipolar Lead Acid Power Source For Hybrid Vehicles (BILAPS).




I think large commercial vehicles and trucks/SUVs are a much better use of hybrid technology as the average familly car does not use anything like as much fuel.


Hey James, although they use more gas than regular cars, there are a million more cars on the road than large vehicles. Common man, where do you live?



Don't take offense at being called a common man, I consider myself one too. The fact that there are more cars than large vehicles reinforces James' point even more. The expense of fitting millions of cars with control systems and batteries will not be small. But how about fitting the UPS fleet? I think the right technology might have a very quick payback for them, whereas a soccer mom might have to drive the lifetime of the car to see the cost savings. Sure there are other considerations, but trying to consider everything hurts my head, so I just keep score by looking at cost savings.

Ultimately it would be nice to have every vehicle fitted, but it makes sense to develop the technology where it is most suitable.



My guess is that Richard meant "come on, man". It's all good.


I think Lithium batteries are the solution to bipolar batteries.


I'm taking it the guy mean 'come on man'. Haha.

Near where I grew up is the heaviest used bit of road by HGVs in europe.
Like Jrod says, the cost per unit to a large fleet would be easy to take than for the average driver.


It has a clutch and an automatic transmission? What's up with that?


i guess the electric motor helps shift the gears? syncing it like GM two mode hybrid. At least these new generation lead acid batteries can last a very long time if taken care properly.

Rafael Seidl

(a) Some 80% of all freight in Europe is transported by trucks, because of technical incompatibilities between the national railway systems. Therefore, improving truck fuel consumption has a much bigger impact here than in the US, both economically and in terms of environmental parameters.

(b) Hybrids are generally thought to bring benefits in urban stop-and-go traffic. This is because a car engine is typically operated in (low) partial load where internal friction sharply cut fuel efficiency.

Heavy duty truck engines spend most of their life near their torque limit. Adding a hybrid electric motor saves fuel by recuperating energy on descents and time (= money) due to more rapid ascents. This is why the power rating of the batteries matters more than their capacity.

Of course, like cars, hybrid trucks also save fuel in traffic jams. Another benefit is reduced emissions during transients, because the electric drive can reduce torque demand dynamics on the diesel engine.

(c) Li-Ion batteries will make sense for cars. In an HDV, battery weight and acceleration performance are far less critical than battery cost and life expectancy - return on investment is the top priority, environmental benefits a distant second. I just hope Volvo is prepared to accept the recycling burden of its lead-acid design.

(d) Some automatic transmissions also feature a clutch. It lets them bypass the wasteful torque converter except in first gear and during gear changes. Fuel economy then becomes comparable to a manual transmission. Moreover, recuperative braking reduces the load on the retarder, which typically uses the transmission fluid. In combination, due to lower average temperatures, that fluid will last longer.


Hi Marc. The I shift transmission is NOT an automatic as you find in your car. infact it is a manual gearbox, with a clutch but NO clutch pedal or shifter. The gearbox is airshifted. The control unit selects rev range, clutch in, selects gear, clutch out and sets correct revs in the same time you could push the clutch in. you can select gears from a control lever or allow fully automatic control. Developed due to the lack of experienced drivers in Europe.


Great conversation, all. The clutch can be used for a number of functions with the I-SAM. IF there is another clutch downstream the I-SAM motor can be spun to high rpm then an "inertial start" can occur by closing the upstream clutch. This allows the I-SAM to start the engine without sizing the motor to produce huge starting torque. Also, if the I-SAM motor is large enough, it can propel the truck at low loads without running the diesel. Cheers.


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