Microhybridization at 48v. What is a "micro-hybrid" car?

Microhybridization at 48V with the Mercedes Benz W222

The latest technical advance presented and already marketed in the automotive sector is the 48v microhybridization of vehicles such as the Mercedes-Benz W222, equipped with an electrical system attached to the thermal block that reduces fuel consumption and direct emissionsyes This technology is supposed to be an intermediate chapter between thermal engines and a not so distant future that passes through the generalization of electric motors. In fact, more and more countries have set a deadline for the commercialization of vehicles powered by internal combustion engines.

This microhybridization at 48v also represents the beginning of a radical change in terms of the way we Europeans will drive or, with the autonomous vehicle at the door, as they say, simply to get around. Logically, this new form of mobility must be introduced progressively both for the study of its social acceptance and for the economic limitations that the development of these new and complex technologies implies for manufacturers.

The electric vehicle in the Spanish market

Sales of electric and/or plug-in hybrid vehicles increase in Spain at a dizzying pace: between January and September 2017, sales of this type of car have almost doubled in relation to the same period in 2016. However, if we take into account the total number of registered vehicles, we can see that in our country we are still moving in quite modest figures: 5% of the total sales that goes up to 6% if we focus on tourism vehicles.

Smart Fortwo ED example of a microhybrid car

It is to be hoped that these figures will not be explained without analyzing in detail the offer of electric passenger cars or plug-in hybrids available in our country. In the Spanish market, the cheapest electric car for sale is the Smart Fortwo; its price exceeds 23.300 euros and it is not a car that meets the basic mobility needs of a wide spectrum of the population. As far as passenger cars equipped with plug-in hybrid mechanics are concerned, the cheapest we can find is the hyundai ioniq; With a price close to 30.000 euros, again we are facing a vehicle that is not within the reach of many family economies.

6, 12 or 48v but what is a volt?

I'm very sorry, but the first thing I'm going to do is go back to our high school classes to remember some of the physics of electricity that is essential to better understand the article.

The volt is a electric potential unit which can be defined as the potential difference across a conductor when a current of one ampere consumes one watt of power. From the definition itself, it can be deduced that if we change the electrical potential from 12v to 48v, the system will allow the inclusion of elements that require greater intensity and/or greater power.

I am not going to develop more but if I ask you please to keep the idea that In an electrical system, concepts such as intensity and power must be taken into account..

electrical consumption in a car

The first car I drove, at an age that was as illegal as it was recommended, was a Peugeot 505 from the year 80. This vehicle did not have electric windows, power steering or any of the many comfort features that we nowadays consider essential. Also, with the engine idling, if the high beams or rear window defogger were turned on, the revs would drop a bit and the engine rotation would even become unstable.

Today the vast majority of us we travel in cars with the air conditioning on, we listen to the music that comes from the radio equipment, we guide ourselves with the navigatorWe dream of digital dashboards like the one on the BMW G11, we take the opportunity to charge our mobile phones and use tablets so that the little ones can be entertained and not bother us, something that in my time was "fixed" in another way than not I am going to name so as not to alert social services.

Microhybridization and electrical consumption of cars

Every time we use the car we are demanding a certain amount of energy which is increasing over the years. But it is also that, even when we are not using the car, the vehicle's own system of the vehicle is also consuming electricity: although we do not realize it, the clock continues to keep time, the trip computer keeps the data, the alarm is vigilant … In short, that a modern car consumes electricity all the time, moving and stopped.

Although it had been in use for some twenty years in the automotive world, it was not until the fifties of the last century when the use of a 12v electrical system became widespread to the detriment of systems with only 6v. Since then, there has been no variation in terms of electrical potential, although cars increasingly have a greater number of electronic elements.

Microhybridization at 48v

To explain microhybridization at 48v avoiding an excess of technicalities and/or theoretical classes, I will rely on the example that I particularly consider as the most advanced micro-hybrid thermal block of the moment, the Mercedes Benz M256 engine.

What is microhybridization. Mercedes Benz micro-hybrid engine

This block represents the return of the house of the star to the six-cylinder engines in line after years using vee six cylinder blocks. It has a capacity of 2.987 cubic centimeters and is offered in two versions of 270+16 and 320+16 kilowatts (367+22 and 435+22 horsepower, respectively). In addition, not only are they relatively powerful engines for their displacement, but they are also capable of delivering a torque of 500 and 520 newton meters at 1.600 and 1.800 revolutions per minute, respectively.

This new engine block has a particularity that differentiates it from both the usual thermal blocks and the hybrid ones: It does not have any type of strap or chain but what equips it is a series of small electric motors distributed in different points of the engine and that work thanks to the use of a 48v electrical system. The fact that there are no belts or chains makes the motor run much smoother and quieter.

Starter motor and alternator

This new Mercedes Benz engine has an electrical element located between the engine block and the transmission that is powered by a 48v battery and joins the starter and alternator functions in one device. With regard to its function as a starter motor, this device, which Mercedes Benz calls ISG, rotates the crankshaft at a speed of less than 550 revolutions per minute (idle speed of this engine) before the electric engine management system engine starts the injection process.

Also, also It is responsible for restarting the rotation of the engine when the automatic engine shutdown system is activated when stopped (Start&Stop) and turning the vehicle engine on and off when traveling between 50 and 150 kilometers per hour on a downhill gradient without the driver depressing the accelerator pedal (sailing driving). This last feature would be unthinkable with a 12v electrical system. In fact, the first time I drove a car “under sail” was with a BMW F10 with automatic gearbox by torque converter and although the transmission was disengaged, the engine did not come to a standstill but kept turning at idle speed.

Other functions of This integrated device is to act as an electricity generator to charge the battery, thus replacing the alternator., and to serve as support for the thermal engine during acceleration phases thanks to the 16 kilowatts and 250 newton meters it offers, which allows fuel consumption to be reduced at times when a thermal block requires a greater energy contribution.

supercharging

This M256 block is equipped with a twin-scroll turbo and electric compressor. The turbo is moved by the pressure of the exhaust gases and therefore needs the engine to turn at a certain number of revolutions so that the pressure of the exhaust gases can move the turbine blades, so its efficiency increases as it increases. the rotational speed of the engine. For its part, the compressor moves not by a belt that synchronizes it with the crankshaft but thanks to an electric motor that in three tenths of a second is capable of bringing the compressor from rest to 70.000 revolutions per minute.

Other systems

Another brands that have already opted for 48v microhybridization have been Audi, with many similarities in with the previously mentioned system for Mercedes Benz. However, the premiere of this technology has taken place with the coming-out of the Audi A8 D5. I say this because although it is true that the Audi SQ7 4M used a 48v electric compressor, it actually had a 12v alternator and a 48v transformer to power the compressor's electrical system.

Microhybridization and other systems

The new flagship of Audi, unlike the all road, bets on a technology similar to that of Mercedes Benz in which the 48v electrical system is the main one, leaving the 12v as secondary. However there is a fundamental difference when it comes to starting the engine. While Mercedes Benz entrusts it to the ISG system, Audi has kept a starter to start the engine cranking in low temperature conditions.

Suzuki

A few months ago the Japanese brand developed the SHVS system formed by a small electric motor that assists the thermal block during acceleration and is responsible for restarting the car after the Start&Stop automatic detention system has stopped it. As with Mercedes Benz or Audi, this system is not capable of moving the car by itself, but unlike the previous ones, the SHVS works with the main 12v electrical system.

Hybrids "to use"

There is a basic difference that makes me distinguish the hybrid vehicles we know so far from the microhybrids: in the former, the electric motor is capable of driving the car by itself, while in light hybrids the electric motor only supports the thermal engine in accelerations.

Present or future?

Maybe both. Microhybridization or light hybridization has already arrived. Currently it is only offered in unthinkable vehicles for the vast majority of domestic economies but I dare to say that, as happened with most of the technical advances in the automotive world, will be progressively extended to more popular segments becoming an intermediate system between the internal combustion engine and pure electric motors.

Remember, for example, that in 1989 only 0% of new vehicles registered in Spain had anti-lock brakes, in 6 half of the vehicles registered had it and in 1998 it became mandatory. It's all about time…


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  1.   zaca said

    Sorry but I didn't understand anything...