Having become essential to avoid heavy ecological penalties, hybrid technology therefore allows combustion engines to prolong their career a little longer, which is doomed in advance (2035).
Obviously more complex than the 100% thermal car, the hybrid car is also distinguished by the many possibilities it offers in terms of design and technical architectures. There are indeed several possible assemblies, with capacities which are also more or less important, ranging from anecdotal micro-hybridization to the rechargeable hybrid which can exceed 100 km in all-electric mode.
Let's try to stay as clear and simple as possible in order to avoid getting lost, but you'll see that in the end there's nothing very rocket science in this type of technology despite the growing number of solutions offered by brands.
Basic principle
Limit the use of the heat engine
Whether it is rechargeable hybrid or micro hybrid, the principle remains the same for all technologies: namely placing an electric motor connected to the wheels (or to the engine in the case of the MHEV) in order to be able to relieve the heat engine which emits CO2 (and many other things of course). The homologation cycles (WLTP), which determine the ecological bonus, therefore only count the emissions produced at the level of the exhaust and not those which have been produced to recharge the battery (at the level of the power stations in the case of a Plug-in hybrid = Rechargeable).
The objective is therefore to transfer CO2 emissions to power stations (battery charging) and no longer to the automobile.
Recover energy
Being able to recover energy on deceleration (kinetic energy transformed into electricity), the electric motor can therefore serve both as a motor and as an electric generator (thanks to the reversibility of electric motors). Of course, the energy recovered during braking remains very limited and it does not make it possible to collect large quantities of electricity (the more you drive in town the more energy you recover).
Driving modes
The driving modes depend on the type of hybridization we are dealing with. To learn more about these, please see this dedicated article.
The 3 types of hybrids:
micro (12/48V), light (HEV/MHEV) and rechargeable (PHEV)
Whatever the assembly or the architecture, it must first be specified that there are 3 main types of hybrid cars: the micro MHEV (12 to 48V), the mild hybrid HEV and the rechargeable hybrid PHEV.
Micro-hybrid 12 to 48V
It is the assembly that stands out from the others because it is so light that to speak of hybridization is almost an aberration. Indeed, we are talking here more about alternator-starter rather than hybridization (it is the same assembly as the Stop And Start, and therefore it is a reversible alternator which can be used as a generator, starter or more support for the heat engine via the accessory belt).
Here, the electric motor is very small (less than 20 hp generally) with a battery that is just as small (less than 0.8 kWh).
The electric motor cannot directly drive the wheels, and this is because of two reasons. The first, and I have just said it, its power is so low (12 to 48V only) that it would not be possible.
The other problem, much stronger, is that the combustion engine is here between the electric motor and the wheels... It is therefore impossible to turn the wheels directly by means of the electric motor, because the latter is located at the place of the alternator which is driven by the engine accessories belt.
To put it simply, the electric motor is in a way one of the components of the heat engine, and it only serves here to give it a little force (which is called torque in the jargon) to the heat engine in order to reduce its consumption.
It cannot therefore work alone without the use of a combustion engine.
It's an assembly that is both simple and very economical, so that's why the majority of modern heat engines are equipped with this kind of hybridization.
The fuel economy will not exceed 10%, and it is a question of reducing the figures a little in order to lower the ecological penalties which are incremented from year to year.
Mild hybrid (HEV)
The light hybrid has nothing to do with the micro-hybrid since here we have the possibility of driving in 100% electric by completely dispensing with the combustion engine. It is therefore a "true" hybrid, namely a "full-hybrid".
So here we have two very distinct powertrains: one for the electric and one for the internal combustion engine, each of which can work alone (drive the wheels) without the other getting in the way.
We talk about mild hybrid because the size of the battery remains modest, namely a value between 1 and 3 kWh, which generally allows electric driving between 1 and 3 km, knowing that it is very rare to do more than 500 meter in this mode. The voltage is about 200 Volts and the power of the electric motor is around 30 to 80 hp.
Fuel economy can range from 10 to 30%.
Plug-in hybrid (PHEV)
The PHEV plug-in hybrid (P for Plug-in = recharge) uses exactly the same installation as the mild hybrid. The difference here is that the battery is much larger (between 8 and 30 kWh) and is connected to an external port so that it can be recharged via an electrical outlet.
The power of the voltage reaches 400 Volts with engine power ranging from 70 to sometimes more than 200 hp.
The fuel economy can go up to 100% in the case of a fully charged battery over a distance less than the 100% electric range.
HEV and PHEV: the different assemblies
There are a whole bunch of setups that exist for these hybrid technologies, let's see them briefly.
Remember that hybrids are systematically associated with automatic gearboxes for practical reasons (the electric motor must not be able to be disengaged by the user, and it is the electronics which must be able to choose which motor is linked to the wheels according to the modes driving, which makes things difficult with a mechanical clutch).
Motor in clutch/converter
This is the most widespread solution because it adapts very well to existing 100% thermal solutions. Indeed, there are only a few modifications to be made, namely electrifying the torque converter (BVA) or the clutch (robotic box).
Examples include the e-Tron / TFSIe, the HYbrid2 from PSA/Stellantis or the EQ from Mercedes. In short, the vast majority of the current offer.
Engine in the box
These are proprietary solutions, ie they are electrified boxes that have been designed by their manufacturer. In this case there is generally no clutch or converter between the thermal unit (engine) and the hybrid device (which takes the place of the gearbox).
These solutions arrived after the one described above, because it is not only a question of adding an electric motor to the traction chain but of completely reviewing the architecture of the box (by integrating an electric motor, or rather two in general: one that serves as a generator and the other as a motor, although the two can sometimes reverse their roles...).
The diversity of assemblies leads to very different solutions in terms of logic. While sometimes it's just classic electrified gearboxes (with parallel trains), other times it goes as far as systems that are similar to a generator that only recharges the battery (the heat engine cannot drive the wheels but only charge the high-voltage traction battery, which itself will then power the electric traction motor).
Examples include Toyota's HSD (original process which brings together the heat and electric motors on a common axis embodied by a planetary gear train), Renault's E-Tech (classic 4-speed gearbox with two electric motors) or the e:HEV which consists of using the internal combustion engine as a simple electric generator.
Electric motor on a different axle
This is the simplest and most understandable solution, namely that here we have a train (= pair of front or rear wheels) driven by the heat engine and a second train driven by an electric motor.
Some cars even go so far as to combine a motor in the converter/clutch + another on the remaining axle, like the Stellantis HYbrid4 for example.
Which technology to choose?
Not all shoes fit all feet, and that's a bit of a problem here when choosing a hybrid technology...
However, it seems obvious to me that the rechargeable hybrid is the most problematic technology, despite the fact that it is the one that is the most popular in the media and the scales of ecological bonuses.
One thing is certain, however, you will take less financial risk to acquire a micro-hybrid or a light hybrid HEV / MHEV.
Post a Comment