In the world of modern automotive engineering, the pursuit of fuel economy no longer goes only through full electrification. And while batteries and charging cables occupy the headlines, a more discreet, but extremely popular technology has quietly taken over the market. We are talking about MHEV (Mild Hybrid) or the so-called “mild hybrid“. Although built into almost every new model of major European brands, it is still shrouded in mystery for the average driver.
If you think that this is a complex machine that requires special care – you are mistaken. In essence, MHEV is a standard car with an internal combustion engine, reinforced by an intelligent 48-volt electrical network. It is important to clarify right away: this car cannot run on electricity alone. Here, the electric motor is not the main engine, but rather a faithful assistant that "hits a shoulder" to the internal combustion engine at the most critical moments.
What do you gain as a driver? First of all - noticeably lower fuel consumption, especially in the urban jungle, where constant stopping and starting drains the tank. In addition, starting the engine becomes velvety smooth, and during sharp acceleration you will feel that pleasant extra thrust that makes overtaking easier.
The magic of the 48V system is based on the “holy trinity“ of components. The first is the starter-generator (BSG), which not only starts the engine instantly, but also collects energy when braking. The second is the compact 48-volt battery – the energy store of the system. And finally comes the DC/DC converter, which plays the role of a customs officer, transferring energy between the powerful 48V network and the standard 12V installation of the car.
But be careful! No matter how reliable this configuration is, it is not immortal. Most often, it is the starter-generator that causes headaches, as it is subjected to serious mechanical and electrical loads. The converter is no less capricious, which sometimes “gives up the ghost“ due to sudden voltage drops.
And a little trick from the kitchen: the 48V battery itself is actually extremely durable, but it also has its Achilles heel. If the starter-generator fails, the battery stops charging and can fall into a state of “deep coma“ (deep discharge). In such a case, a regular charger will not help you – you will need specialized service equipment to bring the system back to life.