48V Mild-Hybrid

48V Mild-Hybrid technology, or mild hybridization, has established itself as an essential solution for automakers seeking to optimize the efficiency of their internal combustion engines. Simpler and less costly than full hybridization, it delivers significant gains in terms of fuel economy and driving dynamics. Here is a breakdown of an intelligent system that now equips a growing number of new vehicles.

How does a 48V Mild-Hybrid system work?

The core of MHEV technology relies on combining the primary internal combustion engine (gasoline or diesel) with a secondary 48-volt electrical network. This system consists of three key components:

• The belt-driven starter generator (or BSG): This centerpiece replaces the traditional alternator and starter motor. Connected to the engine via a belt, it serves a dual function: starting the combustion engine almost instantly and smoothly, and assisting the engine by providing an extra boost of torque during acceleration phases.
• The 48V battery: This is a small lithium-ion battery, much more compact than those found in hybrid or electric vehicles. Its sole function is to store energy recovered during braking and deceleration phases to power the starter generator.
• The DC/DC converter: This converter bridges the 48V network and the traditional 12V onboard network, which continues to power the vehicle's conventional equipment (headlights, infotainment, etc.).

In practice, during deceleration or braking, the starter generator reverses its operation to act as a generator. It converts the vehicle's kinetic energy (previously lost as heat) into electricity to recharge the 48V battery. This is the principle of regenerative braking. This energy is then reused to assist the engine at low speeds, thereby reducing the amount of fuel required to launch or accelerate the vehicle.

What are the concrete advantages of mild hybridization?

The integration of a 48V Mild-Hybrid system brings several tangible benefits for the driver:

• Fuel savings: By relieving the load on the internal combustion engine, the MHEV system enables a reduction in fuel consumption of up to 10 to 15% in urban driving cycles, where stop-and-start phases are frequent.
• Enhanced driving dynamics: The additional electric torque available instantly eliminates the "turbo lag" effect at low revs and makes acceleration more linear and responsive. Furthermore, restarting via the enhanced Stop & Start system is much faster and more discreet than with a conventional 12V starter.
• "Coasting" mode (or sailing): On certain models, the system can completely shut down the internal combustion engine when the vehicle is traveling at a steady speed (for example on the highway), while maintaining steering and braking assists. The vehicle coasts on its momentum, not consuming a single drop of fuel for several hundred meters.
• Simplicity and transparency: For the driver, everything is automatic. There is no plug to connect; the battery manages itself. The driving experience is identical to that of a conventional internal combustion vehicle, but smoother and more economical.

Mild-Hybrid vs Full-Hybrid: What are the differences?

It is crucial not to confuse mild hybridization (MHEV) with full hybridization (HEV), such as the technology popularized by Toyota. The fundamental difference lies in the ability to drive in 100% electric mode. A Full-Hybrid vehicle features a more powerful electric motor and a larger-capacity battery, enabling it to cover short distances (generally 1 to 3 km) without starting the combustion engine. A Mild-Hybrid vehicle, on the other hand, cannot propel itself using its electric motor alone; the latter merely assists the combustion block. Consequently, mild hybridization is less complex, lighter, and cheaper to produce, which explains its widespread adoption across all market segments.