What is a mild hybrid?

Audi 48-Volt Mild-Hybrid System — Audi Mild-Hybrid System

A mild hybrid system (typically abbreviated MHEV for Mild Hybrid Electric Vehicle) is the simplest and most basic form of hybrid powertrain found in modern vehicles. A MHEV system combines a conventional internal combustion engine with a small electric motor and a relatively modest battery. Ram’s “eTorque” option is one such system.

What is a mild hybrid?

Elements of an MHEV system include:

Regenerative Braking

Captures energy normally lost as heat during braking and stores it in the battery.

Battery

Most modern mild hybrids use a 48-volt electrical system that is independent of the vehicle’s normal 12-volt setup. This system stores energy collected by the regenerative brakes, and powers the motor which assists in launching the vehicle from a stop. This low-voltage system is much less expensive than that found in most “full” hybrid vehicles.

Motor

The electric motor provides extra torque during acceleration, reducing the load on the engine.

Engine Stop/Start System

Automatically shuts off the engine when the vehicle is stopped (a traffic light, for example) and instantly restarts it using the electric motor when needed. This is smoother than traditional start-stop systems.

Limited Efficiency Gains

Note that, unlike full hybrid systems, a MHEV setup cannot propel the vehicle on its own for any significant distance or at meaningful speeds.

For this reason, economy gains can seem modest, typically in the range of 10-15 percent improvement in fuel economy, versus up to 50 percent for full hybrid systems.

Modest Cost/Luxury Implementation

A typical MHEV system typically costs less to incorporate into a vehicle than does a full hybrid system. For this reason, MHEV systems are popularly found on European luxury vehicles as standard equipment, and are not advertised as hybrid.

Audi, BMW, Mercedes-Benz, Land Rover, and Volvo make use of MHEV systems to improve the fuel economy of their most-popular models.

CG Says:

A mild hybrid is best thought of as an enhanced conventional vehicle with electric boost and smart energy recovery, rather than a true hybrid. It’s a cost-effective way for automakers to meet stricter fuel economy and emissions regulations without costly full-hybrid-system implantation.