Audi is working on a prototype, the “eROT” system, to capture the mechanical energy of a vehicle's suspension and convert it into electricity that could be used to help power accessories.

Diagram of Audi's prototype suspension system. Image credit: Audi.

The system replaces the hydraulic dampers in use in its current vehicles with electromechanical rotary dampers, and swaps out telescopic shock absorbers with horizontally arranged electric motors. “Every pothole, every bump, every curve induces kinetic energy in the car. Today’s dampers absorb this energy, which is lost in the form of heat,” notes Dr. Stefan Knirsch, board member for technical development at Audi. "

To convert the kinetic energy of the suspension's compression and rebound strokes into electricity, a lever arm absorbs the motion of the wheel carrier. The lever arm transmits this force via a series of gears to the electric motor, which converts it into electricity.

Audi says the recuperation output is 100 to 150 watts, on average, during testing on German roads—from 3 watts on a freshly paved freeway to 613 watts on a rough secondary road. Under customer driving conditions, the company says this translates to a CO2 savings of up to three grams per kilometer (4.8 g/mi).

The new eROT technology is based on a high-output 48-volt electrical system. As currently configured, its lithium-ion battery offers an energy capacity of 0.5 kilowatt hours and peak output of 13 kilowatts. A DC converter connects the 48-volt electrical subsystem to the 12-volt primary electrical system, which includes a high-efficiency, enhanced output generator.

Audi says that the promising results achieved in initial tests of the eROT technology make the likelihood of its inclusion in future Audi production models "certainly plausible." The company says the 48-volt system, a prerequisite of the eROT system, has already been green-lighted for use as the primary electrical system on an unnamed new Audi mild hybrid-drive model that will be unveiled in 2017.