German vehicle-maker Audi is in the middle of testing a 48V lithium-ion system for full electric and mild-hybrid vehicles.
The prototype system allows the battery to offer 0.5 kWhs and a peak output of 13 kW through the use of electromechanical rotary dampers to harness regenerative breaking energy.
The system, called “eROT,” (electromechanical ROTary damper), replaces traditional hydraulic dampers that waste energy in the form of heat.
The 48-Volt electrical subsystem, which includes a high-efficiency, enhanced output generator, is connected to the 12-Volt primary electrical system through a dc converter.
It is believed the system will be ready to serve as the primary electrical system in a new Audi model and feed a high-performance mild hybrid drive by 2017.
Dr. Stefan Knirsch, board member for Technical Development at Audi AG, said: “Every pothole, every bump, every curve induces kinetic energy in the car.
“With the new electromechanical damper system in the 48-Volt electrical system, we put this energy to use.”
The eROT system uses a lever arm to absorb the motion of the axle, and then transmits the energy via a series of gears to an electric motor, which converts it into electricity.
During tests on German roads, researchers found the recuperation output was 100-150-Watts on average.
Mild Hybrid 48V is an option being investigated by OEMs such as Ford, Hyundai, Bentley and Volkswagen, in a bid to meet 2025 and 2030 carbon dioxide emissions regulations as cheaply as possible.
Mercedes-Benz is introducing the 48V system modification on almost its entire range over the next few years— the first in next year’s S-Class model.
The model will use a boost recuperation machine (BRM) – a reversing electric motor integrated directly to the crankshaft to harvest regenerative braking energy.
The use of regenerative energy is nothing new in the automotive industry.
UK-based powertrain producer Controlled Power Technologies (CPT) have shown its switched-reluctance technology could power a 48V lead-carbon system in mild hybrid vehicles.
Meanwhile, ADEPT (advanced diesel-electric powertrain) consortium programme is due to demonstrate its advanced mild hybrid technologies with 48V ‘intelligent electrification’ this September.