24 July 2008
At the British International Motorshow in London, Land Rover presented a diesel hybrid vehicle featuring the new Electric Rear Axle Drive (ERAD) system. Based on the Freelander 2 model, the concept is a parallel hybrid designed to reduce CO2 emissions by 20% while enhancing the all-terrain capability of the vehicle.
The hybrid can be driven by the diesel engine, by electric power only, or in combination of both modes. The ERAD unit, mounted in the rear axle, includes a brushless motor capable of 25 kW continuous power, with a peak of 35 kW. The maximum torque of 200 Nm, available from rest, is a source of strong low-speed performance ideal for all-terrain vehicles.
A Haldex coupler unit is integrated with the ERAD, which allows the diesel engine to be de-coupled from the rear axle for front-wheel drive only. By leaving the coupler closed during periods of electric-only driving, torque can be transmitted from the electric motor to all four wheels. The ERAD also provides regenerative braking, with the brushless motor operating as generator.
The ERAD system includes the Crankshaft Integrated Starter Generator (CISC)—a second brushless electric motor/generator, which starts the diesel engine whenever required (including stop-start functionality), and also functions as a generator. The CISC, operating at high speed, can restart the engine in only 400 milliseconds.
The ERAD Hybrid uses a Lithium NanoTitanate battery that produces 288 V and can accept a high-energy fast charge. The specific power-to-weight ratio is 2500 W/kg, compared to 1400 W/kg for a NiMH battery.
The Diesel ERAD Hybrid was developed as part of a multi-million-pound project supported by the UK Government’s Energy Saving Trust, under the low carbon research and development program.
Source: Land Rover, ATZ