Audi can look back on over 20 years of experience in hybrid technology. The first generation of the Audi duo had its debut as early as 1989 – a concept car based on an Audi 100 Avant. A five-cylinder gasoline engine drove the front wheels, and a part-time electric motor developing 9 kW (12 hp) drove the rear wheels. Nickel-cadmium batteries served as energy stores. Another duo variant based on an Audi 100 Avant quattro followed two years later.
In 1997 Audi advanced to become the first European carmaker to build a limited edition of a hybrid vehicle – the Audi duo based on the A4 Avant. The drive was provided by a 1.9-liter TDI developing 66 kW (90 hp) and a water-cooled electric motor developing 21 kW (29 hp), powered by a lead gelatin battery in the rear. Both units drove the front wheels.
As in the two previous studies, the production duo followed the trend-setting plug-in concept – its battery could be charged from a socket. Its electric motor could also recover energy during deceleration. In electric mode the duo attained 80 km/h (49.71 mph), and a maximum of 170 km/h (105.63 mph) with TDI power. The concept was far ahead of its time – too far for the market.