Equipped with four roof-mounted batteries, the 7900e has a range of some 20-25km between overhead pantograph charging points distributed along the route in a so-called opportunity charging network developed with either ABB or Siemens.
This system allows the bus to run 24 hours a day; rooftop bars are used for the 3-6 minute recharge. In addition, a four-hour 'battery balance' session is required of every bus once a week. This model is said not to be suitable for overnight depot recharging.
The bus was fitted 35 seats, two double doors, and had a sloping floor and single step to the rear seats to accommodate the rear-wheel-drive powertrain. Apart from the position of the driver’s cab, it is similar in specification to a single-door fleet operating in Gothenberg, Sweden. Volvo makes the powertrain and chassis in Sweden and the body in Poland.
As it was a working demonstration, the short ride given to attendees was notable for its quiet running – the only mechanical sound was the drone of the air conditioning, plus sometimes the brakes.
Expected to run for a 12-15 year operating life, the buses are made more attractive to purchase by Volvo through the battery and maintenance service contracts that it offers.
The model’s first commercial use, as well as the country’s first such network, will begin next year. Transdev Blazefield has bought a fleet of eight for the Harrogate Bus Company, plus three ABB recharging points at the Harrogate bus station, in a project funded by government’s Office for Low Emission Vehicles.
Also at the London event, Volvo demonstrated an autonomous refuse vehicle developed in a Swedish government-funded research project with waste company Renova, and an electric-powered digger.