Economy drive

A retired electrical engineer has revamped his Toyota Prius drive system to improve its fuel economy from the normal 60mpg to 100mpg — with the addition of a Li-ion battery pack and off-the-shelf control technology.

Jim Fell, from Peterborough, said he first had the idea of converting a Prius into a full electrical car in 2005. 'The interesting thing about the Prius was that it could run for a limited period as an electric vehicle,' he said.

The Prius, he explained, works like a traditional car with the addition of an electric motor/generator in the drivetrain. When the driver slows down, the brake pedal puts the 'motor' into generator mode, which charges the battery. At low speeds the motor assists the conventional petrol engine, which decreases fuel consumption.

Fell said the vehicle, along with most modern cars, has a complex electronic control system with CANbus to manage the drive and battery. The operation of the drive is based on the state of charge (SOC) of the battery pack.