Exide provides battery systems for urban transport

An Exide Technologies product story

Edited by the Engineeringtalk editorial team Aug 31, 2009

Exide Technologies has provided battery technology for the Ultra personal rapid transit system.

Ultra (urban light transport) has recently started operational testing at Heathrow Airport.

It will use a fleet of 21 low-power driverless electric vehicles on a dedicated guideway route network.

It will initially transfer passengers from the Business Car Park to Terminal 5.

The system began development in 1995 and has had GBP25m worth of investment to date.

Exide became involved in around 1998 and was said to be instrumental in determining the optimum way of ensuring that sufficient capacity was maintained within the batteries.

A partial state-of-charge (PSoC) system was developed and tested at the company's Over Hulton facility.

Advanced Transport Systems (ATS), the developer of Ultra, wanted to use the latest technology - largely derived from the automotive industry - employing off-the-shelf systems and components to ensure an efficient and financially viable transport solution.

Four adult passengers with luggage travel comfortably non-stop to their chosen destination in a personal vehicle.

Sophisticated software and the use of stations separate from the main network ensure that they usually wait no more than 15 seconds for the next vehicle.

The maximum speed is 25mph (40km/h), meaning that journey times are faster and more energy efficient than cars because there is no stop-starting.

Exide has supplied four 45Ah spiral-wound batteries per vehicle.

This battery design gives a greater surface area of positive and negative plate within the cell and is said to be an efficient way of liberating the stored energy from a lead-acid battery.

These AGM batteries suspend the electrolyte in a glass microfibre mat, as opposed to conventional lead-acid flooded batteries where the dilute sulphuric acid acts as the electrolyte.

This technology offers the advantages of high performance and is suitable where a high-power draw is required over a short period of time.

The batteries are maintenance free and vibration resistant and they have a low operating temperature and very few health-and-safety implications, according to the company; no electrolyte is spilt if the battery case is damaged as there is no free electrolyte.

The batteries are mounted in the rear of the vehicle and will be partially recharged each time it stops to collect passengers.

Occasionally, the batteries will be given a full recharge when required and when it is convenient to do so.

Each vehicle weighs 820kg, is 3.7m long and 1.47m wide and employs a 7kW synchronous AC drive motor.

Guidance is autonomous and sensors along with wireless communications plan the vehicle's journey.

Passengers go to the nearest station to request their journey.

The selection is passed to a central control, which assigns a vehicle and plans the optimal route.

Nigel Harris, product support manager from Exide, said: 'We have been involved with ATS since the early days, advising on battery and charger selection as well as developing new monobloc battery technology to cope with the PSoC regime.

'More recently, we have been involved in developing a special charge profile that will be used to fully recharge the vehicles while they are also subject to alternating standing loads,' he added.