Fresh air fare

A California taxi firm is the first business in the US to use electric cars that can run for 100 miles on a single charge.

The company has bought cars that use large-scale lithium-ion batteries, making it the first business to meet California’s standard for emission-free driving — the toughest in the US.

The batteries are produced by Valence Technology for production cars built by Californian manufacturer Phoenix Motorcars. Valence’s business development manager Marc Kohler said that meeting the Californian standard ‘was a driving decision for them to come to us’.

Five of the world’s seven largest car manufacturers are currently working with the company to launch production cars that use its Saphion battery.

Hybrid and battery-powered cars have been slow to win mainstream popularity because the most flexible type of batteries — lithium-ion — can explode. Car manufacturers have been stuck with nickel and lead-acid batteries, which have been largely replaced by lithium-ion batteries in laptops and mobile phones as the latter have higher energy densities.

The Saphion battery uses phosphates rather than toxic heavy metals to reduce the likelihood of it exploding. In safety tests, the US army fired at a Saphion battery and a standard lithium-ion battery of the same size. While the bullets destroyed the Saphion battery, the damage caused to the standard battery was more spectacular.

‘Once one caught fire, it heated up the next,’ Kohler confirmed. ‘It was very fierce.’

Large-scale lithium-ion batteries are still more expensive to run than nickel and lead-acid ones, which cost just 10 cents per W/h to run. Large-scale nickel metal hydride batteries cost 60 to 70 cents per W/h, with lithium-ion batteries 80 to 90 cents. ‘There is a 10–15 per cent premium to nickel batteries and quite a bit more for lead acid,’ Kohler confirmed.

Lead-acid batteries, however, are heavier and less flexible than either lithium-ion or nickel metal hydride units. Lithium-ion batteries last 10 years — a lifespan that can only be equalled by the best nickel metal hydride batteries. A lead-acid battery, by comparison, will probably have to be replaced twice during a 10-year-period.

According to Kohler, the running costs of Saphion batteries will drop to those of metal hydride batteries within 12 months. ‘Over the longer term, we can compete against lead acid,’ he said.

The availability of lithium-ion batteries will improve over the next few years as the 75 companies currently developing Valence’s battery bring products to market.