Study adds spark to battery-powered cars

A US study has revealed that batteries used in electric and hybrid cars could have a lifespan of up to 20 years – much longer than car-makers are guaranteeing.

Some brands, including General Motors and Toyota, will only guarantee the batteries in their cars for up to eight years.

However, the American Chemical Society paper that investigated the question of battery life in cars only looked at the more expensive lithium-ion units, and not the nickel-metal hydride types used on Australia’s longest-running hybrid car, the Toyota Prius.

“The (lithium-ion) battery pack could be used during a quite reasonable period of time ranging from five to 20 years depending on many factors,” Mikael Cugnet, a project manager at France’s Atomic and Alternative Energy Commission, told the society’s meeting in New Orleans.

“That’s good news when you consider that some estimates put the average life expectancy of a new car at about eight years.” Toyota introduced its Prius hybrid to Australia in 2001, however, since its launch here the car has used the cheaper, less energy-dense nickel-metal hydride batteries in favour of the more expensive lithium-based ones.

Only one model, the recently introduced Prius V petrol-electric hybrid people-mover, uses the more expensive batteries.

Toyota Australia product public relations manager Steve Coughlan said the car-maker had sold more than 50,000 Toyota- and Lexus-badged hybrids in Australia since their introduction more than a decade ago.

“Over the past 11-plus years in Australia – and since 1997 in Japan – these batteries have been proven in terms of reliability,” Mr Coughlan said.

“The durability of the hybrid battery is designed to be consistent with other major driveline components.

“We are aware of many examples of high-mileage hybrids in Australia, including Prius taxis in tropical Queensland that have covered in excess of 500,000km on the original battery – equivalent to more than 25 years of driving by the average Australian,” he said.

However, Dr Cugnet’s study noted that deterioration in lithium-ion batteries was affected most by heat, with temperatures above 30 degrees affecting performance “instantly and even permanently” if it was for an extended period.

Dr Cugnet also said electric vehicle owners needed to closely monitor a battery’s charge in hot weather, as a fully charged battery was “more vulnerable to losing power”.

The study ranked a battery as beyond its useful life after it had lost more than 20 per cent of its original charge capacity.

Nissan’s Leaf electric car came under close scrutiny last year after US owners started to complain about big drops in the lithium-ion battery pack’s ability to hold a charge.

Owners in warmer parts of the US, including Arizona, Texas and California, started noting that their Leaf was losing up to a quarter of its battery capacity in a matter of months.

Nissan Australia has not reported any problems with Australian customers’ cars.

A table at mynissanleaf.com estimating the rate of battery deterioration in Leaf electric cars worldwide predicts that a car driven in Melbourne, Australia will last about 11 years before it falls to 70 per cent of its recharge capacity.

It estimates the Leaf driven in Melbourne would fall to 82 per cent of charge capacity – just above the study’s cut-off of a 20 per cent loss of charge capacity – within five years.

The website also warns to take its battery life predictions “with a grain of salt”.