Improvements in hybrid drivetrain technology mean that battery pack life should be the same as the vehicle, and that could mean as long as 15 years, according to Katsuhiko Hirose, project general manager of Toyota’s Power Train Development Centre in Japan.
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Speaking exclusively to just-auto deputy editor Graeme Roberts, Hirose acknowledged a few early production problems with battery packs on early Prius hybrid models sold in Japan in 1997 but said they had been quickly overcome.
The Toyota drivetrain chief said that hybrid technology had advanced far more than he had expected over the last five years.
For example, improvements in current flow management had ensured the batteries were properly discharged and recharged, maximising battery life. “It’s like fully discharging a cellphone battery before recharging it – you get longer ‘talk time’ and more battery life,” Hirose said.
He is particularly proud of the power boost for the latest Prius, being shown to European media today, from 33kW to 50kW without any increase in powerplant size. Such an increase in output from the same size petrol engine takes at least a decade, Hirose said.
He noted that Toyota’s latest Hybrid Synergy Drive powertrain in the new Prius could be combined with a lighter and more efficient gearbox than that used in Honda’s IMA system which used standard drivetrain parts. Current flow had actually been reduced despite the boost to 50Kw which required a smaller and cheaper inverter.
Hirose said the Prius had been increased in size from the C to D segments in response to customer demand but fuel economy had been improved thanks to the new drivetrain and he believes this will be a major selling feature, along with boosted cabin room and the greater flexibility of the rear hatchback in place of the old model’s boot.
Hirose warned that hydrogen fuel cell-powered vehicles would not be practical until a more efficient method of producing hydrogen without CO2 emissions had been developed. It was possible, he said, but not yet commercially viable. The bulk of current hydrogen production is as a by-product of oil or natural gas refining – it’s used as part of a ‘cracking’ process, he explained.
The challenge to powertrain engineers like himself was to keep on reducing CO2 output, Hirose added. The developing world – including China and India – wanted mobility and the world’s car industry was happy to supply it. But, with the world’s car population forecast to double within one or two decades, engineers would have to find ways to at least halve CO2 emissions so the effect on the world environment of the world’s car parc was no worse or even improved.
