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Engineers at Toyota Motor Corp say they have tamed volatile lithiumion battery technology, and can now safely pack more power at no significant extra cost, giving the Japanese automaker the option to enter the growing all electric car market.
While rivals including Tesla Motors and Nissan Motor Company began adopting lithium-ion battery technology nearly a decade ago, Toyota has largely held back due to concerns over cost, size and safety.
Lithium-ion batteries can be unstable and have been blamed for incendiary Samsung smartphones and smoking Dreamliner airplanes. Having Toyota endorse lithium-ion will be a fillip for the developing technology, and gives the automaker the option to produce for an all-electric passenger car market which it has avoided, preferring to put its heft behind hydrogen fuel-cell vehicles (FCVs).
Toyota says its Prius Prime, a soon-to-be-launched plug-in electric version of the world’s top-selling gasoline hybrid, will use lithium-ion batteries, with enough energy to make the car go around 60km when fully charged before the gasoline engine kicks in.
Many lithium-ion car batteries use a chemical combination of nickel, cobalt and manganese. These store more energy, take a shorter time to charge, and are considered safer than other Liion technologies.
But they can still overheat and catch fire if not properly designed, manufactured and controlled. “It’s a tall order to develop a lithium-ion car battery which can perform reliably and safely for 10 years, or over hundreds of thousands of kilometres,” said Koji Toyoshima, the chief engineer for the Prius.
“We have double braced and triple braced our battery pack to make sure they’re fail-safe. It’s all about safety, safety, safety.” Toyota’s confidence in its battery’s safety and stability
comes from improved control technology that precisely monitors the temperature and condition of each of the 95 cells in its new battery pack.
“Our control system can identify even slight signs of a potential short-circuit in individual cells, and will either prevent it from spreading or shut down the entire battery,” said Hiroaki Takeuchi, a senior Toyota engineer involved in the development.
Working with battery supplier Panasonic - which also produces Li-ion batteries for Tesla - Toyota has also improved the precision in battery cell assembly, ensuring battery chemistry is free of impurities.
The introduction of even microscopic metal particles or other impurities can trigger a short-circuit, overheating and potential explosion. “The environment where our lithium-ion batteries are produced is not quite like the clean rooms where semiconductors are made, but very close,” Takeuchi said.
Battery experts say increasingly sophisticated systems that can track individual cell conditions are becoming closely-held trade secrets. They also say lithium-ion battery cell prices have fallen by about 60 per cent in five years to around $145 per kilowatt hour as larger-scale production has made them cheaper to make.
Falling battery prices have enabled Toyota to develop its more compact, efficient battery, while also adding more sophisticated controls into its battery pack as technological developments move at a fast pace in the industry.
A smartphone app with the company’s pocket plug-in hybrid (PHV) service on the cockpit of the latest Prius hybrid vehicle was recently shown during Toyota’s ‘connected strategy’ press briefing in Tokyo.
Customers can access the vehicle’s systems using their smartphone, check charge status and operate air conditioning before entering the vehicle, among other functions.
