Warm­ing to lithium-ion, Toy­ota charges up its bat­tery op­tions Li-ion bat­ter­ies of­fer Toy­ota more ‘green’ car op­tions

Kuwait Times - - TECHNOLOGY -

En­gi­neers at Toy­ota Mo­tor Corp say they have tamed volatile lithium-ion 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 Co 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-be­launched 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 60 kms (37.3 miles) when fully charged be­fore the gaso­line en­gine kicks in. Be­cause of dif­fer­ent method­ol­ogy in mea­sur­ing a car’s elec­tric mode range, the Prime’s 60 km range will be listed in the United States as around 25 miles (40.2 kms).

“Safety, safety, safety”

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 kilo­me­ters,” 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,” he told Reuters.

Toy­ota has mainly used the more ma­ture nickel-metal hy­dride bat­ter­ies to power the mo­tor in the con­ven­tional Prius, widely re­garded as the fore­fa­ther of the ‘green’ car, though it did use some lithium-ion bat­ter­ies from 2009 in its first plug-in hy­brid Prius, around the time the first all-elec­tric cars pow­ered by lithium-ion bat­ter­ies - such as the Tesla Road­ster and Nis­san Leaf - came on to the mass mar­ket.

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 Corp - 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. “State of charge man­age­ment, safety man­age­ment and al­go­rithm devel­op­ment is be­com­ing one of the higher tiers of pro­pri­etary in­ter­nal devel­op­ment,” said Eric Rask, prin­ci­pal re­search en­gi­neer at Ar­gonne Na­tional Lab­o­ra­tory, a US Depart­ment of En­ergy fa­cil­ity out­side Chicago. “It’s very in­ter­nal, very strate­gic, and com­pa­nies are see­ing man­age­ment al­go­rithms as a com­pet­i­tive ad­van­tage.”

Toy­ota has also been able to shrink the size of each cell, for ex­am­ple, clos­ing the dis­tance be­tween the an­ode and cath­ode, where ac­tive ions travel when charg­ing and dis­charg­ing.

This has dou­bled bat­tery ca­pac­ity to around 8.8 kilo­watt hours, while only in­creas­ing the bat­tery pack size by around two-thirds and its weight by a half. Bat­tery ex­perts say lithium-ion bat­tery cell prices have fallen by about 60 per­cent 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, Toyoshima said. Toy­ota de­clined to say more on its costs.

While Toy­ota sees FCVs as the ul­ti­mate ‘green’ car, the United States and China are en­cour­ag­ing au­tomak­ers to make more al­l­elec­tric bat­tery cars as they push al­ter­na­tive en­ergy strate­gies. “De­vel­op­ing lithium-ion bat­ter­ies for both hy­brids and plug-ins will en­able us to also pro­duce all-elec­tric cars in the fu­ture,” said Toyoshima said. “It makes sense to have a range of bat­ter­ies to suit dif­fer­ent pow­er­trains.”—Reuters

CRAN­BERRY TOWN­SHIP, PENN­SYL­VA­NIA: In this Thurs­day, Jan. 16, 2014, file photo, a Gen­eral Elec­tric logo is dis­played at a store. —AP

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