Top 10 Tech Cars - 2005 TOYOTA VITZ CVT4 Lithium-ion to go

Toyota often tests new and advanced technologies in the Japanese market years before launching them elsewhere. For example, all-wheel drive using only an electric motor to power the rear wheels—soon to be offered on the company's Lexus RX 400h luxury hybrid sport-utility—was first seen on hybrid delivery vans sold only in Japan.

So it's worth looking at one home-market version of the Toyota Vitz, a small four-door hatchback related to the Echo sold in North America. Along with a continuously variable transmission (CVT), the CVT4 model features a 14.4-volt, 12-ampere-hour, four-cell lithium-ion battery pack—the first in a low-cost production vehicle. The battery is part of the car's idle-stop system, which shuts the engine off when the car stops, switching to those battery cells to power the lights, heater, air conditioner, and radio. The cells also restart the engine when the driver releases the brake. Unlike those in a full-hybrid system, the Vitz's batteries don't actually move the car.

The batteries are charged by the engine's alternator as well as through regenerative braking. A motor-driven hydraulic pump keeps pressure on the pulley of the CVT to ensure the car can move away from stops without pause.

The small Vitz batteries store about 180 watthours, equivalent to a couple of laptop batteries. But the resulting fuel economy in highly urban Japanese driving cycles is impressive: 3.92 L/100 km (60 mpg), the highest in Japan for vehicles other than hybrids or microcars.

The Vitz is not the first Japanese-market auto ever to use lithium-ion batteries. The Nissan Almera Tino Hybrid was powered by a 1.8-liter, 74-kilowatt (99 horsepower) four-cylinder engine, combined with a three-phase 20-kW electric motor driving a CVT. Its 345-V, 25-kW lithium-ion battery pack lets the electric motor power the vehicle from a stop and at low speeds and also lets it supplement the engine under higher load conditions. Nissan built only 100 Tino Hybrids, however.

Lithium-ion batteries do have some drawbacks. Most use metal-oxide cathodes that are highly flammable when heated. Also, calendar life, as opposed to just accumulated charge-discharge cycles, is a concern for lithium-ion batteries. Still, energy densities of 110 to 130 Wh per kilogram, as compared with, typically, 60 to 70 Wh/kg for nickel-metal hydride, make them extremely attractive to automakers. Last June, Japan's Hitachi, Hitachi Maxell, and Shin-Kobe Electric Machinery Co. announced they had formed a joint venture to make rechargeable lithium-ion batteries specifically for hybrid cars..READ MORE...