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“LITHIUM-ION IS SUBJECT TO A LOT OF DEVELOPMENT for next-generation energy storage,” noted Pete Savagian, GM Hybrid Powertrain Systems engineering director. “Several technology options are being presented, all by serious players trying to capture what they think is a growing business, but not all of these technologies are fully proven, nor is there evidence from all of them of sufficient capacity to service all hybrid vehicles. The suppliers are working to establish credibility.”

Savagian said GM (www.gm.com) has many different batteries under test, though most of its testing is done by the United States Advanced Battery Consortium (www.uscar.org), which includes the U.S. Department of Energy (www.doe.gov) as well as Daimler-Chrysler (www.daimlerchrysler.com), Ford (www.ford.com) and General Motors.

Although the size and cost of NiMH batteries could bear improvement, according to Savagian, especially considering the run-up in the price of nickel within the past few years, he said NiMH batteries are sufficient for near-term hybrid vehicle requirements due to the proven durability of NiMH and current suppliers' high-quality production capabilities. NiMH battery makers include Cobasys (www.cobasys.com), Matsushita Battery Industrial Co. Ltd. (http://panasonic.co.jp/mbi/en/) Panasonic EV Energy (www.peve.panasonic.co.jp/) and Sanyo Electric Co. Ltd. (www.global-sanyo.com).

Battery makers Johnson Controls (www.johnsoncontrols.com) and Saft (www.saftbatteries.com) have joined forces to supply NiMH and Li-ion batteries for current and future-generation hybrid vehicles (Figure 1). Last summer, the USABC awarded Johnson Controls-Saft Advanced Power Solutions a 24-month contract to develop Li-ion batteries for hybrid vehicles. The firms will supply cell modules that can be tested for abuse tolerance, pulse power, calendar life, and cycle life.

In September, Johnson Controls-Saft Advanced Power Solutions was awarded a Li-ion battery development contract from a major vehicle manufacturer.

The first Li-ion-equipped vehicles may go into production as early as 2008, according to Dave Hermance, executive engineer for advanced technology vehicles at Toyota's Technical Center (www.toyota.com). Migration from NiMH to Li-ion is likely to occur over a decade, as happened in consumer electronics applications. “The issue is durability,” he said. “A consumer product may be designed to last three years, but a battery in a hybrid vehicle needs to last for the life of the car.” The Toyota Prius II battery stack (Figure 2) consists of 38 prismatic NiMH modules connected in series.