Vehicle Energy Storage Systems

This section will focus on advanced battery technologies with potential to be fully developed and available for use in Hybrid Electric Vehicles (HEVs), Full Performance Battery Electric Vehicles (FPBEVs) and Plug in Hybrid Electric Vehicles (PHEVs) within the next 5-10 years.

Two of the more important characteristics of batteries are Energy Density (Wh/kg) and Power Density (W/kg). Energy Density is a measure of how much energy a battery can hold. The higher the energy density, the longer the runtime will be. Typical applications are cell phones, laptops, and digital cameras. Power Density indicates how much power a battery can deliver on demand. The focus is on power bursts rather than runtime.

6.8.1.1 Nickel Metal Hydride Batteries (NiMH)

High power NiMH technology for HEVs is now mature and mass manufactured in Japan in plants with capacities up to 500,000 systems annually. High cost remains the greatest challenge for battery and HEV manufacturers, with an estimated cost (price to Original Equipment Manufacturers [OEMs]) of $2,000 for compact and $4,000 for a midsize HEV battery produced at a rate of 100,000 systems per year. These costs appear to account for much of the current price difference between hybrid and conventional vehicles. At a production rate of one million systems, battery costs are projected to drop to $1,300 and $2,500, respectively.

Medium power/medium energy NiMH technology has promise to meet the technical requirements for PHEVs with relatively short (e.g., 10-20 miles) nominal electric range. In mass production, medium power/medium energy NiMH technology's incremental cost over that of HEV batteries, estimated to be about $800-1,200, is probably less than the difference in lifetime fuel costs. However, no substantial efforts to develop or capabilities to fabricate medium power NiMH technology appear to exist.

High-energy NiMH technology was used successfully in FPBEVs manufactured by major automobile manufacturers under the California ZEV program. However, energy density is fundamentally limited and marginal for FPBEV applications, and costs remain as high as or higher than in 2000 and are unlikely to decline. High-energy NiMH technology for possible FPBEV applications does not appear to have advanced in recent years.

6.8.1.2 Lithium Ion Batteries (Li Ion)

Li Ion batteries are making impressive technical progress worldwide especially with regard to calendar and cycle life and safety, the areas of special concern for automotive applications. Promising new materials and chemistries are expanding the capabilities and prospects of all Li Ion technologies.15

15 More than half the world's reserves of lithium are located high in the Andes, in a remote corner of Bolivia and there are indications that the country may resist efforts to allow outsiders to control the production. Therefore there has been speculation that shortages may occur as early as 2015 unless other sources are found or an accommodation can be made with Bolivia.

High power Li Ion technology for HEVs appears close to commercialization. A variety of materials, manufacturing techniques and companies are competing to achieve the performance and cost goals for this established battery application which increases the probability of technical and market success. Importantly, for HEV applications Li Ion batteries have potentially lower cost than NiMH because they promise to deliver the required power with smaller capacities and lower specific cost.

Medium energy/power Li Ion technology has sufficient performance for PHEVS and small FPBEVs, and it can be expected to meet the life requirements for FPBEVs. Recent test results indicate good potential to also deliver the very demanding cycle life for PHEVs. The projected costs for shorter-range PHEV Li Ion batteries are about $3,500-4,000 in mass production; this is generally less than the fuel cost savings expected over the life of the vehicle. Low volume cell production and prototype battery fabrication is underway in Asia and Europe, and limited fleet demonstrations are underway or planned.

High energy Li Ion technology has sufficient performance for small FPBEVs, and good potential to meet all performance requirements also of midsize and larger FPBEVs with batteries of modest weight (e.g., less than 250-300 kg). Cell and battery technology designed for these applications are likely to also meet cycle life goals. However, battery cost remains high even in mass production, well in excess of expected lifetime fuel cost savings. While high energy Li Ion technology probably will benefit from general progress in Li Ion technology, no efforts seem underway to advance technology designed for FPBEV applications.

Batteries assembled from large numbers (typically, 5,000 or more) of small, high energy Li Ion cells mass-manufactured for laptop computers and other electronic applications are now being used in FPBEVs (and PHEVs) fabricated on a small scale. However, such small-cell batteries, although providing early opportunities to demonstrate the technical capabilities of PHEV conversions and modern FPBEVs, have inherently high costs and uncertain calendar and cycle life.

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