Outline of the Presentation

* Introduction and objectives

* Approaches

o USABC

o IEC

o UC Davis

* IEC Committee on testing EDLCs

o Proposed procedures

o Application of procedures and test data

* UC Davis test procedures and data

* Determination of resistance

o Theoretical basis

o Methods

* Summary and modifications to test procedures

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2.

Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Proceedings of the 32nd Intersociety Energy Conversion Engineering Conference, Honolulu, HI, July 27 - August 1, 1997

A spreadsheet model for the analysis of batteries of various types has been developed that permits the calculation of the size and performance characteristics of the battery based on its internal geometry and electrode/electrolyte material properties. The method accounts for most of the electrochemical mechanisms in both the anode and cathode without solving the governing partial differential equations. The spreadsheet calculations for a particular battery design are performed much like a battery test in that the C/3 capacity of the battery to a specified cut-off voltage is determined and then the pulse power capability at a given state-of-charge is determined by finding the maximum current density (A/cm2) for which the cell voltage equals a specified minimum value. For a multi-cell module, the module characteristics are calculated using the cell results and packaging input information. The spreadsheet model has been validated for existing lead-acid (Sonnenschein), nickel cadmium (Saft), and nickel metal hydride (Ovonic) batteries for which test data and internal geometry information are available. Various battery designs were then evaluated using the method to show how batteries having high power densities (greater than 500 W/kg) could be designed. The spreadsheet model permitted the determination of the critical design parameters for high power lead-acid, nickel cadmium, and nickel metal hydride batteries.

In January 2001, the California Air Resources Board adopted significant modifications to the ZEV Mandate. These changes affect the options available to large auto companies marketing cars in California that must meet the requirements of the Mandate starting in 2003. In the new regulations, up to 50% (2% of sales) of the ZEV requirement (4% of sales) may be met with grid-connected, plug-in hybrid vehicles having a 20-mile or longer all-electric range. In addition, city EVs that may or may not be freeway worthy are designated for full ZEV credit and can be used to meet the 4% ZEV requirement. In the case of both types of vehicles, there is much less information available concerning their design, cost, and marketing than for full function electric vehicles (FFEVs) – which have in the past been the focus of meeting the ZEV Mandate. This two-day workshop will consider in-depth how the inclusion of the grid connected hybrids and city EVs in the Mandate may affect how it will be met in 2003-2006. In addition, each of the new technology options will be reviewed in terms of vehicle design, utility, cost, and marketing.

California’s Advanced Clean Trucks regulation requires sales of zero-emission tractor-trailer trucks starting in 2024, increasing to 30% by 2030. Since most of these trucks will travel predominantly on the state’s major highways, a robust network of battery charging infrastructure will be needed along these routes. The California Department of Transportation (Caltrans) maintains an extensive series of roadside rest areas throughout the state that are widely used by long-haul trucks. Providing charging at roadside rest areas, especially those along interstate highways, could help meet the needs of battery-electric tractortrailer trucks making multi-day trips. Thus, Caltrans should consider becoming involved with the establishment of battery charging facilities at its rest areas.

Researchers at the University of California, Davis assessed the possibilities for and barriers to providing charging infrastructure for heavy-duty, long-haul trucks at rest areas in California. This policy brief summarizes the findings from that research and provides policy implications.

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This paper is concerned with batteries for use in plug-in electric vehicles. These vehicles use batteries that store a significant amount (kWh) of energy and thus will offer the possibilities for second-use in utility related applications such as residential and commercial backup systems and solar and wind generation systems. Cell test data are presented for the performance of lithium-ion batteries of several chemistries suitable for use in plug-in vehicles. The energy density of cells using NiCo (nickelate) in the positive electrode have the highest energy density being in the range of 100-170 Wh/kg. Cells using iron phosphate in the positive have energy density between 80-110 Wh/kg and those using lithium titanate oxide in the negative electrode can have energy density between 60-70 Wh/kg. Tests were performed for charging rates between 1C and 6C. The test results indicate that both iron phosphate and titanate oxide battery chemistries can be fast charged. However, the fast charge capability of the titanate oxide chemistry is superior to that of the iron phosphate chemistry both with respect to temperature rise during charging and the Ah capacity retention for charging up to the maximum voltage without taper.

There are a number of possible second-use applications. Some of these applications are closely linked to utility operations and others are connected to commercial and residential end-users. Since the energy storage and power requirements for the end-user applications are comparable to those of the original vehicle applications and would require only minor reconfiguring of the packs, these applications are well suited for second-use. The applications closely related to utility operations do not seem well suited for second-use. Those applications require MW power and MWh of energy storage which are orders of magnitude larger than that of the vehicle applications. The primary barrier to implementation of the second-use is demonstrating the economic viability of the reuse of the batteries in terms of the cost of the batteries to the second owners and a guarantee that the used batteries would have satisfactory calendar and cycle life.