Paul C. Butler

Lithium battery thermal models

Thermal characteristics and thermal behavior of lithium batteries are important both for the batteries meeting operating life requirements and for safety considerations. Sandia National Laboratories has a broad-based program that includes analysis, engineering and model development. We have determined thermal properties of lithium batteries using a variety of calorimetric methods for many years. We developed the capability to model temperature gradients and cooling rates of high-temperature primary lithium thermal batteries several years ago. Work is now under way to characterize the response of ambient-temperature rechargeable lithium-ion batteries to thermal abuse. Once the self-heating rates of lithium cells have been established over a range of temperatures, the thermal response can be estimated under a variety of conditions. We have extended this process to isolate the behavior of individual battery components and have begun to understand the chemical nature of the species responsible for heat evolution within the cells. This enhanced level of understanding will enable more accurate modeling of cell thermal behavior and will allow model-based design of safer, more abuse-tolerant lithium batteries for electric vehicles (EVs) and hybrid electric vehicles (HEVs) in the future. Progress toward this goal and key information still needed to reach it are discussed.

Test profiles for stationary energy-storage applications

Evaluation of battery and other energy-storage technologies for stationary uses is progressing rapidly toward application-specific testing. This testing uses computer-based data acquisition and control equipment, active electronic loads and power supplies, and customized software, to enable sophisticated test regimes which simulate actual use conditions. These simulated-use tests provide more accurate performance and life evaluations than simple constant resistance or current testing regimes. Several organizations are cooperating to develop simulated-use tests for utility-scale storage systems, especially battery energy-storage systems (BESSs). Some of the tests use stepped constant-power charge and discharge regimes to simulate conditions created by electric utility applications such as frequency regulation (FR) and spinning reserve (SR). Other test profiles under development simulate conditions for the energy-storage component of remote-area power supplies (RAPSs) which include renewable and/or fossil-fuelled generators. Various RAPS applications have unique sets of service conditions that require specialized test profiles. Almost all RAPS tests and many tests that represent other stationary applications need, however, to simulate significant time periods that storage devices operate at low-to-medium states-of-charge without full recharge. Consideration of these and similar issues in simulated-use test regimes is necessary to predict effectively the responses of the various types of batteries in specific stationary applications. This paper describes existing and evolving stationary applications for energy-storage technologies and test regimes which are designed to simulate them. The paper also discusses efforts to develop international testing standards.

Battery evaluation methods and results for stationary applications

Evaluation of flooded lead-acid, valve regulated lead-acid (VRLA), and advanced batteries is being performed in the power sources testing labs at Sandia National Laboratories (SNL). These independent, objective tests using computer-controlled testers capable of simulating application-specific test regimes provide critical data for the assessment of the status of these technologies. Several different charge/discharge cycling regimes are performed. Constant current and constant power discharge tests are conducted to verify capacity and measure degradation. A utility test is imposed on some units which consists of partial depths of discharge (pulsed constant power) cycles simulating a frequency regulation operating mode, with a periodic complete discharge simulating a spinning reserve test. This test profile was developed and scaled based on operating information from the Puerto Rico Electric Power Authority (PREPA) 20 MW battery energy storage system. Another test conducted at SNL is a photovoltaic battery life cycle test, which is a partial depth of discharge test (constant current) with infrequent complete recharges that simulates the operation of renewable energy systems. This test profile provides renewable system designers battery performance data representative conditions. This paper describes the results of these tests to date, and include analysis and conclusions.

Battery energy storage and superconducting magnetic energy storage for utility applications: A qualitative analysis

This report was prepared at the request of the US Department of Energy`s Office of Energy Management for an objective comparison of the merits of battery energy storage with superconducting magnetic energy storage technology for utility applications. Conclusions are drawn regarding the best match of each technology with these utility application requirements. Staff from the Utility Battery Storage Systems Program and the superconductivity Programs at Sandia National contributed to this effort.

Reliability of valve-regulated lead-acid batteries for stationary applications.

A survey has been carried out to quantify the performance and life of over 700,000 valve-regulated lead-acid (VRLA) cells, which have been or are being used in stationary applications across the United States. The findings derived from this study have not identified any fundamental flaws of VRLA battery technology. There is evidence that some cell designs are more successful in float duty than others. A significant number of the VRLA cells covered by the survey were found to have provided satisfactory performance.

Performance of valve-regulated lead-acid batteries in real-world stationary applications — utility installations

A multi-phase project to investigate the reliability of valve-regulated lead-acid (VRLA) batteries in the field has been conducted by US industry and government research organizations. The focus of the study has been to characterize the relationships between VRLA technologies, service conditions, performance, and field failures. Two surveys were conducted: one of VRLA end users, and the other of VRLA manufacturers. Data from end users were obtained for over 56,000 telecom and utility installations representing over 740,000 cells. Seven manufacturers participated in the study. Preliminary correlations between utility end-user data, manufacturer information, and battery reliability have been developed and will be reported. Data for telecommunications installations will be reported in a separate publication when completed.

International Lead Zinc Research Organization-sponsored field-data collection and analysis to determine relationships between service conditions and reliability of valve-regulated lead-acid batteries in stationary applications

Abstract The International Lead Zinc Research Organization (ILZRO), in cooperation with Sandia National Laboratories, has initiated a multi-phase project with the following aims: to characterize relationships between valve-regulated lead–acid (VRLA) batteries, service conditions, and failure modes; to establish the degree of correlation between specific operating procedures and PCL; to identify operating procedures that mitigate PCL; to identify best-fits between the operating requirements of specific applications and the capabilities of specific VRLA technologies; to recommend combinations of battery design, manufacturing processes, and operating conditions that enhance VRLA performance and reliability. In the first phase of this project, ILZRO has contracted with Energetics to identify and survey manufacturers and users of VRLA batteries for stationary applications (including electric utilities, telecommunications companies, and government facilities). The confidential survey is collecting the service conditions of specific applications and performance records for specific VRLA technologies. From the data collected, Energetics is constructing a database of the service histories and analyzing the data to determine trends in performance for particular technologies in specific service conditions. ILZRO plans to make the final report of the analysis and a version of the database (that contains no proprietary information) available to ILZRO members, participants in the survey, and participants in a follow-on workshop for stakeholders in VRLA reliability. This paper presents the surveys distributed to manufacturers and end-users, discusses the analytic approach, presents an overview of the responses to the surveys and trends that have emerged in the early analysis of the data, and previews the functionality of the database being constructed.

Preliminary results of an ILZRO-sponsored field-data collection and analysis to determine relationships between service conditions and reliability of VRLA batteries in stationary applications

The International Lead and Zinc Research Organization (ILZRO), in cooperation with Sandia National Laboratories, has initiated a multi-phase project to characterize relationships between VRLA technologies, service conditions, and failure modes; establish the degree of correlation between specific operating procedures and premature capacity loss (PCL); identify operating procedures that mitigate PCL; identify best-fits between the operating requirements of specific applications and the capabilities of specific VRLA technologies; and recommend combinations of battery design, manufacturing processes, and operating conditions that enhance VRLA performance and reliability. In the first phase of this project, Energetics Incorporated is identifying manufacturers and users of VRLA batteries for stationary applications; conducting a confidential and anonymous survey of battery manufacturers and users regarding service conditions of specific applications and performance records for specific VRLA technologies; constructing a database of the service histories; and analyzing the data to determine trends in performance for particular technologies in specific service conditions. ILZRO plans to make the final report of the analysis and a version of the database available to ILZRO members, participants in the survey, and participants in a follow-on workshop for stakeholders in VRLA reliability. This paper presents the actual surveys distributed to manufacturers and end-users; discusses the analytic approach; reviews the preliminary results of the survey analysis; and provides a preview of the functionality of the database being constructed.