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The potential for operating automotive battery packs at high upper cutoff voltages (UCV) has been explored using preliminary data on eight cathode materials. The pack level energy density, specific energy, and battery cost are calculated using the spreadsheet tool BatPaC. The tool used experimental data for some cathode materials such as the lithiated oxides of nickel manganese cobalt (NMC), nickel cobalt aluminum (NCA), layered lithium- and manganese-rich nickel manganese cobalt (LMRNMC). The half-cell data were obtained at UCVs between 4.2 and 4.7 V vs. Li/Li+. The experimental data showed LMRNMC with the highest lithiation capacity gain, increasing from 176 mAh·g−1 at 4.2 V to 260 mAh·g−1 at 4.7 V; this advantage is partly offset by its lower average voltage. Assuming optimized cell materials/design and an area-specific impedance of 12 Ω⋅cm2 for all the materials, the BatPaC results indicate that the specific energies or energy densities of the battery electric vehicle (BEV) and plug-in hybrid electric vehicle (PHEV) battery packs with the LMRNMC and NMC cathodes can exceed 180 (BEV) and 160 (PHEV) Wh·kg−1 at UCV>4.6 V vs. Li/Li+. The costs of these battery packs are lowest at UCV = 4.7 V (vs. Li/Li+); estimated at 135–145 and 210–220 $·kWh−1 for BEV and PHEV packs, respectively.

The introduction of Li-ion batteries for grid applications has become evidence as the cost per kWh is continuously decreasing. Although the Li-ion battery is a mature technology for automotive applications and portable electronics, its use for stationary applications needs more validation. The Li-ion technology is considered safe enough for grid storage application, but its lifetime is generally evaluated to be around 10 years. Higher market penetration will be achieved if a longer lifespan could be demonstrated. Therefore, aging evaluation of the batteries becomes crucial. In this paper we investigated the effects of aging after a three years' standby field deployment of a 250 kW/500 kWh Li-ion battery integrated with the grid and solar farm under the harsh climate conditions of Qatar. The development of tools for acquisition and analysis of data from the battery management system (BMS) allows the assessment of the battery performance at the battery stack, string and cell levels. The analysis of the residual capacity after aging showed that the stack suffered from a low decrease of capacity, whereas some inconsistencies have been found between the strings. These inconsistencies are caused by misalignment of a small number of cells that underwent self-discharge during standby at high state of charge.

A thermal management system is necessary to control the operating temperature of the lithium ion batteries in battery packs for electrical and hybrid electrical vehicles. This paper proposes a new battery thermal management system based on one type of phase change material for the battery packs in hybrid electrical vehicles and develops a three dimensional electrochemical thermal model. The temperature distributions of the batteries are investigated under various operating conditions for comparative evaluations. The proposed system boils liquid propane to remove the heat generated by the batteries, and the propane vapor is used to cool the part of the battery that is not covered with liquid propane. The effect on the thermal behavior of the battery pack of the height of the liquid propane inside the battery pack, relative to the height of the battery, is analyzed. The results show that the propane based thermal management system provides good cooling control of the temperature of the batteries under high and continuous charge and discharge cycles at 7.5C.

The design and optimization of the battery pack in an electric vehicle (EV) is essential for continued integration of EVs into the global market. Reconfigurable battery packs are of significant interest lately as they allow for damaged cells to be removed from the circuit, limiting their impact on the entire pack. This paper provides a simulation framework that models a battery pack and examines the effect of replacing damaged cells with new ones. The cells within the battery pack vary stochastically and the performance of the entire pack is evaluated under different conditions. The results show that by changing out cells in the battery pack, the state of health of the pack can be consistently maintained above a certain threshold value selected by the user. In situations where the cells are checked for replacement at discrete intervals, referred to as maintenance event intervals, it is found that the length of the interval is dependent on the mean time to failure of the individual cells. The simulation framework as well as the results from this paper can be utilized to better optimize lithium ion battery pack design in EVs and make long term deployment of EVs more economically feasible.

Battery degradation strongly depends on temperature, and many plug-in electric vehicle applications employ thermal management strategies to extend battery life. The effectiveness of thermal management depends on the design of the thermal management system as well as the battery chemistry, cell and pack design, vehicle system characteristics, and operating conditions. We model a plug-in hybrid electric vehicle with an air-cooled battery pack composed of cylindrical LiFePO4/graphite cells and simulate the effect of thermal management, driving conditions, regional climate, and vehicle system design on battery life. We estimate that in the absence of thermal management, aggressive driving can cut battery life by two thirds; a blended gas/electric-operation control strategy can quadruple battery life relative to an all-electric control strategy; larger battery packs can extend life by an order of magnitude relative to small packs used for all-electric operation; and batteries last 73–94% longer in mild-weather San Francisco than in hot Phoenix. Air cooling can increase battery life by a factor of 1.5–6, depending on regional climate and driving patterns. End of life criteria has a substantial effect on battery life estimates.

Lithium(-ion) batteries are and will be the battery technology of choice for a wide range of applications – including electric vehicles – for several years to come. Nonetheless, to foster the transition from combustion engine vehicles to a fully electrified transportation, further progress is needed. In this regard, the annual International Conference on Advanced Lithium Batteries for Automobile Applications (ABAA) targets the intensive exchange of the involved industrial and research entities to jointly ensure the further progress of this technology. During the past meeting, ABAA-10, held in October 2017 in Chicago, IL, USA, representatives of China, Germany, Japan, and the USA provided a comprehensive overview of the current and future battery R&D activities in their countries, depicting a highly insightful survey about partially concurrent, partially complementary research and funding strategies. The given presentations are provided in the Supplementary Material for this Special Perspective, while this perspective article may serve as brief introduction to the general development in the field concerning the overall EV sales and common considerations regarding future material developments.

Highlights:\ud \ud • Experimental evaluation of energy imbalance within parallel connected cells.\ud • A validated new method of combining equivalent circuit models in parallel.\ud • Interdependence of capacity, voltage and impedance for calculating cell currents.\ud • A 30% difference in impedance can result in a 60% difference in peak cell current.\ud • A difference of over 6% in charge throughput was observed during cycling.\ud \ud Abstract:\ud \ud Variations in cell properties are unavoidable and can be caused by manufacturing tolerances and usage conditions. As a result of this, cells connected in series may have different voltages and states of charge that limit the energy and power capability of the complete battery pack. Methods of removing this energy imbalance have been extensively reported within literature. However, there has been little discussion around the effect that such variation has when cells are connected electrically in parallel. This work aims to explore the impact of connecting cells, with varied properties, in parallel and the issues regarding energy imbalance and battery management that may arise. This has been achieved through analysing experimental data and a validated model. The main results from this study highlight that significant differences in current flow can occur between cells within a parallel stack that will affect how the cells age and the temperature distribution within the battery assembly.

Accurate state monitoring is required for the high performance of battery management systems (BMS) in electric vehicles. By using model-based observation methods, state estimation of a single cell can be achieved with non-linear filtering algorithms e.g. Kalman filtering and Particle filtering. Considering the limited computational capability of a BMS and its real-time constraint, duplication of this approach to a multicell system is very time consuming and can hardly be implemented for a large number of cells in a battery pack. Several possible solutions have been reported in recent years. In this work, an extended two-step estimation approach is studied. At first, the mean value of the battery state of charge is determined in the form of a probability density function (PDF). Secondly, the intrinsic variations in cell SOC and resistance are identified simultaneously in an extended framework using a recursive least squares (RLS) algorithm. The on-board reliability and estimation accuracy of the proposed method is validated by experiment and simulation using an NMC/graphite battery module.

We conduct a techno-economic analysis of Li-ion NMC-G prismatic pouch battery and pack designs for electric vehicle applications. We develop models of power capability and manufacturing operations to identify the minimum cost cell and pack designs for a variety of plug-in hybrid electric vehicle (PHEV) and battery electric vehicle (BEV) requirements. We find that economies of scale in battery manufacturing are reached quickly at a production volume of ∼200–300 MWh annually. Increased volume does little to reduce unit costs, except potentially indirectly through factors such as experience, learning, and innovation. We also find that vehicle applications with larger energy requirements are able to utilize cheaper cells due in part to the use of thicker electrodes. The effect on cost can be substantial. In our base case, we estimate pack-level battery production costs of ∼$545 kWh−1 for a PHEV with a 10 mile (16 km) all-electric range (PHEV10) and ∼$230 kWh−1 for a BEV with a 200 mile (320 km) all-electric range (BEV200). This 58% reduction, from $545 kWh−1 to $230 kWh−1, is a larger effect than the uncertainty represented by our optimistic and pessimistic scenarios. Electrodes thicker than about 100 or 125 microns are not currently used in practice due to manufacturing and durability concerns, but relaxing this constraint could further lower the cost of larger capacity BEV200 packs by up to an additional 8%.

It has been demonstrated experimentally that a capacitor bank when connected in parallel with a battery increases the energy output by mitigating the effects of high current spikes in the load. High current draws are taken from the capacitor bank which can furnish a small amount of energy quickly. The battery which can furnish substantial energy over a period of time then recharges the capacitor bank during times of decreased load. With a current square wave (P–P of 1.5 to 2× the average), capacitors afforded an increase in the retrievable energy of approximately 8% for a lead acid battery, 40% for a rechargeable lithium ion battery, and 46% for a non-rechargeable lithium ion battery.

Now the lithium ion batteries are widely used in electric vehicles (EV). The cycle life is among the most important characteristics of the power battery in EV. In this report, the battery cycle life experiment is designed according to the actual working condition in EV. Five different commercial lithium ion cells are cycled alternatively under 45 °C and 5 °C and the test results are compared. Based on the cycle life experiment results and the identified battery aging mechanism, the battery cycle life models are built and fitted by the genetic algorithm. The capacity loss follows a power law relation with the cycle times and an Arrhenius law relation with the temperature. For automotive application, to save the cost and the testing time, a battery SOH (state of health) estimation method combined the on-line model based capacity estimation and regular calibration is proposed.

Lithium ion batteries offer an attractive solution for powering electric vehicles due to their relatively high specific energy and specific power, however, the temperature of the batteries greatly affects their performance as well as cycle life. In this work, an empirical equation characterizing the battery's electrical behavior is coupled with a lumped thermal model to analyze the electrical and thermal behavior of the 18650 Lithium Iron Phosphate cell. Under constant current discharging mode, the cell temperature increases with increasing charge/discharge rates. The dynamic behavior of the battery is also analyzed under a Simplified Federal Urban Driving Schedule and it is found that heat generated from the battery during this cycle is negligible. Simulation results are validated with experimental data. The validated single cell model is then extended to study the dynamic behavior of an electric vehicle battery pack. The modeling results predict that more heat is generated on an aggressive US06 driving cycle as compared to UDDS and HWFET cycle. An extensive thermal management system is needed for the electric vehicle battery pack especially during aggressive driving conditions to ensure that the cells are maintained within the desirable operating limits and temperature uniformity is achieved between the cells.

Several commercial automotive battery suppliers have developed lithium ion cells which use cathodes that consist of a mixture of two different active materials. This approach is intended to take advantage of the unique properties of each material and optimize the performance of the battery with respect to the automotive operating requirements. Certain cathode materials have high coulombic capacity and good cycling characteristics, but are costly and exhibit poor thermal stability (e.g., LiNixCo1−x−yAlyO2). Alternately, other cathode materials exhibit good thermal stability, high voltage and high rate capability, but have low capacity (e.g., LiMn2O4). By blending two cathode materials the shortcomings of the parent materials could be minimized and the resultant blend can be tailored to have a higher energy or power density coupled with enhanced stability and lower cost. In this review, we survey the developing field of blended cathode materials from a new perspective. Targeting a range of cathode materials, we survey the advances in the field in the current review. Limitations, such as capacity decay due to metal dissolution are also discussed, as well as how the appropriate balance of characteristics of the blended materials can be optimized for hybrid- and electric-vehicle applications.

This paper presents a powertrain control strategy for a series hybrid electric vehicle (SHEV) based on the integrated design of an active charging scenario and fixed-boundary-layer sliding mode controllers (FBLSMCs). An optimized charging curve for the battery is predetermined rather than subject to engine output and vehicle power demand, which is a total inverse of normal SHEV powertrain control process. This is aimed to remove surge and high-frequency charge current, keep the battery staying in a high state-of-charge (SOC) region and avoid persistently-high charge power, which are positive factors to battery lifetime extension. Then two robust chattering-free FBLSMCs are designed to locate the engine operation in the optimal efficiency area. One is in charge of engine speed control, and the other is for engine/generator torque control. Consequently, not only fuel economy is improved but also battery life expectancy could be extended. Finally, simulation and experimental results confirm the validity and application feasibility of the proposed strategy.

In backup power sources for telecommunications equipment, it is desirable that the lithium-ion (Li-ion) cells have large capacity to minimize installation size of backup systems and to improve reliability of them by reducing a number of cells and accompanying protective devices. On the other hand, large-capacity Li-ion cell is difficult to manage safety problems. Therefore, safety improvement must be done to replace lead-acid batteries in conventional backup power sources. Improvement of lifetime has also to be achieved under the float-charging condition. We have been developing large-capacity Li-ion cells of which safety are improved by adding phosphazene flame retardant. In this work, 200-Ahs cell is fabricated and several safety tests under the assumption of telecommunications backup use are carried out. The results show no explosion, ignition, or thermal runaway. Forced thermal runaway test of a cell in the module which involves 13 cells are also carried out. There is no explosion, ignition, or thermal runaway in other 12 cells. In addition, 36-kW Li-ion battery system consisted of the 200-Ahs cells and battery management system (BMS). The system was operated for about 400 days in a state of floating charge. More than 95% of initial capacity is obtained.

Battery management system monitors and mitigates the operation of battery cells and stacks and is important for battery safety and reliability. This paper presents a dual-objective optimal charging strategy for two types of Li-ion batteries, which considers the conflict objectives of charging time and charging loss. The battery models developed in a prior research are used in the charging optimization. The influences of the charging voltage threshold, temperature, and health status on the charging results are analyzed for both lithium nickelemanganeseecobalt oxide (LiNMC) and lithium iron phosphate (LiFePO4) batteries. A comparison with the charging results based on the models that cannot describe the entire battery dynamics is also performed.

Lithium ion batteries are commonly employed in hybrid electric vehicles and achieving high energy density in the battery has been among the most critical issues in the automotive industry. Since thermal management is very important in the automotive batteries with layout limitation, a design strategy for effective cooling should be carefully opted. Particularly, a forced air cooling has been considered as a practical option in the automotive industry. In this article, a specific design of air-cooled battery system is theoretically investigated and numerically modelled to satisfy the required thermal specifications. Since a typical battery system in hybrid electric vehicles consists of the stacked multiple battery cells, cooling performance is determined mainly by the uniform distribution of air flow in the coolant passage which dissipates heat generated from the battery cells. It is demonstrated that the required cooling performance can be achieved by employing the tapered manifold and pressure relief ventilation even without changing the layout/design of the existing battery system. Furthermore, a theoretical analysis is performed as a design guideline to enhance the cooling performance.

The battery is a key component in any Electric Vehicle (EV) and its method of operation may have a tremendous effect on its life. In this paper we focus on improving the battery's life. Each battery is a pack of cells designed to be discharged and charged with specific optimal currents, whereby other currents, i.e. higher or lower than the optimal currents, may have negative effects on its life. We model these negative effects as penalties that are aggregate over time and propose a discharge method to minimize them. The common discharge method is very simple but far from optimal since the current demand is supplied using all the battery's cells where the current from each is the same. The method we propose is advanced switching algorithms that select a subset of the battery's cells for each current demand and control the discharge current from each, based on the electrochemical properties of the individual cells. We evaluate our proposed algorithms using simulations on world-wide driving cycles. The results reveal that compared to the common discharge method almost all penalties can be eliminated and the battery's life can be significantly extended.

Compared with other commonly used batteries, lithium-ion batteries are featured by high energy density, high power density, long service life and environmental friendliness and thus have found wide application in the area of consumer electronics. However, lithium-ion batteries for vehicles have high capacity and large serial-parallel numbers, which, coupled with such problems as safety, durability, uniformity and cost, imposes limitations on the wide application of lithium-ion batteries in the vehicle. The narrow area in which lithium-ion batteries operate with safety and reliability necessitates the effective control and management of battery management system. This present paper, through the analysis of literature and in combination with our practical experience, gives a brief introduction to the composition of the battery management system (BMS) and its key issues such as battery cell voltage measurement, battery states estimation, battery uniformity and equalization, battery fault diagnosis and so on, in the hope of providing some inspirations to the design and research of the battery management system.

The concept of a passive hybrid system consisting of fuel cell stacks, Li-ion battery packs, and two diodes was tested. The diodes take the place of the DC/DC converter that is usually used to align fuel cell and battery voltages, thereby directly connecting the fuel cell and the battery. Prototype equipment was built for collecting characteristic data on the static and dynamic behavior of the hybrid system. The measurement results indicate that increasing the operation efficiency and simplifying the system were possible by applying the direct hybridization concept. The dynamic behavior results showed an interesting combination of output signals from the fuel cell stack and the battery pack. The quick response of the battery output completely compensated for the delay in fuel cell output response, indicating that the direct hybrid system is also applicable to high-frequency electric loads such as brushless DC motors. The ability to recharge without a DC/DC converter was also successfully validated for the direct hybrid system. From the measurement results, the design method, and the system sizing, this passive hybrid system appears promising for application in the Antares DLR-H2 electric aircraft test bed.

Lithium–titanate batteries have become an attractive option for battery electric vehicles and hybrid electric vehicles. In order to maintain safe operating temperatures, these batteries must be actively cooled during operation. Liquid-cooled systems typically employed for this purpose are inefficient due to the parasitic power consumed by the on-board chiller unit and the coolant pump. A more efficient option would be to circulate ambient air through the battery bank and directly reject the heat to the ambient. We designed and fabricated such an air-cooled thermal management system employing metal-foam based heat exchanger plates for sufficient heat removal capacity. Experiments were conducted with Altairnano's 50 Ah cells over a range of charge-discharge cycle currents at two air flow rates. It was found that an airflow of 1100 mls−1 per cell restricts the temperature rise of the coolant air to less than 10 °C over ambient even for 200 A charge-discharge cycles. Furthermore, it was shown that the power required to drive the air through the heat exchanger was less than a conventional liquid-cooled thermal management system. The results indicate that air-cooled systems can be an effective and efficient method for the thermal management of automotive battery packs.

The electrification of vehicle power trains using batteries and fuel cells is an important technological step forward in the effort to improve the efficiency and reduce the tailpipe emissions of vehicles. The production of electricity and hydrogen in a renewable fashion, such as using solar energy, can provide a clean and sustainable energy source for electric-powered vehicles. In the present work we develop a charging system to prove the concept of direct, efficient, solar-powered charging for battery-electric vehicles using solar photovoltaic-powered charging of the high-voltage nickel-metal hydride (NiMH) battery that is used in the GM 2-mode hybrid system. We utilize a protocol for high-voltage battery charging that was developed in an earlier study that included a DC–DC converter to boost the low-voltage produced by the PV array to the high voltage needed to charge the battery. However, no power conversion was used in the present study. Rather, we use a high-voltage solar array capable of outputting a wide range of voltages, from approximately 250 to 400 V in 50 V increments, at the photovoltaic system maximum power point. By varying the solar system output voltage we measured the solar energy to battery charging efficiency under a variety of conditions to determine the optimal photovoltaic system configuration. The system and methods developed in this work can be used to efficiently charge a range of battery electric vehicles by adapting the PV system output to the battery charging voltage.

The vanadium flow battery has emerged as one of the most favourable types of flow batteries for a number of reasons, including the lack of cross-contamination that troubled many earlier systems such as the Fe/Cr flow battery. Because the vanadium flow battery employs the same metal ion in both electrolytes, albeit in different oxidation states, there is no cumulative loss in performance, just an effective reversible self-discharge current. The self discharge that occurs in the vanadium flow batteries is limited to the electrolyte volume in the cells. However it can become substantial under low load conditions. The pumps also use power from the battery and may be considered as another source of self discharge. Taking these and maintenance considerations into account the layout of a 10 kW, 100 kWh, 48 V vanadium flow battery was designed as a “Multi-Stage-Operation” system to provide maximum performance at all levels of load, ease of use and optimum maintenance conditions. Experimental A complete energy storage system with 10 kW in power and 100 kWh in energy was designed. It consists of a vanadium flow battery with smart controller and configurable power electronics housed in a weatherproof housing. The battery can be charged and discharged at up to 10 kW and provides up to 100 kWh of energy. The smart controller ensures that the battery operates at maximum efficiency at all times and allows remote observation of various battery parameters, including a reliable state of charge (SOC) measurement. The option of different arrangements of power electronics gives almost complete freedom in specification of electrical output (dc, single or three-phase ac). The battery can also be connected to photovoltaic, wind turbine, diesel/petrol/gas/biogas generators, fuel cells and water turbines to form discrete autonomous power supplies or to be part of a micro-, mini- or smart-grid. The FB10/100 battery for “Multi-Stage-Operation” is comprised of 5 strings of 36–40 cells each in 3 separate fluid circuits. The first fluid circuit, containing a single string, is always actively pumped with electrolyte and electrically connected to the charger and load. The second and third fluid circuits contain 2 strings each and are only actively pumped and electrically connected when the voltage reaches preset limits. When the circuits are in “standby”, i.e. not actively pumped and electrically connected, the self discharge is limited to the small volume of electrolyte in the cells. There is also a significant saving of pumping energy, because 3 pairs of small pumps are used in place of 1 pair of more powerful pumps. Results In “Multi-Stage-Operation” mode, the overall battery performance is improved significantly. This is very important in off-grid installations, where loads are typically small compared to the power levels necessary for charging; i.e. a solar powered telemetric station may use 500 W continuous power but requires fast charging due to the narrow time window when solar energy is available. In example, at a 1 kW load the battery provides 25% more energy when operated in “Multi-Stage-Operation” mode compared to all stacks in operation. Since 2008, several power station have been equipped with FB10/100 storage units and put into operation. Within the presentation a report on the latest results including technical performance and cost issues will be given.

This article evaluates the methods to characterise the behaviour of lithium ion cells of several chemistries and a nickel metal hydride cell for automotive applications like (plug-in) hybrid vehicles and battery electric vehicles. Although existing characterisation test methods are used, it was also indicated to combine test methods in order to speed up the test time and to create an improved comparability of the test results. Also, the existing capacity tests ignore that cells can be charged at several current rates. However, this is of interest for, e.g. fast charging and regenerative braking. Tests for high power and high energy application have been integrated in the enhanced method. The article explains the rationale to ameliorate the test methods. The test plan should make it possible to make an initial division in a group of cells purchased from several suppliers.

The high cost of lithium ion batteries is a major impediment to the increased market share of plug-in hybrid electric vehicles (PHEVs) and full electric vehicles (EVs). The reuse of PHEV/EV propulsion batteries in second use applications following the end of their automotive service life may have the potential to offset the high initial cost of these batteries today. Accurately assessing the value of such a strategy is exceedingly complex and entails many uncertainties. This paper takes a first step toward such an assessment by estimating the impact of battery second use on the initial cost of PHEV/EV batteries to automotive consumers and exploring the potential for grid-based energy storage applications to serve as a market for used PHEV/EV batteries. It is found that although battery second use is not expected to significantly affect today's PHEV/EV prices, it has the potential to become a common component of future automotive battery life cycles and potentially to transform markets in need of cost-effective energy storage. Based on these findings, the authors advise further investigation focused on forecasting long-term battery degradation and analyzing second-use applications in more detail.

There are an increasing number of vehicle choices available that utilize batteries and electric motors to reduce tailpipe emissions and increase fuel economy. The eventual production of electricity and hydrogen in a renewable fashion, such as using solar energy, can achieve the long-term vision of having no tailpipe environmental impact, as well as eliminating the dependence of the transportation sector on dwindling supplies of petroleum for its energy. In this report we will demonstrate the solar-powered charging of the high-voltage nickel-metal hydride (NiMH) battery used in the GM 2-mode hybrid system. In previous studies we have used low-voltage solar modules to produce hydrogen via the electrolysis of water and to directly charge lithium-ion battery modules. Our strategy in the present work was to boost low-voltage PV voltage to over 300 V using DC–DC converters in order to charge the high-voltage NiMH battery, and to regulate the battery charging using software to program the electronic control unit supplied with the battery pack. A protocol for high-voltage battery charging was developed, and the solar to battery charging efficiency was measured under a variety of conditions. We believe this is the first time such high-voltage batteries have been charged using solar energy in order to prove the concept of efficient, solar-powered charging for battery-electric vehicles.

Plug-in hybrid electric vehicles (PHEVs) capable of drawing tractive energy from the electric grid represent an energy efficient alternative to conventional vehicles. After several thousand charge depleting cycles, PHEV traction batteries can be subject to energy and power degradation which has the potential to affect vehicle performance and efficiency. This study seeks to understand the effect of battery degradation and the need for battery replacement in PHEVs through the experimental measurement of lithium ion battery lifetime under PHEV-type driving and charging conditions. The dynamic characteristics of the battery performance over its lifetime are then input into a vehicle performance and fuel consumption simulation to understand these effects as a function of battery degradation state, and as a function of vehicle control strategy. The results of this study show that active management of PHEV battery degradation by the vehicle control system can improve PHEV performance and fuel consumption relative to a more passive baseline. Simulation of the performance of the PHEV throughout its battery lifetime shows that battery replacement will be neither economically incentivized nor necessary to maintain performance in PHEVs. These results have important implications for techno-economic evaluations of PHEVs which have treated battery replacement and its costs with inconsistency.

This paper proposes a perfect energy source supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for modern distributed generation system, particularly for future fuel cell vehicle applications. The energy in hybrid system is balanced by the dc bus voltage regulation. A supercapacitor module, as a high dynamic and high power density device, functions for supplying energy to regulate a dc bus voltage. A battery module, as a high energy density device, operates for supplying energy to a supercapacitor bank to keep it charged. A FC, as a slowest dynamic source in this system, functions to supply energy to a battery bank in order to keep it charged. Therefore, there are three voltage control loops: dc bus voltage regulated by a supercapacitor bank, supercapacitor voltage regulated by a battery bank, and battery voltage regulated by a FC. To authenticate the proposed control algorithm, a hardware system in our laboratory is realized by analog circuits and numerical calculation by dSPACE. Experimental results with small-scale devices (a PEMFC: 500-W, 50-A; a battery bank: 68-Ah, 24-V; and a supercapacitor bank: 292-F, 30-V, 500-A) corroborate the excellent control principle during motor drive cycle.

Starter batteries have to withstand a quite large temperature range. In Europe, the battery temperature can be −30 °C in winter and may even exceed +60 °C in summer. In most modern cars, there is not much space left in the engine compartment to install the battery. So the mean battery temperature may be higher than it was some decades ago. In some car models, the battery is located in the passenger or luggage compartment, where ambient temperatures are more moderate. Temperature effects are discussed in detail. The consequences of high heat impact into the lead-acid battery may vary for different battery technologies: While grid corrosion is often a dominant factor for flooded lead-acid batteries, water loss may be an additional influence factor for valve-regulated lead-acid batteries. A model was set up that considers external and internal parameters to estimate the water loss of AGM batteries. Even under hot climate conditions, AGM batteries were found to be highly durable and superior to flooded batteries in many cases. Considering the real battery temperature for adjustment of charging voltage, negative effects can be reduced. Especially in micro-hybrid applications, AGM batteries cope with additional requirements much better than flooded batteries, and show less sensitivity to high temperatures than suspected sometimes.

We participated in a national project, to develop lithium batteries for use in fuel cell hybrid electric vehicles (FCHEVs), etc., in Japan as a battery developer. The lithium battery in an FCHEV system has to supply the system with not only power but also energy. We have developed an elliptic single cell, a 4-cell module, and an application-specific integrated circuit to monitor and control the cells. Our developed single cell has achieved a specific energy of 83 Wh kg −1 , a specific power output of 3380 W kg −1 at 50% state of charge (SOC) for 10 s. The performance of the 3 kWh pack was evaluated using the 4-cell module data: the specific energy was 75 Wh kg −1 and specific power output was 2250 W kg −1 . Introduction of a lithium-ion battery into the FCHEV definitely suggested a reduced fuel consumption to 2/3 of that without the lithium-ion battery based on our measurements and calculations for the 10–15 driving mode.

The UltraBattery, developed by CSIRO Energy Technology in Australia, is a hybrid energy storage device which combines an asymmetric super-capacitor and a lead–acid battery in single unit cells. This takes the best from both technologies without the need for extra, expensive electronic controls. The capacitor enhances the power and lifespan of the lead–acid battery as it acts as a buffer during high-rate discharging and charging, thus enabling it to provide and absorb charge rapidly during vehicle acceleration and braking. The initial performance of the prototype UltraBatteries was evaluated according to the US FreedomCAR targets and was shown to meet or exceed these in terms of power, available energy, cold cranking and self-discharge set for both minimum and maximum power-assist hybrid electric vehicles (HEVs). Other laboratory cycling tests showed a fourfold improvement over previous state-of-the-art lead–acid batteries under the RHOLAB test profile and better life than commercial nickel/metal hydride (NiMH) cells used in a Honda Insight when tested under the EUCAR HEV profile. As a result of this work, a set of twelve 12 V modules was built by The Furukawa Battery Co., Ltd. in Japan and were fitted into a Honda Insight instead of the NiMH battery by Provector Ltd. The battery pack was fitted with full monitoring and control capabilities and the car was tested at Millbrook Proving Ground under a General Motors road test simulation cycle for an initial target of 50 000 miles which was extended to 100 000 miles. This was completed on 15th January 2008 without any battery problems. Furthermore, the whole test was completed without the need for any conditioning or equalisation of the battery pack.

Car manufactures have announced the launch in coming months of vehicles with reduced emissions due to the introduction of new functions like stop–start and regenerative braking. Initial performance request of automotive lead-acid batteries are becoming more and more demanding and, in addition to this, cycle life with new accelerated ageing profiles are being proposed in order to determine the influence of the new functions on the expected battery life. This paper will show how different lead-acid battery technologies comply with these new demands, from an improved version of the conventional flooded SLI battery to the high performance of spiral wound valve-regulated lead-acid (VRLA) battery. Different approaches have been studied for improving conventional flooded batteries, i.e., either by the addition of new additives for reducing electrolyte stratification or by optimisation of the battery design to extend cycling life in partial state of charge conditions. With respect to VRLA technology, two different battery designs have been compared. Spiral wound design combines excellent power capability and cycle life under different depth of discharge (DoD) cycling conditions, but flat plate design outperform the latter in energy density due to better utilization of the space available in a prismatic enclosure. This latter design is more adequate for high end class vehicles with high electrical energy demand, whereas spiral wound is better suited for high power/long life demand of commercial vehicle. High temperature behaviour (75 °C) is rather poor for both designs due to water loss, and then VRLA batteries should preferably be located out of the engine compartment.

The main battery type employed in standby applications is the valve-regulated lead-acid (VRLA) battery. Float charging is normally used to maintain the battery in its fully charged state, however, float charging has limitations that can damage the battery and shorten its life. New charge regimes have evolved in recent years to tackle the intrinsic problems of float charging. The intermittent charge (IC) regime and the interrupted charge control (ICC) regime have been developed to prolong the service life of the battery in standby applications. The battery is normally maintained in the standby mode for a long period of time and there are infrequent discharge tests to verify the efficacy of the battery. Hence, the service life of the battery is highly correlated to its charge regime. This paper reviews the charge regimes for VRLA batteries, and assesses their charging performance and their impact on the service life of the battery. Recognising that temperature plays a significant role in battery operation, temperature compensation schemes are described for different charge regimes.

著者人数：11名, Accepted: 2008-02-18, 資料番号: SA1000164000

The results of road tests on valve-regulated lead-acid (VRLA) batteries in an idling-stop (stop and go) vehicle are reported. Idling-stop systems are simple systems to improve fuel economy of automobiles. They are expected to spread widely from an environmental perspective. Performances of a conventional flooded battery, a conventional VRLA battery, and an improved VRLA battery were compared in road tests with an idling-stop vehicle. It was found that the improved VRLA battery was suited to idling-stop applications because it had a smaller capacity loss than the conventional flooded battery during partial-state-of-charge (PSoC) operation. The positive grid was corroded in layers, unlike the usual grain boundary corrosion of SLI battery grid. It is because the corrosion proceeded mainly under PSoC conditions. The corrosion rate could be controlled by potential control of positive plates.

This paper presents a review of existing dynamic electrical battery models and subsequently describes a new mathematical model of a lead acid battery, using a non-linear function for the maximum available energy related to the battery discharge rate. The battery state of charge (SOC) is expressed in a look-up table relative to the battery open circuit voltage (VOC). This look-up table has been developed through low discharge experiments of the battery modelled. Further, both the internal resistance and self-discharge resistance of the battery are subsequently expressed as functions of the open circuit voltage. By using an electrical model with these characteristics and a temperature compensation element to model different rates of charge and discharge, a relatively simple and accurate battery model has been developed. The new model takes into account battery storage capacity, internal resistance, self-discharge resistance, the electric losses and the temperature dependence of a lead acid battery. It is shown in this paper how the necessary parameters for the model were found. The battery modelled was a Hawker Genesis 42 Ah rated gelled lead acid battery. The simulation results of the new model are compared with test data recorded from battery discharge tests, which validate the accuracy of the new model.

A maintenance-free, dry calcium (MFDC) developed by the Panasonic Battery (Thailand) Co. Ltd. The battery is designed for automotive applications and is ready for use upon injection of the electrolyte. The MFDC battery employs grids made from a lead–calcium-based alloy. This feature suppresses undesirable loss of electrolyte and enables good recovery of capacity after a long time of storage or a long cycle-life. Moreover, the batteries is a dry-charged type and requires only a low frequency of recharging due to its suppressed self-discharge during storage. Transportation costs are reduced as the battery contains only a small amount of electrolyte during storage.

Lead–antimony alloys used for the positive grids in lead–acid batteries for cycling service have generally used antimony contents of 4.5 wt.% and above. Tubular batteries for cycling service that impart high compression of the active material to the grid surface via gauntlet use alloys with antimony contents as low as 1.5 wt.%. These batteries are generally employed in less-severe cycling service. Value-regulated lead–acid (VRLA) batteries can give good cycling service without lead–antimony in the positive grid, but require a high tin content and high compression. The change in automotive battery positive grid alloys to lead–calcium–tin and the tin contents of VRLA positive grids and straps have dramatically increased the tin content of the recycled grid and strap lead in the USA, Europe, and Australia. The higher tin contents can contaminate the lead used for lead–antimony battery grids and generally must be removed to low levels to meet the specifications. This study describes a low-antimony alloy that contains a substantial amount of tin. The high tin content reduces the rate of corrosion of low-antimony positive grid alloys, improves conductivity, increases the bond between the grid and the active material, and cycles as well as the traditional 5–6 wt.% antimony alloys employed in conventional flat-plate batteries. The alloy is also used as a corrosion-resistant cast-on strap alloy for automotive batteries for high temperature service, as well as for posts, bushings, and connectors for all wet batteries.

Bipolar nickel metal hydride batteries are of interest for intermediate power storage in hybrid electric vehicles. The special design allows to gain additional information on the state of charge (SOC). In order to keep a nickel metal hydride battery in a limited SOC range a battery management system is required. The influence of external conditions, like temperature, mode of operation and load profile to the quality of the operation of the quality of the battery management system are discussed.

Introduction of new fuel economy, performance, safety, and comfort features in future automobiles will bring up many new, power-hungry electrical systems. As a consequence, demands on automotive batteries will grow substantially, e.g. regarding reliability, energy throughput (shallow-cycle life), charge acceptance, and high-rate partial state-of-charge (HRPSOC) operation. As higher voltage levels are mostly not an economically feasible alternative for the short term, the existing 14 V electrical system will have to fulfil these new demands, utilizing advanced 12 V energy storage devices. The well-established lead–acid battery technology is expected to keep playing a key role in this application. Compared to traditional starting–lighting–ignition (SLI) batteries, significant technological progress has been achieved or can be expected, which improve both performance and service life. System integration of the storage device into the vehicle will become increasingly important. Battery monitoring systems (BMS) are expected to become a commodity, penetrating the automotive volume market from both highly equipped premium cars and dedicated fuel-economy vehicles (e.g. stop/start). Battery monitoring systems will allow for more aggressive battery operating strategies, at the same time improving the reliability of the power supply system. Where a single lead–acid battery cannot fulfil the increasing demands, dual-storage systems may form a cost-efficient extension. They consist either of two lead–acid batteries or of a lead–acid battery plus another storage device.

The electrical power requirements for vehicles are continuing to increase and evolve. A substantial amount of effort has been directed towards the development of 36/42 V systems as a route to higher power with reduced current levels but high implementation costs have resulted in the introduction of these systems becoming deferred. In the interim, however, alternator power outputs at 14 V are being increased substantially and at the same time the requirements for batteries are becoming more intensive. In particular, stopg for reserve or back-up batteries, the SOC and SOH are monitored to verify that the battery is always capable of carrying out the duty cycle if required. Practical methods of battery condition monitoring will be described.

The automotive battery is being asked to carry out more challenging duties than ever before. Many of these duties are a result of new types of electrical load. The way in which a battery is operated and managed within a vehicle can be optimized significantly through the use of battery-related electronics with embedded software. Potential benefits include extended life, early warning of deterioration and failure, greater availability and an improved match to the vehicle's requirements. The impact of electronics in other areas shows that there is considerable potential to go much further in this direction with battery systems. There are, however, important system-wide issues to be considered. The battery system must conform to a wide range of standards and practices applicable to automotive electronic systems and embedded software. The automotive industry is itself trying to come to terms with the inherent difficulties involved in developing, qualifying and upgrading complex networks of software-based controllers within the vehicle. The battery system must be compatible with the results of these initiatives. Cost will always be a major influence, but the cost model is different from that familiar to battery producers. This study outlines the main areas where the battery industry must consider a change from being a component to a system supplier, and makes some recommendations for an industry wide approach to smooth the transition.

The ultimate objective of this project is to demonstrate that a valve-regulated lead–acid battery of dual-tab design can be successfully substituted for the nickel−metal hydride battery pack in a Honda Insight hybrid electric vehicle. While the realization of the construction of the battery modules, the battery management system and the associated software has been more complex and time-consuming than was originally envisaged, the battery has now been fitted into the vehicle. With the initial system integration work now complete, the project plan is to test the vehicle with its lead–acid battery for up to 50,000 miles over a combination of the high speed, hill and urban circuits at the Millbrook Proving Grounds in the UK, as well as in general road driving. Prior to this, the developmental battery will have new cells fitted because of the uncertain cycling history of the original cells during the prolonged development period.