Electric Vehicle Power Battery Research Articles

Relevance between fractional-order hybrid model and unified equivalent circuit model of electric vehicle power battery

Relevance between fractional-order hybrid model and unified equivalent circuit model of electric vehicle power battery

Machine learning an alternate technique to estimate the state of charge of energy storage devices

State of charge (SOC) estimation plays a critical role in the operation of an electric vehicle (EV) power battery. In this Letter, the authors propose machine learning (ML) algorithms as alternate to the existing filtering algorithms used for SOC estimation of an EV battery. The SOC estimation approach is evaluated by the simulation experiments in advanced vehicle simulator (ADVISOR). For the modelling of ML algorithms, the input parameters that affect the SOC estimation are battery current, battery module temperature, power out of the battery (available and requested), battery power loss and heat removed from the battery. Training and testing stages of the models are carried out using the data collected from ADVISOR. As the drive cycle conditions provided by ADVISOR are universal therefore present method is applicable to all kinds of batteries used in EVs including lithium ion, nickel metal hydride and lead acid batteries. Thus, the proposed models for SOC estimation provide an alternative approach in SOC estimation.

Design and simulation of liquid cooled system for power battery of PHEV

Various battery chemistries have different responses to failure, but the most common failure mode of a cell under abusive conditions is the generation of heat and gas. To prevent battery thermal abuse, a battery thermal management system is essential. An excellent design of battery thermal management system can ensure that the battery is working at a suitable temperature and keeps the battery temperature diffenence at 2-3 °C. This paper presents a thermal-elcetric coupling model for a 37Ah lithium battery using AMESim. A liquid cooled system of hybrid electric vehicle power battery is designed to control the battery temperature.A liquid cooled model of thermal management system is built using AMESim, the simulation results showed that the temperature difference within 3°C of cell in the pack.

Life Cycle Assessment of Electric Vehicle Power Battery

Based on Life cycle assessment (LCA) methodology, this paper analyzes the total energy consumption and greenhouse gas (GHGs), NOx, SOx and PM emissions during material production and battery production processes of nickel-metal hydride battery (NiMH), lithium iron phosphate battery (LFP), lithium cobalt dioxide battery (LCO) and lithium nickel manganese cobalt oxide (NMC) battery, assuming that the batteries have same energy capacity. The results showed that environmental performance of LFP battery was better than the other three, and that of NiMH battery was the worst. The experimental results also showed the total energy consumption of LFP battery was 2.8 times of NiMH battery and GHGs emission was 3.2 times during material production, and the total energy consumption was 7.6 times of NIMH battery and GHGs emission was 6.6 times during battery production

Joint Estimation of the Electric Vehicle Power Battery State of Charge Based on the Least Squares Method and the Kalman Filter Algorithm

An estimation of the power battery state of charge (SOC) is related to the energy management, the battery cycle life and the use cost of electric vehicles. When a lithium-ion power battery is used in an electric vehicle, the SOC displays a very strong time-dependent nonlinearity under the influence of random factors, such as the working conditions and the environment. Hence, research on estimating the SOC of a power battery for an electric vehicle is of great theoretical significance and application value. In this paper, according to the dynamic response of the power battery terminal voltage during a discharging process, the second-order RC circuit is first used as the equivalent model of the power battery. Subsequently, on the basis of this model, the least squares method (LS) with a forgetting factor and the adaptive unscented Kalman filter (AUKF) algorithm are used jointly in the estimation of the power battery SOC. Simulation experiments show that the joint estimation algorithm proposed in this paper has higher precision and convergence of the initial value error than a single AUKF algorithm.

Two-layer distributed equalization management system for electric vehicle power battery

The battery inconsistency affects the lifetime of the battery, and the equalization management system can improve the battery inconsistency, but the present equalization management schemes cannot solve the battery inconsistency problem well. A two-layer distributed electric vehicle power battery equalization management system is proposed in this paper, and the equalization circuit is designed and the related control strategy is given. On the aspect of equalization circuit design, the two-layer distributed topology with top and bottom layers is designed. The coaxial multi-winding DC-DC converter is used to achieve energy transfer between the top-layer modules. The capacity and resistance equalizations are used to charge when the voltage between the cells in the bottom-layer modules is low, and discharge when the voltage is high. For the equalization control strategy design, the cell voltage, battery SOC and battery voltage dispersion are used to control the equalization process, and different equalization standards are selected according to different battery work states. Specially, during the discharge period, the electric vehicle running status is considered, and the voltage difference between the cells in the module is used to calculate the equalization step, and the equalization operation is conducted layer-by-layer and step-by-step. Finally, the resistance equalization system, the capacity equalization system and the two-layer distributed equalization system were tested on a battery with 12 cells. Before the equalization, the maximum voltage deviation among the cells was 90 mV. After two hours’ equalization operation, the maximum voltage deviation was reduced to 25 mV for the two-layer distributed equalization system, to 36 mV for the capacity equalization system and to 37 mV for the resistance equalization system. The test results indicate that the proposed equalization system has the highest equalization speed and efficiency.

Thermal analysis of large-capacity LiFePO4 power batteries for electric vehicles

Excellent design of a thermal management system requires good understanding of the thermal behaviors of power batteries. In this study, the electrochemical and heat performances of a prismatic 40 Ah C/LiFePO4 battery are investigated with a focus on the influence of temperature on cell capacity in a mixed charge–discharge cycle. In addition, the heat generation and energy efficiency of a battery are determined during charge and discharge at different current rates. The experimental results indicate that in certain temperature ranges, both the charging and discharging capacities increase significantly as the temperature increases. In addition, the energy efficiency reaches more than 95% when the battery runs at a current rate of 0.33 C–2 C and temperature of 25–45 °C. A thermal mathematical model based on experimentally obtained internal resistances and entropy coefficients is developed. Using this model, the increase in the battery temperature is simulated based on specific heat values that are measured experimentally and calculated theoretically. The results from the simulation indicate that the temperature increase agrees well with the experimental values, the measured specific heat provides better results than the calculated specific heat and the heat generated decreases as the temperature increases.

Simplified electrochemical multi-particle model for LiFePO4 cathodes in lithium-ion batteries

A simplified physics-based model is developed to predict the performance of an LiFePO4 cathode at various operating and design conditions. Newman's full-order porous-electrode model is simplified using polynomial approximations for electrolyte variables at the electrode-level while a multi-particle model featuring variable solid-state diffusivity is employed at the particle level. The computational time of this reduced-order model is decreased by almost one order of magnitude compared to the full-order model without sacrificing the accuracy of the results. The model is general and can be used to expedite the simulation of any composite electrode with active-material particles of non-uniform properties (e.g., size, contact resistance, material chemistry etc.). In a broader perspective, this model is of practical value for electric vehicle power train simulations and battery management systems.

Optimizing Configuration Theory Research and System Development on Electric Vehicle Power Battery

To reduce energy consumption and improve energy utilization efficiency of electric vehicles (EVs), the relationship among power battery pack, dynamics performance, and driving range is revealed in this paper. A power battery optimizing configuration model has been developed to meet the requirements of driving range and dynamics of electric vehicles, and the corresponding design steps are given in this paper. A set of special software of power battery optimization configuration for electric vehicles is developed, which is both convenient and practical. A case was employed to validate the accuracy of the power battery optimizing configuration system software.

A comparative study of commercial lithium ion battery cycle life in electric vehicle: Capacity loss estimation

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.

Environmental Analysis of Pure Electric Vehicle Battery Recycling and Utilization

Car brings convenience to people's work and life, however, there are too many environmental issues such as energy shortages, atmospheric pollution and greenhouse effect have been caused by using a lot of traditional fuel cars, which threaten mankind survival. Pure electric vehicle (PEV) has its unique advantage for high efficiency, low noise, less environmental pollution and can use alternative energy sources, therefore, PEV has achieved rapid development with governments and automobile manufacturers support. Lithium-ion (Li-ion) batteries are considered to be the best choice of power batteries for electric vehicles due to their high energy density, high working voltage, long cycle life and low self-discharge rate. With the production, use and scrap of Li-ion battery, the recycling and the utilization of Li-ion will become the focus of attention.

Experimental study of an OHP-cooled thermal management system for electric vehicle power battery

Excessive high and low temperature can significantly reduce the performance of power battery. To extend the cycle life of battery and then improve the performance of electric vehicles, an oscillating heat pipe (OHP)-cooled battery thermal management (BTM) system was designed and experimentally studied in this paper. The results showed that the higher temperature section of battery should be near the condensation section of OHP. The OHP should not be placed horizontally in order to reduce the reflow resistance of the working fluid within OHP. The start-up temperature of OHP is determined by the desired maximum temperature and the acceptable maximum temperature difference of the battery. The conclusions can be used as reference for the design of OHP-based battery thermal management system.

Study of Electric Vehicle Lithium Batteries

Electric vehicle power battery is one of the key technologies for electric vehicle charging and discharging. This paper summarized the characteristics of lithium iron phosphate battery firstly, then adopted intermittent discharge method to get the battery OCV-SOC curve under experimental tests, determined the parameters of OCV-SOC models, analyzed the advantages and disadvantages of commonly used cell performance model, finally built electric vehicle battery charging model.

The Review on Fault Diagnosis Methods for Power Batteries in Electric Vehicles

As the only power source of electric vehicles (EVs), power battery pack is also the main fault source in EVs. The faults of power battery affect its performence and life, and even endanger vehicle security in extremly situation. Early fault diagnosis of power batteries can reduce losses, minimize maintenance, guarantee vehicle performence, security and realibility. In this study, the faults of power batteries are summarized, four fault diagnosis methods are concluded and analyzed, and the applicability of each method is compared and discussed. The principle of choosing the diagnosis method is that choosing according to the diagnostic condition.

Study on Effect of Electric Vehicle Industry to Energy and Environment

With the deterioration of the environment and energy crisis is becoming more and more serious, the development of low carbon industry has risen to national strategies. In the energy utilization and environmental effect, electric vehicle to the fuel vehicle has the advantages of energy saving and emission reduction prominent; the whole life cycle analysis, the electric vehicle complete life cycle into electric energy transmission cycle and vehicle life cycle of two parts; electric vehicle power battery as storage unit, strengthen the relationship between electric vehicle, new energy and smart grid among the three, promotes the development and application of clean energy, speed up the construction of smart grid, realize the real energy-saving and emission-reduction.

Dynamic Measurement and Estimation of Power Battery Residual Capacity

This paper takes battery cell as research object, presents a new method to estimate the state-of-charge(SOC) of battery, which solves the problem of real-time estimation of power batteries for electric vehicles in the working condition. By a constant current load, periodically measured working voltage of the battery, the remaining time can be calculated using phase-slope based on voltage in the moment, which calculates the battery SOC. The thesis proves the feasibility of that the dynamic work point can be convert to static working point, the relative error of the method is less than 7%. Through software can implement compensation of temperature and aging. The error analysis results show that the method error is small, measurement precision is high.

Energy Model of Electric Vehicle Filling Station

With the increasingly grim world environmental degradation and energy crisis, the industrial development of electric vehicles and charging for electric facilities has risen to national strategy. Based on the introduction of electric vehicle energy supply mode, proposed for power mode is the main push of the State Grid Corporation of business model. The Large-scale construction of electric vehicle filling station presents a challenge to Power grid, but through the application of V2G technology, electric vehicle power battery become smart grid energy storage structure, strengthen the new energy, electric vehicle charging the relationship between the three power stations and smart grid, and accelerate the integration process among the three.

Research on Maglev Flywheel Energy Storage System for Electric Vehicle

In order to improve the energy efficiency of electric vehicle (EV) power battery, and increase the start-up power of EV, a kind of maglev flywheel battery storage energy system is designed on EV, it is active suspension controlled at five degrees of freedom. The system suspension control principle is expounded, and the radial single freedom transfer function of the maglev flywheel is established combining with a digital PID control algorithm. The frequency spectrum characteristic of the transfer function and the flywheel rotor trajectory curve are simulated, and the 30000 r/min rotation experiment of the maglev flywheel battery prototype is realized. The experiment result shows that the maglev flywheel rotor may high speed and steadily spin, and has good energy storage ability. The maglev flywheel battery storage energy system can assist the EV power battery work, improves the battery charge and discharge properties and prolongs the service life of the motive power battery.

Transportation Bipolar Ni-MH Battery

A novel bipolar packaging design for a nickel metal hydride (NiMH) battery has been developed. As with other bipolar designs, advantages include reduced battery resistance and volume when compared with more conventional approaches. These advantages make the bipolar NiMH an excellent energy and power source for existing and emerging high voltage, high power applications. In this paper, we give an account of our recent experiences with the design, with a focus on designs for high power batteries for hybrid electric vehicles and high energy batteries for plug-in hybrids. In addition, we discuss results from a hybrid electric vehicle to plug-in hybrid electric vehicle conversion utilizing a high energy bipolar NiMH battery. The conversion and results demonstrate the successful implementation of the battery design in an automotive application.

Advances in alkaline batteries

Alkaline rechargeable battery systems have been under development for more than 100 years yet. Different electrochemical couples of positive and negative materials have been subject of research and development, but only the nickel–cadmium system (NiCd) and, since about 10 years, the nickel–metal hydride system (NiMH) have achieved the stage of large volume production. Particularly, sealed NiCd and NiMH cells have been established in a variety of applications. Recent advances with the NiMH system have brought about portable batteries with energy storing capabilities coming close to those of alkaline primary cells. Although representing a technically interesting solution even for electric vehicles, relatively high cost will limit the use of rechargeable alkaline batteries to small high power batteries for hybrid electric vehicles. Basic technological developments for materials suitable for high energy and high power design are described.