Battery Internal Resistance Research Articles

SOC estimation algorithm for Li-ion battery in electric or hybrid vehicles

As over-charging and over-discharging can cause damage to batteries, to guarantee the stability and duration of batteries, it is necessary to avoid being over-charged and over-discharged. Therefore, knowing the batteries' state of charge (SOC) is essential. In this paper, the author describes in detail the procedure of building a SOC estimation algorithm. The SOC estimation algorithm is based on unscented Kalman filter. Moreover, changes of battery capacity and internal resistance are considered. The impact of these changes on the estimation accuracy is explored. Experiments on an Iron Phosphate Li-ion battery cell with real load were conducted to justify this method. This method was verified to be not only precise but also stable.

A Novel Rectification Method for a High Level ac Voltage Converting to a Low Level dc Voltage: Example of Scooters Idling Stop System

This paper proposed a novel rectification method for a high-level ac voltage convert to a low-level dc voltage, in which the Permanent Magnet Synchronous Motor (PMSM) Matlab/Simulink model in generation mode has been established in order to analyze the energy characteristics of PMSM operating in scooters at full drive speed. From the simulation results, the terminal voltage and line current in load-side have a wide convert rate when the internal resistance of battery is a great value. In design, the gate driver signals can be generated, referring to the virtual hall signals, to chop the different back Electromotive Force (back-EMF). Then, the ac voltages of back-EMF can be rectified to the dc voltage by Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) at the same time. Finally, the proposed method has been implemented in scooters idling stop system successfully, and a safe low level dc voltage always can be obtained to charge battery immediately (in general 12V) no matter what a variable speed in scooters.

Steady State Analysis of Wind Driven SM-BDFIG in the Super-Synchronous Range of Operation

In this paper a simplified mathematical model of a single machine brushless double fed induction generator (SM-BDFIG) connected to a variable speed wind turbine is presented. The SM-BDFIG consists of a slip ring induction machine, which is the main generator, a converter, and a battery pack mounted on the same shaft. In the super- synchronous speed range of operation, which is investigated in this research paper, the rotor voltage is rectified and used to charge the batteries. The steady state performance of the proposed generator is studied at different values of battery open circuit voltage, different values of the battery internal resistance, and different ratios of rotor leakage reactance to rotor resistance. Results revealed that the parameter that had a significant effect on the machine performance is the ratio of rotor leakage reactance to rotor resistance.

Battery State-of-Charge Estimation Algorithm Using Dynamic Terminal Voltage Measurement

When a battery is discharging, the battery's current and terminal voltage must both be measured to estimate its state of charge (SOC). If the SOC can be estimated by using only the current or voltage, hardware costs will decrease. This paper proposes an SOC estimation algorithm that needs to measure only the terminal voltage while a battery is discharging. The battery's SOC can be deduced from its open circuit voltage (OCV) through the relationship between SOC and OCV. But when the battery is discharging, it is not possible to measure the OCV due to the voltage drop in the battery's internal resistance (IRdrop). The proposed algorithm calculates OCV by estimating IRdrop using a dynamic terminal voltage measurement. This paper confirms the results of applying the algorithm in a hardware environment via algorithm binarization. To evaluate the algorithm, a Simulink battery model based on actual values was used.

Empirical Modeling of Lithium-ion Batteries Based on Electrochemical Impedance Spectroscopy Tests

An empirical model for commercial lithium-ion batteries is developed based on electrochemical impedance spectroscopy (EIS) tests. An equivalent circuit is established according to EIS test observations at various battery states of charge and temperatures. A Laplace transfer time based model is developed based on the circuit which can predict the battery operating output potential difference in battery electric and plug-in hybrid vehicles at various operating conditions. This model demonstrates up to 6% improvement compared to simple resistance and Thevenin models and is suitable for modeling and on-board controller purposes. Results also show that this model can be used to predict the battery internal resistance obtained from hybrid pulse power characterization (HPPC) tests to within 20 percent, making it suitable for low to medium fidelity powertrain design purposes. In total, this simple battery model can be employed as a real-time model in electrified vehicle battery management systems.

Study on the thermal behaviors of power lithium iron phosphate (LFP) aluminum-laminated battery with different tab configurations

The thermal response of the battery is one of the key factors affecting the performance and life span of lithium iron phosphate (LFP) batteries. A 3.2 V/10 Ah LFP aluminum-laminated batteries are chosen as the target of the present study. A three-dimensional thermal simulation model is established based on finite element theory and proceeding from the internal heat generation of the battery. The study illustrates a three-dimensional relationship among the total internal heat generation rate of the battery, the discharge rate of the battery, and the depth of discharge. The effects on the heat distribution of the battery cells by different types of tab distributions are also explored. Results show that the thermal behavior of the discharge process can be effectively simulated with the Bernardi equation, by coupling the dynamic changes of the battery temperature, internal resistance and voltage temperature coefficient. The interior chemical reversible heat of the battery is manifested by the endothermic process when DOD (Depth of Discharge) is smaller than 0.7 and by the exothermic process when DOD is larger than 0.7. The irreversible heat takes an increasingly dominant role with the increase of discharge rate; under the condition of high-rate discharge, batteries with a single-side tab distribution are generally found to have a non-uniform cell temperature distribution, while those with a double-side tab distribution have improved cell temperature distributions. Widening the tabs can also greatly reduce the maximum temperature of the cell.

Research of DC Panel Battery Fault Detection Method

This paper elaborates the DC screen and battery DC screen fault detection method. The method of measuring battery’s internal resistance and voltage is analyzed and studied in this paper, and the two methods are optimized. Besides, the structure of the battery internal resistance, internal resistance equivalent principle and other aspects are also introduced in this paper. The optimal measurement scheme can be chosen by comparing the internal resistance measurement of DC discharge method and the AC signal injection method.

On-line Measurement of Internal Resistance of Lithium Ion Battery for EV and Its Application Research

Internal resistance of the battery can really reflect its own characteristics, which including health status of the battery, inconsistency, state of charge, thermal runaway. On-line measurement of internal resistance can real-time monitor the running state of each battery and accurately, can report fault state of the battery and handle fault in time. This paper implements the practical engineering module of on-line measurement of internal resistance of lithium ion battery for EV (Electric Vehicle) using AC analysis. The detection precision and stability of the module are less than 0.3%. Based on experiments, the paper studies the stability and temperature characteristic of internal resistance of lithium battery. It also studies the relationship between the internal resistance and SOC, charging current with experiments. This paper analyzes the relationship between the internal resistance and default of the battery, such as inconsistency of batteries, excessive charging current, changing of work state, overcharging.

A modified model based state of charge estimation of power lithium-ion batteries using unscented Kalman filter

Accurate estimation for the state of charge (SOC) is one of the most important aspects of a battery management system (BMS) in electric vehicles (EVs) as it provides drivers with the EVs' remaining range. However, it is difficult to get an accurate SOC, because its value cannot be directly measured and is affected by various factors, such as the operating temperature, current rate and cycle number. In this paper, a modified equivalent circuit model is presented to include the impact of different current rates and SOCs on the battery internal resistance, and the impact of different temperatures and current rates on the battery capacity. Besides, a linear–averaging method is presented to calculate the internal resistance and practical capacity correction factors according to data collected from the experimental bench and saved as look-up tables. The unscented Kalman filter (UKF) algorithm is then introduced to estimate the SOC according to the presented model. Experiments based on actual urban driving cycles are carried out to evaluate the performance of the presented method by comparing with two existed methods. Experimental results show that the proposed method can reduce the computation cost and improve the SOC estimation accuracy simultaneously.

Electrochemical Analysis and Novel Characterization of Porous Electrodes By Using Transmission Line Model for Lithium-Ion Batteries

The excellent performance battery with high power and high energy density is required for automobile application.To realize such batteries, it is necessary to comprehend the internal resistance of battery. In this study the novel electrochemical analysis method are applied to porous electrode of Lithium-ion battery by using transmission line model.To study on the internal resistances of porous electrodes of Lithium-ion batteries in more detail, we examined how to separate constituent of resistance in porous electrode, such as electric resistance (Re), ionic resistance inside pore (Rion), and charge-transfer resistance (Rct). The real electrode of Lithium-ion batteries is composed of insertion material (improved NCA based cathode material), conductive carbon, binder and pore filled with the electrolyte1, 2. We investigated electrochemical impedance spectroscopy using symmetric cell and treated the electrolyte/porous electrode interface by using transmission line model with or without charge transfer resistance3. From transmission line model4, the overall impedance (Z) is derived as Eq.1 without charge transfer reaction. (L: pore radius, X: pore length, CdL:double-layer capacitance)The overall impedance is derived as Eq.2 with charge transfer reaction.Fig.1 shows the experimental impedance spectra and the spectra calculated by inputting each parameter into Eq.1 and Eq.2. The experimental results of the impedance spectra agree well with that of the theoretical calculations. This result shows that the resistance constituents inside electrode are separated well by this method.To investigate the factors that affect Rion and Rct inside electrode, the analysis methods as mentioned above were applied to various kinds of electrode of Lithium-ion battery. Fig.2 shows the relation between the resistance constitution (Ri on and Rct) and thickness of electrode with different composition ratio of the insertion material, conductive carbon and binder. (The area of the electrodes in symmetric cell is constant.) The value of Rion increases with increasing in thickness of electrode, and the Rion is directly proportional to thickness. The value of Rct decreases with the increase in thickness, and the value of Rct are inversely proportional to thickness. Similar results are derived from Eq.1 and Eq.2. These results mean that the rate of Rion becomes larger among total resistance in the thick electrodes. Correlation between the Rion and the thickness vary depending on composition of the electrodes, whereas the Rct does not vary so much. The results show that the ionic resistance was dependents on the structure of electrode, and the charge transfer resistance dependents on state of the insertion material. We conclude that these results are very important. These results indicate that the decrease of the Rion is key point in the high energy density battery with thick electrode for excellent performance battery with high power and high energy density. The Rion represents the ease of movement of the lithium-ion inside pore filled with the electrolyte, and the pore size and distribution inside electrode are closely related.In the following, the values of each resistance were measured in a wide temperature range and the values of activation energies were calculated. Especially the value of Rct increased as the low temperature and the activation energy of Rct is greater than that of Rion. The results show that the decrease of Rct was important under low temperature. In summary, the Rion is more important on thick electrode in normal temperature. It is necessary to improve electrode structure for excellent performance battery in this case. The Rct is more important on thin electrode under low temperature. It is necessary to improve insertion material for excellent performance battery in that case.These analytical tools as mentioned above can provide very useful information in electrode design for excellent performance battery. More quantitative analyses and applications will be discussed in the presentation. Reference 1. Y. Itou and Y. Ukyo, J. Power Sources, 146, 39 (2005)2. H. Kondo and Y. Itou, J. Power Sources, 174 (2007) 11313. N. Ogihara and Y. Itou, J. Electrochem. Soc., 159(7) A1034 (2012)4. J. H. Jang and S. M. Oh, J. Electrochem. Soc., 151 A571 (2004)

Calculation and Characteristics Analysis of Lithium Ion Batteries’ Internal Resistance Using HPPC Test

Internal resistance of battery can really reflect its own characteristics, which including health status of the battery, inconsistency, state of charge, thermal runaway. Method to calculate the internal resistance of the battery using HPPC (Hybrid Pulse Power Characterization) test which proposed by the FreedomCAR is introduced. Ohmic resistance, polarization resistance, discharge resistance and regen resistance are calculated based on MATLAB programming using HPPC test. The differences between the four kinds of internal resistance of lithium ion batteries are compared. Characteristics of the four kinds of internal resistance in charged-state and discharged-state are analyzed.

Filter Design of Power Battery Resistance Measuring for New Energy Vehicle

In order to measure the internal resistance of new energy vehicle power battery precisely, the high quality factor analog band-pass filter circuit and switched-capacitor circuit was studied. And the circuit was redesigned by using a switched capacitor circuit for digital control. Combined with the requirements of vehicle battery internal resistance measurement, the resistance measurement system architecture which is based on microcontroller and programmable logic devices is proposed. Finally, the system is validated via error calculation and the actual experiments.

Calculation Method of Lithium Power Battery Internal Resistance Based on Freedom Model

Lithium power battery as the power source of the electric vehicle in series and parallel way, due to the performances of each monomer battery are inconsistent, it will seriously influence on the performance of the battery charges and discharges, and the incomplete consistency of the battery internal resistance is one of the reasons that affect these differences. In order to obtain the internal resistance of electric vehicle lithium power battery accurately, this article uses the FreedomCAR equivalent circuit model, adopting multiple linear regression algorithm which based on LINEST function. And the model and algorithm are verified and tested, the experimental results show that if adjusting the polarization time parameter constantly, we may reduce the estimation error, and we can calculate the internal resistance of the battery accurately.

The Application of UKF Algorithm for 18650-type Lithium Battery SOH Estimation

Lithium battery is widely used in recent years. In this paper, an improved battery model combined with the equivalent circuit model and the electrochemical model is established. The main efforts of our study are: Firstly, the Ohmic resistance of the battery model is identified online based on the Unscented Kalman Filtering (UKF) algorithm. Secondly, the estimation model of the State of Health (SOH) for the 18650-type battery is established. Thirdly, an improved battery SOH estimation method based on UKF algorithm is proposed. The experimental results indicate that our new battery model considers the different value of the battery internal resistance on the different working condition, like the different voltage, the different current and the different temperature.

The Application of UKF Algorithm for 18650-type Lithium Battery SOH Estimation

Lithium battery is widely used in recent years. In this paper, an improved battery model combined with the equivalent circuit model and the electrochemical model is established. The main efforts of our study are: Firstly, the Ohmic resistance of the battery model is identified online based on the Unscented Kalman Filtering (UKF) algorithm. Secondly, the estimation model of the State of Health (SOH) for the 18650-type battery is established. Thirdly, an improved battery SOH estimation method based on UKF algorithm is proposed. The experimental results indicate that our new battery model considers the different value of the battery internal resistance on the different working condition, like the different voltage, the different current and the different temperature.

Al/Pb lightweight grids prepared by molten salt electroless plating for application in lead-acid batteries

In this paper, a lightweight Pb plated Al (Al/Pb) grid was prepared by molten salt electroless plating. The SEM and bonding strength test show that the lead coating is deposited with a smooth surface and firm combination. CV test shows that the electrochemical properties of Al/Pb electrodes are stable. 2.0 V single-cell flooded lead-acid batteries with Al/Pb grids as negative collectors are assembled and the performances including 20 h capacity, rate capacity, cycle life, internal resistance are investigated. The results show that the cycle life of Al/Pb-grid cells is about 475 cycles and can meet the requirement of lead-acid batteries. Al/Pb grids are conducive to the refinement of PbSO4 grain, and thereby reduce the internal resistance of battery and advance the utilization of active mass. Moreover, weight of Al/Pb grid is only 55.4% of the conventional-grid. In this way, mass specific capacity of Al/Pb-grid negatives is 17.8% higher and the utilization of active mass is 6.5% higher than conventional-grid negatives.

A Method for Pre-determining the Optimal Remanufacturing Point of Lithium ion Batteries

A new way to determine the optimal remanufacturing point of lithium ion batteries for electric vehicle has been proposed in this paper. The proposed optimal remanufacturing point can avoid the sharp degradation stage of battery and ensure most of active materials covered in electrodes reused in remanufacturing process with modest cost and energy. In order to find out the optimal remanufacturing point in our experiment, the charge-discharge cycle of lithium ion batteries was carried out by using battery testing system and internal resistance meter, which can obtain enough data such as the degradation of capacity, the change of internal resistance, the charging and discharging rate and the cycle life of battery for analysis. Then the optimal battery's remanufacturing point about 500-550 cycle times has been found.

Измерение внутреннего сопротивления свинцово-кислотного аккумулятора в режиме его зарядки

Method and the resultsof measurementof the internalresistance ofbattery duringitschargeanddischarge are described.It was establishedthat the internal resistance ofthe batteryin operatingvoltage range is almost equallywhencharging and dischargingand does not dependon the current.

Coupling Between Component Sizing and Regulation Capability in Microgrids

Increasing energy security and reliability concerns are intensifying the interest in microgrids. In this setting, design optimization is vital to achieve a reliable infrastructure without overbuilding. This paper considers the impact of frequency and voltage regulation on the optimal design of a conceptual, autonomous military microgrid. This microgrid comprises a solar panel and vehicles as power sources, with each vehicle incorporating a battery and generator. The power output and terminal voltage of these inverter-based sources must be regulated. The paper investigates the effects of battery DC voltage variations on a decentralized regulation scheme, and the resulting influence on optimal component sizing. To this end, controllers are first designed based on the typical assumption that the voltage on the DC side of each inverter is constant. The battery internal resistance is then considered and its impact on regulation performance is investigated. The results show that the battery internal resistance can affect the performance of both frequency and voltage regulation, and consequently must be taken into account in component sizing decisions. Thus, the paper identifies an important coupling between regulation and component sizing problems through battery characteristics, and highlights the need for a combined sizing and regulation framework for microgrid design.

Adaptive State of Charge Estimation for Li-Ion Batteries Based on an Unscented Kalman Filter with an Enhanced Battery Model

Accurate estimation of the state of charge (SOC) of batteries is one of the key problems in a battery management system. This paper proposes an adaptive SOC estimation method based on unscented Kalman filter algorithms for lithium (Li)-ion batteries. First, an enhanced battery model is proposed to include the impacts due to different discharge rates and temperatures. An adaptive joint estimation of the battery SOC and battery internal resistance is then presented to enhance system robustness with battery aging. The SOC estimation algorithm has been developed and verified through experiments on different types of Li-ion batteries. The results indicate that the proposed method provides an accurate SOC estimation and is computationally efficient, making it suitable for embedded system implementation.