Showing papers on "State of charge published in 2003"

Method and apparatus for generalized recursive least-squares process for battery state of charge and state of health

Abstract: A method for determining a voltage based or current based state of charge (SOC) and state of health (SOH) of a battery system is provided. The method includes: providing a model of the battery system including an equivalent circuit having both low frequency and high frequency elements; establishing a plurality of functional relationships comprising relationship of the equivalent circuit with SOC; reducing at least part of the plurality of functional relationships into a set of time segmented recursive functional relationships, wherein a state at a first time t can be modeled by a functional presentation of a state at a second time t−Δt that occurred before the first time t; and computing a set of data points based upon the set of time segmented recursive functional relationships using a matrix for operation in matrix algebra.

Experimental Study on Heat Generation Behavior of Small Lithium-Ion Secondary Batteries

Abstract: The overpotential resistance and the entropy change of two small lithium-ion secondary batteries, which are the heat source terms to increase the battery temperature, have been measured by several methods, changing the battery temperature and the state of charge. The temperature increase and the total heat generation rate of the batteries were calculated during the discharge cycle by using the measured resistance and entropy, being compared with the experimental results of the temperature increase and the total heat generation rate. The overpotential resistance was estimated by four measurement methods, i.e., the battery voltage-current characteristics during the constant current discharge, the difference between the open-circuit voltage and the cell voltage, the voltage change during the intermittent discharge for 60 s, and the ac impedance measurement. The overpotential resistance by the voltage-current characteristics is almost the same as by the difference between the open-circuit voltage and the cell voltage. However, in some cases the resistances by the intermittent discharge and the ac impedance are smaller than the former two resistances. The entropy change measured by the temperature change of the open-circuit voltage agrees almost with the measured by the heat production difference between the charge and discharge cycle. The temperature increases and the total heat generation rates estimated from the overpotential resistances by the voltage-current characteristics and by the temperature change of open-circuit voltage agree well with the measured ones for the two batteries during the constant current discharge. © 2003 The Electrochemical Society. All rights reserved.

Safety method, device and system for an energy storage device

Abstract: A method, device and system is disclosed for rapidly and safely discharging remaining energy stored in an electrochemical battery 104 in the event of an internal short circuit or other fault. In its best mode of implementation, if a sensor 116 detects one or more parameters such as battery temperature 204 or pressure 206, exceeding a predetermined threshold value 334, the terminals 144 of the battery or cell are intentionally short-circuited external to the battery through a low or near zero resistance load 150 which rapidly drains energy from the battery 104. Heat generated by such rapid drain is absorbed by a heat absorbing material 151 such as an endothermic phase-change material like paraffin. The rate energy is drained via the external discharge load 150 may be controlled with an electronic circuit 136 responsive to factors such as state of charge and battery temperature. Devices such as inductive charging coils 160, piezoelectric and Peltier devices 300, may also be used as emergency energy discharge loads. Heat absorption material 163 may be used to protect adjacent issue in medically-implanted devices.

Estimating the state of charge of a battery

Abstract: This work considers the state of charge (SOC) estimation problem for electrochemical batteries. Using an electric circuit model of the battery given in the literature, it is shown how the open circuit voltage (which is directly related to the SOC) can be estimated based on the terminal voltage and current measurements provided there is sufficient variation in the battery current.

Two electrical models of the lead-acid battery used in a dynamic voltage restorer

Abstract: Two electrical models of a lead-acid battery, a short-term discharge model and a long-term integrated model, were used to investigate the system performance of a battery-supported dynamic voltage restorer (DVR). The short-term model provides a simple but effective description when the DVR compensates voltage sags over a short period. The integrated model can predict accurately the terminal voltage, state of charge, battery capacity and gassing current. It gives a good description of the battery response during both discharge and charge. Parameters of both models can be determined easily from measured battery output voltages obtained from load-step tests. Both models were successfully implemented in EMTDC/PSCAD and interfaced with the digital model of a 10 kVA DVR physical prototype. They gave a very close agreement between extensive experimental data and simulation results. Application issues such as current harmonics and microcycles during charge/discharge are discussed with respect to their impact on loss of capacity and reduced lifetime of the lead-acid battery.

System and method for determining and balancing state of charge among series connected electrical energy storage units

Abstract: A system and method for determining and balancing state of charge among plural series connected electrical energy storage units is provided. State of change of a selected storage unit in a string of storage units is determined by (i) applying a non-dissipative load to the selected storage unit, resulting in an energy transfer between the selected storage unit and the string of electrical energy storage units through the non-dissipative load and (ii) determining the state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer. When the state of charge of the selected unit is different than a target state of charge, energy can be transferred energy between the selected unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Range prediction in fleet management of electric and fuel-cell vehicles

Abstract: A method of managing power cell information resources of a non-petroleum fueled vehicle, particularly electric or fuel cell vehicles of a fleet of vehicles. Such vehicles have power pack instrumentation for wirelessly reporting data to a base station computer including power pack charge parameters and GPS location in real-time. This data is applied to a database which documents past vehicle performance as well as contains minimal acceptable vehicle parameters. A prediction is made regarding remaining range, state of charge and vehicle scheduling, considering vehicle load or mileage efficiency. The remaining range is viewed in combination with the GPS location of the vehicle so that judgments can be made regarding whether particular vehicles can take a job request, complete the job without recharging, then go to a recharging location, or have the vehicle dispatched for service.

Battery assembly system and electric-motor vehicle system using the same

Abstract: The battery assembly system 100 includes a battery assembly including a plurality of storage batteries C1 to Cn connected in series, a voltage detector 3 for detecting respectively voltages generated in the storage batteries, a current detector 4 for detecting a current flowing in the plurality of storage batteries, a state-of-charge (SOC) calculator 2 for calculating the state of charge (SOC) of the storage batteries, respectively, based on the voltages detected respectively by the voltage detectors 3 and the current detected by the current detector 4, and a charging/discharging unit 1 for charging or discharging at least one of the plurality of storage batteries so as to equalize the SOC of the storage batteries calculated respectively by the SOC calculator 2

Battery voltage reduction

Abstract: A regulator voltage control includes measuring a current of a battery, determining a state of charge (SOC) of the battery based on the current, and determining a nominal optimum charging voltage as a function of the SOC of the battery. The nominal optimum charging voltage is converted to a % duty cycle, and a generator is operated relative to the % duty cycle for charging the battery. The nominal optimum charging voltage is reduced when either a battery charge current is below a predetermined value, or a current drawing accessory is turned on.

Method of estimating state of charge and open circuit voltage of battery, and method and device for computing degradation degree of battery

Abstract: A method of estimating a state of charge of a battery, a method of estimating an open circuit voltage of a battery, and a method and device for computing a degradation degree of a battery are provided. As a degradation degree, a ratio of a total electrical quantity chargeable or dischargeable of a battery at any time point to an initial electrical quantity that is a total electrical quantity chargeable or dischargeable of the battery upon non-degradation is computed, and by using the degradation degree, a state of charge or an open circuit voltage of the battery is accurately estimated.

System and method for balancing state of charge among series-connected electrical energy storage units

Abstract: A system and method of balancing state of charge among plural series connected electrical energy storage unit is provided. Individual storage units are selectively coupled by semiconductor switches for monitoring and balancing state of charge. When the state of charge of a selected unit is greater than a target state of charge, energy is transferred from the selected unit to the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge. Conversely, when the state of charge of a selected unit is less than a target state of charge, energy is transferred from the string of storage units to the selected unit, such that the state of charge of the selected unit converges toward the target state of charge.

Simple optimal estimator for PbA state of charge

Abstract: A state of charge estimator for a battery includes a meter that generates a terminal voltage signal of the battery and a terminal current signal of the battery A controller employs a linearized model of the battery and a time-varying state estimator The controller process a synthesized input based on the terminal current and the terminal voltage to estimate the battery state of charge

Mathematical Modeling of Current-Interrupt and Pulse Operation of Valve-Regulated Lead Acid Cells

Abstract: Electric and hybrid electric vehicles use valve-regulated lead acid ~VRLA! cells that are subjected to dynamic operation with charge, rest, and discharge periods in the order of seconds. Such operation requires more sophisticated models that incorporate the electrochemical double layer. While this effect has been incorporated in a handful of electrochemical systems, the lead-acid cell, with its sluggish reaction kinetics, is one of the few where it is significant. This significance is demonstrated with use of the current-interrupt technique, where the model is used to provide guidelines for the estimation of various resistances. The usefulness of the modeling approach is exemplified by its ability to explore the effect of changing electrochemical area and concentration with state of charge, and the role of parasitic side reactions in the voltage response of the cell. Simulations of pulse charging and dynamic stress test of VRLA cells, where considerable differences are shown when including the double layer, illustrate the need for modifying the presently used modeling approach. In addition, simulations are compared to current-interrupt experiments on commercial cells in order to evaluate the applicability of the model and to identify the differences.

Design, construction and performance of a buck-boost converter for an ultracapacitor-based auxiliary energy system for electric vehicles

Abstract: This paper describes step by step the process of designing, constructing and testing a bidirectional buck-boost converter. This converter is conceiving to be used as a controlled energy-transfer-equipment between the main energy source of an electric vehicle (a battery pack in this case) and an auxiliary energy system based on ultracapacitors. The converter is able to transfer energy in both directions, at rates of more than 40 kW. The battery pack's nominal voltage is 330 V, while the ultracapacitor's voltage depends on their state of charge (SOC), ranging from 100 V to 300 V. Equations governing current transfer and current ripple are analyzed. These equations will be used as guidelines for the control system design and smoothing inductor size requirement. The topology used is a buck-boost configuration. Special care had to be taken in designing the smoothing inductor and managing thermal loses, for these are critical to the overall performance. The inductor constructed, rating l.5 mH, is capable of transferring 200 A for several minutes with low loses and no core saturation (air core was used). A special water-cooled heatsink was designed and constructed, with a very low volume of less than 900 cc and a thermal resistance of less than 0.011/spl deg/C/W. The control system was implemented on a TMS320F241 DSP from Texas Instruments, which consists in two control loops. The first one controls the converter's current, using as a reference the value obtained from the second loop, which controls the ultracapacitors state of charge (SOC). Criteria ruling this second loop are not discussed in this paper. Finally, some experimental results of the overall system are displayed.

EV battery state of charge: neural network based estimation

Abstract: Different electric vehicles (EV) types have been developed with the aim of solving pollution problems caused by the emission of gasoline-powered engines. Environmental considerations promote the adoption of EV for urban transportation. As it is well known one of the weakest points of electric vehicle is the battery system. Vehicle autonomy and therefore accurate detection of battery state of charge are among the main drawbacks that prevent the spread of electric vehicles in the consumer market. This paper deals with the analysis of battery state of charge: performances of a few sizes of batteries are analyzed and their state of charge is estimated with a neural network (NN) based system. The obtained results have been used to design a lithium-ion battery pack suitable for electric vehicles. The proposed system presents high capability of energy recovering in braking conditions, together with charge equalization, over and under voltage protection. Moreover a neural network based estimation of battery state of charge has been implemented in order to optimize autonomy instead of performances or vice-versa depending on journey.

Vehicle control apparatus and vehicle control method

Abstract: A vehicle control apparatus which starts an engine to generate electric power, and charges a battery for supplying electric power to a motor with the generated electric power when a state of charge (SOC) of the battery is reduced. The vehicle control apparatus starts the engine earlier when a load of the vehicle is larger than a predetermined set value than when the load is not larger than the predetermined set value.

Battery control apparatus

Abstract: There is provided a battery control apparatus that, when the battery temperature is low, repeats the charge and discharge of a battery on a short cycle such that the state of charge (SOC) of the battery lies in the range of 30 to 40% if the present SOC is less than 50%, and repeats the charge and discharge of the battery on a short cycle such that the SOC lies in the range of 50 to 60% if the present SOC is equal to or greater than 50%, thus increasing the temperature of the battery. Therefore, it is possible to increase the battery temperature in an efficient manner, and to prevent the available input-output power of the battery from being reduced due to a decrease in the battery temperature.

Method and system of requesting engine on/off state in a hybrid electric vehicle

Abstract: A method and system of engine start/stop control for a HEV that monitors the battery and requests a specific engine state based on condition of the battery. A battery parameter such as discharge power limit (DPL) or state of charge (SOC) is compared with a set of threshold levels including a MIN level, an ON level, and an OFF level and the result of the comparison provides inputs to a state machine. The state machine includes an ON state, an OFF state and a OPPORTUNISTIC state. The machine transitions between the various states as a function of DPL and SOC relative to the sets of threshold levels.

Integrated drive cycle analysis for fuzzy logic based energy management in hybrid vehicles

Abstract: This paper proposes a "traffic situation awareness" driven intelligent agent for energy management of parallel hybrid vehicles A coordinating device that governs energy flow in the powertrain is proposed based on the idea that driving environment (traffic situation) as well as the vehicle's mode of operation and the style of driver behavior directly affect fuel usage and pollutant emissions For the realization of driving situation awareness, identification processes for roadway type is performed by extracting the driving information from the (past) driving data Expert knowledge that characterizes the relationship between the driving situation and fuel consumption and emissions is implemented in the fuzzy torque distributor that performs intelligent decisionmaking for the torque distribution task Charge sustenance operation is performed in the State-of-Charge (SOC) compensator to keep the level of the state of charge within prescribed levels The mission of the energy management system, so called Intelligent Energy Management Agent (IEMA), is to enable the vehicle to be driven in an economically and environmentally friendly way while satisfying the driver's performance demand Simulation work is carried out for the validation of proposed IEMA, and the results reveal its viability for energy management of a parallel hybrid vehicle

Cell balancing system for equalizing state of charge among series-connected electrical energy storage units

Abstract: A system and method of balancing state of charge among plural series connected storage unit is provided. Individual storage units (105) are selectively coupled by semiconductor switches (300) for monitoring and balancing state of charge. When the state or charge of a selected unit is different than a target state of charge, energy is transferred between the selected unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge. System and method is provided for determining state of charge and for balancing state of charge among plural series connected storage units. A power converter is provided for equalizing state of charge to a target state of charge in a non-dissipative manner.

Method of improving fuel economy

Abstract: A fuel economy control method includes estimating a temperature of a battery, measuring a current of the battery, and measuring a voltage of the battery. A nominal optimum charging voltage is determined as a function of a state of charge (SOC) of the battery and the estimated temperature. The nominal optimum charging voltage is reduced to a fuel economy minimum charging voltage if the SOC is above a predetermined level and the current is within a predetermined range.

Method and device for determining the state of function of an energy storage battery

Abstract: In a method for determining the state of function SOF of an energy storage battery, in particular a starter battery for a motor vehicle, as the capability to supply at least one load with an amount of energy, by determining a characteristic value for the state of charge SOC of the energy storage battery and a characteristic value for the state of health SOH when an electrical load is applied to the energy storage battery, with state of health (SOH) being the suitability of the energy storage battery to emit a specific amount of energy to the at least one load while maintaining a minimum voltage, a characteristic value for the state of function (SOF) is determined by linking the characteristic values for the state of charge (SOC) and for the state of health (SOH).

Method and apparatus for charging batteries in a system of batteries

Abstract: A method and apparatus for charging batteries in a system of batteries. The method and apparatus involve producing a set of state of charge signals indicative of the states of charge of each battery in the system, successively identifying, from the state of charge signals, a most discharged battery in the system and applying a charging current to the most discharged battery for at least part of a first period of time less than a period of time required to fully charge the most discharged battery before identifying a succeeding most discharged battery in said system. The batteries are charged according to a dynamic charging sequence in which batteries are added into the charging sequence in order of increasing state of charge as batteries already in the charging sequence are charged to exceed the state of charge of a battery having the next higher state of charge relative to the state of charge of the batteries already in the charging sequence.

System and method for battery charge control based on charge capacity headroom

Abstract: A charging and discharging strategy for a rechargeable battery pack is disclosed. The strategy involves monitoring and learning the battery pack's condition (a cycle life parameter) in terms of its progression through its life cycle. The life cycle parameter may be determined as a function of both time (i.e., the battery pack's age) as well as the number of discharge/recharge cycles. The strategy intentionally under-utilizes the battery during the initial stages of its life, based on the cycle life parameter, by charging it to a first level less then the maximum state of charge. This approach reduces charge voltages, reducing stress on the battery's active materials, thereby increasing its life.

Vehicle electrical system including battery state of charge detection on the positive terminal of the battery

Abstract: In a vehicle electrical system powered by a battery for supplying a plurality of loads, an integrated module is provided between the positive terminal of the battery and the loads, and the integrated module includes an arrangement for detecting a state of charge of the battery, a control unit for power management of the vehicle electrical system, and at least one supply output for supplying power to the loads.

Method for estimating time to full-charge in a rechargeable battery

Abstract: A method for determining time to completion is provided for a battery charging system. The system preferably includes a charger having a microprocessor and a battery with a memory. The memory includes information about the battery, including battery identifiers, charging states, charging procedures and charging termination information. The charger reads this battery and then determines the charging states associated with the battery. The charger then determines the present state of charge, and calculates a time to completion for that state. The charger then determines times to completion for the remaining charge states, optionally compensating for self discharge within the battery. A total time to completion is determined by summing the times to completion for the respective charging states.

Method and system for controlling fuel-cell power for fuel-cell hybrid electric vehicle

Abstract: A fuel-cell power control method for a fuel-cell hybrid electric vehicle is provided, which comprises determining a target fuel-cell power based on motor power demand and a state of charge of a battery. Furthermore, the method comprises determining a target fuel-cell voltage responding to the target fuel-cell power and controlling a voltage of a fuel-cell to be the target fuel-cell voltage.

Adaptive algorithm to control and characterize super-capacitor performance

Abstract: A method for determining a state of charge (SOC) of a super-capacitor (SC) system includes modeling the SC system with an equivalent circuit having first and second parameters. The method further includes estimating a value of the first and second parameters based on a measured voltage and determining the SOC based on the first and second parameters.