Showing papers on "State of charge published in 2005"

Nonlinear observers for predicting state-of-charge and state-of-health of lead-acid batteries for hybrid-electric vehicles

Abstract: This paper describes the application of state-estimation techniques for the real-time prediction of the state-of-charge (SoC) and state-of-health (SoH) of lead-acid cells. Specifically, approaches based on the well-known Kalman Filter (KF) and Extended Kalman Filter (EKF), are presented, using a generic cell model, to provide correction for offset, drift, and long-term state divergence-an unfortunate feature of more traditional coulomb-counting techniques. The underlying dynamic behavior of each cell is modeled using two capacitors (bulk and surface) and three resistors (terminal, surface, and end), from which the SoC is determined from the voltage present on the bulk capacitor. Although the structure of the model has been previously reported for describing the characteristics of lithium-ion cells, here it is shown to also provide an alternative to commonly employed models of lead-acid cells when used in conjunction with a KF to estimate SoC and an EKF to predict state-of-health (SoH). Measurements using real-time road data are used to compare the performance of conventional integration-based methods for estimating SoC with those predicted from the presented state estimation schemes. Results show that the proposed methodologies are superior to more traditional techniques, with accuracy in determining the SoC within 2% being demonstrated. Moreover, by accounting for the nonlinearities present within the dynamic cell model, the application of an EKF is shown to provide verifiable indications of SoH of the cell pack.

Supervisor control for a stand-alone hybrid generation system using wind and photovoltaic energy

Abstract: A comprehensive supervisor control for a hybrid system that comprises wind and photovoltaic generation subsystems, a battery bank, and an ac load is developed in this paper. The objectives of the supervisor control are, primarily, to satisfy the load power demand and, second, to maintain the state of charge of the battery bank to prevent blackout and to extend the life of the batteries. For these purposes, the supervisor controller determines online the operation mode of both generation subsystems, switching from power regulation to maximum power conversion. Decision criteria for the supervisor based on measurable system variables are presented. Finally, the performance of the supervisor controller is extensively assessed through computer simulation using a comprehensive nonlinear model of the plant.

Method and system for battery protection

Abstract: An electrical combination. The combination comprises a hand held power tool, a battery pack and a controller. The battery pack includes a battery pack housing connectable to and supportable by the hand held power tool, a plurality of battery cells supported by the battery pack housing, each of the plurality of battery cells having a lithium-based chemistry, being individually tapped and having an individual state of charge. A communication path is provided by a battery pack sense terminal and a power tool sense terminal. The controller is operable to monitor a state of charge of a number of battery cells less than the plurality of battery cells and to generate a signal based on the monitored state of charge of the number of battery cells less than the plurality of battery cells, the signal being operable to control the operation of the hand held power tool.

Estimating the state of charge of a battery

Abstract: This brief 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.

State-of-the-art of battery state-of-charge determination

Abstract: From the early days of its discovery, humanity has depended on electricity, a phenomenon without which our technological advancements would not have been possible. With the increased need for mobility, people moved to portable power storage—first for wheeled applications, then for portable and finally nowadays wearable use. Several types of rechargeable battery systems, including those of lead–acid, nickel–cadmium, nickel–metal hydride, lithium ion and lithium-ion polymer exist in the market. The most important of them will be discussed in this review. Almost as long as rechargeable batteries have existed, systems able to give an indication about the state-of-charge (SoC) of a battery have been around. Several methods, including those of direct measurements, book-keeping and adaptive systems (Bergveld et al 2002 Battery Management Systems, Design by Modelling (Philips Research Book Series) vol 1 (Boston: Kluwer)) are known in the art for determining the SoC of a cell or battery of cells. An accurate SoC determination method and an understandable and reliable SoC display to the user will improve the performance and reliability, and will ultimately lengthen the lifetime of the battery. However, many examples of poor accuracy and reliability can be found in practice (Bergveld et al 2002, cited above). This review presents an overview on battery technology and the state-of-the-art of SoC methods. The goal of all the presented SoC indication methods is to design an SoC indication system capable of providing an accurate SoC indication under all realistic user conditions, including those of spread—in both battery and user behaviour, a large temperature and current range and ageing of the battery.

State of charge indicator for battery

Abstract: A state of charge indicator includes a current sensing circuit for sensing and converting charge or discharge current of a battery into a bipolar voltage. A counter circuit counts battery charge. A charge/discharge circuit is operatively connected to the current sensing and counter circuits and detects the voltage polarity from the current sensing circuit and sets the counter circuit to a count mode with an up or down count for a respective charge or discharge. A reset circuit is operative with the current sensing circuit, counter circuit and charge/discharge circuit for resetting the counter circuit to an actual state-of-charge of the battery after delay when the battery is idle representative of a battery open circuit voltage.

A new online state-of-charge estimation and monitoring system for sealed lead-acid batteries in Telecommunication power supplies

Abstract: This paper presents a new, online, battery state-of-charge estimation and monitoring system for both the discharge and charge periods of sealed lead-acid batteries, commonly used in telecommunication power systems as backup power supplies. The proposed monitoring system is based on discharge time versus discharge rate data given in manufacturers' data sheets, and coulometric measurements, without the need for any battery voltage measurement under open-circuit conditions. The corresponding battery management system can perform both the online monitoring and battery charging tasks by the use of the same low-cost 8-bit microcontroller. Battery state-of-charge monitoring tests have been carried out under both constant and dynamic load conditions and for alternate charge-discharge cycles of lead-acid batteries of different capacities, and for different operating temperatures. The test results have shown that a very good accuracy (better than 3%-4%) in the estimation of available capacity is obtained for various charge-discharge strategies corresponding to practical operating conditions. Changes in battery characteristics which occur due to aging are also taken into account by estimating the actual capacity of the battery and adopting the corresponding recharacterization of the aged cells automatically.

An energy management and charge sustaining strategy for a parallel hybrid vehicle with CVT

Abstract: An energy management control system for a parallel hybrid electric vehicle is presented. The proposed system incorporates an optimization scheme to assess the amount of engine torque for generating propulsive power (torque distribution task) as well as a charge sustaining scheme to ensure that battery's state of charge is maintained at sufficiently high level. In order to accomplish the torque distribution task, torque distribution control problem is formulated as a multi-objective nonlinear optimization problem, and recast and solved as a single objective linear optimization problem. Furthermore, a new vehicle-mode-based state-of-charge compensator is developed to accomplish the charge sustaining task. Computer simulation work is carried out to evaluate the proposed energy management system. Finally, through sensitivity analysis, robustness of the solution to changes in the parameters of the objective functions is investigated.

Method and system for battery charging

Abstract: A combination including a battery pack and a battery charger operable to supply a charging current to the battery pack. The battery pack includes a first battery terminal, a second battery terminal, and a battery cell having a present state of charge. The battery cell is coupled to at least one of the first battery terminal and the second battery terminal. The battery pack also includes a battery microcontroller coupled to at least one of the first battery terminal and the second battery terminal. The microcontroller is operable to measure the present state of charge of the battery cell to produce battery cell present state of charge measurements. The battery charger includes a first charger terminal configured to couple to at least one of the first battery terminal and the second battery terminal and a second charger terminal configured to couple to at least one of the first battery terminal and the second battery terminal. The first charger terminal is configured to supply charging current to the battery pack. The battery charger also includes a charger microcontroller coupled to the second charger terminal and operable to receive the battery cell present state of charge measurements from the battery microcontroller. The charger microcontroller is also operable to supply the charging current to the battery pack in pulses, wherein each pulse includes a first time interval where charging current is being supplied to the battery and a second time interval where charging current is being suspended from the battery. The microcontroller is further operable to modify the first time interval of a pulse based at least in part on the battery cell present state of charge measurements received from the battery microcontroller.

Portable solar energy system

Abstract: The portable solar energy system stores electrical energy generated by a solar panel, which is made of an array of photovoltaic cells, in a dc storage battery, and upon demand converts the dc voltage of the battery to an ac output suitable for supplying conventional electrical appliances. The battery is a sealed lead-acid type and may be an Absorbed Glass Mat (AGM) battery. The system includes an energy storage and converting unit, which houses the battery and a dc-to-ac inverter. The inverter converts the stored energy of the battery, supplied at a low dc voltage, into the ac voltage and current required for supplying conventional appliances. A charge controller manages the flow of current from the solar panel to optimize the state of charge of the battery and to maximize the useful life of the battery. Additional circuitry monitors the discharge level of the battery to limit deep discharging.

Control device for hybrid vehicle.

Abstract: A control device for a hybrid vehicle which comprises an engine (2) and a motor-generator (3) that is capable of generating electrical power as power sources, and in which the power of at least one of the engine (2) and the motor-generator (3) is transmitted to an output shaft (5) for driving the hybrid vehicle The control device comprises a battery (8) which is capable of supplying energy to the motor-generator (3), a state of charge measuring section (12) for measuring the state of charge of the battery (8), and a drive control section that preliminarily stores information of a motor drive permissible vehicle speed below which a motor drive mode, in which the engine (2) outputs no power and the motor is operated solely for driving the hybrid vehicle, is employed The drive control section is adapted to control so to increase the motor drive permissible vehicle speed when the state of charge of the battery (8) measured by the state of charge measuring section (12) is equal to or gre ater than a predetermined value

Neural network-based residual capacity indicator for nickel-metal hydride batteries in electric vehicles

Abstract: This paper presents a new estimation approach for the battery residual capacity (BRC) indicator in electric vehicles (EVs). The key of this approach is to model the EV battery by using a neural network (NN) with a newly defined output and newly proposed inputs. The inputs are the discharged and regenerative capacity distribution and the temperature. The output is the state of available capacity (SOAC) which represents the BRC. Various SOACs of the nickel-metal hydride (Ni-MH) battery are experimentally investigated under different EV discharge current profiles and temperatures. The corresponding data are recorded to train and verify the proposed NN. The results indicate that the NN can provide an accurate and effective estimation of the BRC. Moreover, this NN can be easily implemented as the BRC indicator or estimator for EVs by using a low-cost microcontroller.

Regeneration control for hybrid vehicle

Abstract: Disclosed is a control apparatus for a hybrid vehicle having an engine, a drive motor ( 3 ) that regenerates power, and an electric power storage device ( 6 ) that gives/receives power to/from the drive motor ( 3 ). The control apparatus includes power consumption means ( 2 ) for consuming power; a sensor ( 26, 27 ) that detects a state of charge of the electric power storage device; means ( 18, 23, 51 ) for detecting a driving state of the vehicle; and a controller ( 9 ). The controller ( 9 ) is programmed to calculate a chargeable energy amount Ecap in the electric power storage device ( 6 ) on the basis of a difference between a fully charged state of the electric power storage device and the detected state of charge; set a power |Pgen0| regenerated by the drive motor ( 3 ); calculate a chargeable power Pmax in the electric power storage device according to the detected state of charge; calculate a regenerated energy E resulting from regenerative braking from the detected driving state of the vehicle; calculate a charging power limit Pgenlmt according to the calculated regenerated energy E; and control the power consumption means ( 2 ) to consume a power equal to a difference between the power |Pgen0| regenerated by the drive motor ( 3 ) and the charging power limit |Pgenlmt| when the calculated regenerated energy E is greater than the chargeable energy amount Ecap in the electric power storage device and when the charging power limit |Pgenlmt| is smaller than the chargeable power |Pmax|.

Vehicle-mounted power supply system

Abstract: A vehicle-mounted power supply system comprises a first storage battery, an automotive generator for generating electrical energy and charging the first storage battery with the generated electrical energy. A second storage battery is connected to an electrical load and a power converter supplies electric energy from the first storage battery to the second storage battery. A controller, or battery-monitoring unit, sets the power converter in a sleep mode when the vehicle engine is stopped, periodically detects the voltage of the second storage battery as a pseudo-open circuit voltage during the sleep mode of the power converter if current of the second storage battery is within a predetermined range, estimates a state of charge of the second storage battery from the detected pseudo-open circuit voltage and sets the power converter in a run mode when the estimated state of charge is lower than a predetermined value.

Z-source inverter control for traction drive of fuel cell - battery hybrid vehicles

Abstract: This paper presents a Z-source inverter control strategy used to control power from the fuel cell, power to the motor, and state of charge (SOC) of the battery. The Z-source inverter utilizes an exclusive Z-source (LC) network to link the main inverter circuit to the fuel cell (or any dc power source). A new concept is revealed that substitutes a high voltage battery for one (or both) of the capacitors from the Z-source network. By controlling the shoot-through duty cycle we can control the battery voltage (thus controlling SOC) therefore there is no need for a separate dc-dc converter. By controlling the shoot-through duty cycle and modulation index we can produce any desired output ac voltage, thus there is no need for a dc-dc boost converter. These facts make the Z-source inverter highly desirable for use in hybrid electric vehicles, as the cost and complexity is greatly reduced when compared to traditional inverters. These new concepts are demonstrated by simulation and experimental results.

Method for managing the “stop-and-start” mode in a motor vehicle equipped with an internal combustion engine

Abstract: A method for managing the “stop-and-start” mode in a motor vehicle equipped with an internal combustion engine; the method provides for the “stop-and-start” mode to be enabled or disabled as a function of a state of charge (SOC) of a battery of the motor vehicle, as a function of a state of motion of a crankshaft of the internal combustion engine and as a function of the electric power consumed overall by the electrical consumers of the motor vehicle.

Parallel Operation of Battery Power Modules

Abstract: Operating batteries in parallel is attempted to overcome the problems with the conventionally used battery bank in which the batteries are operated in series With parallel operation, a more reasonable management can be made to prevent the batteries from being over-charged or over-discharged The discharging currents of the parallel batteries are independently controlled but are coordinated to execute a full amount of the load current Some of the batteries may take rest or be isolated from the system for the detections at a time This facilitates the estimations of the state of charge (SOC) and the state of health (SOH) In addition, sophisticated discharging profiles can be realized to efficiently utilize the available stored energy in batteries

Optimal neuro-fuzzy control of parallel hybrid electric vehicles

Abstract: In this paper an optimal method based on neuro-fuzzy for controlling parallel hybrid electric vehicles is presented. In parallel hybrid electric vehicles the required torque for driving and operating the onboard accessories is generated by a combination of internal combustion engine and an electric motor. The power sharing between the internal combustion engine and the electric motor is the key point for efficient driving. Therefore, we are dealing with a highly nonlinear and time varying plant. Moreover, the estimation of the state of charge of the battery pack is a very important point, which has been considered in this paper. The control strategy will be implemented using the ANFIS method. The controller will be designed based on the desired torque for driving and the state of charge of batteries. The output of controller adjusts the throttle in the combustion engine. The main contribution of this paper is the development of optimal control based on neuro-fuzzy, which maximizes the output torque of the vehicle while minimizing fuel consumption used by the internal combustion engine. Simulation results show very good performance of the proposed controller.

Observer techniques for estimating the state-of-charge and state-of-health of VRLABs for hybrid electric vehicles

Abstract: The paper describes the application of observer-based state-estimation techniques for the real-time prediction of state-of-charge (SoC) and state-of-health (SoH) of lead-acid cells. Specifically, an approach based on the well-known Kalman filter, is employed, to estimate SoC, and the subsequent use of the EKF to accommodate model non-linearities to predict battery SoH. The underlying dynamic behaviour of each cell is based on a generic Randles' equivalent circuit comprising of two-capacitors (bulk and surface) and three resistors, (terminal, transfer and self-discharging). The presented techniques are shown to correct for offset, drift and long-term state divergence-an unfortunate feature of employing stand-alone models and more traditional coulomb-counting techniques. Measurements using real-time road data are used to compare the performance of conventional integration-based methods for estimating SoC, with those predicted from the presented state estimation schemes. Results show that the proposed methodologies are superior with SoC being estimated to be within 1% of measured. Moreover, by accounting for the nonlinearities present within the dynamic cell model, the application of an EKF is shown to provide verifiable indications of SoH of the cell pack.

Apparatus and method for estimating battery state of charge

Abstract: A method for training a support vector machine to determine a present state of charge of an electrochemical cell system includes choosing a training data, preprocessing the training data, finding an optimal parameter of the support vector machine, and determining support vectors.

A combined ultracapacitor-lead acid battery storage system for mild hybrid electric vehicles

Abstract: Improvements in ultracapacitor technology indicate that the automotive industry should re-examine the energy storage system for hybrid electric vehicles (HEVs). With the combination of an ultracapacitor and a lead acid battery, a system can be implemented in which the lead acid battery can be maintained at 100% state of charge, lengthening the lifetime of the battery. Although performance of the current technology, nickel metal hydride, seems satisfactory, this technology is still very expensive. The ultracapacitor-lead acid battery system described here will provide a cheaper solution if ultracapacitor prices continue to drop as predicted by manufacturers.