Showing papers on "State of charge published in 1997"
••
23 Feb 1997TL;DR: A clocked switched-capacitor circuit can exchange charge between adjacent batteries in a series string, without regard to component values, battery technology, or state of charge as mentioned in this paper.
Abstract: A clocked switched-capacitor circuit can exchange charge between adjacent batteries in a series string. This exchange drives all batteries to identical voltages, without regard to component values, battery technology, or state of charge. This equalization process can proceed while the batteries are in use or under charge, or separately. Transformer-based and transformerless implementations are given, and results of experimental tests are provided. The process is much faster and less stressful than the conventional approach, and is simpler than some active approaches.
480 citations
••
04 Jun 1997TL;DR: In this paper, a rule-based control and energy management strategy for a series hybrid vehicle is presented, which is based on splitting the power demand between the engine and the battery such that these power sources are operated at high efficiency.
Abstract: A rule-based control and energy management strategy for a series hybrid vehicle is presented. The strategy is based on splitting the power demand between the engine and the battery such that these power sources are operated at high efficiency. The power demand is estimated as the output of a high gain PI controller that controls the longitudinal acceleration of the vehicle. The focus was to improve the fuel economy of the vehicle by suitable power assignment to the power sources. This power split (assignment) is implemented under a rule-base frame. The rules depend on the values of selected variables: the power demand itself, the driver's acceleration command and the status of the SOC (state of charge) of the battery. The rules ensure that the engine and the battery operate at high efficiency whenever possible. At high power demand the engine will operate at its maximum rated power. Simulation results of the proposed strategy showed improvement in fuel economy over the "thermostat" strategy. An improvement of 11% in the urban cycle and of 6% in the highway cycle have been achieved for a series hybrid vehicle driven by a 40 KW diesel engine and a 60 kW lead acid battery.
329 citations
•
01 Aug 1997
TL;DR: In this paper, a control system for a hybrid vehicle ensures the best possible utilization of onboard energy resources for different operating conditions of the vehicle by modifying a strategy modified in real time depending on the input from sensors measuring vehicle speed, the current and voltage levels at different locations in the system.
Abstract: A control system for a hybrid vehicle ensures the best possible utilization of onboard energy resources for different operating conditions of the vehicle. The control system utilizes a strategy modified in real time depending on the input from sensors measuring vehicle speed, the current and voltage levels at different locations in the system. The vehicle has an auxiliary power unit, at least one energy storage device and at least one electric drive motor for traction. The vehicle has a high load driving condition, a low load driving condition and a regenerative braking condition. A voltage control sets system voltage to a charging voltage in the low load condition and regenerative braking condition, and sets system voltage to an output voltage from the energy storage device for the high load condition. A current control system sets output power from the auxiliary power unit to a charging level in the low load condition and regenerative braking condition, and sets the power level from the auxiliary power unit based on vehicle speed, motor load and state of charge of the energy storage device for the high load condition.
244 citations
••
TL;DR: Simplified models based on porous electrode theory are used to describe the discharge of rechargeable lithium batteries and derive analytic expressions for the specific capacity against discharge rate in terms of the relevant system parameters as mentioned in this paper.
Abstract: Simplified models based on porous electrode theory are used to describe the discharge of rechargeable lithium batteries and derive analytic expressions for the specific capacity against discharge rate in terms of the relevant system parameters. The resulting theoretical expressions are useful for design and optimization purposes and can also be used as a tool for the identification of system limitations from experimental data. Three major cases are considered that are expected to hold for different classes of systems being developed in the lithium battery industry. The first example is a cell with solution phase diffusion limitations for the two extreme cases of a uniform and a completely nonuniform reaction rate distribution in the porous electrode. Next, a discharge dominated by solid phase diffusion limitations inside the insertion electrode particles is analysed. Last, we consider an ohmically-limited cell with no concentration gradients and having an insertion reaction whose open-circuit potential depends linearly on state of charge. The results are applied to a cell of the form Li|solid polymer electrolyte|LiyMn2O4 in order to illustrate their utility.
224 citations
•
10 Nov 1997TL;DR: A battery management system (100) comprises input means (102) for receiving input signals, such as current or voltage, which represent a physical quantity of a battery as mentioned in this paper, and output means (104) for outputting an output signal which is derived from a state of the electrochemical storage reaction.
Abstract: A battery management system (100) comprises input means (102) for receiving input signals, such as current or voltage, which represent a physical quantity of a battery. In operation, processing means (105) of the battery management system (100) calculate a physical quantity of the battery, such as the State of Charge, based on the input signals by using an electrochemical/physical model of the battery. The model includes a representation of a main electrochemical storage reaction, whose behaviour is calculated in dependence on a battery temperature. The processing means (105) calculates the battery temperature based on a temperature model of a temperature development in the battery. The battery management system (100) comprises output means (104) for outputting an output signal which is derived from a state of the electrochemical storage reaction. The battery management system (100) is, advantageously, used in a smart battery (10) or a battery charger/discharger (200). The model is, advantageously, also used in a battery simulator.
202 citations
••
TL;DR: In this article, a numerical model is developed to predict transient behaviors of electric vehicle lead-acid batteries during discharge and charge processes, which not only accounts for coupled processes of electrochemical kinetics and mass transport occurring in a battery cell, but also considers free convection resulting from density variations due to acid stratification.
Abstract: A numerical model is developed to predict transient behaviors of electric vehicle lead-acid batteries during discharge and charge processes. The model not only accounts for coupled processes of electrochemical kinetics and mass transport occurring in a battery cell, but also considers free convection resulting from density variations due to acid stratification. A single set of conservation equations valid for both porous electrodes and the free electrolyte region is derived and numerically solved using a computational fluid dynamics technique. This numerical methodology is capable of simulating a two-dimensional cell with the fluid flow taken into consideration and requires only tens of minutes of central processing unit time on engineering workstations. Four sample calculations are presented in this work to provide rigorous validation of the developed simulator. The simulator is capable of predicting the transient behavior of the acid concentration, the porosity of the electrodes, and the state of charge of the battery during discharge, rest, and charge cycles. The model can also be used to investigate the effects of various system parameters, such as electrode dimensions, separator design, temperature, and electrolyte composition on the battery performance (voltage, power, cold cranking amperage, etc.).
140 citations
•
27 Feb 1997TL;DR: In this paper, a hybrid electric vehicle (HEV) is equipped with an energy storage system (ESS) and the main power unit (HPU) and, using an optimal fuel cost strategy, scans all possible combinations of power from the HPU and ESS that satisfy the motive demand power.
Abstract: An operating strategy for a hybrid electric vehicle (HEV) manages the flow of energy to both supply the motive demand power of the HEV and maintain the charge of the energy storage system (ESS). A controller operates the main power unit (HPU) and ESS and, using an optimal fuel cost strategy, scans all possible combinations of power from the HPU and ESS that satisfy the motive demand power. The combination with the lowest fuel cost is selected and the ESS is charged, when possible, using marginal charging; but, if the state of charge of the ESS falls below a certain level, fast charging is invoked. A minimum power threshold strategy can be used rather than the fuel cost strategy. The minimum power threshold strategy determines the optimal compromise of HPU operation and ESS operation to maximize fuel economy by using a motive power threshold below which the HPU is not operated except to recharge the ESS.
122 citations
•
27 Apr 1997
TL;DR: In this paper, nonsinusoidal voltages applied to battery and battery current are recorded and expanded into harmonic F-series, and by values of amplitudes and initial phases of voltage and current harmonics, complex impedance of battery for each harmonic are determined and also their resistive and reactive components.
Abstract: FIELD: electrical engineering. SUBSTANCE: nonsinusoidal voltages applied to battery and battery current are recorded and expanded into harmonic F-series, and by values of amplitudes and initial phases of voltage and current harmonics, complex impedance of battery for each harmonic are determined and also their resistive and reactive components. By frequency characteristics of chemical supply source one can judge serviceability of supply sources, their condition, state of charge and carry out automatic control of charging process. EFFECT: increased accuracy of checking of amplitude-frequency and phase-frequency characteristics of all types of storage batteries within wide frequency.
82 citations
•
08 Apr 1997TL;DR: An apparatus for displaying the charging of the battery of an electric vehicle has a charging connector mounted on an outer panel of a vehicle body of the electric vehicle, a lid openably mounted on the panel in covering relation to the charging connector and a cavity defined in the outer panel, and a display panel disposed in the cavity for displaying a period of time required until the battery is fully charged and/or a charged capacity.
Abstract: An apparatus for displaying the charging of the battery of an electric vehicle has a charging connector mounted on an outer panel of a vehicle body of the electric vehicle, a lid openably mounted on the panel in covering relation to the charging connector and a cavity defined in the outer panel, and a display panel disposed in the cavity for displaying a period of time required until the battery is fully charged and/or a charged capacity of the battery. The driver of the electric vehicle can easily recognize the remaining time required until the battery is fully charged and a percentage of the fully charged capacity of the battery to which the battery is presently charged, from outside of the electric vehicle. The driver is not required to confirm the state of charge of the battery with an indicator on a battery charger or within the passenger's compartment of the electric vehicle, but can easily confirm the state of charge of the battery from outside of the electric vehicle.
79 citations
•
30 Apr 1997TL;DR: In this paper, a tester for voltage and state-of-charge determination of a battery is presented. But the tester can be permanently mounted on the battery and employs an electrochromic cell which changes visual appearance, for example, color or intensity of color when electrically connected across the terminals of the battery.
Abstract: A tester for use in determining the voltage and state-of-charge of a battery. The tester can be permanently mounted on the battery and employs an electrochromic cell which changes visual appearance, for example, color or intensity of color when electrically connected across the terminals of a battery. The electrochromic cell undergoes an oxidation/reduction reaction on direct application of the DC potential of the battery. The color of the electrochromic cell can be compared with a color comparison chart to determine the condition of the battery. The tester can be permanently electrically connected to the battery or, preferably, can be connected momentarily to determine the state of the battery.
71 citations
••
TL;DR: The Intelligent Battery Controller (IBC) as mentioned in this paper is an on-board management device developed with the Intelligent Electronic Systems company, which is mainly characterized by a state-of-charge indicator that is corrected for temperature, rate of discharge, and ageing of the battery.
••
TL;DR: Several enhancements made to autonomous renewable energy systems (ARES)-I, the Cardiff School of Engineering's hybrid photovoltaic and wind energy simulation program, produce a simple, accurate and reliable method for hybrid system design and LoL prediction as a function of the combined variability in the weather and load.
••
TL;DR: In this paper, the behavior of the nonaqueous bromine complexing electrolyte phase of a zinc-flow battery is studied by means of Raman spectroscopy over a total charge-discharge cycle.
••
TL;DR: In this article, a home-made optical hydrometer was used for automatic monitoring of the specific gravity of the electrolyte in relation to the state-of-charge of the battery.
•
16 Jan 1997TL;DR: In this paper, the authors proposed a charge-discharge control circuit to prevent overcharging and over-discharging of a plurality of series connected batteries, which is provided with a detection circuit to determine the state of charge and discharge of the batteries, at least one bypass circuit connected in parallel with one battery, and a connection circuit which, in response to results from the detection circuit, selectively connects the bypass circuit to a battery determined to be in an approximately fully charged state or approximately fully discharged state.
Abstract: The charge-discharge control circuit prevents over-charge and over-discharge of a plurality of series connected batteries. It is provided with a detection circuit to determine the state of charge and discharge of the batteries, at least one bypass circuit connected in parallel with one of the batteries, and a connection circuit which, in response to results from the detection circuit, selectively connects the bypass circuit to a battery determined to be in an approximately fully charged state or approximately fully discharged state.
•
08 Jul 1997TL;DR: In this article, the authors proposed a method of constructing and interrogating electrochemical cells, especially those having lithium thionyl chloride (Li/SOCl 2 ) chemistry, that permits rapid estimation of remaining discharge capacity.
Abstract: The present invention relates to a new method of constructing and interrogating electrochemical cells, especially those having lithium thionyl chloride (Li/SOCl 2 ) chemistry, that permits rapid estimation of remaining discharge capacity. A preferred embodiment of the present invention employs cells with specially modified anode structures and a method for testing the state of charge and remaining life of these cells, as well as depassivating these cells, prior to their intended use or re-use. The test method can be performed using an inexpensive DC circuit and voltmeter at ambient conditions anytime prior to cell use or re-use. There is also disclosed an oilfield services downhole tool battery having a remaining life indicator comprising a housing containing one or more electrochemical cells having an internal anode means which selectively gets consumed at a predetermined state of discharge thereby creating a step change in the cell output voltage which is imperceptible to the tool while in operation at downhole temperatures, and which is capable of being detected at the surface under ambient temperatures upon administering of a suitable current load enabling the user to determine the remaining battery life at the surface prior to subsequent use or reuse of the battery in downhole oilfield services operations.
•
30 Oct 1997
TL;DR: In this article, a monitoring system uses at least two switches (42,43,44,45) respectively connected in parallel with each of the battery cells (2,3,4,5).
Abstract: The monitoring system uses at least two switches (42,43;44,45) respectively connected in parallel with each of the battery cells (2,3,4,5). The switches are provided by semiconductor switch elements e.g. MOSFETs, with current limiting elements, e.g. resistances, preventing short-circuiting of the battery cells when the switches are open. A control circuit may compare the voltages of at least two battery cells with one another or with given reference values, to provide signals for operation of at least one of the switches for balancing the state of charge of the cells of for diverting the current of at least one cell or bridging at least one of the cells.
••
TL;DR: In this paper, a double cell design was used to increase the battery performance of an implantable defibrillator, and the design features of a high-rate, pulse-power, manganese dioxide double cell were described.
•
06 Oct 1997
TL;DR: In this article, a battery power source device equipped with various sensors to detect a voltage, a current and a temperature of a battery pack and a battery control part to externally output an operating condition of the battery.
Abstract: PROBLEM TO BE SOLVED: To provide a battery power source device equipped with various sensors to detect a voltage, a current and a temperature of a battery pack and a battery control part to externally output an operating condition of the battery. SOLUTION: This device controls a battery pack 8, containing plural battery modules in series connection which are formed by connecting plural unit cells as a secondary battery in series, a blower 5 to keep the battery modules at a proper temperature by forcibly air-cooling the battery pack 8, a battery ECU2 to control the blower 5, based on data detected by various sensors for measuring a voltage, a current and a temperature, and also to output the detected data and SOC(state of charge) data to the outside, and a charge and discharge circuit unit 3 containing a relay and a rush current preventive resistance to cut off a charge and discharge circuit when encountering an abnormal situation and a current sensor, and a proper operating conditions without overcharging and maintaining overdischarging.
•
11 Sep 1997
TL;DR: In this paper, a method of operating a battery in a geosynchronous spacecraft for maximizing its service life is presented, where the battery is maintained at a state of charge at least sufficient to satisfy the sum of the energy requirements of the battery at each of the plurality of incremental events.
Abstract: A method of operating a battery, for example, in a geosynchronous spacecraft is presented for maximizing its service life. According to this method, the energy requirements are determined, specifically those to be satisfied by the battery at a plurality of incremental events over a predetermined operating period as when the spacecraft is in the shadow of the earth. Then, the battery is maintained at a state of charge at least sufficient to satisfy the sum of (i) the energy requirements of the battery at each of the plurality of incremental events and (ii) an energy reserve for the battery in the event of a malfunction of the spacecraft. The charge capacity of the battery is preferably adjusted in a stepwise fashion in accordance with its predetermined energy requirements. By utilizing the invention, the battery is maintained at a full state of charge for less than approximately half of the earlier mentioned predetermined operating period such that the service life of the battery is enhanced.
••
01 Oct 1997TL;DR: An amp-hour counting battery charge control algorithm has been defined and tested using the Digital Solar Technologies MPR-9400 microprocessor based photovoltaic hybrid charge controller and shown to be more effective than conventional voltage regulated sub-array shedding in returning the lead-acid battery to a high state of charge.
Abstract: An amp-hour counting battery charge control algorithm has been defined and tested using the Digital Solar Technologies MPR-9400 microprocessor based photovoltaic hybrid charge controller. This work included extensive laboratory and field testing of the charge algorithm on vented lead-antimony and valve regulated lead-acid batteries. The test results have shown that with proper setup, amp-hour counting charge control is more effective than conventional voltage regulated sub-array shedding in returning the lead-acid battery to a high state of charge.
•
06 Aug 1997
TL;DR: In this paper, the authors proposed to reduce engine noise and vibration arising from charging, while preventing the lack of stored electricity in an electricity storage device when a vehicle is in a state of near-stopping with its speed dropping to a given value or lower in a power generation controlling device for a hybrid vehicle, which drives a generator with an engine for charging the electricity storage devices.
Abstract: PROBLEM TO BE SOLVED: To reduce engine noise and vibration arising from charging, while preventing the lack of stored electricity in an electricity storage device when a vehicle is in a state of near halt with its speed dropping to a given value or lower in a power generation controlling device for a hybrid vehicle, which drives a generator with an engine for charging the electricity storage device. SOLUTION: If it is discriminated that a speed V of a vehicle is equal to a given value α or lower (SA4) and that state of charge SOC is equal to a given capacity β or lower (SA6), target engine speed is reduced by a given value (SA11) so that the current of a motor generator is controlled, in such a way as to generate regenerative braking torque which matches a target engine speed (SA12) to reduce the charging capacity. On the other hand, if the amount of change of the stored electricity capacity ΔSOC becomes negative, the power consumption of an electrical load is lowered (SA and SA4) in such a way that the charging and discharging of an electricity storage device is almost balanced.
01 Dec 1997
TL;DR: In this article, the authors developed an advanced hybrid electric transit bus using ultra-capacitors as the primary energy storage system, which is the largest vehicle of its kind ever built using this advanced energy storage technology.
Abstract: The power requirements for inner city transit buses are characterized by power peaks about an order of magnitude larger than the average power usage of the vehicle. For these vehicles, hybrid power trains can offer significantly improved fuel economy and exhaust emissions. A critical design challenge, however, has been developing the energy storage and power management system to respond to these rapid power variations. Most hybrid vehicles today use chemical energy storage batteries to supplement the power from the fuel burning generator unit. Chemical storage batteries however, present several difficulties in power management and control. These difficulties include (1) inadequate life, (2) limited current delivery as well as absorption during regenerative braking, (3) inaccurate measurement of state of charge, and (4) stored energy safety issues. Recent advances in ultra-capacitor technology create an opportunity to address these concerns. The NASA Lewis Research Center, in cooperation with industry and academia, has developed an advanced hybrid electric transit bus using ultra-capacitors as the primary energy storage system. At over 15,000-kg gross weight, this is the largest vehicle of its kind ever built using this advanced energy storage technology. Results of analyses show that the vehicle will match the performance of an equivalent conventionally powered vehicle over typical inner city drive cycles. This paper describes the overall power system architecture, the evolution of the control strategy, and analysis of power flow and vehicle performance.
••
19 Oct 1997TL;DR: In this paper, the authors describe findings gathered during a field trial of a remote, nonintrusive battery monitoring and management system in telecommunications applications, including identification of marginal and failed cells.
Abstract: Backup power battery installations and UPS systems, particularly those subject to extreme weather conditions, both hot and cold, experience accelerated aging. High ambient temperatures coupled with continuous charging, which in turn further increases cell temperatures, result in accelerated grid corrosion that cuts battery life in half or more. Continuous charging current and voltage cannot be controlled to compensate for manufacturers' specifications because each cell in a string behaves differently. Temperature compensation practices have resulted in inadequate cell charging. The practice of float charging has been accepted as a standard for batteries. A new system that uses an entirely different approach to battery management is being tested in field applications. The system is nonintrusive and it continuously monitors the state of charge (SOC), charges the batteries only when needed and as much as needed, performs operational tests, identifies cell degradation at early stages, and identifies failures. This paper describes findings gathered during a field trial of a remote, nonintrusive battery monitoring and management system in telecommunications applications. Preliminary findings include identification of marginal and failed cells, identification of marginal charging, possible design issues, and detailed monitoring of ambient conditions.
••
19 Oct 1997
TL;DR: In this paper, the influence of two a.m. variables, temperature and charging voltage, on the endurance of VRLA-batteries under float charge has been investigated.
Abstract: To optimize the endurance of VRLA-batteries under float charge the charging voltage is a very important parameter. The charging voltage at different temperatures must be fixed to the value at which the following conditions are fulfilled: a high state of charge of battery electrodes, even at the end of design life; low gassing rate and waterless; high recombination rate without thermal-run-away; small varieties between the single cells in strings; and low corrosion of positive electrode and negative top lead. In this paper the influence of two a.m. variables, temperature and charging voltage, on the endurance was investigated. An endurance test of four different designs of dryfit-batteries in Gel-technology, and measurements of polarization at different temperatures, are described.
•
11 Mar 1997TL;DR: In this article, a method of charging or discharging a battery involving an indicator of low battery charge and a device for determining a charged or discharged state in which a nominal capacity of the battery is taken as the basis of the method is presented.
Abstract: A method of charging or discharging a battery (1,2) involving an indicator of low battery charge and a device for determining a charged or discharged state in which a nominal capacity of the battery is taken as the basis of the method. The battery is initially charged for a given length of time (t1) after which depending on the nominal capacity and a given (specified) charge current I1, the battery is fully charged. The battery is then re-charged for a given length of time (t2) at reduced charging current (I2). The battery is then discharged by operation of an electric or electronic consumer device, but avoiding re-charge until the lower threshold of the battery charge (low battery) is reached. The value of the actual maximum battery capacity (max capacity) is then set by the value determined by the device for determining the discharged (C-count, D-count) state of charge of the battery.
•
06 Feb 1997
TL;DR: In this paper, the state of battery charge is verified and the vehicle is then placed into a condition suitable for travel if after verification, the battery charge condition of the brake battery (8) equals a specified minimum charging condition.
Abstract: Verification of the state of battery charge takes place, and the vehicle is then placed into a condition suitable for travel if after verification, the battery charge condition of the brake battery (8) equals a specified minimum charging condition. Recharging of the braking battery results, if the monitoring establishes a state of charge that is too low and the vehicle is then converted to a condition suitable for travel if, as a result of the verification testing, by recharging of at least one of the braking batteries the minimum state of charge has been reached.
•
17 Jan 1997TL;DR: In this paper, the authors proposed a charge-discharge control circuit to prevent overcharging and over-discharging of a plurality of series connected batteries, which is provided with a detection circuit to determine the state of charge and discharge of the batteries, at least one bypass circuit connected in parallel with one battery, and a connection circuit which, in response to results from the detection circuit, selectively connects the bypass circuit to a battery determined to be in an approximately fully charged state or approximately fully discharged state.
Abstract: The charge-discharge control circuit prevents over-charge and over-discharge of a plurality of series connected batteries. It is provided with a detection circuit to determine the state of charge and discharge of the batteries, at least one bypass circuit connected in parallel with one of the batteries, and a connection circuit which, in response to results from the detection circuit, selectively connects the bypass circuit to a battery determined to be in an approximately fully charged state or approximately fully discharged state.