Showing papers on "State of charge published in 1994"

Battery monitoring and charging control unit

Abstract: A unit that can be a tiny module within a battery pack includes a microprocessor operating through onboard sensors and read circuitry to monitor battery current, voltage and temperature and to develop fast charge termination control data. Various termination schemes are available including negative delta V, dT/dt, dV/dt, absolute temperature, absolute voltage, and override timer. The microprocessor also operates to develop state of charge, percentage of capacity charge and other status data, to store such data along with setup and calibration data, in an EEPROM, to report data to a host periodically or when polled to and to operate automatically or at a user's request to initially perform and update a calibration as to actual battery capacity. During times when the pack is idle, the unit automatically reverts to a low-power mode in which measuring circuitry is deenergized but during such times, it operates periodically to compensate for self-discharge as a function of temperature. In the read circuitry, a ramp generator generates a linear ramp voltage that is compared with voltages proportional to battery voltage, supply voltage, battery current and temperature, using comparators connected to pins of a common port of the microprocessor and using a mask to obtain all readings from a single generation of the ramp. Voltage dividers of the read circuitry are so arranged as to permit accurate readings of current in either direction and to operate in a bridge configuration to obtain normalized measurements independent of ramp slope. Dynamic correction of readings and other features are also provided.

Method and means for adjusting battery monitor based on rate of current drawn from the battery

Abstract: In a preferred embodiment, a metering system for measuring and indicating the state of charge of an electrical storage battery, including: apparatus for storing a numerical value indicative of the state of charge of the battery and for providing an output voltage signal representative thereof; apparatus for detecting the terminal voltage of the battery, coupled to the apparatus for storing, and being operable to generate a function of the battery terminal voltage which is a substantially proportional fraction of the terminal voltage and to provide an input to the apparatus for storing if the function is below a threshold variable reference voltage signal; apparatus for receiving the output voltage signal and for generating the variable reference voltage signal therefrom, the variable reference voltage signal being lowered as a function of the output voltage signal as the output voltage signal indicates progressively lower states of charge; and apparatus for measuring the level of current drawn from the battery and adjusting the apparatus for receiving and generating, in proportion to the current level, such that the variable reference voltage signal will be greater or lesser depending on the current level.

Battery recharging system with state of charge detection that initially detects whether a battery to be charged is already at or near full charge to prevent overcharging

Abstract: A state of charge test is first performed on the battery by applying a current pulse and then observing the voltage decay characteristics which result. Batteries which are initially nearly fully charged exhibit a larger voltage decay than batteries which are not as fully charged. The result of this initial state of charge test is used to determine how to best terminate battery charging. In this way battery overcharging is prevented regardless of the initial state of charge of the battery.

Method and apparatus for monitoring the state of charge of a battery

Abstract: A method of monitoring ion mobility in an electro-conductive fluid, such as an electrolyte in a lead-acid battery to determine the state of charge of the battery, includes the steps of immersing a pair of test electrodes in the electro-conductive fluid, and generating a test signal having a pulsed waveform The pulsed waveform of the test signal has a voltage which remains constant over a predetermined portion of the signal's period, that portion being selected to ensure that ion mobility in the electro-conductive fluid has reached a steady state velocity The method further includes the steps of applying the test signal to the pair of test electrodes to cause a current to flow through the test electrodes and the electro-conductive fluid, and sensing the current flow through the test electrodes and fluid The sensed current is indicative of ion mobility in the electro-conductive fluid

Generator controller and controlling method for hybrid vehicle

Abstract: A voltage V B of a battery (16) is compared with a predetermined value V max (100) and when the battery voltage V B is lower than the predetermined value V max as a result of the comparison, a state of charge (SOC) of the battery (16) is discriminated (104). In the case of an SOC of at least 70%, an output P G of a generator (18) is controlled on the basis of an output P M of a motor (10) (106 - 116), and in the case of an SOC of less than 70%, while the output P G of the generator (18) is controlled to a relatively high value a , the output P M of the motor (10) is limited (120). When the SOC is restored to more than 75%, steps on and after 106 are executed. When the battery voltage V B is at least the predetermined value V max , an idle control of an engine (22) is carried out (124). As a result, the SOC of the battery (16) can be ensured and overcharging of the battery (16) can be prevented.

Microprocessor controlled portable battery charger and method of charging using same

Abstract: A portable battery charger (102) for use with a variety of battery packs (106) is capable of determining and applying the appropriate charge voltage and current. Electronic circuitry (128) within the portable battery charger identifies the type of battery pack to be charged and selects the appropriate set of battery banks (120) in the charger. Sensors (132) determine the state of charge of the battery pack and a controller (128) controls the functions of the charger. A multiplicity of connectors (314) on the portable battery charger are provided to allow connection to a variety of battery packs. The charger first identifies the type of battery pack and determines the charging profile to be used to charge the battery pack. The charging profile is set in the portable charger by selecting the appropriate sources of electrical power, and the battery pack is then appropriately charged.

Non-dissipative battery charge equalizer

Abstract: The battery charger 10 is recharging the reusable battery The charger includes a voltage source and, lossless shunt configuration in order to be produced in order to charge the battery a predetermined number. Charger 10 may be current limited voltage source, which is controlled by the state of charge of the battery voltage or to be recharged. Lossless shunt pair of transistors for each pair of batteries (Q Same, controlling each of the transistors opposite to the two phases (Φ1 and Φ2) an oscillator (14 and 204), the first phase the charge for a predetermined supplying a charge to the battery and a second phase during which the so equalized between batteries pairs It is used to. Equalization is continued until one not overcharge the battery reaches full charge before the two batteries.

Process for monitoring the charge level of a battery, and for informing the user of the battery when the monitored charge level is no longer reliable

Abstract: The invention relates to a method of monitoring the state of charge of the battery of a hybrid vehicle, in which the charge level of the battery is determined by balancing the charge quantities extracted and supplied, and is indicated to the driver. Because of the inaccuracy of the charge balancing, resetting of the balancing from a reliable limit value must be carried out from time to time. In order to assist the operator of the hybrid vehicle in monitoring the battery charge level, according to the invention an error variable is calculated which indicates a discrepancy between the indicated charge level and the actual charge level, and the vehicle operator is provided with an indication if this variable exceeds a maximum value. In a representative embodiment, the error variable is set to be proportional to the current through the battery.

Method of state-of-charge indication by measuring the thickness of a battery

Abstract: The state of charge of a cell that has flexible packaging and that expands and contracts with variations in state of charge is determined by measuring changes in thickness of the cell. The invention is particularly applicable to cells having a flat geometry. A battery having a state-of-charge indicator includes at least one battery cell free to expand and contract with variations in state of charge of the battery cell and a device for measuring expansion or contraction of the battery cell, a resulting measurement indicating the state of charge of the battery cell. By measuring expansion or contraction of the battery the state of charge of a battery may be readily detected. The measurement may be directly displayed so as to be visually observable, or a signal containing measurement information may be sent to a remote location to be displayed or used for control purposes. Expansion or contraction of the battery may be measured in various ways, including measuring physical displacement of the cell package or measuring a change in pressure exerted upon a member as a result of the expansion or contraction of the battery.

Improvements in or relating to battery pack arrangements

Abstract: The present invention provides a battery pack arrangement of standard 3-terminal, for example camcorder battery configuration. This enables the use of the battery pack as both an intelligent and non-intelligent pack which can function normally on standard camcorder type devices and also can communicate with intelligent equipment or devices and display charge status without the need for additional battery pack terminals. The battery pack includes a negative and a positive terminal for supplying the equipment or device with a voltage from the cells and a "T" terminal that permits thermal measurement of the cells. It is proposed that this standard thermal measurement terminal of the battery pack be used as a multipurpose terminal, operating normally as a thermal measurement means and as a thermal measurement means and then as a data port or charge control output when used by a computer, a charger or other intelligent device or equipment. The battery pack is capable of communicating with the device using predefined digital code(s) placed on the multipurpose terminal by the intelligent device. This will typically be a request, a transmission of a certain amount of information in a short time period concerning for example the state of charge of the cells or an output charge control signals. The device will then respond by transmitting the requested data along the multipurpose terminal. In the absense of digital data on the multipurpose terminal the intelligence within the battery pack returns the "T" terminal to the default standard state thus reverting its use to thermal measurements of the cells.

Method and apparatus for indicating electric charge remaining in batteries based on electrode weight and center of gravity

Abstract: In most electrochemical batteries which generate electricity through the reaction of a battery electrode with an electrolyte solution, the chemical composition, and thus the weight and density, of the electrode changes as the battery discharges. The invention measures a parameter of the battery which changes as the weight of the electrode changes as the battery discharges and relates that parameter to the value of the parameter when the battery is fully charged and when the battery is functionally discharged to determine the state-of-charge of the battery at the time the parameter is measured. In one embodiment, the weight of a battery electrode or electrode unit is measured to determine the state-of-charge. In other embodiments, where a battery electrode is located away from the geometrical center of the battery, the position of the center of gravity of the battery or shift in the position of the center of gravity of the battery is measured (the position of the center of gravity changes with the change in weight of the electrode) and indicates the state-of-charge of the battery.

Battery monitor adjusted by rate of current

Abstract: In a preferred embodiment, a metering system (600) for measuring and indicating the state of charge of an electrical storage battery (610), including: apparatus (742) for storing a numerical value indicative of the state of charge of the battery (610) and for providing an output voltage signal representative thereof; apparatus (744, 746) for detecting the terminal voltage of the battery (610), coupled to the apparatus (742) for storing, and being operable to generate a function of the battery terminal voltage which is a substantially proportional fraction of the terminal voltage and to provide an input to the apparatus (742) for storing if the function is below a threshold variable reference voltage signal; apparatus (706, 708, 710) for receiving the output voltage signal and for generating the variable reference voltage signal therefrom, the variable reference voltage signal being lowered as a function of the output voltage signal as the output voltage signal indicates progressively lower states of charge; and apparatus (704) for measuring the rate of current drawn from the battery and adjusting the apparatus (706, 708, 710) for receiving and generating, in proportion to the rate, such that the variable reference voltage signal will be greater or lesser depending on the instantaneous level of the rate.

Method and apparatus for informing a driver of the propulsive capability of a vehicle powertrain

Abstract: The accelerator command signal from an accelerator pedal sensor of an electric vehicle is mapped to a generally lower value in view of a reduced state of charge of the traction battery of the vehicle. The mapping requires the driver of the vehicle to depress the accelerator pedal farther to provide an equivalent accelerator command to the controller which controls the traction motor of the vehicle. The driver is thus given intuitive indication that the powertrain of his vehicle has reduced propulsive capability.

Assessment of lead-acid battery state of charge by monitoring float charging current

Abstract: In 1988, one user of flooded Pb-acid secondary batteries in a nuclear power plant began to measure float current in addition to specific gravity readings. A total of 780 cells were monitored. The results of this experience are summarized in this paper. A review of some of the electrochemistry involved is also presented. The analysis of the collected data has led to the conclusion that float current monitoring is preferred over specific gravity readings for assessing the state of charge of a Pb-acid battery. Now the problem turns to the availability of cost-effective, accurate provisions for measuring float current. The last part of this paper presents a test instrument design specifically for taking float current readings. >

A microcontroller controlled battery fuel gauge and charger

Abstract: State-of-charge indication for a secondary battery is becoming increasingly important for battery-operated electronics. Consumers are demanding fast charging times, increased battery lifetime, and fuel gauge capabilities. This paper presents an effective method of determining the state of charge in secondary cell batteries. A NiMH battery is used for the test since it is one of the more difficult batteries to determine state of charge. This method monitors the battery's temperature, voltage, and discharge/charge rate. A microcontroller then manipulates the information, using look-up tables to determine the state of charge. This technique can be used for both charge and discharge, without having to completely discharge the battery before each charging cycle. Also, by modifying the look-up tables, this technique can be employed in many other battery technologies, and is not limited to NiMH. >

A battery model for monitoring of and corrective action on lead-acid EV batteries

Abstract: With the oil crisis in the early 1970s an intensive development of electric vehicles, i.e. passenger cars, delivery vans, and buses was initiated. Already in an early stage of the demonstration phase it became quite clear that the lead-acid battery, more precisely the battery pack, requires more attention than can be provided by simple meters for current, voltage, and ampere-hours. This led to the requirement for a sophisticated monitoring system, which should be extended to a supervisory system. The author discusses the main objectives of the supervisory system and the algorithm for determining the residual capacity. Weak cells or modules may be called those with a capacity significantly lower than the average or those with extremely high self discharge, e.g. due to internal shorts. They may be supported by energy transfer either full battery or from modules via DC/DC converters. The pros and cons as well as hardware cost and reliability implications of these methods is discussed. The actual power which can be transferred depends on the state of charge as well as on the actual load on the full battery and also on the capacity deficit of the modules to be assisted. An applicable algorithm is demonstrated. >

Imperfectness as a useful approach in battery monitoring

Abstract: Ability to monitor secondary battery state of health and state of charge has become increasingly important. Earlier methods were entirely based on cell or block voltages. In the case of valve-regulated batteries, information of plain cell or block voltage can no longer be used as a sign of failure due to high normal deviation. Discharging a battery is still the only reliable method by which battery state-of-health and state-of-charge can be verified. This paper describes a practical and simple method, as well as the circuitry used, for a battery monitor. The method is based on measurement and comparison of the voltage differences of series connected battery blocks in a way which reduces the number of measurement channels as well as comparisons. For a typical 24-cell battery string containing four 12 V monoblocks, the measuring channels and comparison needed are three. The monitoring process also contains periodical battery discharges. The discharge interval and time can be chosen to ensure sufficient reliability and availability performance of the battery system. >

A microcontroller-based intelligent battery system

Abstract: State-of-charge indication for a secondary battery is becoming increasingly important for battery-operated electronics. Consumers are demanding fast charging times, increased battery lifetime, and fuel gauge capabilities. All of these demands require that the state of charge within a battery be known. One of the simplest methods employed to determine state of charge is to monitor the voltage of the battery. However, this method alone is not a good indicator of battery energy, since both NiMH and NiCd batteries have voltage-versus-energy curves that are essentially flat. This paper presents a more effective method of determining the state of charge in secondary cell batteries. A NiMH battery is used as our test vehicle, since it is one of the more difficult batteries to determine state of charge. This method monitors the battery's temperature, voltage, and discharge/charge rate. A microcontroller then manipulates the information, using look-up tables to determine the state of charge. Also, by modifying the look-up tables, this technique can be employed in many other battery technologies and is not limited to NiMH. >

Multi=cell battery charging method - connecting cells to diagnostic device and regulating charge voltage according to highest clamp voltage

Abstract: A micro-controlled charging device contg. a charger and voltage-free recharger analyses the state of charge of a battery contg. several sub-batteries (1.1, etc.). At least one sub-battery can be switched (2.1,etc.) in connection with one of a network of double lines (3.1, etc.) connected to a diagnosis circuit. A voltage measurement device (10) produces a charge current signal for the battery charger computed using a control algorithm so that the voltage of the cell with the highest clamp voltage is changed to and maintained at a desired voltage level. The desired voltage is pref. the manufacturer's voltage limit for the optimum charge characteristic. USE/ADVANTAGE - Enables multi=cell batteries to be charged while reliably preventing overcharging of individual cells and enabling extension of battery life.

Method and apparatus for maintaining the state of charge of a battery

Abstract: In a vehicle having a voltage regulated electric alternator (14') driven by an engine (31) for supplying power to drive electrical loads (18') and to charge a vehicle battery (10'), a method of maintaining state of charge of the battery includes adaptively learning a system voltage set-point during a first mode of engine operation resulting in an electrical system operative in set-point regulation. The method determines from the learned system voltage set-point and a current system voltage during a second mode of engine operation that the electrical system is operating in an auto-regulation mode. Idle speed is controlled in response to the regulation state of the electrical system to maintain the system in set-point regulation so as to ensure adequate battery charge or minimal battery discharge during the second mode of engine operation.

Performance of the Horizon advanced lead-acid battery

Abstract: Using new lead-composite materials and innovative cell-design and packaging design rules, Electrosource has developed a high-specific-energy, long-cycle-life, valve regulated lead-acid battery. This paper presents performance and cycle-life data for this revolutionary new design. Specific energy exceeds 40 Whrs/kg at C/2. Under sustained moderately-high current density loads, specific power exceeds 300 W/kg at 100% state of charge, and 250 W/kg at 50% depth of discharge. C/2 cycle life exceeds 900 cycles under constant current discharge to an average depth of discharge > 80% with recharge time >

State of charge indicator for a battery

Abstract: A state of charge indicator (10) monitors a voltage produced by a depletable energy source (11) and provides an indication when the state of charge of the depletable energy source (11) falls below a predetermined threshold. The state of charge indicator (10) includes an input circuit (13) for sensing the voltage and producing a plurality of tap voltages. The state of charge indicator (10) further includes a monitor circuit (65) for comparing each tap voltage with a corresponding threshold voltage and producing a result for each tap voltage falling below its corresponding threshold. The state of charge indicator (10) still further includes a storage device (75, 95, 115) for storing each result and producing an accumulated status and an output circuit (152) for producing the indication when the accumulated status exceeds an accumulated status threshold.

Method of determining and indicating battery state of charge

Abstract: A method of determining and indicating a state of charge of a battery for a vehicle includes the steps of applying an electrical load to the battery and measuring a voltage level of the battery, maintaining the electrical load to the battery, waiting a predetermined time period, measuring another voltage level of the battery, determining whether a difference between the voltage levels is greater than a predetermined value, and indicating to a vehicle operator if the difference is greater than the predetermined value.

State-of-charge indicators

Abstract: Prediction of the capacity remaining in used batteries is important information to the user. Each year millions of dollars are spent on batteries for use in portable electronics equipment. In order to maintain readiness, users currently replace batteries on a conservative schedule. This practice results in the waste of millions of dollars in battery energy every year. Figure 1 shows that this practice results in the discarding of approximately 40 percent of available battery capacity. For many battery systems there is no convenient method of determining the available capacity remaining in partially used batteries; hence, users do not take full advantage of all the available battery energy. Knowledge of capacity remaining in used batteries results in their better utilization. It is a well documented and accepted that the available capacity in a battery is a function of the conditions that the battery has been subjected. Capacity remaining is a complex function of current drain, temperature and time. External devices are available for most battery systems. However these devices are, in many cases, not portable and imprecise. Therefore a continuous internal means of determining remaining capacity is desirable, These internal methods require extensive calibration and in many cases are difficult to implement. The pursuit of an universal state-of-charge indicator has been elusive due to the variation in behavior of battery systems. Figure 2 shows the variation of load voltage between three battery systems. Reliable methods of predicting remaining capacity has been actively sought. This presentation will describe different methods of determining battery state-of-charge and the application of these methods to different battery systems.

Solar-powered battery-recharging circuit with by=pass diodes - uses intelligent processor control for switching-in more battery cells as solar panel photovoltage rises, and conversely.

Abstract: A number of solar modules are connected in series so as to provide the max. voltage at all times. Each module has its own bypass diode for balancing-out any voltage differences within the series circuit, due e.g. to partial solar shading. The battery also has a bypass diode for each of its series-connected cells, so as to balance-out differences in state of charge. The intelligent processor connects more or fewer cells in accordance with the measured solar panel voltage. ADVANTAGE - Efficiency of the overall installation is improved with almost complete utilisation of the solar panel voltage during hours.

Battery with state-of-charge indicator

Abstract: A coulometer for use as a battery state-of-charge indicator is provided in which said indicator is located on a battery, preferably to form part of the label.