Abstract: An apparatus is provided for testing a first storage battery in a bank of storage batteries, the bank formed of at least two storage batteries electrically coupled together. The apparatus includes a first Kelvin connection configured to couple to the bank of storage batteries, the first Kelvin connection including a first and second electrical connection and a second Kelvin connection configured to couple to the bank of storage batteries, the second Kelvin connection including a first and a second electrical connection, the first and second Kelvin connections configured to couple across at least the first battery. A time varying forcing function source is configured to apply a forcing function between the first electrical connection of the first Kelvin connection and the first electrical connection of the second Kelvin connection.

Abstract: A battery charger includes a first pair of electrical connectors configured to couple to a positive terminal of the battery and a second pair of electrical connectors configured to couple to a negative terminal of the battery. The first pair and second pair of connectors forming Kelvin connections to the battery. A microprocessor is configured to selectively charge the battery and measure a dynamic parameter of the battery as a function of an AC signal applied to the battery.

Abstract: A microprocessor couples to a voltage sensor through an analog to digital converter. The voltage sensor is adapted to be coupled across terminals of a battery. A small current source is also provided and adapted to be coupled across the terminal to the battery. The current source is momentarily applied to the battery and the resulting change in voltage is monitored using the microprocessor. The microprocessor calculates battery conductance based upon the magnitude of the differential current and the change in voltage and thereby determines the condition of the battery.

Abstract: A battery's impedance is measured by a technique that normally uses a current divider network which is connected to the battery. The circuit used according to this technique has a current generator producing a regulated current signal and has one or more sensing impedances which are normally positioned electrically parallel, or in some alternate embodiments in series, with the battery. A DC-blocking capacitor prevents the battery voltage from draining into the one or more sensing impedances. A magnetic field sensor or comparable device measures the magnitude and/or phase of current passing through the sensing impedances. Substitution of a number of calibrated impedances into the circuit in place of the battery permits an initial mathematical computation of the battery's impedance utilizing this technique. Thereafter battery impedances can be computed with the current without using calibrated impendances.

Abstract: A device measures complex self-immittance of a general element at a discrete frequency by implementing “sine/cosine correlation” in software. An active source excites the element with a periodic voltage or current having fundamental period equal to the reciprocal of the desired measurement frequency. Linear circuitry senses two signals; one proportional to the periodic voltage or current excitation, the other proportional to the periodic current or voltage response. Identical low-pass or band-pass filter-response functions process each signal to remove higher-order harmonics. The resulting band-limited signals are each sampled in synchronism with the excitation, digitized, and inputted to a microprocessor or microcontroller which performs the appropriate calculations.

Abstract: A periodic time-varying current with smallest period 1/f1 excites a cell/battery and provides a timing reference. Linear circuitry produces two signals, one proportional to the excitation current, the other proportional to the responding time-varying voltage. These signals are processed with identical frequency-limiting filter characteristics to attenuate higher-order harmonics and noise. Using the timing reference for synchronization, a microprocessor/microcontroller commands analog to digital converters to sample the frequency-limited current and voltage signals at equally-spaced times over a period and accepts the digitized samples as inputs. The digital samples are averaged over multiple periods and employed to calculate averaged Fourier coefficients of in-phase and quadrature components of frequency-limited current and voltage at frequency f1.

Abstract: A microprocessor couples to a voltage sensor through an analog to digital converter. The voltage sensor is adapted to be coupled across terminals of a battery. A small current source is also provided and adapted to be coupled across the terminal to the battery. The current source is momentarily applied to the battery and the resulting change in voltage is monitored using the microprocessor. The microprocessor calculates battery conductance based upon the magnitude of the differential current and the change in voltage and thereby determines the condition of the battery.

Abstract: A battery charging apparatus 1 includes a full-charging detecting system 11. While a battery is charged, the full-charging detecting system operates as follows. A charging current supplied from an DC power source is detected. The internal impedance is computed on the basis of the charging current thus detected and charging voltage of the DC power source. The full-charging of the battery is detected on the basis of the comparison between the internal impedance thus computed and a prescribed value. In this configuration, even when the full-charging capacity varies owing to the degradation of the battery, the full-charged state of the battery can be detected precisely.

Abstract: A method and system for calibrating analog integrated circuits. Initially, a single calibration circuit is formed integral with a group of analog integrated circuits. A control signal and a calibration signal are generated from the calibration circuit. Next, the control signal and the calibration signal are selectively coupled to an input of a particular analog integrated circuit among the group of analog integrated circuits. The particular analog integrated circuit is then selected for calibration via the control signal.

Abstract: An apparatus for testing a storage battery includes battery test circuitry configured to perform a battery test on the storage battery. The battery test circuitry responsively provides a test result output related to a condition of the storage battery. A test count memory configured to store a test count and test count circuitry is configured to maintain a test count in response to an occurrence of a battery test performed by the battery test circuitry.

Abstract: A device includes a microprocessor or microcontroller and measures real and imaginary parts of complex immittance of a cell or battery at n discrete frequencies, where n is an integer number equal to or greater than 2. The device determines cell/battery properties by evaluating components of an equivalent circuit model comprising 2n frequency-independent elements. Equating real and imaginary parts of measured immittance to values appropriate to the model at the n measurement frequencies defines a system of 2n nonlinear equations. Introducing 2n intermediate variables permits solving these equations and leads to values for the 2n model elements. A table of element values contains virtually the same information as the spectrum of complex immittance over a wide frequency range but provides this information in a more concise form that is easier to store, analyze, and manipulate. Thus, the 2n element values may themselves comprise the desired result.

Abstract: Provided with a method of measuring battery capacity by impedance spectrum analysis, which is to measure a characteristic impedance spectrum of primary and secondary batteries and determine the battery capacity the method including the steps of: (1) measuring the characteristic impedance spectrum of a battery in a predetermined frequency region; (2) determining a parameter from the measured impedance spectrum; (3) monitoring in advance the correlation between the determined parameter and the battery capacity measured by a real-time discharge technique; and (4) determining the battery capacity from the characteristic impedance spectrum of a battery having an unknown capacity based on the monitored correlation.

Abstract: A device and method for determining the state of charge of a battery includes a microprocessor-controlled arithmetic unit connected in parallel to the terminal voltage of the battery. The arithmetic unit is selectively connectable with an ohmic reference resistance placed in parallel with a load resistance which is arranged in series with the battery, and with a capacitor chargeable or dischargeable via the arithmetic unit. The arithmetic unit is further capable of acquiring a value of the voltage drop across the capacitor. The arithmetic unit is operable in a first operating state in which it is disconnected from the reference resistance, and a second operating state in which the arithmetic unit is connected with the resistance. After the capacitor is charged to the terminal voltage of the battery, it is allowed to discharge. With the arithmetic unit in the first operating state, a first point in time marked by the voltage across the capacitor reaching a first threshold value is registered.

Abstract: A periodic time-varying current with smallest period 1/f1 excites a cell/battery and provides a timing reference. Linear circuitry produces two signals, one proportional to the excitation current, the other proportional to the responding time-varying voltage. These signals are processed with identical frequency-limiting filters to attenuate higher-order harmonics and noise. Using the timing reference for synchronization, a microprocessor/microcontroller commands analog to digital converters to sample the frequency-limited current and voltage signals at equally-spaced times over a period and accepts the digitized samples as inputs. The digital samples are averaged over multiple periods and employed to calculate averaged Fourier coefficients of in-phase and quadrature components of frequency-limited current and voltage at frequency f1.

Abstract: An apparatus for electronically testing or monitoring the condition of a storage battery is provided. The apparatus includes an inductance cancellation circuit for use in a Kelvin probe of an electronic battery tester. The induction cancellation circuit reduces inductive coupling between leads of the Kelvin probe. The apparatus also includes a DC coupled AC amplifier for amplifying an AC response signal of an electronic battery tester. Other aspects include a critically damped band-pass filter a response signal, a DC to DC convertor isolation circuit, operator editable test criteria, a battery temperature sensing element, an automatically adjustable gain stage and the use of an internal reference standard for a self calibration.

Abstract: A method and system for evaluating lead-acid battery jars in a battery backup or standby system applies, in a stepwise manner, a current load across a group of adjacent jars. Voltage measurements are taken across each jar in the group at various times during the application of the current load. These measurements are utilized to calculate the ohmic resistance, the charge transfer resistance and the double layer capacitance of each jar.

Abstract: A system and method for comprehensive analysis of a multi-cell battery, such as of the nickel-cadmium type, on an individual cell level basis and overall battery basis. For an unsealed battery, which affords access to the individual battery cells, (FIG. 2) tests are carried out to determine the presence of any shorted or reversed cells, and these can be repaired or replaced ((6)-(11)). The individual cells are then tested for sufficient electrolyte on the basis of comparing the cell internal resistance to a maximum internal resistance for the cell and electrolyte added as needed ((12)-(15)). A sealed battery, to which there is no access to the individual cells, is first tested for shorted or reversed cells on a battery level basis ((16)-(19)).

Abstract: A method of measuring battery capacity using a voltage response signal based on a pulse current, where the method includes the steps of: measuring a voltage response signal based on a pulse current signal applied to a primary or secondary battery; performing an approximation of the measured voltage response signal to an equivalent circuit model composed of resistors, capacitors and transmission lines to determine the model parameters; and determining the unknown battery capacity from the voltage response characteristics based on a correlation between the measured capacity and the model parameters, which correlation is previously determined by a real-time discharge method, thereby takes a shorter time than a real-time discharge method and delivering efficiency and reliability in determining model parameters of an equivalent circuit which are in close correlation with the charge/discharge condition of the battery.

Abstract: A battery capacity tester method and apparatus are provided. The battery capacity tester determines the present internal battery impedance by measuring terminal voltages during successive applications of a known load, each load drawing a predetermined current from the battery. This calculated internal battery impedance is used to determine battery capacity based on a precharacterization of the battery that establishes a relationship between the internal battery impedance and the remaining battery capacity.

Abstract: A vehicle starting battery cold-cranking amps meter and associated method includes providing a current source, a voltage meter, a current meter and a control. The current source produces a current pulse during a brief time interval at a known magnitude that is less than rated cold-cranking amps of the vehicle starting battery being tested. The volt meter measures battery terminal voltage of the vehicle storage battery being tested while the current source is sourcing current to or sinking current from the vehicle starting battery being tested. The control determines internal impedance of the vehicle starting battery being tested from the terminal voltage of the vehicle starting battery while the current source is sourcing current to or sinking current from the vehicle starting battery being tested and determines cold-cranking amps from the internal impedance and an output of the temperature meter.

Abstract: Apparatus and method are provided for measuring the series resistance of each individual cell of a battery bank for establishing the readiness of the batteries. The invention comprises a switch in series with a load, connected across each cell of the battery. An electronic switch momentarily imposes the load on the cell and the value of the current drawn from the battery and the voltage across it is measured with an A/D device. A controller directs a plurality of the switched loads on a plurality of cells. The A/D device and controller on each cell communicates their measurements to a remote host computer, preferably via an RF serial modem. The host computer calculates the internal resistance and provides alarm and other reporting functions. Further, as the measurement imposes a small energy drain on the cell, through independent adjustment of the frequency of measurement for each cell, over-charging of the individually cells can be equalized.

Abstract: A controller for a hybrid electric system such as a hybrid electric vehicle includes a load, a battery, and a controllable source of auxiliary electricity. The state of charge (SOC) of the battery is estimated, and an error signal is generated which represents the difference between a desired and actual SOC. The SOC error signal is processed by at least integration, to produce a source signal representing the desired auxiliary source current. A second error signal is generated between the actual current. from the auxiliary source and the desired current from the auxiliary source. The second error signal is processed, at least by integration, to produce a control signal for controlling the auxiliary signal source.

Abstract: A method for charging a secondary battery is disclosed. The method comprises the steps of detecting an impedance of the battery; charging the battery with a substantially constant first current having a value smaller than a predetermined current value if the detected impedance of the battery is equal to or greater than a predetermined impedance value; charging the battery with a substantially constant second current having a value equal to or greater than the predetermined current value if the detected impedance is less than the predetermined impedance value; and terminating charging the battery with the first and second constant currents when the closed circuit voltage of the battery reaches a predetermined voltage value.

Abstract: A device includes a microprocessor or microcontroller and measures real and imaginary parts of complex immittance of a cell or battery at n discrete frequencies, where n is an integer number equal to or greater than 2. The device determines cell/battery properties by evaluating components of an equivalent circuit model comprising 2n frequency-independent elements. Equating real and imaginary parts of measured immittance to values appropriate to the model at the n measurement frequencies defines a system of 2n nonlinear equations. Introducing 2n intermediate variables permits solving these equations and leads to values for the 2n model elements. A table of element values contains virtually the same information as the spectrum of complex immittance over a wide frequency range but provides this information in a more concise form that is easier to store, analyze, and manipulate. Thus, the 2n element values may themselves comprise the desired result.

Abstract: A periodic time-varying current with smallest period 1/f.sub.1 excites a cell/battery and provides a timing reference. Linear circuitry produces two signals, one proportional to the excitation current, the other proportional to the responding time-varying voltage. These signals are processed with identical frequency-limiting filters to attenuate higher-order harmonics and noise. Using the timing reference for synchronization, a microprocessor/microcontroller commands analog to digital converters to sample the frequency-limited current and voltage signals at equally-spaced times over a period and accepts the digitized samples as inputs. The digital samples are averaged over multiple periods and employed to calculate averaged Fourier coefficients of in-phase and quadrature components of frequency-limited current and voltage at frequency f.sub.1.

Abstract: A method for testing electrical loads in a vehicle electrical system is provided, in which the loads, which are fed by a vehicle battery, are selectively switched on and off. The load-specific current consumption in the switched-on state is determined and assessed in each case. The battery voltage is measured immediately before and shortly after the switching-off of a previously switched-on load in order to determine the load-specific current consumption value from the load-specific battery voltage difference. The internal resistance of the battery serves indirectly as the measuring resistance, which is determined by loading the battery with a known load on a trial basis.

Abstract: A charging technique (200) charges a battery pack (102) by taking into account the additional internal circuit impedance of the battery pack. An optimum pack voltage value for the battery pack is calculated (208) based on the rated internal cell voltage as well as the charge current and the internal battery pack circuitry impedance. The battery pack can now be charged such that the internal battery cell voltage is maintained at the rated voltage throughout the charging process. The optimum pack voltage is also updated (220) to account for variations in the battery pack circuitry impedance over temperature (216, 218) as well as variations in charge current (222, 224) during the charging process.

Abstract: The method and the apparatus for detecting a deteriorating condition in a bank of standby batteries includes injecting an audio frequency current into one of the battery buses or cables, detecting an audio frequency current signal, matched to the injected audio frequency current signal, that is carried by the battery bus and detecting a voltage drop, at the audio frequency, across the bank of standby batteries. In one embodiment, current transformers are utilized in connection with an oscillator (to inject the AF current signal) and detection circuits (comparators and operational amplifiers) are utilized to generate a representative current signal and a representative voltage signal. The device detects when the standby batteries are operating in a normal, stable condition, that is, when the bank is neither being recharged nor is discharging DC power to the load.

Abstract: A device for testing a battery includes circuitry adapted to measure a first conductance of a first portion of a string of cells that makes up the battery. Further circuitry is adapted to measure a second conductance of a second portion of the string of cells that makes up the battery. Comparison circuitry compares the first conductance and the second conductance and provides an output based upon the comparison which is related to a condition of the battery.

Abstract: A microprocessor couples to a voltage sensor through an analog to digital converter. The voltage sensor is adapted to be coupled across terminals of a battery. A small current source is also provided and adapted to be coupled across the terminal to the battery. The current source is momentarily applied to the battery and the resulting change in voltage is monitored using the microprocessor. The microprocessor calculates battery conductance based upon the magnitude of the differential current and the change in voltage and thereby determines the condition of the battery.

Abstract: A battery remaining capacity measuring apparatus comprises a temperature sensor 5 and a remaining capacity operation portion 19. A temperature sensor 5 detects a temperature of a battery 3. A remaining capacity operation portion 19, wherein when a detected temperature of a battery 3 from a temperature sensor 5 is not within the range of a predetermined temperature in the state of an open circuit, a load 1 and a battery 3 which are previously obtained according to a detected temperature correct a line pattern in the state of an open circuit and when a load is connected to a battery, a remaining capacity can be obtained on the corrected line. Accordingly, it is possible to obtain a remaining capacity according to this temperature, even if a temperature of a battery 3 is not within the range of a predetermined temperature.

Abstract: A battery condition detecting method is provided which includes the steps of setting a current required during standard discharge of a battery as a set current, detecting a discharge current and a voltage of the battery, determining a battery voltage when the battery discharges the set current based on the discharge current and the voltage of die battery, and projecting an actual voltage of the battery based on the battery voltage determined.

Abstract: A battery tester is formed at an AC constant-current generator for applying an AC current for measurement to a battery BT under test via a coupling capacitor, an internal resistance detecting device for detecting the internal resistance of the battery BT according to a voltage signal therefrom when the AC current is applied, a voltage detecting device for detecting the terminal voltage across the battery, and a deterioration judging unit for judging the deterioration of the battery from the internal resistance and terminal voltage detected by the internal resistance detecting device and the voltage detecting device. The internal resistance and terminal voltage of the battery are measured simultaneously, and deterioration of the battery is judged from the measurement data.

Abstract: A volt meter changes the dividing resistance across the terminals of a voltage source between first and second different resistances and measures voltage across the dividing resistor at the different resistances to determine an accurate voltage source magnitude from the measured voltages and the ratio of second to first resistances despite an unknown source resistance.

Abstract: In estimating the residual capacity of a battery according to the maximum output estimating process, a reference point is established in advance at the intersection of a plurality of current/voltage characteristic linear curves corresponding to various residual capacities of the battery or in an area in the vicinity of the intersections of the curves. A current/voltage characteristic linear curve is determined so as to pass through the reference point and a measured operating point of the battery which corresponds to the present discharging current and output voltage values measured when the battery is discharged. Then, a maximum transfer power value of the battery is determined from the current/voltage characteristic linear curve thus determined, and the present residual capacity of the battery is estimated from the maximum transfer power value.

Abstract: Connections between batteries and impedance measuring circuitry in a system for on-line measurement of battery cell impedance is effected by twisted wire triplets.

Abstract: Various embodiments of an improved electronic device for testing or monitoring storage batteries that may be only partially charged are disclosed. The device determines the battery's small-signal dynamic conductance in order to provide either a proportional numerical readout, displayed in appropriate battery measuring units, or a corresponding qualitative assessment of the battery's relative condition based upon its dynamic conductance and electrical rating. The device also determines the battery's terminal voltage in an essentially unloaded condition and utilizes this information to automatically correct the measured dynamic conductance. The automatic correction is performed by the electronic device using information or functions which are tailored for the particular type of battery being tested.

Abstract: The method of calculating rechargeable battery charge capacity of this invention has steps to temporarily interrupt charging and calculate battery internal impedance, to calculate a no-load battery voltage by subtracting the product of internal impedance and charging current from the battery voltage when charging current is supplied, to calculate charging power by multiplying no-load voltage and charging current, and to repeatedly perform the charging power calculation integrating that charging power result to compute battery charge capacity.

Abstract: A battery impedance monitor includes a driver section having an oscillator which produces a pulsating loading signal which controls periodic loading of the battery to produce at its output terminals a pulsating voltage component having a peak-to-peak amplitude superimposed on the DC output voltage of the battery. This pulsating voltage component is detected in a measuring section, which applies the battery output through a voltage divider to a peak detector which outputs an indicating voltage level proportional to the peak-to-peak amplitude of the pulsating output signal, this indicating level being held on a storage capacitor. The voltage divider includes a Zener diode which shifts the DC level of the battery output without affecting the amplitude of the pulsating component.

Abstract: Available battery life of a rechargeable battery is assessed and indicated to a user (300). A temporary load is switched onto a fully charged battery (304, 308) and voltage measurements are taken in both unloaded and loaded conditions (306, 310). The battery's internal impedance is determined (312) based on the measured voltages and is compared to a predetermined threshold (314). The predetermined threshold is set based on a value representing a selected minimum available capacity of the battery. An indicator alerts the user as to the status (316, 318) of the available battery life of the battery.

Abstract: An intelligent automated battery multimeter system having data storing and multi-cell reading capabilities in a self-contained unit for automatically performing in-service DC load testing on battery cells without requiring the removal of battery chargers wherein the tester measures, records and displays load voltages, float voltages, internal cell resistance, intercell connection resistance and other cell integrity measurements. The battery tester is also computer compatible wherein it provides PC links for extracting data from the system and downloading it into computer networks.

Abstract: An apparatus and method for measuring electrical characteristics of an energy delivery system utilizes a voltage sensitive circuit such as a voltmeter, a controllable current source or sink and a microcomputer. The microcomputer controls the current source or sink in order to source at least one predetermined current pattern or to sink at least one predetermined current pattern from a portion of an energy delivery system. The voltage sensitive circuit responds to a voltage developed in response to the current pattern and the microcomputer calculates at least one electrical characteristic of the energy system as a result of the response.

Abstract: A method for determining whether an electrochemical cell is substantially fully charged. The determination is made by ascertaining the rate of change of the impedance of the cell with changing frequency, at low frequency. A method for determining the state of charge of an electrochemical cell by comparing the impedance of the cell at two or more frequencies or by comparing the impedance of the cell, at a medium frequency, with the impedance at high frequency. Apparatus for generating output signals representative of the magnitude of resistive and reactive components of an impedance (30). The apparatus has a signal generator (70) for passing AC current through the impedance, and a synchronous demodulator circuit (88) for demodulating AC signal appearing across the impedance pursuant to passing the current through it. A phase shift circuit (130, 132, 136, 138, 140) selectively generates control signals in phase or 90.degree.

Abstract: A method of and apparatus for centrally monitoring the capacity of batteries in a battery string includes electrical leads connected to each battery terminal of the battery string. A capacity testing system a) switches between the electrical leads for sequentially selecting the leads associated with the terminals of each battery, b) measures the internal resistance of the battery associated with each selected pair of electrical leads, c) compares the internal resistance of each battery cell to an internal resistance threshold, and d) triggers an alarm when the internal resistance of a battery exceeds the internal resistance threshold.

Abstract: A voltage sensor detects a terminal voltage of a battery connected to a load and a current sensor detects a current flowing through the load. A voltage-current changing tendency calculation unit reads a detected voltage and a detected current detected by the voltage sensor and the current sensor and outputs, every predetermined period of time, plural data of the detected voltage and the corresponding detected current as dispersed data. A voltage-current approximating line calculation unit inputs the dispersed data and determines, based on the dispersed data, a voltage-current approximating linear function each time the predetermined period of time. A battery remaining capacity calculation unit determines, each time the voltage-current approximating linear function is determined, a remaining capacity of the battery based on the voltage-current approximating linear function.

Abstract: Detected values of a voltage and a current of a battery which are supplied from a voltage and current detector are stored in a memory at a plurality of times while the battery is being discharged. A regression line calculator determines an internal resistance and an open-circuit voltage (non-load voltage or electromotive force) of the battery based on the detected values stored in the memory. Even when the battery is in use with the voltage and the current frequency varying while it is being discharged, a memory effect on the battery can be determined from a reduction in the open-circuit voltage and a deterioration of the battery can be determined from an increase in the internal resistance.

Abstract: The present invention relates to a method of measuring residual capacity of a Ni/MH (nickel/metal hydride) cell by measuring the change in the electrical resistivity of a Ni/MH cell according to the change of the concentration of hydrogen in metal hydride. According to the present invention, a method for measuring residual capacity of a Ni/MH cell comprises the steps of measuring electrical resistivity of a first Ni/MH cell, and determining the residual capacity of the first Ni/MH cell (i) from a predetermined data of n-pairs of electrical resistivity values and residual capacity values of a second Ni/MH cell which has substantially the same composition as the composition of the first Ni/MH cell, or (ii) based on a predetermined functional relationship between the electrical resistivity and residual capacity of the second Ni/MH cell.

Abstract: A low battery condition is determined by sampling battery terminal voltage with a voltage comparator under light and heavy loading, and indicating a low battery condition when the rate of change of the sampled voltage or the rate of change of the internal resistance of the battery is greater than a predetermined limit.

Abstract: A continuously monitored battery operated power supply for maritime applications includes four batteries which form a parallel connected pair of banks in which the cells in each bank are series connected to each other. A Wheatstone bridge circuit connects a midpoint between the plurality of cells in the first bank of battery cells and a midpoint between the plurality of cells in the second bank of batteries. The circuit also includes a volt meter for indicating a voltage change due to the degeneration of a cell when the voltage change exceeds a predetermined value.

Abstract: A technique for measuring battery characteristics comprises measuring a battery terminal voltage, a charge/discharge current and a charge/discharge time. The technique entails arithmetically determining an integrated power, an integrated charge quantity and an integrating time interval over a period extending from a start of a charge/discharge process to an end thereof, determining a mean terminal voltage by dividing the integrated power by the integrated charge quantity, determining a mean charge current by dividing the integrated charge quantity by the integrating time interval, determining a polarization resistance of the battery on the basis of the mean terminal voltage and the mean current by using a battery polarization resistance model, and finally determining an open-circuit voltage of the battery on the basis of the polarization resistance. The information culled from the above technique may be used to control a charge/discharge process and to predict the remaining life of the battery.