Abstract: The present invention provides a method for enabling qualification of at least a portion of a fuel cell system. The method includes electronically obtaining at least one result of a test of the at least a portion of a fuel cell system and electronically comparing the at least one result to at least one qualifying criteria.

Abstract: In a diagnostic method for a fuel cell battery, the amount of cross leak is determined by supplying the anode of the fuel cell battery with a hydrogen or hydrogen-containing gas, and supplying the cathode with an inert gas or vacuuming the cathode, and measuring the voltage of each cell.

Abstract: A method for providing information to a user of a fuel pump includes steps of: (A) performing an initial step of bidirectionally coupling a microprocessor of the fuel pump to a communications network, the communications network having a plurality of remote computers bidirectionally coupled thereto; (B) entering a user's information request into the microprocessor of the fuel pump; (C) transmitting data representing the information request from the microprocessor of the fuel pump to the communications network; (E) directing the data representing the request to a remote computer over the communications network; (F) fulfilling the information request with the remote computer and transmitting the requested information back to the microprocessor of the fuel pump over the communication network; and (G) using an output device of the fuel pump, presenting the requested information to the user in a human perceptible format.

Abstract: Voltage reversal in fuel cell stacks may be detected and/or prevented by monitoring each cell or small groups of cells in the stack for low voltage conditions. An improved cell voltage monitor is constructed using a plurality of voltage monitoring units in which each unit comprises a heating resistor, a rectifier in series therewith, and a sensing thermistor in thermal communication with the heating resistor. The heating resistor is electrically-connected across a cell or cells and heats the associated sensing thermistor in accordance with the voltage of the cell(s). Since the resistance of the sensing thermistor is indicative of its temperature and hence also of voltage of the cell(s), the sensing thermistor resistance can be used to signal a low voltage condition.

Abstract: A battery is a collection of cells place in series, parallel, or both. A telemetry circuit is presented for determining the individual voltage of each cell making up a battery. This device uses a high voltage isolation circuit to isolate each cell from the remainder of the measuring circuitry. This is to ensure precision cell voltage measurements are made even at high common-mode voltages. This is an inherent problem for high voltage battery telemetry designs.

Abstract: A power source device comprises a cell unit 12 comprising a plurality of cells 12a. Connected between a positive side terminal and a negative side terminal of the cell unit 12 is a first current line 34 having two voltage dividing resistors 30, 32 interposed therebetween, and is a second current line 22 having two protection resistors 14, 16 and two detection resistors 18, 20 interposed therebetween. An intermediate point 24 of the second line 22 is grounded to a grounding 26 via an insulation resistor 28. The voltage difference between a voltage (V1, V2) detected by the detection resistors 18, 20 and a reference voltage (Vc) obtained from a point of connection 35 between the voltage dividing resistors is input to two Op-Amps 36, 38 serving as the input voltage (V1IN, V2IN). Based on the output voltage (V1OUT, V2OUT) obtained from the Op-Amps 36, 38, leakage occurrence is detected.

Abstract: A battery system including a main battery cell having a first capacity; a sense battery cell connected in series with the main battery cell, the sense battery cell having a second capacity less than the first capacity; and a battery capacity indicator monitoring a parameter of the sense battery cell. A method of determining a battery condition in a battery operated device, the method including providing a battery system, the battery system comprising a main battery cell having a first capacity and a sense battery cell, the sense battery cell having a second capacity less than the first capacity, the main battery cell and the sense battery cell being coupled in series; monitoring a parameter of the sense battery cell; and determining a condition of the main battery cell from the monitored sense battery cell parameter.

Abstract: An apparatus and method for measuring conductance are provided. The method and apparatus are particularly well adapted for use with a removable or replaceable cartridge in a blood analysis system. The apparatus generally involves providing a system having a first, unfiltered, conductance measurement cell and a second, filtered, conductance measurement cell. The preferred method involves relating values measured in the two cells for a whole blood sample and for a known calibrant together, to obtain a value, for example hematocrit, for the unknown whole blood sample.

Abstract: A method for grouping unit cells of a similar impedance spectrum uses pattern matching technology to optimize the performance of a battery pack made of primary or secondary batteries as the unit cells connected in series, in parallel or in combination of them. To make an optimal battery pack with unit cells of a different internal characteristic, the method includes measuring the impedance spectrum of the individual unit cell in a wide frequency region at the same temperature and in the same state of charge (SOC), digitizing the difference in impedance spectrum among the unit cells into a relative value using the pattern matching technology, and selecting unit cells of a most similar impedance spectrum (i.e., a smallest relative difference in impedance spectrum) to make a battery pack.

Abstract: In a battery pack which includes a plurality of parallel blocks, each of which comprises a plurality of cells connected in parallel, and which are themselves connected in series, the voltage of each parallel block of the battery pack before and after discharge or before and after charge of a predetermined amount of capacity is detected, and abnormality of the cells connected in parallel within each parallel block is determined based upon the amount of change of voltage of each parallel block.

Abstract: A technique that is usable with a fuel cell stack includes providing a fuel flow to the stack, changing the fuel flow and observing a response of at least one cell voltage of the stack to the change in the fuel flow. An efficiency of the stack is regulated based on the observation.

Abstract: An automated battery configuration system for a telecommunications power system includes at least one rectifier module, a controller and at least one backup battery. A database system is associated with the controller stores a plurality of records that include a plurality of backup battery parameters. A user interface that is associated with the controller receives user-provided input of at least one battery specifying parameter. The user interface communicates with the database system to retrieve a selected one of the records based on the battery specifying parameter. The controller communicates with the database system and employs at least one of the parameters of the selected record to alter an operating setting of the telecommunications power system. The battery specifying parameters include a manufacturer designation and a model designation of the backup battery.

Abstract: A battery voltage measurement device includes: a plurality of first switching sections, wherein each pair of adjacent first switching sections sequentially selects two output terminals of each of a plurality of battery blocks included in a battery pack; a level change section for changing a level of a battery voltage of each battery block which is input to the level change section via the first switching section; an A/D conversion section for performing an A/D conversion of battery voltage data output from the level change section; and a reference voltage control section for controlling an output of a reference voltage of the level change section according to the polarity of the voltage input to the level change section.

Abstract: A battery voltage measurement device includes: a plurality of first switching sections, wherein each pair of adjacent first switching sections sequentially selects two output terminals of each of a plurality of battery blocks included in a battery pack so that each of the selected output terminals are connected to one of a pair of conductor wires; a voltage detection section for detecting a battery voltage of each of the plurality of battery blocks via the pair of conductor wires; and second switch sections each being provided on a respective one of the pair of conductor lines and being serially connected to each group of the plurality of first switch sections connected in parallel to one of the pair of conductor lines.

Abstract: In a voltage measuring circuit for a composite fuel cell system, the potential of at least one point of the composite fuel cell system is detected by tapping the potential of such point, and feeding it to an input of an arrangement for evaluating the voltage. A potential shifting element is interposed between the at least one point of the composite fuel cell system and the input of the arrangement, which element is connected in series with a current sink or current source. A voltage supply circuit for such voltage measuring circuit of a composite fuel cell system comprising a plurality of individual fuel cells connected in series includes at least one voltage stabilization element connected in parallel with the circuit which is to be supplied with voltage by the composite fuel cell system. At least one current source or current sink is connected in series with this parallel circuit.

Abstract: Cell controllers provided to control modules each constituted of a plurality of cells each calculate deterioration factors indicating the extents to which the cells under its control have become depleted and detect the deterioration factor of the cell in the most advanced state of depletion. The cell controller provided at the uppermost stage transmits the detected deterioration factor to the cell controller at the next stage. The subsequent cell controllers connected at the stages succeeding the uppermost stage each compare the deterioration factor detected therein and the deterioration factor transmitted from the cell controller at the proceedings stage and transmits the deterioration factor with the smaller value to the cell controller at the next stage. The cell controller at the lowermost stage, too, executes the processing described above and transmits the deterioration factor with the smaller value to a battery controller.

Abstract: A plurality of battery pack blocks connected in series-parallel have their operation states monitored by battery ECUs, respectively based on detected voltage, current, and temperature. Detection outputs by current sensors provided at the charge/discharge circuits of the battery pack blocks are added up for the parallel-connected battery pack blocks in an analog data state before A/D conversion, so that the total charge/discharge current in the battery power source device is obtained.

Abstract: A multiplex voltage measurement apparatus includes: (N+1) voltage detection terminals connected to N serially connected voltage sources; a capacitor which is charged with a voltage value of any of the N voltage sources; a first sample switch for selectively connecting odd-numbered voltage detection terminals among the (N+1) voltage detection terminals to a first terminal of the capacitor; a second sample switch for selectively connecting even-numbered voltage detection terminals among the (N+1) voltage detection terminals to a second terminal of the capacitor; a voltage measurement circuit for measuring the voltage value stored in the capacitor; a third sample switch for connecting the first terminal and the second terminal of the capacitor to the voltage measurement circuit; and a polarity controller for controlling the first and second sample switches such that one of the N voltage sources is selected while the third sample switch is open.

Abstract: An apparatus for measuring the voltage of a plurality of voltage sources mounted in a stack includes a plurality of contact units, each having a plurality of electrical contacts mounted therein, for voltage tapping of the voltage sources. The contact units are held in a support module, arranged side by side along a longitudinal axis. An evaluation unit is coupled in communication with the contacts contained in the contact units, either directly, or via an intermediate unit that includes addressing and processing capability. The number of contact units that are arranged in the support module is variable in accordance with the number of voltage sources contained in the stack, and the contact units themselves are movable longitudinally within the support module to accommodate spacing of the voltage sources in the stack.

Abstract: A system for monitoring performance of one or more batteries in a battery plant facility. A set of sensors for each battery are used to measure a plurality of battery operation parameters comprising the battery current, battery voltage, and internal battery temperature of each said battery. A processor generates, for each battery, a plurality of battery status parameters comprising a true age parameter and a float capacity parameter. During a float period, the true age parameter is updated based on elapsed time corrected for battery temperature history and the float capacity is updated based on the most recent true age parameter. During a discharge period, the float capacity parameter is updated based on the evolution of plant voltage during the discharge. After the discharge period, at the beginning of a subsequent float period, the true age parameter is updated based on the float capacity parameter determined during the immediately previous discharge period.

Abstract: A battery-monitoring system in accordance with the principles of the present invention includes one or more cell sensors modules linked to a battery sensor module via a data interface. In turn, the one or more battery sensor modules may be linked to an alarm interface. Each cell sensor module includes one or more sensors that monitor physical parameters, such as cell voltage and temperature, related to the corresponding cell. Each battery sensor module monitors physical parameters, such as battery voltage, discharge current, and temperature related to the battery. The battery sensor module also gather cell monitoring information from the plurality of cell sensor modules. Various battery monitor-related analytical, control, and reporting functions may be performed by the various modules.

Abstract: By finding a voltage difference &Dgr;V between the maximum value and the minimum value of voltage of each cell constituting a battery set and then combining the voltage difference &Dgr;V with current I passing through the battery set into a value pair and store a plurality of the value pairs, the relationship between the voltage difference &Dgr;V and the current I is a relation represented by a straight line with the slope &Dgr;R thereof corresponding to an internal-resistance difference. Therefore, fault in the battery set can be determined from the magnitude of the slope &Dgr;R computed by a least-squares method. Fault determination for a battery set is made more accurate because variations in electromotive force caused by charge-and-discharge patterns and by changes in temperature are canceled when the voltage difference &Dgr;V is determined.

Abstract: A system for measuring voltages of batteries in a battery pack. The system has an isolation circuit operative to isolate a voltage for each of the batteries. A buffer of the system is in electrical communication with the isolation circuit and operative to store the voltage of each of the batteries when the batteries are isolated. The system further includes a voltage measuring device in electrical communication with the buffer. The voltage measuring device is operative to measure the voltage in the buffer and provide a stable measurement of the battery voltages therefrom.

Abstract: In a method and an apparatus for monitoring a selected group of fuel cells of a high-temperature fuel cell stack, a change over time in an averaged electrical voltage of the fuel cells of the selected group is ascertained and compared with a reference value that detects at least a change over time in a voltage of other fuel cells. The method permits a reliable detection of the failure of one fuel cell of a stack with simple measures.

Abstract: A long-lived, lightweight, and quickly and precisely charged storage capacitor power supply capable of stably supplying electric power to a load. The power supply has a capacitor block consisting of capacitors connected in series, in parallel or in any combination of series and parallel. The power supply further includes a charging circuit for charging the block, a charging power supply connected with the block via the charging circuit, and a charge-limiting circuit. This charge-limiting circuit detects the voltage across the terminals of the block and limits charging of the block if the voltage reaches a given value. One embodiment of the invention further includes a charge-limiting circuit, a full charge-detecting circuit, and a residual electricity-detecting circuit connected in parallel with the block. The charge-limiting circuit senses that the voltage across the terminals of the block exceeds the given value and causes the charging current to bypass the block.

Abstract: An electronic circuit for measuring voltage signals in an energy storage device is disclosed. The circuit includes a plurality of battery segments forming the energy storage device. An amplifier circuit is connected across one of the battery segments for converting a differential voltage to a reference current. A sense resistor is associated with the amplifier circuit to convert the reference current to a voltage signal which is proportional to the voltage across the battery segment. A voltage measurement node associated with the sensing resistor may be used for measuring the voltage signal. In one embodiment of the invention, a multiplexing and sampling circuit provides digitized voltage samples to a processor. The voltage level of each cell within the battery pack can then be monitored by the processor.

Abstract: A battery voltage measurement device includes: a plurality of first switching sections, wherein each pair of adjacent first switching sections sequentially selects two output terminals of each of a plurality of battery blocks included in a battery pack; a level change section for changing a level of a battery voltage of each battery block which is input to the level change section via the first switching section; an A/D conversion section for performing an A/D conversion of battery voltage data output from the level change section; and a reference voltage control section for controlling an output of a reference voltage of the level change section according to the polarity of the voltage input to the level change section.

Abstract: Frequency of judgment of welding of relays is increased to increase likelihood of early detection of welding. It is determined that a battery 22 is not being recharged or discharged when a vehicle speed V of an electric vehicle is approximately 0 and a brake pedal 54 is pressed, and a switching element of an inverter 24 is controlled to be switched to discharge electric charges which are stored in a capacitor 44. After discharging, relays 30, 32 are turned off, and voltages RV1, RV2 between the terminals of the relays 30, 32 are detected by voltmeters 40, 42 to judge whether either of the voltages RV1, RV2 has a threshold value RVref (approximate value 0) or less. When it is so determined, it is judged that the relays 30, 32 are welded, and an LED 70 is illuminated.

Abstract: The voltage measuring apparatus of the present invention comprises: a capacitor configured of a plurality of capacitor elements and divided at a connection point into two sections of the same capacitance; a first switching device for connecting a voltage source to be measured to both terminals of the capacitor; a differential amplifier; a second switching device for connecting both terminals of the capacitor to inputs of the differential amplifier; and a third switch for connecting the connection point in the capacitor to signal reference potential of the differential amplifier in time synchronization with the second switching device.

Abstract: A device for testing a battery of the type which consists of a string of individual cells includes circuitry adapted to measure a dynamic parameter of the cells or groups of cells that make up the battery. Measurements are used to construct a reference standard or to calculate a statistical parameter of a cell or group of cells that make up the battery. A output is provided which relates to the condition of the battery.

Abstract: A set battery which generates a high voltage comprises a number of battery modules connected to each other in series. A module voltage of each of the battery modules is detected by a corresponding differential voltage detecting circuit and is transmitted to an A/D convertor. Each of Several voltage detecting blocks is constituted by a plurality of the differential voltage detecting circuits for detecting module voltages of a plurality of the battery modules contiguous to each other. Each of the differential voltage detecting circuits belonging to the same voltage detecting block is applied with a common reference potential which is used to detect the module voltage. The reference potential is set to values which differ from each other for the respective voltage detecting blocks.

Abstract: A system includes a divider network, a memory and a circuit. The divider network is adapted to be coupled to fuel cells of a fuel cell stack and provide pairs of signals. Each pair of signals is associated with a different fuel cell and indicates a terminal voltage of the associated cell and another voltage common to the pair of signals. The memory stores indications of different common mode gains, and each common mode gain indication is associated with a different one of the pairs of signals. The circuit is coupled to the memory and adapted to generate an indication of the terminal voltage from each pair based on the associated common mode gain indication.

Abstract: A modification to existing mono-block battery design for positively indicating the operating condition of the battery by adding a failure detector. The voltage of two groups of internal series connected cells are measured and compared. An indicator of one color indicates the battery is operating normally and an indicator of a contrasting color indicates the battery is defective. The indicator may be located remotely from the failure detector. An additional embodiment provides for an optical indicator located remotely from the failure detector such that luminous energy is transferred from the failure detector to the remote indicator by an optical-conductor.

Abstract: A power storage device has a plurality of series-connected storage battery units, battery circuits associated with the storage battery units to control or monitor the storage battery units, respectively; a main circuit of a potential level different from that of the battery circuits; and a potential level changing circuits connecting the battery circuit to the main circuit. The power storage unit is small in construction and operates at a low power consumption in a high control accuracy.

Abstract: A battery bank in an enclosed battery compartment is provided with subsidiary connectors that run from the battery compartment to an external test panel. Subsidiary connectors from each of the batteries connect to test jacks on the test panel so that each battery can be individually tested by an external test device without exposing the operator to danger by opening the battery compartment doors. Besides increased safety, the benefit is a faster, more convenient test process that facilitates greater timeliness in testing and maintenance, an especially important feature in an uninterruptible power supply.

Abstract: A system that is usable with a stack of fuel cells that have cell terminals includes a circuit and scanning units. The circuit provides a selection signal that indicates selection of at least one of the fuel cells for a voltage measurement. The scanning units are coupled to the stack to establish different groups of the fuel cells. Each group is associated with a different one of the scanning units, and each scanning unit has a ground that is referenced to a different one of the cell terminals. Each scanning unit is adapted to, in response to the selection signal, measure and indicate a voltage of each selected fuel cell within the group of fuel cells associated with the scanning unit.

Abstract: A battery unit includes a plurality of cells connected in parallel with one another, and a switch connected in series with at least one of the cells. The battery unit further includes a control circuit for controlling the on or off state of the switch, and a voltage detection terminal at which a voltage produced by a cell, to which the switch is connected, is developed. The switch can be turned off even with the battery unit connected to a load. A cell in series with which the switch is connected is disconnected from the load. In this state, the state of the cell can be detected through the voltage detection terminal. Even when a resistor is substituted for the switch, the same advantage can be provided. Moreover, the battery unit is freely detachably attached to a main unit of an information processing apparatus. The battery unit then supplies power to the main unit. A power supply control circuit for requesting notification of the state of each cell in the battery unit is incorporated in the main unit.

Abstract: Disclosed is an electrical power generation system comprised of a network of metal-air fuel cell battery (FCB) subsystems connected to an output power bus structure and controlled by a network control subsystem. The operation of each metal-air FCB subsystem is controlled so that, on the average, the amount of metal-fuel in each of the FCB subsystem is substantially the same, regardless of the total amount of metal-fuel remaining within the system available for electrical power generation. The electrical power generation system can be used as an electrical power plant that can be installed in virtually any system, device or environment in which there is a need to satisfy the peak power demand of an electrical load (e.g. motor, appliance, machinery, tools, etc.) independent of the total amount of metal-fuel remaining within the system.

Abstract: A temperature/voltage detecting unit has a temperature detector and a voltage detector. The temperature detector has a light electric system stabilized power supply for stabilizing a light electric system power supply voltage, a temperature resistance element provided close to a corresponding battery element, for changing its resistance value based on a change in temperature, and a voltage-to-frequency converter operating based on a voltage from the light electric system stabilized power supply, for detecting a terminal voltage of the temperature resistance element to which a constant current flows from the light electric system stabilized power supply, converting this value into frequency information and outputting the frequency information.

Abstract: A measurement circuit for a system of electrical modules in series with which are associated individual measurement interfaces and a measurement transducer to which the interfaces successively supply their measurement signals via a first serial link in response to interface selection pulses from a common logic unit transmitted serially from one interface to the next via a link. Each measurement signal is transmitted to the transducer either directly for the one closest to the transducer or via one or more interfaces which are not selected and which it crosses, depending on the position within the sequence of interfaces of the interface which produced it. To this end a routing unit, a measurement signal generator and a bypass are associated with each other in each interface. Protective diodes are connected in series in the link elements between the interfaces of two successive modules.

Abstract: A cell grading test fixture includes an array of cell sockets electrically interconnected in series so that current through the entire array of cells flows through each of the cells once inserted into the fixture. Associated with each socket is an indicator which indicates to the operator when a cell voltage has fallen to a predetermined level. Each socket of the test fixture includes a spring-loaded switch contact such that upon removal of a cell which has dropped below a threshold voltage, the movable contact engages the contact of an adjacent socket, shorting out the cell location such that the series circuit of cells continues to provide a current path for the remaining cells.

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: An electronic circuit for measuring voltage signals in an energy storage device is disclosed. The electronic circuit includes a plurality of energy storage cells forming the energy storage device. A voltage divider circuit is connected to at least one of the energy storage cells. A current regulating circuit is provided for regulating the current through the voltage divider circuit. A voltage measurement node is associated with the voltage divider circuit for producing a voltage signal which is proportional to the voltage across the energy storage cell.

Abstract: The invention provides a method and apparatus for controlling an alternator (605) by turning it ON or OFF depending upon the battery conditions and the operating conditions of the automobile monitored by various sensors (606, 609 and 611). By allowing the batteries of the automobile (610), controlled by a battery control unit (608), to charge and discharge based on its state of charge (SOC), the load imposed by the alternator (605) can be reduced such that the fuel efficiency of the automobile is optimized. By setting SOC limits, the alternator (605) can be turned ON or OFF, using an alternator control unit (604), depending on whether the SOC of the batteries is within the SOC limits. In addition, power loading limits can be preset so that the alternator (605) can be turned ON or OFF depending on the power loading conditions. The alternator (605) may be turned ON or OFF, using an alternator control unit (604), based on other conditions as well.

Abstract: Differential amplifiers (2) are provided to each of the batteries (1) for obtaining output voltages corresponding to the two terminal voltages of each battery (1). These differential amplifiers (2) are divided into groups (5) of a suitable number, and for each group (5), mutually insulated ground terminals (6) and mutually insulated control power sources (7) are provided. Each control power source (7) is connected between the power source terminal (2a) of each differential amplifier (2) and each ground terminal (6) of the respective group (5).

Abstract: A system that is usable with a stack of fuel cells that have cell terminals includes scanning units and a circuit. The scanning units are coupled to the stack and establish different groups of the fuel cells. Each scanning unit has a ground that is referenced to a different one of the cell terminals, and each scanning unit is adapted to measure the voltages of the fuel cells in an associated one of the groups and indicate the measured voltages. The circuit is adapted to communicate with the scanning units to receive the indicated voltages.

Abstract: A modification to existing mono-block battery design for positively indicating the operating condition of the battery. The voltage of two groups of internal series connected cells are measured and compared. An indicator of one color indicates the battery is operating normally, an indicator of a contrasting color indicates the battery is defective.

Abstract: In one embodiment of the present invention, a distributed electronic system includes a plurality of electronic modules. Each of the electronic modules is coupled to one battery in a series connection of batteries. The electronic modules are coupled to a central controller via a data bus. Addresses are assigned to the electronic modules based on the potentials of corresponding nodes within the modules.

Abstract: Each voltage sensor is provided one to one for a plurality of batteries, for detecting a terminal voltage of each battery. A current sensor detects a current flowing from the plurality of batteries to a load. A reading section reads for each battery a voltage value detected by a corresponding voltage sensor and a current value detected by the current sensor at every predetermined period of time, and collects a predetermined number of detected voltage values and corresponding detected current values. A remaining capacity calculator calculates a battery remaining capacity for each battery based on the plurality of detected voltage values and the plurality of corresponding detected current values, selects a battery remaining capacity having a minimum value from out of a plurality of calculated battery remaining capacities, and calculates a remaining capacity of the whole of the plurality of batteries based on the selected battery remaining capacity.

Abstract: Gas gauge circuitry for monitoring and accumulating various operating parameters of a rechargeable battery with selected parameters being used to determine the remaining operating life of a rechargeable battery, and includes a current monitor for measuring the current flow into and out of the rechargeable battery. An integrated current accumulator is connected to the current monitor and is used to maintain a net accumulated total of current flowing into and out of the rechargeable battery. A charging current accumulator, which is also coupled to the current meter is used to maintain the total current flowing into the rechargeable battery, while a discharging current accumulator is used to maintain the total current flowing out of the rechargeable battery. A highly accurate, oscillatory circuit is used to drive the accumulators to increase the accuracy of the gas gauge functions therefrom.