Abstract: This invention is a method and device for monitoring and storing data regarding the “life history” of a battery with which it is associated and interpreting the data to create an accurate record of use and abuse patterns. A manufacturer's specified life expectancy, measured in battery cycles, is established for the battery under normal use, and then the actual use of the battery is monitored and stored. Complete cycles, partial cycles, and operation of the battery outside of acceptable specifications are automatically derived into a value in units equivalent to a number of battery cycles, and this derivation is compared with the manufacturers life expectancy, and adjustments to the manufacturers life expectancy are made so that a more accurate and up-to-date estimation of battery life can be evolved over the life of the battery.

Abstract: A method of operating a power system with an electrical energy-storage device is disclosed. The method may include estimating with at least one information-processing device a present charge capacity of the electrical energy-storage device. This may include determining an estimated fatigue-adjusted discharge value by determining an estimated amount of electrical energy discharged from the electrical energy-storage device and applying a fatigue factor to the estimated amount of electrical energy discharged. The fatigue factor may be determined based on a magnitude of electricity discharged from the electrical energy-storage device. The method may also include estimating the present charge capacity of the electrical energy-storage device based on the estimated fatigue-adjusted discharge value and an estimated full capacity of the electrical energy-storage device.

Abstract: A method is provided for determining a state variable such as aging of an electrochemical cell comprising an electrode plate group, that includes analyzing at least a portion of a response spectrum of the electrochemical cell to application of an electromagnetic wave in a frequency ranging from 10 kHz to 10 GHz, so as to determine an indicator of the value of the state variable.

Abstract: Systems and methods are provided for monitoring the deterioration of a rechargeable battery. A battery monitoring system may be used to store charging information, discharge information and storage information for a rechargeable battery to a data store. The charging information may include a number of charge cycles incurred by the rechargeable battery. The discharge information may include a number discharge cycles incurred by the rechargeable battery. The storage information may include information relating to periods when the rechargeable battery is not being actively charged or discharged. The battery monitoring system may be further used to determine an amount of deterioration of a battery performance characteristic based on the stored charging information, discharge information and storage information.

Abstract: The method includes the simultaneous measurement of the current I, of the positive plate potential V+, and of the temperature T at the positive terminal of the battery, the determination of a temperature compensated value Vc+ of the positive plate potential and the use of the temperature compensated value Vc+ for estimation of the state of charge. This method is more particularly used for estimation of the state of charge of an alkaline battery having a NiOOH positive plate.

Abstract: A magnetic sensor for measuring the magnetic properties of a battery cell, and converting the magnetic properties to a battery cell SOC. The magnetic sensor includes a magnetic core formed of laminated high permeability plates provided in a C-shape. An extended portion of the battery cell extends through a transverse opening in the core so that it is positioned within the core. A driving coil is wrapped around one end of the magnetic core and generates a magnetic field in the core that extends across the transverse opening and through the battery cell. A receiving coil is wrapped around an opposite end of the core that receives the magnetic field, and converts the magnetic field to a representative current. A detection circuit converts the receiving coil current to the battery cell SOC.

Abstract: According to one embodiment, an apparatus for selecting a battery voltage table including current consumption information of applications, and applying an offset to a battery output voltage according to current consumption of applications. The apparatus for determining a battery status in a portable terminal includes a memory unit configured to store a battery voltage table defined according to current consumption, a control unit configured to determine an executed application, and a power estimation unit configured to estimate a battery level using the battery voltage table defined for each current consumption of applications and a battery output voltage.

Abstract: A method of predicting an electrochemical mapping parameter in a vehicle that derives at least a portion of its motive power from an energy storage system is provided. The method may comprise providing a plurality of electrochemical mapping parameter sources capable of rendering one or more electrochemical mapping parameters selected from the group consisting of resistance and capacitance and selecting at least one electrochemical mapping parameter source capable of rendering one or more electrochemical mapping parameters based on the state of the energy storage system. The method may also comprise determining an adaptive gain and determining an adaptive factor based on the operating state of the vehicle or the energy storage system. The method may also comprise adapting the one or more electrochemical mapping parameters based on the adaptive factor and adaptive gain to provide an adapted electrochemical mapping parameter value.

Abstract: According to one embodiment, a method for measuring the remaining capacity of a battery in a portable terminal includes calculating an elapsed time when a voltage of the battery, which increases while the battery is being charged, arrives at a fully charged voltage, and providing a remaining capacity of the battery, which corresponds to a ratio of the calculated elapsed time to a threshold time.

Abstract: An electronic apparatus has a multiplicity of display units including an electronic viewfinder and a liquid crystal display (LCD) panel. The apparatus has various display modes. The remaining battery power, i.e., estimated amounts of remaining battery times relative to a current remaining battery capacity, are calculated for the respective display modes. The calculated remaining battery power is collectively displayed as the remaining battery power information on the respective display units. The remaining battery power can be obtained for all the display modes even when the battery is being charged, so that a user can always grasp the remaining battery power of any of the display modes.

Abstract: A degradation determination device includes: a measuring unit measuring an open-circuit voltage characteristic indicating an open-circuit voltage variation with respect to a lithium ion secondary battery capacity variation; and a determining unit determining a degradation state due to wear and precipitation of lithium using a parameter for identifying the open-circuit voltage characteristic that substantially coincides with the measured open-circuit voltage characteristic.

Abstract: An MPU performs a degradation diagnosis based on an open circuit voltage characteristic of a rechargeable lithium ion battery indicating how the battery varies in open circuit voltage as the battery varies in capacity to obtain a capacity ratio of a positive electrode, a capacity ratio of a negative electrode, and a deviated capacity of the battery. The MPU applies the capacity ratio of the positive electrode and the capacity ratio of the negative electrode to a predetermined map for degradation attributed to wear to estimate a deviated capacity resulting from degradation attributed to wear and separates the deviated capacity into the deviated capacity resulting from degradation attributed to wear and a deviated capacity resulting from deposition of lithium. The MPU uses at least the deviated capacity resulting from deposition of lithium to determine whether a rechargeable lithium ion battery subject to determination of degradation is reusable and/or recyclable.

Abstract: A method of monitoring battery capacity comprises determining a starting capacity of a battery; determining an activity coefficient for a device connected to the battery; determining a voltage and current profile for the battery using the starting capacity; determining a voltage and current operating point for the device using the activity value for the device; and determining an updated capacity of the battery using the voltage and current profile for the battery and the voltage and current operating point for the device.

Abstract: A vehicle includes a charging unit receiving electric power from an external power source and externally charging a power storage unit. When a connector unit is coupled to the vehicle and a state ready for charging by the external power source is attained, a controller predicts degradation ratio of the power storage unit at the time point of completion of external charging based on degradation characteristic of the power storage unit in connection with SOC and battery temperature obtained in advance, and sets target state of charge of each power storage unit based on the battery temperatures so that the predicted degradation ratio does not exceed tolerable degradation ratio at the time point of completion of external charging. Then, the controller controls corresponding converters such that SOCs of power storage units attain the target states of charge.

Abstract: A multimeter includes a main body, two probes extending from the main body, a battery unit arranged in the main body, and a charging system arranged in the main body and configured for charging the battery. The charging system includes a microcontroller with an external input voltage sampling circuit, a battery voltage sampling circuit and a voltage regulator circuit each electrically connected the microcontroller. The microcontroller compares sampled signals from the external input voltage sampling circuit and the battery voltage sampling circuit, and controls the voltage regulator circuit to regulate the external input voltage to be applicable to the battery based on the comparison.

Abstract: A battery pack and a method of controlling the battery pack are disclosed. In one embodiment, the battery pack includes a battery, a monitoring unit configured to monitor a voltage of the battery and provide a monitoring result, a memory storing a full-charge capacity (FCC) of the battery, and a controller configured to update the stored FCC when the monitoring result satisfies predetermined conditions during a falling period of the voltage.

Abstract: A rechargeable battery is used with a plurality of battery cells restrained by a restraint member. After the rechargeable battery has the restraint member removed therefrom and is thus disassembled when the rechargeable battery is subsequently re-restrained by the restraint member and thus reused an internal resistance measurement unit measures the rechargeable battery's internal resistance based on battery data detected after the rechargeable battery is re-restrained. At least for the internal voltage, from a value thereof as measured after the battery is re-restrained an evaluation unit evaluates a value of the rechargeable battery that is reused.

Abstract: Provided are a portable electronic device which accurately judges service life of a battery even when the battery is replaced, and a method for controlling such portable electronic device. A control block (48) is provided with a voltage measuring section (100), which is connected to a rechargeable battery (32) and measures a voltage value of the rechargeable battery (32); and a control section (101), which measures the voltage of the rechargeable battery (32) by means of the voltage measuring section (100) each time recharging of the rechargeable battery (32) is started and ended, and controls to store recharge count information specified based on the measured voltage value in a storage section (42).

Abstract: Disclosed herein is a switch for turning on/off the connection between a first terminal and a second terminal. The switch includes a first transistor circuit configured from two transistors connected in series between the first terminal and the second terminal; and a second transistor circuit having a gate terminal connected to source terminals of the two transistors and a source terminal connected to gate terminals of the two transistors. The connection between the first terminal and the second terminal is changed over between on and off states by changing over a potential to the source terminal of the second transistor circuit between high and low levels.

Abstract: In an embodiment, a system includes a battery management unit (BMU) coupled to a battery pack of an xEV. Further, the BMU is configured to determine an energy remaining value for the battery pack based, at least in part, on a minimum cell temperature and a minimum cell state of charge percentage (SOC %) determined by the BMU for the battery pack.

Abstract: A method and system for manipulating, adjusting or otherwise controlling a state-of-charge (SOC) operating range for a high voltage vehicle battery, such as the type used for hybrid or electric vehicle propulsion. By providing a dynamic SOC operating range that changes in response to changing battery conditions, the battery performance may be improved so that the battery life is extended. Depending on the particular embodiment, the dynamic SOC operating range may have different combinations of hard and/or soft boundaries or limits.

Abstract: A battery capacity test system includes one or more wireless battery capacity test (“BCT”) sense modules, a continuous load unit, and a wireless data collection unit. The wireless data collection unit interfaces with a computer. During a battery capacity test, the wireless BCT sense module (or modules) continuously monitors the voltage of the battery cell (or cells) to which it is connected. In an aspect, it also continuously monitors the temperature of the battery cell (or cells) and intercell voltage (or voltages) across an intercell connector (or connectors). Each wireless BCT sense module wirelessly transmits the voltage and temperature data it collects to the wireless data collection unit.

Abstract: There is provided a measuring system capable of rendering a power source voltage of an internal circuit higher than a drivable voltage of the internal circuit by removing or reducing a chloride film with greater certainty, thereby enabling operation, and initial activation of the internal circuit to be normally executed, or preventing the internal circuit from running away. The measuring system comprises a thionyl chloride based primary cell, a cell voltage measurement unit, and an internal circuit provided with state-transition controller wherein in the case of transition of the internal circuit to a state thereof, having a discharge current larger than the discharge current in the present state thereof, the transition is made according to results of comparison of a voltage measured by the cell voltage measurement unit with a threshold on the basis of a discharge current in a state before, or after the transition of the internal circuit.

Abstract: A method that includes affixing a radio frequency identification tag on a storage battery at a battery manufacturing plant. The method also includes storing battery manufacturing information into the radio frequency identification tag at the battery manufacturing plant. The battery manufacturing information includes a battery algorithm suitable for use in testing the storage battery.

Abstract: A battery pack updating method updates firmware stored in internal control circuit memory via an update signal sent from a main device that supplies power. When battery pack memory is updated, an AC adapter is connected to the main device, and power is supplied to the main device from the AC adapter. The updating method transmits a charging and discharging blocking signal from the main device to the battery pack control circuit via a communication line. The charging and discharging blocking signal stops discharge from the battery pack rechargeable battery, and stops charging of the rechargeable battery. With rechargeable battery discharging and charging to and from the main device stopped by the charging and discharging blocking signal, the updating method transmits update data from the main device to the battery pack control circuit to update memory.

Abstract: A circuit system is disclosed. The system comprises a master circuitry, at least one slave circuitry which has a battery sensor for checking battery status of a power supply battery and a shut down mechanism for controlled shut down upon detection of low battery by the battery sensor, and a battery sensor manipulation circuit controlled by the master circuitry. The battery sensor manipulation circuit is arranged to manipulate sensed battery status for the battery sensor of at least one of the at least one slave circuitry to force the controlled shut down of the at least one of the at least one slave circuitry upon provision of a shut down control signal from the master circuitry. A method of controlling power management of such a circuit system is also disclosed.

Abstract: The car battery system of the present invention is provided with a battery block 2 that retains a plurality of battery cells 1 in a stacked configuration and has a terminal plane 2A, which is coincident with terminal surfaces 1A established by positive and negative battery cell 1 electrode terminals 13; and with a battery state detection circuit 30 that connects with the electrode terminals 13 of each battery cell 1. The battery system is provided with a circuit board 7 with surface-mounted electronic components 40 that implement the battery state detection circuit 30. The circuit board 7 is a single-sided board with electronic components 40 mounted on only one side, and the circuit board 7 is attached to the battery block 2 opposite the terminal plane 2A with the side having no electronic components 40 facing the battery block 2. The positive and negative electrode terminals 13 of each battery cell 1 are connected with the circuit board 7 for connection to the battery state detection circuit 30.

Abstract: A method of controlling charging of a battery (16) of a totally implantable auditory prosthesis and a control system (50) therefor. The method comprises determining a first charge related characteristic of the battery (16) such as the predetermined minimum amount of charge (58), and a second charge related battery characteristic such as the preset charge level or charge rate of the battery (16). The method further comprises detecting when a charge cycle of the battery (16) commences and monitoring where the charge level of the battery (16) is in relation to the first charge related battery characteristic when the charge cycle commences and adjusting the second charge related battery characteristic depending on the relationship between the charge level and the first charge related battery characteristic at the commencement of the charge cycle. The control system and method has the potential to increase the operational life of the battery (16).

Abstract: Methods and systems for determining a state of charge of a battery exhibiting a transient response are provided. At least one property of the battery is measured. The state of charge of the battery is determined based on the at least one measured property and a transient response of the battery.

Abstract: A method for determining the health of the membranes in a fuel cell stack. The total parasitic current of the fuel cells in the stack is determined. From the total parasitic current, the shorting resistance and the cross-over parasitic current are determined. The health of the membranes is then determined from the cross-over parasitic current and the shorting resistance.

Abstract: A system and method are provided for battery control of hybrid vehicles such as, but not limited to, hybrid locomotives. The system and method are implemented to sense a present state of charge (SoC) of one or more batteries and generate present SoC data there from, sense a present excursion defined by a relationship represented as maximum SoC?minimum SoC for a desired cycle and generate present excursion data there from, and control the one or more battery power/current charging limits in response to the present SoC data and the present excursion data.

Abstract: The car battery system of the present invention is provided with a battery block 2 that retains a plurality of battery cells 1 in a stacked configuration and has a terminal plane 2A, which is coincident with terminal surfaces 1A established by positive and negative battery cell 1 electrode terminals 13; and with a battery state detection circuit 30 that connects with the electrode terminals 13 of each battery cell 1. The battery system is provided with a circuit board 7 with surface-mounted electronic components 40 that implement the battery state detection circuit 30. The circuit board 7 is a single-sided board with electronic components 40 mounted on only one side, and the circuit board 7 is attached to the battery block 2 opposite the terminal plane 2A with the side having no electronic components 40 facing the battery block 2. The positive and negative electrode terminals 13 of each battery cell 1 are connected with the circuit board 7 for connection to the battery state detection circuit 30.

Abstract: The invention relates to a method and arrangement for determining a power supply state variable, particularly of the maintenance state of a battery or rechargeable battery, in an active medical implant, wherein the power supply is subjected to a predetermined load, and the output voltage thereof is detected multiple times during at least one time segment of the load phase, and the measurement values are subjected to a comparison to a respective comparison value, or the chronological curve of the voltage obtained from the measurement values is subjected to a comparison to at least one comparison curve, wherein the comparison result is considered characteristic for the state variable.

Abstract: Disclosed is a binder, which comprises polymer particles obtained by polymerization of: (a) 1˜80 parts by weight of a (meth)acrylic acid ester monomer; (b) 1˜20 parts by weight of an unsaturated carboxylic acid monomer; and (c) 0.001˜40 parts by weight of a vinyl monomer, based on 100 parts by weight of the binder polymer, and which allows electrode active material particles capable of lithium intercalation/deintercalation to be fixed and linked among themselves, and between the particles and a collector. An electrode comprising the binder, and a lithium secondary battery having the electrode are also disclosed. Further, a method for evaluating interrelation between wettability of a binder to an electrolyte and quality of a battery comprising the binder is disclosed. The binder shows excellent adhesion as well as excellent wettability to an electrolyte, and thus can improve rate characteristics and lifespan characteristics of a battery, when used in an electrode for a lithium secondary battery.

Abstract: In a cell voltage detecting system detecting cell voltages of a fuel cell connected in series, a voltage detector detects cell voltages. An auxiliary power supply generates a voltage equal to or greater than a minimum voltage for driving the voltage detector at positive and negative terminals thereof. First and second diodes are connected to a positive drive terminal of the voltage detector to supply the power to the drive terminal of the voltage detector from a high voltage side between the fuel cell or the auxiliary power supply. A negative terminal of the fuel cell, the negative drive terminal, and the negative terminal of the auxiliary power supply are connected to have a same potential. A method of maintaining a drive voltage for the voltage detector is also disclosed in which the drive voltage for the voltage detector is supplied from the high voltage side.

Abstract: A battery pack is provided which includes: a state detection section which decides whether secondary batteries are in an electricity-charged state or in an electricity-discharging state; a power decision section which decides whether the secondary batteries are in a power-on state or in a power-off state; and a residual-capacity calculation section which, if the state detection section decides that they are in the electricity-charged state, calculates the residual capacity of the secondary batteries by accumulating a current value detected by a current sensor, and if the state detection section decides that they are in the electricity-discharging state, calculates the residual capacity of the secondary batteries by acquiring the voltage of the secondary batteries when the power decision section decides that they are in the power-off state.

Abstract: A method for determining the state of health (SOH) of a battery is provided in which cell impedance is determined continuously, and including determining one or more confidence coefficients that depend on one or several variables selected from cell current, temperature or state of charge or their derivatives or integrals with respect to time, and continuously determining the state of health of the battery at a given point in time, using the state of health of the battery at a preceding point in time corrected as a function of cell impedance determined at the given point in time and weighted by the confidence coefficient or coefficients. The method provides a reliable way of determining the state of health of the battery with greater stability and robustness than existing methods.

Abstract: Methods, apparatus, and computer program products are disclosed for determining a reported state of charge (“SOC”) of a battery system, the methods, apparatus, and computer program products including determining the reported SOC according to a first determining method when a previous SOC is greater than a first SOC threshold percentage and less than or equal to 100%; determining the reported SOC according to a second determining method when the previous SOC is greater than a second threshold percentage and less than or equal to the first SOC threshold percentage; and determining the reported SOC according to a third determining method when the previous SOC is greater than or equal to 0% and less than or equal to the second SOC threshold percentage.

Abstract: A peripheral device and a method for operating a peripheral device is disclosed. The peripheral device includes one or more connection mechanisms for coupling to a computing device, a power supply, and a controller. The controller is configured to enable the peripheral device to communicate with the computing device. When the peripheral device is coupled to the computing device, the controller is configured to determine the amount of power remaining in the power supply of the peripheral device, and based at least in part on the amount of power remaining in the power supply of the peripheral device, enable the peripheral device to charge a power supply of the computing device, and enable the peripheral device to receive power from the power supply of the computing device.

Abstract: A method and apparatus for setting a period for measuring voltage level of a battery are provided. The method includes determining whether the period for measuring the battery voltage level has elapsed, measuring battery voltage level when the period for measuring voltage level has elapsed, extracting and displaying a remaining battery capacity based on the measured battery voltage level, and setting the period for measuring battery voltage level based on the measured battery voltage level.

Abstract: Systems and methods are provided for monitoring the deterioration of a rechargeable battery. A battery monitoring system may be used to store charging information, discharge information and storage information for a rechargeable battery to a data store. The charging information may include a number of charge cycles incurred by the rechargeable battery. The discharge information may include a number discharge cycles incurred by the rechargeable battery. The storage information may include information relating to periods when the rechargeable battery is not being actively charged or discharged. The battery monitoring system may be further used to determine an amount of deterioration of a battery performance characteristic based on the stored charging information, discharge information and storage information.

Abstract: When the load of a battery powered device is removed or significantly reduced, the voltage response may be recorded or analyzed in real time. The parameters of a battery's equivalent circuit can be found by fitting recorded or real time voltage response to a model function. The model function may describe the equivalent circuit voltage response to the load transition through equivalent circuit parameters. The model function may account for a duration of a load application prior to a transition as well as values of the load before and after the transition. Response of battery voltage to load application or load release is time dependent. Modeling of this time dependence can provide significant advantages in fuel gauging implementation, for example, to significantly reduce the waiting time before measured voltages can be used for state of charge (SOC) correlation and to improve the accuracy of the prediction of run-time for devices that drain a battery in short high-current pulses.

Abstract: A battery testing apparatus includes a charge circuit, a discharge circuit, a computer, and a control circuit. The charge circuit is coupled to a direct current (DC) adapter, the DC adapter charges a battery through the charge circuit. The discharge circuit is coupled to the battery and configured to discharge the battery. The computer records charge/discharge time and charge/discharge cycles of the battery, and calculates capacity and cycle life of the battery according to the time and cycles of charge and discharge. The control circuit has an input terminal coupled to the computer, and a plurality of output terminals respectively coupled to the charge circuit and the discharge circuit, the control circuit controls the charge and discharge circuits charging and discharging the battery.

Abstract: A method is provided for determining a state-of-charge of a battery for a vehicle. The vehicle is in a charging state when the engine is operating and a non-charging state when the engine is not operating. A first battery voltage is measured at a first predetermined time period after battery charging is discontinued in the non-charging state. A first temperature of the battery is measured that coincides with the first battery voltage. A second battery voltage is measured at a second predetermined time. The second predetermined time is greater than the first predetermined time. A second temperature of the battery is measured that coincides with the second battery voltage. An average temperature is calculated based on the first temperature measurement and the second temperature measurement. A fixed time constant is determined based on the average temperature. An open circuit voltage is estimated as a function of the first voltage measurement, the second voltage measurement, and the fixed time constant.

Abstract: An electronic vehicle tester includes a battery tester configured to measure a parameter of a battery of a vehicle. A tire tester is configured to receive a parameter of a tire of the vehicle. A wireless receiver can be configured to receive pressure information from a transmitter associated with a tire of a vehicle.

Abstract: A device detects a battery capacity of a lithium ion rechargeable battery having at least one inflection point or more within a range of 10% to 90% of the SOC thereof. The inflection point indicates a change of a correlation between a battery voltage and the SOC of the battery. The device fetches a battery capacity corresponding to an inflection point from a capacity table, and sets the fetched battery-capacity as a first battery capacity when an inflection point detection section detects the inflection point. A current integration section integrates a current from the time to detect the inflection point to the time when the battery voltage detected by a voltage detection section reaches a full charging voltage. The integrated current is used as a second battery capacity. The device adds the first and second battery capacities, and uses the added result as a full charging capacity of the battery.

Abstract: A system and method for use with a vehicle battery pack having a number of individual battery cells, such as a lithium-ion battery commonly used in hybrid electric vehicles. In one embodiment, the method evaluates individual battery cells within a vehicle battery pack in order to obtain accurate estimates regarding their average transient voltage effect, open circuit voltage (OCVCell) and/or state of charge (SOCCell) so that a cell balancing process can be performed. These cell evaluations may be performed fairly soon after the vehicle is turned off and in a manner that utilizes a minimal amount of in-vehicle resources.

Abstract: There is provided a battery condition detecting apparatus which comprises: means for detecting a discharging and charging current from the battery; means for detecting whether or not a negative acceleration of charging current changes in its sign from negative to zero during charging of the battery based on a result of detecting the discharge current; means for calculating an integrated charged capacity of the battery by integrating an instantaneous charging current during charging of the battery; means for controlling an alternator mounted in an automotive vehicle so as to control an output electric power generated by the alternator such that a discharging current from the battery is kept to be constant; and means for determining that the charge polarization is cancelled, if the integrated discharged capacity becomes to be equal to the integrated charged capacity.

Abstract: An automotive battery charging system tester for testing the charging system of an automotive vehicle includes AC and DC voltage measurement circuits and a microprocessor controlled testing sequence. The microprocessor is used to perform a series of tests and to instruct an operator to perform steps associated with performing those tests. Through the application of various loads at various engine speeds, the tester is capable of identifying faults in the battery charging system including a bad battery, problems in the alternator or associated electronics, and problems in the starting system.

Abstract: Model-based battery fuel gauges that connect across a rechargeable battery and track the per-cent state of charge of the battery. The model based fuel gauges provide a measure of the open terminal voltage of a battery, even when the battery is powering a load, to provide the state of charge information. Analog and digital implementations of the battery model fuel gauges may be used, and incorporated into a battery powered device in various ways, including constantly powered implementations and implementations that are turned on and off with the battery powered device. Various exemplary embodiments are disclosed.