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.

Abstract: State based full and empty control for rechargeable batteries that will assure a uniform battery empty condition, even in the presence of a load on the battery. A fuel gauge provides a prediction of the open circuit voltage of the battery, and when the predicted open circuit voltage of the battery reaches the predetermined open circuit voltage of an empty battery, the load is terminated, after which the battery will relax back to the predetermined open circuit voltage of an empty battery. A similar technique is disclosed for battery charging, allowing faster battery charging without overcharging. Preferably an RC battery model is used as the fuel gauge to provide the prediction, but as an alternative, a coulomb counter may be used to provide the prediction, with error correction between successive charge discharge cycles.

Abstract: A method of determining a state of health of a battery in real time includes estimating a parameter value associated with the state of health of the battery and determining one or more of a terminal voltage, an accumulated charge, a state of charge, and a temperature of the battery. The method further includes determining, via a computing device, a reserve capacity of the battery based at least in part on the estimated parameter value and one or more of the terminal voltage, the accumulated charge, the state of charge, and the temperature of the battery.

Abstract: A method for estimating the capacity of a vehicle battery while in service. The method includes providing a previous battery state-of-charge, battery temperature and integrated battery current amp-hours, and determining that battery contactors have been closed after they have been opened and disconnected from a load. The method determines if the battery has been at rest for a long enough period of time while the contactors were open, where the battery rest time is based on battery temperature, and determines an initial battery voltage from a last time step when the battery contactors were closed prior to the contactors being open during the battery rest time. The method determines a present battery state-of-charge from the initial battery voltage and the battery temperature and calculates the battery capacity based on the battery integrated current amp-hours divided by the difference between the present battery state-of-charge and the previous battery state-of-charge.

Abstract: A detecting device used to detect storage capacity of a battery is connected to a load by a first output terminal and a second output terminal. The detecting device includes a switch unit, a detecting unit, and a control unit. The switch unit is connected between the first and second output terminals. The detecting unit is connected to the first and second output terminals. The detecting unit detects output voltage and current of the battery when the switch is turned on and off and obtains an internal resistance of the battery according to the detected output voltage and current. The control unit controls the switch unit to turn on and off and compares the detected resistance with a reference resistance, and determines the storage capacity of the battery according to the comparison.

Abstract: The present disclosure provides a processing method for detecting a state of a mobile telephone in standby, the method includes: determining whether a battery electric quantity of the mobile telephone in standby is high or low according to an electric quantity detecting circuit; determining a work state of a Modem module when the battery electric quantity of the mobile telephone is high; and determining a wakeup subsequent flow according to the determined battery electric quantity of the mobile telephone and the determined work state of the Modem module. The present disclosure further provides an electric quantity detecting circuit and a processing device for state detection of a mobile telephone in standby.

Abstract: A voltage balancer device has a plurality of discharge paths. Each pair of the discharge paths correspond to each secondary battery unit. Each of a pair of the discharge paths has a resistance of a different value. Discharging the voltage of each secondary battery unit is at first performed through the discharge path of a smaller resistance value. The voltage balancer device switches the currently used discharge path to another discharge path having a large resistance value at the time the voltage of the secondary battery unit nearly equal a desired voltage.

Abstract: A method of monitoring a maximum available capacity of a battery includes: a) providing a plurality of diverse end-of-discharge-voltage values; b) assigning a counter to each of the plurality of diverse end-of-discharge-voltage values; c) discharging the battery; d) determining one of the plurality of end-of-discharge-voltage values at which the battery is discharged; e) incrementing a counter reading of the counter assigned to the determined end-of-discharge-voltage value; f) repeating steps c-e; g) reading-off the counter readings so as to obtain a plurality of read-off counter readings; and h) determining, based on the plurality of read-off counter readings, a first factor representing a first measure of a decline in the maximum available battery capacity.

Abstract: The rechargeable battery abnormality detection apparatus is provided with an internal short circuit detection section (20b) that monitors rechargeable battery (1) voltage change when no charging or discharging takes place, and detects internal short circuit abnormality when battery voltage drop during a predetermined time period exceeds a preset threshold voltage; a degradation appraisal section (20d) that judges the degree of rechargeable battery degradation; and a threshold control section (20c) that incrementally increases the threshold voltage according to the degree of degradation determined by the degradation appraisal section (20d).

Abstract: Embodiments of the invention include a device and method for improved battery learn cycles for battery backup units within data storage devices. The backup unit includes a first battery pack, a corresponding charge capacity gauge, one or more second battery packs, a corresponding charge capacity gauge, and a controller switch configured to select only one battery pack for a learn cycle at any given time. The charge capacity gauges are such that, at the end of the learn cycle discharge phase, the depth of discharge of the learn cycle battery pack is such that the charge capacity of the learn cycle battery pack combined with the full charge capacity of the remaining battery packs is sufficient for the device cached data to be off-loaded to a physical data storage device, and the data storage device does not have to switch from a write-back cache mode to a write-through cache mode.

Abstract: A rechargeable battery state-of-charge quantifying apparatus for use in a vehicle equipped with an electric motor and a rechargeable battery which supplies electric power to the motor to produce a driving torque. The apparatus quantifies a state-of-charge of the rechargeable battery and defines a minimum value of a state-of-charge of the rechargeable battery at which the rechargeable battery is permitted to produce a degree of electric power required to run the vehicle as a lower limit. The lower limit is increased as the rechargeable battery ages, thereby ensuring the stability in supplying the amount of electric power to the motor which is required to run the vehicle regardless of aging of the battery.

Abstract: During charging of a secondary battery, a rate of voltage change dV/dt is obtained when a voltage V of the secondary battery reaches a predetermined voltage Vpre, a charge current I for charging the secondary battery is detected, and a rate of change dQ/dt in a quantity of charged electricity Q of the secondary battery is calculated on the basis of the result of the detection. Here, the predetermined voltage Vpre is a voltage higher than a discharge cutoff voltage and lower than a charge cutoff voltage. Thereafter, a ratio X: dQ/dV, of the rate of change dQ/dt in the quantity of charged electricity to the rate of voltage change dV/dt is calculated. The calculated ratio X is compared with a reference value Xref, and degradation of the secondary battery is determined on the basis of the result of the comparison.

Abstract: A method for monitoring a lithium-ion battery cell includes monitoring a battery cell voltage and a corresponding state of charge of the battery cell during an electric power event which may include either an electric power charge event or an electric power discharge event. A measured potential-derivative is determined by differentiating the battery cell voltage in relation to the corresponding state of charge of the battery during the electric power event. The measured potential-derivative is compared with a preferred anode potential-derivative of an anode charge curve (for electric power discharge events) or an anode discharge curve (for electric power charge events), and with a preferred cathode potential-derivative of a cathode charge curve (for electric power charge events) or a cathode discharge charge curve (for electric power discharge events).

Abstract: A method for monitoring a lithium-ion battery cell includes monitoring a battery cell voltage and a corresponding charge capacity of the battery cell during an electric power event which may include either an electric power charge event or an electric power discharge event. A measured charge-capacity-derivative is determined by differentiating the charge capacity in relation to the corresponding battery cell voltage during the electric power event. The measured charge-capacity-derivative is compared with a preferred anode charge-capacity-derivative of an anode charge curve (for electric power discharge events) or an anode discharge curve (for electric power charge events), and with a preferred cathode charge-capacity-derivative of a cathode charge curve (for electric power charge events) or a cathode discharge charge curve (for electric power discharge events).

Abstract: A method of estimating a state of charge of a battery in a vehicle undergoing a vehicle assembly process. The method may include the steps of: installing the battery in the vehicle; employing a sensor mounted in the vehicle to automatically sense battery net amp hours during at least a portion of the vehicle assembly process; storing the net amp hours in a control module mounted in the vehicle; mounting a data link connector in the vehicle to provide communication with the controller; temporarily connecting a tool connector of a battery test assembly to the data link connector and transmitting the stored net amp hours data to the battery test tool from the control module; and comparing the net amp hours to a predetermined maximum net amp hours to estimate if the state of charge of the battery is acceptable.

Abstract: The method for controlling the end of discharge of a rechargeable battery according to the invention comprises determining the transition frequency of the battery and determining an end-of-discharge criterion of the battery according to said transition frequency. Said end-of-discharge criterion is representative for example of a predetermined maximum value of the slope of the transition frequency. The transition frequency can be determined periodically during use of the battery, discharging being interrupted by regulating means according to said transition frequency.

Abstract: Integrated MOSFET current sensing for fuel-gauging. A 1st MOSFET through which the current is to be sensed is coupled to a 2nd MOSFET of the same type, the 2nd MOSFET being biased to have the same resistance as the 1st MOSFET. The 2nd MOSFET has a much smaller area than the 1st MOSFET, and is coupled to a current source representing a maximum current through the 1st MOSFET. The voltage across the 1st MOSFET relative to the voltage across the 2nd MOSFET provides a measure of the current through the 1st MOSFET. Various embodiments are disclosed, including embodiments in battery packs to eliminate the need for additional and expensive external components.

Abstract: An apparatus and a method for estimating the SOH of a battery of a vehicle are provided, in which degree of deterioration of the battery is estimated from temperature change and traveling distance. Accordingly, the SOH of the battery and remaining traveling distance can be accurately estimated.

Abstract: A state of charge optimizing device according to the present invention optimizes a state of charge of each of a plurality of cells which are connected in series to form an assembled battery, and conducts the optimization by discharging or charging a part or all of the plurality of cells so that the differences between the amount of charge after the optimization and the amount of charge in a predetermined state of charge become uniform.

Abstract: A method for detecting a state of charge (SOC) of a battery is disclosed. The method includes inputting a pulse to the battery for receiving a response curve of the battery associated with the pulse inputted to the battery, determining a set of parameters for preparing a simulated curve, comparing a difference between the response curve and the simulated curve, determining whether the difference between the simulated curve and the response curve is less than a predetermined threshold before further utilizing the parameters to determine the SOC from a corresponding relationship.

Abstract: A method for detecting SOC and SOH of a storage battery includes: calculating an SOC value of the storage battery with use of an SOC calculation unit based on a measured voltage value or a measured current value of the storage battery and calculating an SOH value of the storage battery with use of an SOH calculation unit based on the SOC value; further calculating a new SOC value with use of the SOC calculation unit based on the SOH value and calculating a new SOH value with use of the SOH calculation unit based on the new SOC value, these further calculations of SOC value and SOH value being repeated a prescribed n times of at least one so as to obtain an nth calculated SOC value and an nth calculated SOH value; outputting the nth calculated SOH value as an SOH output value and outputting the nth calculated SOH value as an SOC output value; and storing the SOH output value into a memory.

Abstract: A circuit that indicates an impedance of a battery dielectric includes a signal generator module that flows a first current from a ground to a first terminal of a battery. A sensor circuit generates a signal based on a second current that flows from a second terminal of the battery through a resistance to ground. The second current includes the first current and a third current that flows to ground via an impedance presented by a battery dielectric housing. A signal conversion module generates an output signal based on the signal. The output signal represents the impedance presented by the battery dielectric housing.

Abstract: A battery capacity test apparatus for indicating capacity of a battery includes a voltage regulator module, a comparator module, and an indication module. The voltage regulator module is configured to receive a voltage signal from the battery, and output a plurality of decreased sub-voltages. The comparator module is configured to receive the plurality of decreased sub-voltages, and compare the plurality of decreased sub-voltages with a reference voltage to output control signals. The indication module is configured to receive the control signals, and indicate capacity of the battery according to the control signals.

Abstract: A method is provided for determining the amount of ammonia which is stored in a storage container by a chemical bond to a solid storage medium, in particular a salt of an earth alkaline metal or the like, and which can be released by supplying heat in order to be supplied to a catalytic exhaust gas purification device of an internal-combustion engine. The storage medium functions as a dielectric of an electric capacitor and the stored amount of ammonia is inferred from the capacity of this capacitor. In the case of a corresponding storage container, at least one wall of the housing of the storage container functions as a first electrode of the capacitor, and, within the storage container, at least one additional electrode of this capacitor is provided and arranged such that at least a partial amount of the storage medium forms the dielectric of this capacitor. The storage container may have an essentially cylindrical shape and, as required, several cylindrical electrodes can be arranged in a coaxial manner.

Abstract: An early warning method for an abnormal state of a lithium battery and a recording medium applicable to a portable electronic device are provided. The method includes the following steps. A plurality of curves of voltage against electric quantity is obtained according to different predicted average current consumptions of the portable electronic device. An operating average current consumption and an operating electric quantity from a first voltage to a second voltage are obtained when the lithium battery at an operating test state in a unit time. One of the curves of voltage against electric quantity is searched, and a warning electric quantity is obtained in a range from the first voltage to the second voltage. The warning electric quantity is compared with the electric quantity, so as to provide an early warning of an abnormal state.

Abstract: A stand-alone battery monitoring system coupled to a battery product having a positive pole and a negative pole, a housing and an electronics package contained within the housing. A sensor is coupled to and communicates with the battery product and the controller. Multiple code segments form software on the controller, the software includes a code segment acquiring battery product data for voltage and internal temperature from the sensor, a segment filters the acquired battery product data into modified battery product data and processing the modified battery product data against stored parameters, a segment stores battery product data in the portion of memory and retains the battery product data to provide historical battery product data. A code segment compares the stored data against threshold levels and an indicator sends an alert if the code segment comparing the stored battery product data against threshold levels determines that data is beyond those levels.

Abstract: A method is provided for determining a battery's state-of-health. An initial battery voltage is measured after a first voltage drop during an initiation of an engine cranking phase. A battery voltage is monitored during the remainder of the engine cranking phase. A lowest battery voltage is determined during the remainder of the engine cranking phase. A determination is made if a voltage difference between the lowest battery voltage and the initial battery voltage at the initiation of the engine cranking phase is less than a voltage threshold. A low battery state-of-health is identified in response to the voltage difference being less than the voltage threshold.

Abstract: Methods and systems for determining a state of charge of a battery are provided. A first component of the state of charge is calculated based on a first property of the battery. A second component of the state of charge is calculated based on a second property of the battery. The first component of the state of charge is weighted based on a rate of change of the first property relative to a change of the state of charge. The second component of the state of charge is weighted based on a rate of change of the second property relative to a change of the state of charge. The state of charge is determined based on the first and second weighted components.

Abstract: A battery state estimating unit estimates an internal state of a secondary battery according to a battery model equation in every arithmetic cycle, and calculates an SOC based on a result of the estimation. A parameter characteristic map stores a characteristic map based on a result of actual measurement performed in an initial state (in a new state) on a parameter diffusion coefficient and a DC resistance in the battery model equation. The parameter change rate estimating unit estimates a DC resistance change rate represented by a ratio of a present DC resistance with respect to a new-state parameter value by parameter identification based on the battery model equation, using battery data measured by sensors as well as the new-state parameter value of the DC resistance corresponding to the present battery state and read from the parameter characteristic map.

Abstract: The method for determining the state of charge of a battery can be used during charging or discharging of the battery at constant current. It comprises placing the battery in open circuit during a recovery period until the voltage at the terminals of said battery stabilizes at a voltage plateau. Then a constant test voltage is applied to the battery terminals during a preset test period. The state of charge of the battery corresponds to the current measured at the end of the test period by means of a previously obtained calibration curve.

Abstract: A diffusion estimation unit follows a diffusion equation in an active material that is represented by a polar coordinate to estimate a distribution in concentration of lithium in the active material. An open circuit voltage estimation unit obtains an open circuit voltage in accordance with a local SOC(?) based on a concentration of lithium obtained at an interface of the active material as estimated by the diffusion estimation unit. A current estimation unit uses a battery's voltage measured by a voltage sensor, the estimated open circuit voltage, and a parameter value that is set for the battery by a battery parameter value setting unit, and follows a voltage-current relationship model expression simplified from an electrochemical reaction expression to estimate the battery's current density.

Abstract: A method for estimating the state-of-charge of a battery. The method includes collecting a plurality of voltage measurements during operation of the system containing the battery and determining a time-constant of relaxation and an open-circuit voltage corresponding to the battery based, at least in part, on the voltage measurements. The method further includes estimating the state-of-charge of the battery based, at least in part, on the open-circuit voltage.

Abstract: The present inventions, in one aspect, are directed to techniques and/or circuitry to determine the state of charge of a battery/cell using data which is representative of a partial relaxation time of the battery/cell. In another aspect the present inventions are directed to techniques and/or circuitry to determine the state of charge of a battery/cell using data which is representative of an overpotential or full relaxation time of the battery/cell. In yet another aspect the present inventions are directed to techniques and/or circuitry to adaptively charge a battery/cell using data which is representative of a state of charge of the battery/cell.

Abstract: An embodiment contemplates a method for estimating a capacity of a battery. A state of charge is determined at a first instant of time and at a second instant of time. A difference in the state of charge is determined between the first instant of time and the second instant of time. A net coulomb flow is calculated between the first instant of time and the second instant of time. The battery capacity is determined as a function of the change in the state of charge and the net coulomb flow.

Abstract: A system and method for estimating internal parameters of a lithium-ion battery to provide a reliable battery state-of-charge estimate. The method uses a two RC-pair equivalent battery circuit model to estimate the battery parameters, including a battery open circuit voltage, an ohmic resistance, a double layer capacitance, a charge transfer resistance, a diffusion resistance and a diffusion capacitance. The method further uses the equivalent circuit model to provide a difference equation from which the battery parameters are adapted, and calculates the battery parameters from the difference equation.

Abstract: A method for estimating a life status of a lithium battery applicable to a portable electronic device is described. The method includes the following steps. Firstly, a plurality of lithium battery life status intervals are sectioned out by a plurality of voltage-electric quantity curves representing characteristics of the lithium battery. Then, an actual voltage and an actual electric quantity of the lithium battery of the portable electronic device are measured. Afterwards, positions of the actual voltage and the actual electric quantity in the lithium battery life status intervals are determined to estimate the life status of the lithium battery.

Abstract: An electronic equipment includes a main body, a mounting portion that is provided in the main body and on which an accessory can be mounted, a battery that is stored in the main body, a battery voltage detection portion that detects an output voltage of the battery, an external power source supply portion which supplies the electric power from the battery to the accessory mounted on the mounting portion, and a control portion which determines the remaining capacity of the battery on the basis of the threshold value to be set based on accessory information on the accessory and a detection result of the battery voltage detection portion.

Abstract: A method for calculating the power consumption of a mobile device, particularly of a mobile station of a mobile radio system, in an observation period ?t based on various possible system states sk in which the device can be in the period ?t. A value of a quantity ?k is determined system-state-dependently for the system states sk occurring in the period ?t. The power consumption in the period ?t is calculated in such a manner that the quantities ?k and state-dependent typical currents ik are taken into consideration.

Abstract: Included are embodiments of an ambulatory infusion device. Some embodiments include an energy storage for storing electrical energy utilized for powering the ambulatory infusion device. The energy storage may serve as a primary power source of the ambulatory infusion device. Also included is a dosing unit with an electrically powered actuator and an electronic controller, where the electronic controller controls operation of the electrically powered actuator. Some embodiments also include a testing unit for testing the energy storage. The testing unit may be configured to repeatedly carry out a test during operation of the ambulatory infusion device. Additionally, the test may include determining a control variable, the control variable being indicative of a capability of the energy storage for further powering the ambulatory infusion device.

Abstract: A method and apparatus is provided for determining when a battery, or one or more batteries within a battery pack, undergoes an undesired thermal event such as thermal runaway. The system uses a conductive member mounted in close proximity to, or in contact with, an external surface of the battery or batteries to be monitored. A resistance measuring system such as a continuity-tester or an ohmmeter is coupled to the conductive member, the resistance measuring system outputting a first signal when the temperature corresponding to the battery or batteries is within a prescribed temperature range and a second signal when the temperature exceeds a predetermined temperature that falls outside of the prescribed temperature range.

Abstract: A fuel gauge circuit detects a residual quantity of a battery 1 and is disposed on a substrate 20 together with a protection circuit 40 which protects charging/discharging of the battery 1. The fuel gauge circuit includes a voltage monitor terminal T1 disposed on a side facing a positive power-supply terminal 21 of the substrate and connected to each of the positive power-supply terminal 21 and a voltage sensor 31 disposed in the circuit, a voltage through terminal T6 disposed on a side facing the protection circuit, opposite to the side facing the positive power-supply terminal 21, and connected to a voltage monitor terminal T11 of the protection circuit, and a wiring 32 disposed within the circuit to connect the voltage monitor terminal T1 of the fuel gauge circuit to the voltage through terminal T11.

Abstract: The present invention allows batteries to be tested in conjunction with being re-charged, and identifies failed or failing batteries before they are put to further use. The present invention can simultaneously test and charge multiple batteries, and can simultaneously test and charge different types of batteries. A method according to various aspects of the present invention comprises: identifying, by a computer system comprising a user interface, a provided battery to be tested; receiving, through the user interface, a selection one or more tests to perform on the battery; and performing, using a battery testing system, the one or more tests on the battery. In this method, the battery testing system is in communication with the computer system, and the battery testing system comprises a battery interface for coupling with the battery.

Abstract: A battery management system and a driving method thereof to manage a battery including a plurality of cells. The battery management system includes a sensing unit, an MCU, and a cell balancing unit. The sensing unit measures cell voltages of the plurality of cells. The MCU detects cells requiring cell balancing according to the plurality of measured cell voltages and generates a plurality of cell voltage signals to control the cell balancing of the detected cells. The cell balancing unit balances the cells according to the plurality of cell voltage signals, and the number of the cell voltage signals is fewer than the number of cells. The cell balancing unit generates a plurality of cell balancing signals corresponding to each of the plurality of cell voltage signals, and at least one of the cell voltage signals balances at least two of cells in the battery.

Abstract: An energy storage level indication circuit includes an energy storage device and a radio control module operable to transmit a wireless heartbeat signal at a rate indicating an amount of energy stored in the energy storage device.

Abstract: An electrical device is powered by a battery. The device includes transition phase determining circuitry operatively connected to the battery to determine that the battery has entered a transition phase based on the occurrence of a change in direction of current flowing through the battery. Battery capacity determining circuitry is operatively connected to the transition phase determining circuitry and configured to determine, in response the transition phase determining circuitry determining that the battery is in the transition phase, a capacity of the battery based on a transition phase battery capacity model of capacity-vs.-voltage. The transition phase determining circuitry is further configured to determine an end of the transition phase based on the transition phase battery capacity model and a non-transition battery capacity model of capacity-vs.-voltage yielding the same capacity value for a given measured voltage of the battery.

Abstract: A method for determining a state of charge value for an electrical power cell comprises obtaining an indication of a charge level of the electrical power cell, obtaining at least one indication of at least one operating condition for the electrical power cell, and determining an available charge indication value and a potential charge indication value based at least partly on the charge level indication and the at least one operating condition indication.

Abstract: The invention provides a system and battery including a state-of-charge indicator (SOCI) to monitor and display the amount of charge within the battery. The SOCI is capable of operating in a hibernate mode, an active mode, and/or a sleep mode. The battery may be manufactured, shipped and/or stored with the SOCI operating in a power-saving hibernate mode. The SOCI may exit the hibernate mode and begin operating in active mode if a physical key connected to the battery is removed. In addition, the SOCI may operate in a sleep mode while the battery is not being used to conserve power. Furthermore, the invention provides a method of making a battery including a SOCI to monitor and display the state of charge of the battery.

Abstract: A method and apparatus that allows for controlling operating time of a portable computer system and a peripheral device. A portable computing system that includes a rechargeable power supply and that includes a connection mechanism for coupling to a peripheral device is used to control operating time of the portable computer system and the peripheral device. In one embodiment, a user can choose between maximizing the operating time of the portable computer, maximizing the operating time of the peripheral device, or maximizing the life of the entire system (maximizing the operating time of the portable computer system and the peripheral device). When operating time of the portable computer system is to be maximized, power is sent from the peripheral device to the portable computer system to extend the operating time of the portable computer system.