JP2010521948A - Adaptive charging apparatus and method - Google Patents

Abstract

  A method of charging a rechargeable battery (12) comprising at least one rechargeable electrochemical cell is disclosed. The method includes measuring electrical characteristics of at least one battery and determining a charging current to be applied to the battery based on the measured at least one electrical characteristic.

Description

  In conventional chargers, the type of battery to be charged is determined by electrical, mechanical or digital signal technology, thereby determining the appropriate type of charge to apply. For example, some technologies use a battery built-in ID register, which determines the charging parameters applied to this particular battery. Mechanical techniques such as using the polarity key position of the connector or the position of a specific connector pin are also used to distinguish different battery models that require different charging parameters. For example, the Smart Battery SMBus standard uses a serial data communication interface to communicate charging parameters to the charging device. The above method requires additional connection points beyond the battery power terminal, or some mechanical additional functions that are not necessary for the basic battery function of supplying stored energy to a portable device. It is.

  In the case of a smart battery standard, such as the SMBus standard, an electrical circuit and at least two additional connector pins are required to implement a smart interface between the charger and the battery, which reduces the cost, complexity, And the dimensions increase.

  In one aspect, a method for charging a rechargeable battery comprising at least one rechargeable electrochemical cell is disclosed. The method includes measuring electrical characteristics of at least one battery and determining a charging current to be applied to the battery based on the measured at least one electrical characteristic.

  Embodiments may include one or more of the following.

  The method may include applying the determined charging current to the battery. The method may further include adjusting a current applied to the battery according to the determined charging current.

  The step of measuring at least one electrical characteristic includes the step of measuring the voltage between the terminals of the battery with respect to the application of current to the battery at the first time and the application of current to the battery at the subsequent time. Measuring the voltage between the terminals of the battery. The step of measuring at least one electrical characteristic is measured at the voltage measured at the first time point and the subsequent time point divided by the difference between the current applied at the first time point and the current applied at the subsequent time point. Calculating a steady state charging resistance based on the difference from the applied voltage.

  Determining the charging current includes accessing a look-up table that stores a plurality of charging power values associated with a corresponding one of the plurality of values for the measured parameter, and calculating at least in part. Selecting one of a plurality of charging current values stored in the lookup table based on the determined values. The measured parameter may indicate the steady state charge resistance of the battery.

  The method includes the steps of periodically measuring the voltage between the battery terminals, and adjusting the charging power applied to the battery when the voltage measured between the battery terminals reaches a predetermined voltage. And maintaining the voltage at a predetermined voltage value.

  The method may further include the step of periodically adjusting the charging current such that a predetermined voltage level between the terminals of the battery is achieved within a specified period. The step of periodically adjusting the charging current includes a step of determining a boosting speed at the battery terminal, and a step of calculating charging power using a predictor corrector calculation method based on the determined boosting speed. Good. The predictor corrector calculation method may be based on a Kalman filter.

  In another aspect, a charging device configured to charge a rechargeable battery comprising at least one rechargeable electrochemical cell is disclosed. The apparatus includes a charging compartment configured to receive a battery (the charging compartment having electrical contacts configured to be coupled to corresponding terminals of the battery) and a controller. The controller is configured to measure at least one electrical characteristic of the battery and is configured to determine a charging current to be applied to the battery based on the measured at least one electrical characteristic.

  Similar to method aspects, an apparatus embodiment may include any feature corresponding to any of the features described above for the method, as well as one or more of the following.

  The controller may comprise a processor-based microcontroller.

  The device may further comprise a rechargeable battery. The rechargeable battery may comprise a lithium iron phosphate rechargeable battery.

  One or more of the above aspects may include one or more of the following advantages.

  The charger adaptively determines the correct charging current for a rechargeable battery or cell that has a specific chemistry based on a dynamic measurement of the internal charge resistance of the rechargeable battery or cell, and this charge. The charging rate is adjusted based on the resistance to achieve full or nearly full charge in the shortest possible time or within a specified target time. This method is useful for general purpose chargers intended to charge a variety of batteries or cells having different battery capacities and speed performance. By using the devices and methods described herein, certain batteries do not require dedicated electrical contacts to allow determination of the charging current, and determine the maximum allowable charging current at the mechanical device. There is no need. By using the devices and methods described herein, a single charging device can be used to quickly charge many different sized cells and / or batteries without the need for prior knowledge of specific types of batteries. Yes, the risk of electrical, chemical or thermal damage to the battery or cell being charged is minimal.

  Other features and advantages of the invention will be apparent from the description and the claims.

1 is a block diagram of an exemplary embodiment of an adaptive charger. The circuit diagram of the charger of FIG. 2 illustrates an exemplary embodiment of an AD-DC switching device. 6 is a flowchart of an exemplary embodiment of a charging procedure for charging a rechargeable battery.

  Disclosed is a charger configured to measure, apply, and control charging current to charge a rechargeable battery without requiring prior knowledge of battery type and / or capacity. The charger is particularly useful for charging batteries of various sizes, including but not limited to batteries used in many modern portable consumer electronics products such as cell phones, MP3 players and digital cameras. . Disclosed chargers include lithium ion batteries, lithium ion batteries, lead acid batteries, nickel hydride batteries having rapid charging performance such as those using lithium iron phosphate or a similar phosphate-based intercalation compound as one of the battery electrodes Can be used in many different types of rechargeable batteries, including nickel cadmium batteries, nickel zinc batteries, and silver zinc batteries. The disclosed charger can be further configured to charge different types of batteries, including, for example, cylindrical batteries, prismatic batteries, button batteries, and the like.

  FIG. 1 illustrates measuring and / or determining at least one electrical characteristic of a battery 12 having one or more electrochemical cells housed in a receptacle or compartment (not shown) of an adaptive charger 10. 1 shows an adaptive charger 10 configured. The battery 12 can be a secondary cell (or battery) or a primary cell (or battery). A primary electrochemical cell means that it is discharged only once, for example until it is completely consumed, and then discarded. The primary cell is not intended for recharging. Primary cells are described, for example, in David Linden, “Handbook of Batteries” (McGraw-Hill, 2nd edition, 1995). Secondary electrochemical cells can be recharged many times, eg, more than 50 times, more than 100 times, or more times. In some cases, secondary batteries can include relatively robust separators, such as separators with many layers and / or separators that are relatively thick. Secondary cells can also be designed to accommodate changes such as expansion that can occur in the cells. Secondary batteries are described, for example, by Falk & Salkind's “Alkaline Storage Batteries”, John Wiley & Sons, Inc., 1969, USA No. 345,124, and French Patent No. 164,681, all of which are incorporated herein by reference. In the embodiments described herein, the battery 12 is a secondary battery or a rechargeable battery.

  The charger 10 is coupled to the power conversion module 11. The power conversion module 11 is electrically coupled to an external AC power source such as a power source that supplies power with a rating of 96 V to 220 V and 50 Hz to 60 Hz, and the AC power supplied from the outside is suitable for charging the rechargeable battery. AC-DC power converter 13 for converting to a DC power (for example, a DC power level of about 3.8 to 4.2 V). The AC-DC power converter 13 may be implemented as an AD-DC switching device configured to receive input power at a first voltage and convert the power to a lower voltage. An exemplary embodiment of the AD-DC switching device 40 is shown in FIG. In some embodiments, the DC-DC power converter 15 includes a power conversion module 11 configured to convert an external DC power source, such as a car DC power source, to a DC power level suitable for charging a rechargeable battery. May be incorporated and used. For example, in some embodiments, the vehicle's DC power supply can provide approximately 12V of DC power, and the DC-DC transformer 15 converts this power level to a suitable power level. In some embodiments, the AC-DC converter 13 is coupled to a DC-DC transformer, whereby the cascaded transformer is configured to provide a DC power source suitable for charging a rechargeable battery. Form. Other power conversion configurations may be used.

  In some embodiments, a DC charging power source (such as DC-DC converter 15 that may be implemented as a DC-DC buck converter) is not used, but instead the current of AC-DC power converter 13 and / or By directly controlling the voltage, the current and / or voltage output is adjusted to the level required to charge the rechargeable battery or cell. As detailed below with respect to FIG. 2, the current feedback rule controls the duty cycle of switch SW1 (14c in FIG. 2), but the output voltage is below a predetermined constant voltage threshold (also referred to as cross voltage). . If the output voltage is equal to or exceeds the cross voltage, current control feedback is disabled and the voltage feedback block is activated. A voltage feedback block then controls the duty cycle of switch SW1 to provide a constant voltage output. If a feedback mechanism is implemented, the current feedback block causes a voltage drop through the current detection register 39 (also shown as R1 in FIG. 2) to a voltage drop through the register 39 with a constant current set value. To a reference voltage approximately equal to Similarly, when the charging mechanism is operating in constant voltage mode, the voltage feedback mechanism compares the battery terminal voltage with a reference voltage approximately equal to the cross voltage value.

  The adaptive charger 10 determines a charging current to be applied to the rechargeable battery 12 based on the measured electrical characteristics of the battery 12. The measured electrical characteristic value indicates the charge rate performance of the battery charged by the charger 10, so that the controller 14 can determine the charge current level applied to the battery 12. For example, batteries based on lithium iron phosphate electrochemical cells generally exhibit low internal charging resistance during charging operations. The charging resistance increases during the charging process, but generally increases as the state of charge increases. Therefore, the internal resistance and charging speed of the battery can indicate the state of charge of the battery. Other types of batteries are generally characterized by different charging resistances. Therefore, the battery type can be confirmed by determining the charging resistance of the battery to be charged, and an appropriate charging current is supplied to the battery type.

  In some embodiments, an identification mechanism that identifies the specific battery chemistry of battery 12 may be used. For example, in some embodiments, the identification mechanism comprises an ID register coupled to the battery, the resistance value indicating the chemistry of the battery. Thus, in such an embodiment, the charger 10 can identify the chemistry of the battery 12 by measuring the resistance of the ID resistor. Other types of chemical property identification mechanisms may be used, such as a mechanism based on RFID technology in which a wireless automatic identification (RFID) device communicates an electrical signal indicating battery chemistry or the like to the charger 10. Other suitable identification mechanisms include, for example, serial communication technology implemented, such as a smart battery SMBus standard that communicates identification data indicating battery chemistry to the charger 10 via a serial data communication interface. And a mechanism for identifying the battery. A detailed description of an exemplary embodiment of a charger and / or battery that communicates battery-related information using an identification mechanism can be found, for example, in “Ultra Fast Battery Charger with Battery”. Sensing) ”, the entire contents of which are hereby incorporated by reference.

  The controller 14 controls the operation of the charger 10, including measurement of electrical characteristics used to identify the type of battery connected to the charger 10, and the charging current and / or charging applied to the battery 12. A characteristic (eg, charging period, adjustment of charging current and / or voltage at a particular point in time, etc.) is configured.

  The controller 14 includes a processor device 16 configured to control the charging operation performed by the battery 12 and to control the operation as described below. The processor unit 16 may be any type of computing and / or processing unit such as a PIC18F1320 microcontroller from Microchip Technology Inc. The processor device 16 used to implement the charger 10 is based on software including computer instructions that allow general operation of the processor-based device, as well as measured electrical characteristics of the at least one rechargeable battery 12. And a volatile and / or non-volatile memory device configured to store an execution program for performing a charging operation on the battery 12 connected to the charger. In this embodiment, the processor 16 includes an analog-to-digital converter (ADC) 20 that receives a signal from a sensor (described below) to the controller 14 indicating the value of the battery voltage and / or current. In some embodiments, the controller 14 may comprise a digital signal processor (DSP) that performs some or all of the processing functions of the controller described herein.

  The controller 14 receives the digital signals generated by the digital-to-analog converter (DAC) 22 and / or the processor device 16 and responds accordingly with an electrical signal that adjusts switching circuitry, such as the buck converter 26 of the charger 10. The pulse width modulator (PWM) 24 is further provided.

  The controller 14 generates one or more input signals corresponding to the current and / or voltage of the battery 12 generated according to the test current or voltage applied to the terminal of the battery 12 by the controller 14 (see FIG. 2). It is received via the terminal 14a) and / or the VSENSE terminal (terminal 14b in FIG. 2). Thus, the signal received by the controller 14 is then used to determine the appropriate charging current to apply to the battery 12. The controller 14 may receive other data including, for example, battery temperature, and such additional data may also be used to determine how to charge the battery. Such additional data may be detected and / or collected using a suitable sensor or probe.

  2 stores energy when the two bipolar transistors (BJT) 28 and 30 and the power conversion module 11 are in electrical communication with the buck converter 26, and the power conversion module 11 stores the buck converter 26. Shown is a buck converter 26 comprising an inductor 32 that releases energy as a current while being electrically isolated from. The buck converter 26 shown in FIG. 2 is also used as an energy storage element and includes a capacitor 34 that functions to reduce voltage ripple.

  The power sent from the power conversion module 11 to the battery 12 is adjusted by controlling the voltage level applied to the bases of the transistors 28 and 30. Specifically, in order to apply the power from the power conversion module 11 to the terminal of the battery 12, an operating electrical signal from the terminal 14 </ b> C (SW <b> 1) of the controller 14 is applied to the base of the transistor 28, and the power conversion module 11 Current flow to transistor 28 and battery 12 occurs.

  When the operation signal applied to the base of the transistor 28 stops, the current flow from the power conversion module 11 stops and the inductor 32 supplies current from the energy stored therein. During the off period of the transistor 28, the second operation signal is applied to the base of the transistor 30 by the terminal 14 d (SW 2) of the controller 14 (the energy stored in the inductor 32 and / or the capacitor 34 during the on period of the transistor 28). Allows current flow from the inductor through the battery 12.

  While the transistor on-period, or duty cycle, initially rises from 0% duty cycle, the controller or feedback loop measures the output current and voltage. Once the determined charging current is achieved, the feedback control loop manages the transistor duty cycle using, for example, a proportional-integral-derivative mechanism, or a closed-loop linear feedback scheme using a PID mechanism. A similar control mechanism may be used to control the transistor duty cycle once the voltage output of the charger, or the terminal voltage of the battery, has reached a crossover voltage.

  Thus, the current provided by the power conversion module 11 during the on period of the transistor 28, and the current provided by the inductor 32 when the inductor 32 discharges during the off period of the transistor, is approximately equal to the required charging power. It becomes current. The controller 14 receives periodically, for example, every 0.1 seconds, a measured value of the current flowing through the battery 12 and / or a voltage at the battery terminal measured by the voltage sensor 36, as measured by the current sensor 38. To do. Based on this received measured current and / or measured voltage, the controller 14 adjusts the duty cycle so that the current through the battery 12 converges to a value approximately equal to the charging current level determined by the controller 14. Adjust. Thus, the buck converter 26 is configured to operate with an adjustable duty cycle that results in an adjustable power level supplied to the battery 12.

  As described above, an additional sensor may be coupled to the battery 12 and communicate a signal corresponding to the controller 14. For example, a temperature sensor (eg, a thermistor) may be coupled to the battery 12 to provide a measurement of the battery temperature. The thermistor can be arranged outside the battery 12 or inside the battery 12. A signal indicating the battery temperature is received by the controller 14 at one of the ports of the controller 14. The controller 14 measures the temperature of the battery from the received signal, and determines any subsequent operation to be performed based on the measured temperature. For example, the measured battery temperature can be compared with a temperature value stored in the controller 14. If the measured temperature is outside the allowable temperature range, the controller 14 can prevent the charging operation from starting, and if the charging operation has already started, the charging operation can be terminated, or an appropriate charging current. And / or the voltage can be reduced. In some embodiments, the charger 10 does not use a thermal monitoring mechanism and / or a thermal control mechanism.

  In order to determine the charging power applied to the battery 12, the controller 14 is coupled to the battery 12 and a voltage sensor 36 configured to measure the voltage across the terminals of the battery 12 and the current through the rechargeable battery. Voltage and current measurements are received from a current sensor 38 configured to measure. In some embodiments, the charger 10 provides a specific level of current (eg, a charge corresponding to 4-5C, where 1C is the current required to charge a rechargeable battery in one hour). Twelve terminals, thereby causing a specific voltage drop at the battery terminals due to the resistance of the battery. The sensed voltage is subsequently received by the VSENSE terminal 14b of the controller 14.

  In some embodiments, the received input signal is processed using an analog logic processing element (not shown), such as a dedicated charge controller device, which may include a threshold comparator, for example, and sensors 36 and / or 38. The voltage and current levels measured by are determined.

  The charger 10 performs signal filtering and processing on analog and / or digital input signals to prevent mismeasurements (eg, mismeasurements of voltage, temperature, etc.) that may be due to external factors such as circuit level noise. Signal adjustment blocks such as filters 35a and 35b may be provided.

  The controller 14 charges the battery based on these signals received from the voltage sensor 36 and current sensor 38 from these measured signals, for example, by calculating a steady state (DC) charging resistance of the battery 12. Therefore, the charging current level applied to the terminal of the battery 12 is determined.

Specifically, the controller 14 applies the first test current input I ₁ at the first time point. For the applied current level I ₁ , a voltage V ₁ is produced at the terminal of the battery 12. The controller 14, as a current I ₁ flowing through the battery 12 is maintained a certain period, thereby to allow the battery 12 reaches the charge steady state. In some embodiments, the time generally required to transition an electrochemical cell of a battery from an open circuit state to a steady state charge state is 30-60 seconds. At a later time (eg, 60 seconds after the controller applied current I ₁ to battery 12), the controller causes battery 12 to apply another current level I ₂ , thereby causing voltage V ₂ is produced. In some embodiments, the applied first current level is a current level equal to 4C (i.e., 15 minutes) so that the charging rate of 4C is equal to 4A current when the battery has a capacity of 1A hours. it may be a current level) for charging the battery, while the second current level I ₂ is equal to 5C level (i.e., may be a current level) for charging the battery in 12 minutes.

For example, once the measured voltage corresponding to the applied current level is obtained, the controller 14 divides the measured closed circuit voltage difference by the applied current difference, i.e., using the following equation: To decide.

  Since the second voltage is measured after the period of time when the steady state (ie, non-transient) resistance value of battery 12 is achieved, the measured charging resistance is referred to as the steady state (DC) charging resistance. Sometimes.

  In some embodiments, other characteristics of the battery 12 are measured and processed to determine the nature of the battery connected to the charger 10, thereby charging power applied to the battery to charge the battery. May be determined.

  The controller 14 uses the calculated resistance to access a look-up table showing the preferred charging current corresponding to the calculated charging resistance. For example, if the calculated charging resistance indicates a particular battery type and / or capacity, a corresponding entry in the look-up table specifies a charging current suitable for charging this battery.

  In some embodiments, a particular battery type may be associated with multiple entries in the lookup table, each entry corresponding to a different charge rate. For example, one entry associated with a particular battery type can specify a charging current that achieves a battery charge level in about 5 minutes equal to about 90% of the capacity of the battery. Another entry associated with the same battery type can specify a different charging rate, for example, a charging current corresponding to the rate of charging the battery to substantially full battery capacity in one hour. User interface (not shown) including, for example, switches, buttons and / or knobs located on the body of the charger when selecting an appropriate entry from a plurality of entries in a lookup table associated with a particular battery Can be used, for example, based on user-specified inputs provided to the charger 10.

  The controller may be configured to determine a specific charge level of the battery 12 and determine charging parameters (eg, charging current and charging period) to be applied to the battery 12. For example, the controller can produce a series of current levels to apply and measure the voltage applied at the terminals of the battery. This series of measured voltages can be used to determine the battery type as well as the charge level of the battery (eg, percentage capacity unit for the battery). Furthermore, the charging period during which the selected charging current is applied can also be determined.

  In some embodiments, the determined charge level of battery 12 can be used to select one of a plurality of entries in a lookup table associated with the determined battery type. For example, if the charging period in which the charging current is applied to the battery 12 is specified as 5 minutes and it is determined that the battery is 50% charged, the battery can be charged to almost 100% within the specified 5 minutes. The first charging current to be selected may be selected from this lookup table. On the other hand, if the battery 12 is only 20% charged, a higher charging current may be selected from this look-up table so that nearly 100% charging is achieved within the specified 5 minutes.

  In some embodiments, the charging period and / or charging rate for charging the battery 12 may be based on the determined charge level of the battery 12. For example, if it is determined that the battery 12 is 50% charged, the charging period is determined such that the battery 12 is charged to a charge level of at least 90% in less than 5 minutes (eg, 3 minutes), for example. May be.

  As described above, the charger 10 may operate in a mode that maintains the voltage at the terminal of the battery 12 substantially constant at this upper limit once a predetermined upper limit voltage (ie, crossing voltage) has been achieved. Specifically, while the battery 12 is substantially charged with a charging current determined based on the charging resistance of the battery, the voltage at the battery terminal increases. To prevent the voltage at the battery terminals from exceeding a predetermined upper limit voltage (so that the battery does not overheat or the battery's operation or expected life is not adversely affected), the sensor 36 is used to The voltage at these terminals is measured periodically (eg, every 0.1 seconds) to determine when a predetermined upper limit voltage is achieved. When the voltage at the terminal of the battery 12 reaches a predetermined upper limit voltage, the current / voltage regulation circuit is controlled to produce a substantially constant voltage at the terminal of the battery 12 (a device that performs such an operation). Is sometimes referred to as a constant current / constant voltage (CC / CV) device).

  In some embodiments, the controller 14 periodically measures the voltage at the terminals of the battery 12 and the charge applied to the battery 12 such that a predetermined upper limit voltage is achieved within a specified boost period. It may be configured to monitor the boosting speed by adjusting the current. Based on the measured boosting speed, the charging current level is adjusted, and the charging current is increased or decreased so that a predetermined upper limit voltage is achieved within the specified boosting period. For example, the charging current level may be adjusted according to a predictor corrector method using a Kalman filter. Specifically, the Kalman filter uses the internal state of the dynamic system to recursively predict system values based on system response measurements to previous excitations or inputs. The Kalman filter method can account for both the uncertainty of the measurement and the uncertainty in the predicted (modeled) system response. Thus, in operation, the predicted system results are used to recursively modify new response measurements based at least in part on previously predicted measurements and actual measurements. This causes the Kalman filter to try to minimize the error between the predicted system response and the actual measured response. Other methods may be used to determine adjustments to the current to achieve the predetermined upper limit voltage.

FIG. 4 illustrates an exemplary embodiment of a charging procedure 50 for charging the rechargeable battery 12. If desired, after inserting the battery 12 into the charging compartment of the charger 10 such that the charging terminal of the charger 10 is electrically coupled to the terminal of the battery 12, the controller 14 may Is measured (52). The controller determines whether the initially measured temperature T ₀ and voltage V ₀ are between a predetermined upper and lower limit (54). These upper and lower limits may be specified in the storage module of the processor-based device 16 used by the controller 14. If it is determined that the measured initial temperature and voltage are not within predetermined tolerances, and therefore it is not safe to perform the charging operation in the current state, the charger does not continue the charging operation and step 50 is performed. finish.

If the initially measured T ₀ and voltage V ₀ are determined to be between a predetermined upper and lower limit, the controller 14 produces two different current levels I ₁ and I ₂ at two separate times. Applied to the battery 12 to facilitate measurement and / or calculation of at least one electrical characteristic (eg, battery terminal voltage) of the battery 12 (56). The measured at least one electrical characteristic indicates itself the type of battery connected to the charger 10 or an inductive characteristic that allows determination of the charging current applied to the battery 12 (eg, steady state charging) Resistance) determination. In embodiments where the charging resistance is determined based on the measured voltage, the controller 14 determines the respective voltages V ₁ and V ₂ corresponding to the applied currents I ₁ and I ₂ . Other types of electrical characteristics (eg, a measured current corresponding to the applied voltage) may be measured.

Once the voltages V ₁ and V ₂ are measured, the charging resistance corresponding to the battery 12 can be determined using the following equation (58).

  The calculated charging resistance is stored, for example, in a storage module and used to determine the charging current to be applied to the battery 12 by accessing a lookup table that indicates a suitable charging current for the calculated charging resistance. (60). The battery type associated with multiple charging current entries relates to the battery type identified from the measured battery characteristics and / or the calculated battery characteristics using a user-specified desired charging period. You can select the appropriate entry. In addition and / or alternatively, other methods (eg, computer-based methods) can be used to determine the charging current.

  If desired, the specific charge level of the connected battery 12 is determined and the charge parameters (eg, charge current and charge period) applied to the battery 12 are calculated (62). As described above, when the battery charge level is determined by, for example, generating a series of current levels to be applied to the battery 12 and measuring the respective voltages generated at the battery terminals, the battery charge level is determined. it can. Charging parameters (eg, charging current and charging period) can be determined based on the measured charging level and battery type.

  When the charging current to be applied to the battery 12 is determined, a charging period and a current / voltage adjusting circuit (such as the buck converter 26 shown in FIG. 2) are controlled as desired to generate a voltage from the power conversion module 11, and the rechargeable battery 12 provides a constant current (64). As described, the charging power level value calculated at 60 is processed to generate a duty cycle signal that causes the battery 12 to apply a current approximately equal to the charging current. Therefore, for example, the output signal of the controller is applied to the transistor 28 of the buck converter 26, and the voltage from the power conversion module 11 is applied to the battery 12. The power conversion module 11 is disconnected from the battery during an off period of a specific duty cycle, and the energy stored in the inductor 32 and / or the capacitor 34 is discharged to the battery as a current. An effective current substantially equal to the charging current is obtained by a current obtained by combining the current applied from the power conversion module 11 and the current discharged from the inductor 32 (and / or the capacitor 34).

  The battery 12 is charged with a substantially constant current, but the voltage at the battery terminal rises. In order to prevent the voltage at the battery terminal from exceeding a predetermined upper limit voltage (crossing voltage), the voltage at the terminal of the battery 12 is measured periodically (for example, every 0.1 second), and the predetermined upper limit voltage is Determine when it will be achieved (66). When the voltage at the terminal of the battery 12 reaches the predetermined upper limit voltage, the power conversion module 11 applies a voltage that keeps the voltage level at the terminal of the battery 12 constant (eg, the electrical power of the transistors 28 and 30). The current / voltage regulation circuit is controlled).

  If desired, the boost rate may be measured periodically to achieve a predetermined upper limit voltage within a specified boost period (68). Based on the measured boost rate, the charge current level is adjusted (by adjusting the corresponding operating signal applied to the current / voltage regulator circuit) so that a predetermined upper limit voltage is achieved within the specified boost period. Increase or decrease the charging current. As described herein, adjustment of the charging current level may be performed according to a predictor corrector method such as a Kalman filter or some other similar method.

  When a period substantially equal to the specified charging period has elapsed, as determined at 70, the charging current applied to the battery 12 is supplied from the power conversion module 11 (eg, the electrical operation of the transistor 28 is stopped). Is stopped) by stopping the power being played. The charging procedure ends after a specified period of time has elapsed after a predetermined upper limit voltage of battery 12 has been achieved, or after a specified charge level of battery 12 has been achieved.

Other Embodiments A number of embodiments of the invention have been described. However, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the claims.

Claims (10)

A method of charging a rechargeable battery comprising at least one rechargeable electrochemical cell comprising:
Measuring at least one electrical characteristic of the battery;
Determining a charging current to be applied to the battery based on the measured at least one electrical characteristic.   The method of claim 1, further comprising applying the determined charging current to the battery.   The method of claim 2, further comprising adjusting a current applied to the battery according to the determined charging current. Measuring the at least one electrical characteristic comprises:
Measuring the voltage between the terminals of the battery with respect to the application of current to the battery at the initial time;
Measuring the voltage across the terminals of the battery with respect to the application of current to the battery at a later point in time. Measuring the at least one electrical characteristic comprises:
Based on the difference between the voltage measured at the first time and the voltage measured at the later time divided by the difference between the current applied at the first time and the current applied at the later time, The method of claim 4, further comprising calculating a steady state charging resistance. Determining the charging current comprises:
Accessing a lookup table that stores a plurality of charging current values associated with a corresponding one of a plurality of values for a measured parameter;
Selecting at least in part one of the plurality of charging current values stored in the look-up table based on the calculated value. Periodically measuring the voltage between the terminals of the battery;
Adjusting the charging current applied to the battery so that the voltage between the terminals of the battery is maintained at the predetermined voltage value when the measured voltage between the terminals of the battery reaches a predetermined voltage value; The method of claim 1, further comprising:   The method of claim 1, further comprising the step of periodically adjusting the charging current such that a predetermined voltage level between the terminals of the battery is achieved within a specified period. The step of periodically adjusting the charging current comprises:
Determining a boosting rate at a terminal of the battery;
Using the predictor corrector calculation method to calculate the charging current based on the determined boost rate. A charging device configured to charge a rechargeable battery comprising at least one rechargeable electrochemical cell comprising:
A charging section configured to receive the battery, the charging section having electrical contacts configured to be coupled to corresponding terminals of the battery;
Configured to measure at least one electrical characteristic of the battery;
And a controller configured to determine a charging current to be applied to the battery based on the measured at least one electrical characteristic.

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