JP2010028876A - Charging/discharging system and portable computer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control charging and discharging so that the total capacity of a battery is the maximum in a dual battery system. <P>SOLUTION: A charging/discharging system includes a battery 100 and a battery 101. A charger 13 charges the battery 100 and the battery 101 in order. An EC 27 controls FET-A to FET-E to select a battery to be charged by the charger or select a battery to be discharged. The EC 27 and a CPU of a note PC 10 compare the specific capacity of battery indicating the proportion of a fully charged capacity to a rated capacity of each battery, and controls the FET-A to FET-E so that the batteries may be each discharged from an order of batteries having less deterioration in capacity. As the result, the charging and discharging are controlled so that the amount of deterioration of each battery may approximate and the total capacity of each battery may be the maximum. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charge / discharge system including a plurality of batteries, and more particularly to a technique for controlling the order of charge / discharge of a plurality of batteries.

  Portable terminals such as notebook personal computers (hereinafter referred to as notebook PCs) and PDA (personal data assistants) are equipped with secondary batteries (hereinafter simply referred to as batteries), and each time they are used in a portable manner. The battery is repeatedly charged and discharged. In recent years, as the functions of mobile terminals have improved and power consumption has increased, dual battery systems have been adopted in which two sets of batteries, a main battery and a second battery, are mounted on the mobile terminal. .

  In the dual battery system, since the inter-battery current flows, two sets of batteries cannot be simply connected in parallel and discharged. Although it is conceivable to insert a diode in the discharge circuit in order to suppress the inter-battery current, it is not preferable because a voltage drop occurs and the battery capacity is substantially reduced. Therefore, normally, the second battery is discharged first, and when the discharge of the second battery is completed, the main battery is discharged. A charger mounted on a portable terminal usually has only a capacity for charging one set of batteries from the viewpoint of cost, space, weight, and the like, and therefore cannot charge two sets of batteries at the same time.

  Therefore, when charging after both battery packs are discharged, the main battery is charged first and then the second battery is charged. The two sets of batteries are charged and discharged in this order because the device bay (also referred to as a shared bay) of the notebook PC in which the second battery is installed is shared with an optical drive or a spare hard disk drive. For this reason, the second battery is not always mounted during portable use, so that the probability that the main battery is sufficiently charged during portable use is increased.

  However, when charge / discharge control is performed in this order, the number of charge / discharge cycles of the second battery is increased as compared with the main battery. Many notebook PCs employ lithium ion batteries. When a lithium ion battery is used for a long period of time, so-called capacity deterioration in which the voltage decreases or the capacity decreases progresses. Causes of capacity deterioration include cycle deterioration related to the number of charge / discharge cycles, storage deterioration related to battery storage time and storage temperature, and use deterioration related to usage conditions such as the degree and frequency of overcharge / overdischarge. There is. FIG. 8 is a diagram showing an example of capacity deterioration based on cycle deterioration of a lithium ion battery.

  In FIG. 8, the horizontal axis indicates the number of charge / discharge cycles (hereinafter simply referred to as the cycle number), and the vertical axis indicates the full charge capacity based on the rated capacity at the start of use. In the example of FIG. 8, the full charge capacity decreases to about 85% when the number of cycles reaches 100 cycles, decreases to about 80% when it reaches 300 cycles, decreases to about 50% when it reaches 500 cycles, and then rapidly increases. Deterioration progresses.

  When there are two batteries here, the number of cycles is uneven in one charge / discharge system, and there are 100 cycles and 500 cycles of battery, and in the other charge / discharge system, there are two 300 cycles. Suppose that there is a battery. At this time, the total number of cycles is 600 in any charge / discharge system, but the total capacity of the two batteries is 135% for the former and 160% for the latter. Therefore, in a charge / discharge system including two batteries, it is desirable that the capacity deterioration of the two batteries progress evenly.

Patent Document 1 discloses a technique for performing a discharge switching control so that the number of cycles of each battery is uniform in a dual battery system including a main battery and a second battery, and preventing a phenomenon in which only one battery deteriorates. Is disclosed. Patent Document 2 discloses a technique for estimating the remaining capacity and life of a storage battery by measuring the internal resistance of the lead storage battery.
JP 2005-168103 A JP 2002-334725 A

  The invention described in Patent Document 1 performs discharge switching control so that the number of cycles is uniform. As described above, the causes of battery capacity deterioration include storage deterioration and use deterioration in addition to cycle deterioration. Therefore, it cannot be said that the capacity deterioration of a battery used for actual use is appropriately reflected only by cycle deterioration. Specifically, in two batteries used in the same charge / discharge system, a battery with a smaller number of cycles may have a smaller full capacity than a battery with a larger number of cycles.

  If the method of Patent Document 1 is applied to such a battery, charging / discharging of a battery having a small number of cycles is preferentially performed, cycle deterioration progresses, and a sudden decrease in full charge capacity is eventually brought about. It will be. In addition, in the method of Patent Document 1, when batteries having different characteristics between the number of cycles and capacity deterioration are used, even if these batteries are controlled to have the same number of cycles, one of the batteries is first Abrupt degradation can occur. Therefore, a charge / discharge system including a plurality of batteries needs to operate so as to control charge / discharge based on an actual deterioration amount and obtain a maximum total capacity.

  Accordingly, an object of the present invention is to provide a charge / discharge system capable of maximizing the total capacity of a plurality of batteries. Furthermore, the objective of this invention is providing the electric equipment and portable computer which employ | adopted such a charging / discharging system. A further object of the present invention is to provide a charge / discharge control method and program in such a charge / discharge system.

  The charging / discharging system of the present invention includes a plurality of batteries, a charger that sequentially charges the plurality of batteries, and a selection circuit that selects charging or discharging for each battery. The charge / discharge system further calculates a deterioration characteristic value based on the full charge capacity of each battery before the next discharge, and a control circuit that controls the selection circuit to discharge in the order of the batteries determined to have little capacity deterioration. Including. Based on such a configuration, the number of battery cycles with little capacity deterioration increases with time, and the capacity deterioration of each battery approaches, so that the total capacity of all the batteries at any point in time can be maximized. It becomes like this.

  The deterioration characteristic value based on the full charge capacity is the full charge capacity of the battery, the specific battery capacity indicating the ratio of the full charge capacity to the rated capacity of the battery, or the full charge capacity with respect to the rated capacity in the number of cycles before the battery is discharged. The ratio calculated from the specific battery capacity indicating the ratio and the cycle capacity value for the same number of charge / discharge cycles obtained in the battery cycle test can be used. If the specific battery capacity is adopted, the degree of capacity deterioration can be compared for batteries having different capacities. The value of the full charge capacity measured by the charge / discharge system may be kept large if capacity learning is not performed for a long period of time. In the present invention, since such a battery is judged to have little capacity deterioration and the priority of discharge increases, the probability that a learning capacity is obtained by complete discharge increases.

  As a result, when the accurate full charge capacity is measured, it is determined that the deterioration is progressing, and the discharge priority is lowered. Therefore, it is desirable that the control circuit updates the deterioration characteristic value based on the full charge capacity at the timing when any one of the batteries is charged or discharged. When the control unit controls the selection circuit so as to charge the batteries in the order of the batteries with the least deterioration when charging the batteries, the capacity deterioration of the batteries can be further progressed equally. In the present invention, if each battery is a lithium ion battery, the tendency of capacity deterioration of each battery is approximated, so that more accurate control can be performed.

  According to the present invention, a charge / discharge system capable of maximizing the total capacity of a plurality of batteries can be provided. Furthermore, according to the present invention, it is possible to provide an electric apparatus and a portable computer that employ such a charge / discharge system. Furthermore, according to the present invention, a charge / discharge control method and program in such a charge / discharge system could be provided.

[Configuration of charge / discharge system]
FIG. 1 is a block diagram illustrating an outline of a charge / discharge system including a battery pack and a notebook PC according to the present embodiment. The charge / discharge system includes a part of the notebook PC 10, an AC / DC adapter 11, a main battery pack 100, and a second battery pack 101. The main battery pack 100 is installed in the battery bay of the notebook PC 10 casing, and the second battery pack 101 is installed in the shared bay of the notebook PC 10 casing. A hard disk drive or an optical drive can be mounted in the shared bay without mounting the second battery pack 101. Both the main battery pack 100 and the second battery pack 101 comply with the standard of the smart battery system (SBS). However, the present invention includes a case where the battery pack does not comply with the SBS standard.

  In FIG. 1, only the structure of the main part relevant to the present invention of the notebook PC 10 is shown. The AC / DC adapter 11 is connected to a power jack of the notebook PC 10, converts an AC voltage into a DC voltage, and supplies power to the notebook PC 10. The charger 13 has a constant current constant voltage (CCCV) charging characteristic. The charger 13 includes a switching control circuit 16 that performs chopper control of the FET 15 and the FET 17 using a PWM method or a PFM method, and a smoothing circuit that includes an inductor 19 and a capacitor 21. The charger 13 converts the DC voltage input from the AC / DC adapter 11 into a DC voltage suitable for charging the battery pack and outputs the DC voltage. The charger 13 generates a constant current by reducing the pulsation of the DC charging current generated by driving the switching control circuit 16 with a smoothing circuit. A detection resistor 23 is connected to the feedback terminal FB of the charger 13.

  The detection resistor 23 includes a voltage dividing resistor that measures the output voltage of the charger 13 and a current sense resistor that measures the output current. The charger 13 uses a voltage corresponding to the output voltage and the output current for feedback control. To supply. The batteries housed in each of the battery packs 100 and 101 are initially charged by constant current control, and are charged by constant voltage control after the voltage of the battery cell has increased to a predetermined value. And charging is complete | finished when charging current falls to a predetermined value under constant voltage control. The charger 13 does not have a capacity for charging the main battery pack 100 and the second battery pack 101 simultaneously. Therefore, when charging the two battery packs 100 and 101 discharged together, it is necessary to charge them in order.

  A voltage from the reference voltage source 25 obtained by dividing a constant voltage generated inside the notebook PC 10 is input to the current setting value input Iset and the voltage setting value input Vset of the charger 13. Based on an instruction from the embedded controller (EC) 27, the reference voltage source 25 inputs the set voltage Vchg to the voltage set value input Vset, and inputs the set current Ichg to the current set value input Iset. The charger 13 operates so that the output voltage does not exceed the set voltage Vchg and the output current does not exceed the set current Ichg. Therefore, the charger 13 operates under constant current control so that the output current matches the set current Ichg at the beginning of charging when the charge current is large. However, when the charging proceeds and the charge voltage rises, the output voltage is set to the set voltage Vchg. Operates with constant voltage control to match. When the output current is larger than the set current Ichg for some reason when operating under constant voltage control, the operation is performed under constant current control so that the output current matches the set current Ichg.

  The EC 27 contains an MPU, ROM, and RAM, and controls devices related to the power supply of the notebook PC 10 and other devices. The EC 27 communicates with each of the battery packs 100 and 101 through a system management (SM) bus, and in addition to basic data such as the rated capacity stored in each battery pack from the beginning, each battery pack generates during operation. Information such as the surface temperature of the battery cell, the battery voltage, the number of cycles, the full charge capacity, the set voltage Vchg and the set current Ichg set in the charger can be acquired.

  The EC 27 sends an instruction to the reference voltage source 25 to operate or stop the charger 13 based on the instruction received from each battery pack. For example, when the main battery pack 100 instructs the EC 27 to set the set voltage Vchg and the set current Ichg to zero, the voltage set value input Vset and the current set value input Iset are set to zero, and the charger 13 stops operating. . When the operation of the charger 13 is started, the EC 27 that has received an instruction from the main battery pack 100 or the second 101 receives a predetermined value as the set voltage Vchg and the set current Ichg in the voltage set value input Vset and the current set value input Iset. Set.

  The FET drive circuit 29 controls on / off of the FET-A to FET-F based on an instruction from the EC 27. The EC 27 controls on / off of the FET-A to FET-D through the FET drive circuit 29 in order to charge or discharge each battery pack 100, 101. FET-A and FET-B are switches for controlling charging / discharging of the main battery pack 100, and are connected to a charging / discharging circuit of the main battery pack 100. FET-C and FET-D are switches for controlling charging / discharging of the second battery pack 101, and are connected to a charging / discharging circuit of the second battery pack 101.

  The FET-E is connected between each of the battery packs 100 and 101 and the DC / DC converter 31 and is a switch for forming a discharge circuit from the main battery pack 100 or the second battery pack 101 to the DC / DC converter 31. . The FET-F is connected to a circuit that supplies power from the AC / DC adapter 11 to the DC / DC converter 31, and from the AC power source when power is supplied from the AC / DC adapter 11 to the DC / DC converter 31. In order to temporarily supply power to the DC / DC converter 31 from the main battery pack 100 or the second battery pack 101 in order to perform so-called peak shift for easing the peak of the AC power source by interrupting reception of the power of Switch.

  The diode 14 prevents a current from flowing backward through the AC / DC adapter 11 when supplying power from the main battery pack 100 or the second battery pack 101 to the DC / DC converter 31. The DC / DC converter 31 converts the DC voltage received from the AC / DC adapter 11, the main battery pack 100 or the second battery pack 101 into a predetermined voltage and supplies it to the system load 33 in the notebook PC 10. The system load 33 includes various devices constituting the functions of a notebook PC such as a CPU, RAM, liquid crystal display, wireless module, hard disk drive, optical drive, and controller.

[Battery pack configuration]
FIG. 2 is a block diagram showing an internal configuration of the main battery pack 100 compliant with the SBS standard according to the embodiment of the present invention. The second battery pack 101 has the same configuration as the main battery pack 100. In the main battery pack 100, a power line 131, a communication line 133, and a ground line 135 are connected to the notebook PC 10 through a P terminal, a D terminal, and a G terminal, respectively. A charge protection switch C-FETb and a discharge protection switch D-FETb, each composed of a p-type MOS-FET, are connected to the power supply line 131 in series. A battery set 106 including three lithium ion battery cells 103 to 105 is connected in series to the discharge protection switch D-FETb. A discharging current from the battery set 106 and a charging current for the battery set 106 flow between the notebook PC 10 through a charging / discharging circuit including a power supply line 131 and a ground line 135.

  The voltage side terminals of the battery cells 103 to 105 are connected to analog input V1 to V3 terminals of the analog / interface 107. One to a plurality of temperature elements 111 such as thermistors are attached to the surface of the battery set 106. The temperature element 111 measures the surface temperature of the battery cells 103 to 105 and supplies a signal to the T terminal of the MPU 113. A current sense resistor 109 is connected to the ground line 135 between the negative terminal and the G terminal of the battery cell 105. Both ends of the current sense resistor 109 are connected to the I1 and I2 terminals of the analog / interface 107.

  The analog / interface 107 includes analog input terminals V1, V2, and V3 that acquire the cell voltages of the battery cells 103 to 105, and analog input terminals I1 and I2 that acquire a potential difference between both ends of the current sense resistor 109. The analog / interface 107 further includes analog output terminals C-CTL and D-CTL for outputting signals for controlling on / off of the charge protection switch C-FETb and the discharge protection switch D-FETb. The analog / interface 107 measures the cell voltage of the battery set 106, converts it into a digital value, and sends it to the MPU 113.

  The analog / interface 107 measures the values of the charging current and discharging current flowing through the battery set 106 from the voltage detected by the current sense resistor 109, converts them into digital values, and sends them to the MPU 113. The MPU 113 is an integrated circuit including a RAM, a ROM, a flash memory, a timer, etc. in one package in addition to a CPU of about 8 to 16 bits. A communication line 133 is connected from the MPU 113 to the EC 27 of the notebook PC 10 through the D terminal, and communication between the MPU 113 and the EC 27 is possible. The communication line 133 includes a clock line. The MPU 113 can communicate with the analog / interface 107. The MPU 113 calculates the charge electricity amount and the discharge electricity amount based on the voltage and current relating to the battery set 106 sent from the analog / interface 107, and further increases the full charge capacity. Calculate and store in RAM or flash memory. The stored data is received by the EC 27 periodically.

  Here, the meaning of the full charge capacity will be described. When charging a battery, it is necessary to set an upper limit on the amount of charge electricity to avoid overcharging. In addition, in order to promote deterioration when the battery is overdischarged, a discharge end voltage that determines the end of discharge is set in the charge / discharge system. Therefore, the amount of electricity that the battery can store or the amount of electricity that the battery can discharge corresponds to the amount of electricity that is charged or discharged between the discharge end voltage and the upper limit of the charge amount. The upper limit of the amount of electricity to charge differs depending on the charging method and environmental temperature, etc., but if you overcharge the battery with an amount of electricity greater than the allowable value, the excess energy becomes heat and the battery temperature rises. It is necessary to stop charging by determining the upper limit of charging at a certain time.

  In a normal charge control circuit, the end of charge is determined by measuring voltage, current, temperature, and time during charge. At this time, since the charging method differs depending on the type of battery, the method for determining the charging end time is also different. For example, in a nickel cadmium storage battery or nickel metal hydride storage battery that employs a constant current charging method, the determination is made based on the amount of change in charging voltage generated at the end of charging or the amount of change in rising temperature per unit time. In lithium ion storage batteries and lead storage batteries that employ a constant current and constant voltage system, the determination is based on the minimum charging current.

  The full charge capacity is the amount of electricity when charging from the discharge end voltage to the upper limit of the amount of charge or the amount of electricity when discharging to the end of discharge voltage after charging to the upper limit of the amount of charge. Here, discharging to the end-of-discharge voltage is referred to as complete discharge. In order to measure the full charge capacity, it is necessary to completely discharge the battery, but this is rarely performed in a normal use state. When charging / discharging is repeated without being discharged to the discharge end voltage, the full charge capacity is not updated.

  Alternatively, the full charge capacity can be calculated by offsetting the charge electricity amount and the discharge electricity amount in the meantime, but the accumulated error becomes large. In order to obtain an accurate full charge capacity, it is necessary to forcibly completely discharge the battery and reset the accumulated error. The full charge capacity obtained by fully charging after fully discharging in this way is called a learning capacity. When the present invention is executed, a learning capacity is inevitably obtained in any battery pack as will be described later. Note that the full charge capacity decreases with the passage of time. This is called capacity deterioration.

  The MPU 113 recognizes that the battery set 106 is in a charged state and a discharged state, counts the number of times of charging / discharging, stores it in the RAM, and supplies data to the EC 27 as the number of cycles. Note that the number of cycles is counted as one when both charging and discharging are performed regardless of the amount of charge electricity or discharge electricity. The MPU 113 also has an overcurrent protection function, an overcharge protection function, and an overdischarge protection function. When an abnormality is detected in the battery cells 103 to 105 from the voltage or current received from the analog / interface 107, the MPU 113 The charge protection switch C-FETb and / or the discharge protection switch D-FETb are turned off. The overcurrent protection function, the overvoltage protection function, the low voltage protection function, the full charge measurement function, and the cycle count function are constituted by programs executed by the MPU 113. The flash memory stores a program executed by the MPU 113, a rated capacity of the battery set 100, a setting value of a charging voltage, a setting value of a charging current, and the like.

[Principle of charge / discharge control]
Next, the principle of charge / discharge control according to this embodiment will be described. FIG. 3 is a diagram showing a state of capacity deterioration of a battery set actually used. In the battery set, the full charge capacity decreases as the usage time elapses. Now, let the full charge capacity before the start of use be the rated capacity, and the ratio of the full charge capacity to the rated capacity after the start of use be the specific battery capacity P (%). The rated capacity is a value corresponding to the maximum amount of electricity that can be stored before the battery set is used, and the full charge capacity is smaller than the rated capacity and gradually becomes smaller due to capacity deterioration. The reason why the deterioration characteristic value is displayed not by the full charge capacity but by the specific battery capacity is to normalize the full charge capacity so that battery sets having different rated capacities can be compared with each other. Therefore, the deterioration characteristics may be set to the full charge capacity between battery sets having the same rated capacity, and the degree of deterioration may be compared.

  Lines 51, 53, 55, and 57 are deterioration curves showing how the specific battery capacity changes with the elapsed time of the battery sets A, B, C, and D. Causes of the specific battery capacity decreasing with elapsed time include cycle deterioration, storage deterioration, use deterioration, and the like. Therefore, even if a plurality of battery sets are incorporated in the same charge / discharge system, the deterioration curve differs for each battery set. In the line 51, the specific battery capacity of the battery set A becomes Px at time tx, and thereafter, the rate of decrease of the specific battery capacity with respect to the elapsed time becomes intense. Thus, the specific battery capacity immediately before the capacity deterioration rapidly proceeds is referred to as critical capacity Px.

  Now, it is assumed that the battery set A and the battery set D constitute the dual battery system 1, and the battery set B and the battery set C constitute the dual battery system 2. As described above, the capacity deterioration includes all of cycle deterioration, storage deterioration, and usage deterioration, so in the dual battery system 1, the number of cycles of two battery packs approaches as in Patent Document 1. When the order of discharge is controlled in this way, when battery set A has less storage deterioration and use deterioration than battery set D, the capacity deterioration of battery set A is represented by deterioration curve 51, and the capacity deterioration of battery set D deteriorates. It can be represented by a curve 57.

  In the present invention, in the dual battery system 2, the order of discharge is controlled so that the specific battery capacities of the battery set B and the battery set C approach each other. In that case, the capacity deterioration of the battery set B can be represented by the deterioration curve 53, and the capacity deterioration of the battery set C can be represented by the deterioration curve 55. The specific battery capacities of the four battery packs at time t1 are Pa, Pb, Pc, and Pd, respectively. The specific battery capacity Pa of the battery set A has not reached the critical capacity, the specific battery capacities Pb and Pc of the battery sets B and C are almost in the vicinity of the critical capacity, and the specific battery capacity Pd of the battery set D is critical. The capacity is severely degraded beyond the capacity. At this time, the total capacity of the two batteries of the dual battery system 1 is Pa + Pd, and the total capacity of the two batteries of the dual battery system 2 is Pb + Pc. -The battery system 2 has a larger total capacity.

  In the present embodiment, paying attention to the feature of such capacity deterioration, control is performed so that the specific battery capacity approaches two battery sets of the dual battery system. Since only the cycle deterioration can control the progress of capacity deterioration when the battery is actually used, the specific battery capacity of the two battery sets is calculated and compared before discharging, and the specific battery capacity is large. The battery set is discharged first to advance the cycle number. The battery set whose cycle number has been advanced undergoes capacity deterioration due to cycle deterioration, and eventually the specific battery capacity of both approaches. In the present embodiment, the number of cycles is not used as a control target value, but is used to make the specific battery capacities of the two battery sets approach each other.

[Charging / Discharging Procedure]
FIG. 4 is a functional block diagram of the sequence control unit 80 that controls the charging / discharging sequence of the main battery pack 100 and the second battery pack 101. The sequence control unit 80 includes a CPU, RAM, and a power management program stored in the hard disk drive included in the system load 33. The CPU executes the power management program on the RAM to realize each component of the sequence control unit 80.

  The basic data storage unit 81 stores the rated capacity of each battery pack 100, 101. The deterioration information acquisition unit 85 acquires and stores the full charge capacity from each of the battery packs 100 and 101. The deterioration information acquisition unit 85 acquires and updates the latest full charge capacity at the timing from the main battery pack 100 or the second battery pack 101 that has been charged or discharged. The calculation unit 83 calculates the specific battery capacity from the rated capacity of each battery pack stored in the basic data storage unit 81 and the full charge capacity of each battery pack stored in the deterioration information acquisition unit 85, and then discharges. Determine priorities when to be done. The charge / discharge order instruction unit 88 instructs the EC 27 on the determined discharge priority order.

  As described with reference to FIG. 3, the calculation unit 83 compares the specific battery capacities of the main battery pack 100 and the second battery pack 101 at that time, and the battery pack with the larger specific battery capacity with less deterioration. Is determined as a battery pack with a high priority. The battery pack with the higher priority is discharged first when the next discharge is performed. In addition, when any one of the battery packs is completely discharged and the other battery pack is discharged and it is necessary to charge both battery packs, the calculation unit 83 charges the battery packs with higher priority. In this way, when the AC / DC adapter 11 is removed while the battery pack is being charged and the battery pack is discharged, the cycle number of the battery pack with a high priority is not increased without increasing the number of cycles of the battery pack with a low priority. The number will increase.

  FIG. 5 is a flowchart illustrating a charge / discharge procedure performed by the charge / discharge system of the notebook PC 10. In block 201, the EC 27 turns on the FET-F to supply power to the DC / DC converter 31 through the diode 14 and also supplies power to the charger 13. The charger 13 operates based on the set current Ichg and the set voltage Vchg set by the main battery pack 100 or the second battery pack 101. The EC 27 turns off the FET-E, turns on the charging circuit of the battery pack to be charged by controlling on / off of the FET-A to FET-D, and turns off the charging circuit of the other battery pack. In block 201, the main battery pack 100 and the second battery pack 101 are both charged to the full charge capacity as a typical state of waiting for discharge.

  In block 203, the sequence controller 80 calculates the specific battery capacity based on the latest full charge capacity before the next discharge of each battery pack 100, 101, and determines the discharge priority. As described above, the sequence control unit 80 determines that the battery pack having the larger specific battery capacity has the higher priority. Here, it is assumed that the specific battery capacity of the main battery pack 100 is larger. Then, the determination result is notified to the EC 27. Upon receiving the notification, the EC 27 can control the FET drive circuit 29 to discharge from the main battery pack 100 determined to have a high priority immediately when the next power failure occurs.

  In block 205, the charging / discharging system waits until the AC / DC adapter 11 is removed and a power failure occurs in the notebook PC 10. The EC 27 monitors the output voltage of the AC / DC adapter 11, and at the same time when a power failure occurs, the block 207 turns on FET-A, FET-B, and FET-E, and turns off FET-C and FET-D. Thus, power is supplied to the system load 33 from the main battery pack 100 having a high priority. The EC 27 changes the power source from the AC / DC adapter 11 to the main battery pack 100 so that the DC / DC converter 31 can supply a stable voltage to the system load 33 without causing an instantaneous voltage drop. .

  When the notebook PC 10 is used for a short period of time, the AC / DC adapter 11 may be connected and recharged in block 209 while the main battery pack 207 is discharged. In this case, in block 221, the EC 27 turns off the FET-E and charges the main battery pack 221. At this time, power is supplied to the DC / DC converter 31 from the AC / DC adapter 11. Therefore, when returning to the block 201, the number of cycles of the main battery pack 100 increases once, and the number of cycles of the second battery pack 101 does not change. When the main battery pack 207 is completely discharged without power recovery in block 209, in block 211, the EC 27 turns on FET-C and FET-D, turns off FET-A and FET-B, and turns the power source to the second battery. Switch to pack 101.

  In block 213, the second battery pack 101 is completely discharged or the AC / DC adapter 11 is connected to the battery pack 101 before it is recharged. When the second battery pack 101 is completely discharged, the operation of the notebook PC 10 stops and waits for power recovery. In block 215, power is supplied from the AC / DC adapter 11 and charging is started. At this time, as instructed by the sequence control unit 80, the EC 27 switches the FET-A to FET-E in the block 215 and charges from the main battery pack 100 having a high priority. In block 217, it is assumed that a power failure occurs while the main battery pack 100 is being charged. When a power failure occurs, the EC 27 discharges from the main battery pack 100 at block 223 by controlling on / off of the FET-A to FET-E because the second battery pack 101 is not yet charged.

  Thereafter, when power is restored in block 225, the process proceeds to block 215, where the number of cycles of the main battery pack 100 increases by one, and the number of cycles of the second battery pack 219 does not change. If power is not restored until the main battery pack 100 is completely discharged in block 225, the notebook PC 10 stops operating in block 227. If a power failure does not occur until the main battery pack 100 is fully charged in block 217, the EC 27 charges the second battery pack 219 in block 219 and proceeds to block 201.

  In the present embodiment, when the charge / discharge path from block 201 to block 219 is established, the number of cycles of main battery pack 100 and second battery pack 101 are both counted once, but the timing of block 209 or block 217 When a power recovery or power failure occurs, only the number of cycles of the main battery pack 100 increases. Accordingly, since the cycle deterioration of the main battery pack 100 proceeds, the specific battery capacities of both gradually approach each other. Note that the charge / discharge system cannot avoid the increase in the number of cycles itself, but only controls which of the battery packs the cycle number is increased.

  By the way, in the present embodiment, it is necessary to accurately measure the full charge capacity. As described above, in order to obtain an accurate full charge capacity, it is necessary to measure the learning capacity by charging or discharging between full discharge and full charge. When the frequency of acquiring the learning capacity decreases, an accurate full charge capacity cannot be obtained. When the conventional method is used for charging / discharging, the second battery pack 101 cannot obtain the learning capacity, and the full charge capacity of the second battery pack 101 is not updated, and old data indicating a large full charge capacity is maintained. Have been. According to the present embodiment, the battery pack having a large full charge capacity is set so that the specific battery capacity is increased and the priority is increased, and the chance of complete discharge increases, so that the learning capacity can be obtained. become.

[Other examples of prioritization]
In the above description, for the two battery packs, the specific battery capacity was selected instead of the cycle number as the deterioration characteristic value to be approached. An example of another deterioration characteristic value instead of the specific battery capacity will be described with reference to FIG. In FIG. 6, the vertical axis represents the specific battery capacity P (%), and the horizontal axis represents the number of cycles. A line 301 is a deterioration curve showing typical cycle deterioration applicable to the main battery pack 100 and the second battery pack 101. Such a deterioration curve can be obtained by a cycle test in which charge and discharge from a fully charged state to a fully discharged state are repeated in advance for a representative battery set having the same structure. The basic data storage unit 81 of the sequence control unit 80 stores the relationship between the cycle number indicating the cycle deterioration curve and the specific battery capacity as data in a table format. The specific battery capacity in this data is referred to as a cycle capacity value in this specification.

  The deterioration information acquisition unit 85 acquires and stores the latest cycle number from each of the battery packs 100 and 101. The calculation unit 83 sets the rated capacity and cycle capacity value of each battery pack stored in the basic data storage unit 81 and the latest full charge capacity and latest cycle number of each battery pack stored in the deterioration information acquisition unit 85. Based on the current cycle number, the specific battery capacity of each battery pack 100, 101 is calculated, and the deterioration characteristic value M (%) is calculated by the following equation.

M = 1-B / A
Here, B is a specific battery capacity at the current cycle number of the main battery pack 100 or the second battery pack 101, and A is a cycle capacity value at the same cycle number. Assume that the specific battery capacity actually measured when the number of cycles of the main battery pack 100 is 100 is P2, and the cycle capacity value in 100 cycles is P1. Further, it is assumed that the specific battery capacity actually measured when the number of cycles of the second battery pack 101 is 250 is P4 and the cycle capacity value at 250 cycles is P3. The deterioration characteristic value of the main battery pack 100 is M = 1−P2 / P1, and the deterioration characteristic value of the second battery pack 101 is M = 1−P4 / P3.

  The calculation unit 83 compares the deterioration characteristic value M of each battery pack, the deterioration of the battery pack with the larger M is progressing, and the priority order when the battery pack with the smaller M is discharged next is given. Set to be higher. In this case, the priority order of the second battery pack 101 becomes higher. This deterioration characteristic value M is for comparing the cycle capacity value and the specific battery capacity at the number of cycles based on the actual number of cycles.

[Application to hybrid battery pack]
The charge / discharge system according to the present embodiment can also be applied to a hybrid battery pack. FIG. 7 is a block diagram showing a basic configuration of hybrid battery pack 400. The hybrid battery pack 400 houses a cylindrical battery block 407 and a rectangular battery block 409 in which four lithium ion battery cells are connected in series in the same casing. The hybrid battery pack 400 further includes protective FETs 403, 405, 415, and 417 corresponding to the battery blocks 407 and 409.

  The CPU 419 includes a RAM and sends commands to the measurement / control circuits 411 and 413 to read the charging current, discharging current, cell voltage, and the like, and calculate the full charge capacity of the battery block 407 and the battery block 409, and the FET 403 , 405, 415, and 417, a command for on / off control is sent to the measurement / control circuits 411 and 413. The CPU 419 communicates with the EC 27 via, for example, an SBS interface, and transfers data such as the full charge capacity of each battery block 407, 409, the number of cycles, and a set value for the charger 13. The EEPROM 425 stores a program executed by the CPU 419 and stores basic information of the battery blocks 407 and 409.

  The EC 27 treats the battery block 407 and the battery block 409 of such a hybrid battery pack 400 as the respective battery sets of the main battery pack 100 and the second battery pack 101 of FIG. Can do. In particular, in the procedure of FIG. 5, when it is determined that the priority order of the main battery pack 207 is high, the probability that the main battery pack 207 is fully charged in the initial stage of discharging is reduced, and the user uses the notebook PC 10 for portable use. Therefore, it is necessary to replace the second battery pack 101 with the main battery pack 100. However, in the hybrid battery pack 400, since the two battery blocks 407 and 409 are housed in the same casing, such a problem arises. Never happen. Further, the case where there are two battery packs and battery blocks has been described above as an example, but the present invention can also be applied to the case where there are three or more battery packs and battery blocks.

  Although the present invention has been described with the specific embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and is known so far as long as the effects of the present invention are achieved. It goes without saying that any configuration can be adopted.

It is a block diagram which shows the outline | summary of the charging / discharging system mounted in the notebook PC concerning this embodiment. It is a block diagram which shows the internal structure of a main battery pack. It is a figure which shows the state of capacity | capacitance degradation of a battery set. It is a functional block diagram of the order control part which controls the order of charging / discharging. It is a flowchart which shows the procedure of charging / discharging which a charging / discharging system performs. It is a figure explaining the example of the substitute characteristic substituted for a specific battery capacity. It is a block diagram which shows the basic composition of a hybrid battery pack. It is a figure which shows an example of capacity | capacitance deterioration based on the cycle deterioration of a lithium ion battery.

Explanation of symbols

10 ... Notebook PC
80 ... Sequence control unit

Claims (13)

A plurality of batteries and a charger for sequentially charging the plurality of batteries;
A selection circuit that selects charging or discharging for each battery;
A charge / discharge system comprising: a control circuit that controls the selection circuit so as to discharge in the order of batteries that are determined to have a small capacity deterioration by calculating a deterioration characteristic value based on a full charge capacity of each battery before the next discharge.   The charge / discharge system according to claim 1, wherein the deterioration characteristic value based on the full charge capacity is a specific battery capacity indicating a ratio of the full charge capacity to a rated capacity of each battery.   The charge / discharge system according to claim 1, wherein the deterioration characteristic value based on the full charge capacity is a full charge capacity of each battery.   The deterioration characteristic value based on the full charge capacity indicates the ratio of the full charge capacity to the rated capacity in the charge / discharge cycle number before discharge of each battery, and the cycle with respect to the charge / discharge cycle number obtained in the battery cycle test. The charge / discharge system according to claim 1, wherein the charge / discharge system is calculated from the capacity value.   The charge / discharge system according to any one of claims 1 to 4, wherein the control circuit updates the deterioration characteristic value at a timing when any one of the batteries is charged or discharged.   The charge / discharge system according to any one of claims 1 to 5, wherein the control circuit controls the selection circuit so that the batteries are charged in the order of batteries with less capacity deterioration when charging each battery.   The charge / discharge system according to claim 1, wherein each of the plurality of batteries is a lithium ion battery. A first battery pack;
A second battery pack;
A charger for sequentially charging the first battery pack and the second battery pack;
A load that receives power supply from the first battery pack or the second battery pack;
A switch circuit for selecting charging or discharging for each battery pack, and calculating a deterioration characteristic value based on the full charge capacity of each battery pack before the next discharge so that the battery packs are discharged in the order in which the capacity deterioration is judged to be small. And an electric device having a control circuit for controlling the switch circuit. Battery bay where the main battery pack is installed,
A shared bay where the second battery pack is installed;
A charger for sequentially charging the main battery pack and the second battery pack;
A system load that receives power from the main battery pack or the second battery pack;
A switch circuit for selecting charging or discharging for each battery pack, and calculating a deterioration characteristic value based on the full charge capacity of each battery pack before the next discharge so that the battery packs are discharged in the order in which the capacity deterioration is judged to be small. A portable computer having a processor for controlling the switch circuit; A battery-only bay for mounting a hybrid battery pack including the first battery block and the second battery block in the same housing;
A charger for sequentially charging the first battery block and the second battery block;
A system load that receives power from the first battery block or the second battery block;
A switch circuit that selects charging or discharging for each battery block, and calculating the deterioration characteristic value based on the full charge capacity of each battery block before the next discharge, so that the battery blocks are discharged in the order that the capacity deterioration is judged to be small. A portable computer having a processor for controlling the switch circuit; A charge / discharge control method in a charge / discharge system including a plurality of batteries,
Charging each battery in turn;
The charge / discharge system calculates a deterioration characteristic value based on the full charge capacity of each battery before the next discharge, and ranks the capacity deterioration of each battery;
And a step of operating the charge / discharge system to discharge in the order of the batteries determined to have little capacity deterioration.   The control method according to claim 11, further comprising a step of operating the charging / discharging system so as to charge in the order of batteries determined to have little capacity deterioration. To a computer equipped with a charging / discharging system containing multiple batteries,
The ability to charge each battery in turn,
A function that ranks the capacity deterioration of each battery by calculating the deterioration characteristic value based on the full charge capacity of each battery before the next discharge,
The program which implement | achieves the function to operate | move so that the said charging / discharging system may discharge in order of the battery judged that there is little capacity deterioration.

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