Battery capacity calculation device and battery capacity calculation method

Abstract

To provide a battery capacity calculation device and a battery capacity calculation method that calculate a full charge capacity at a high frequency.SOLUTION: A battery capacity calculation device includes a controller. The controller acquires the first voltage value and charge current value of a battery during charging of the battery; acquires the second voltage value of the battery while charging of the battery is discontinued; calculates the impedance value of the battery by using the first voltage value, the second voltage value, and the charge current value; acquires a cycle count of the battery; acquires a time during which the battery temperature is included in a prescribed temperature range and the output voltage value of the battery is included in a prescribed voltage range; and calculates the full charge capacity of the battery by using the cycle count, the impedance value, and the time.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a battery capacity calculation device and a battery capacity calculation method.

Background Art

[0002] The development of products that can be used by users for a long time leads to a reduction in carbon emissions. By having users replace the batteries of electronic devices such as notebook PCs (Personal Computers) at an appropriate timing, electronic waste (E-waste) can be reduced, and improvement of environmental problems is expected. Therefore, a function for prompting users to replace the battery at an appropriate timing is desired.

[0003] As a function for notifying users of the degree of battery deterioration, there is a function of estimating the state of the battery based on the capacity retention rate and the number of cycles, and displaying that state. The capacity retention rate is obtained by dividing the full charge capacity (FCC: Full Charge Capacity) by the design capacity. Also, a conventional technique for calculating the full charge capacity based on the current value from the fully charged state to the fully discharged state of the battery is known.

[0004] The device disclosed in Patent Document 1 selects an estimation method for the full charge capacity according to the state of the battery, and estimates the full charge capacity by the selected method.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the conventional technique for estimating the full charge capacity, since it is necessary to completely discharge the battery, the calculation frequency of the full charge capacity is low.

[0007] An object of the present invention is to provide a battery capacity calculation device and a battery capacity calculation method capable of calculating a full charge capacity frequently.

Means for Solving the Problems

[0008] One aspect of the present invention includes a controller. The controller acquires a first voltage value and a charging current value of the battery during charging of the battery, acquires a second voltage value of the battery during a pause in charging of the battery, calculates an impedance value of the battery by using the first voltage value, the second voltage value, and the charging current value, calculates an impedance increase that is a ratio of the impedance value to an initial impedance value pre-recorded in a memory, acquires the number of cycles of the battery, acquires a time during which the temperature of the battery is included in a predetermined temperature range and the output voltage value of the battery is included in a predetermined voltage range, and is a battery capacity calculation device that calculates the full charge capacity of the battery by using the number of cycles, the impedance increase, and the time.

[0009] In one aspect of the present invention, the controller may calculate the full charge capacity according to an equation FCC = 1.0 + a*CYC + b*HTVT + c*IMP. In the equation, FCC is the full charge capacity, CYC is the number of cycles, HTVT is the time, IMP is the impedance increase, and a, b, and c are predetermined coefficients.

[0010] In one aspect of the present invention, the controller may correct the impedance value according to the temperature during charging of the battery.

[0011] In one aspect of the present invention, the controller records the calculated full charge capacity and the time information at the time when the full charge capacity is calculated in a memory, and calculates the time until the full charge capacity of the battery becomes equal to or less than a predetermined capacity by using the full charge capacity and the time information recorded in the memory.

[0012] One aspect of the present invention is a battery capacity calculation device including a controller that acquires a first voltage value and a charging current value of a battery during charging of the battery, acquires a second voltage value of the battery during a charging pause of the battery, calculates an impedance value of the battery by using the first voltage value, the second voltage value, and the charging current value, calculates an impedance increase that is a ratio of the impedance value to an initial impedance value pre-recorded in a memory, acquires the number of cycles of the battery, and calculates the full charge capacity of the battery by using the number of cycles and the impedance increase.

[0013] One aspect of the present invention is a battery capacity calculation method including steps of: acquiring a first voltage value and a charging current value of a battery during charging of the battery; acquiring a second voltage value of the battery during a charging pause of the battery; calculating an impedance value of the battery by using the first voltage value, the second voltage value, and the charging current value; calculating an impedance increase that is a ratio of the impedance value to an initial impedance value pre-recorded in a memory; acquiring the number of cycles of the battery; acquiring a time during which the temperature of the battery is included in a predetermined temperature range and an output voltage value of the battery is included in a predetermined voltage range; and calculating the full charge capacity of the battery by using the number of cycles, the impedance increase, and the time.

[0014] One aspect of the present invention includes steps of obtaining a first voltage value and a charging current value of the battery during charging of the battery; obtaining a second voltage value of the battery during a pause in charging of the battery; calculating an impedance value of the battery by using the first voltage value, the second voltage value, and the charging current value; calculating an impedance increase that is a ratio of the impedance value to an initial impedance value pre-recorded in a memory; obtaining the number of cycles of the battery; and calculating a full charge capacity of the battery by using the number of cycles and the impedance increase. This is a battery capacity calculation method.

Advantages of the Invention

[0015] According to the present invention, a battery capacity calculation device and a battery capacity calculation method can calculate the full charge capacity at high frequency.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0018] (First Embodiment) The first embodiment of the present invention will be described. FIG. 1 is a block diagram showing an example of the hardware configuration of the electronic device 10 according to the present embodiment.

[0019] The electronic device 10 includes a CPU 11, a main memory 12, a video subsystem 13, a display unit 14, a chipset 21, a BIOS memory 22, a storage medium 23, an audio system 24, a WLAN card 25, a USB connector 26, an embedded controller 31, an input unit 32, a power supply circuit 33, and a battery 40.

[0020] The CPU 11 executes various arithmetic processes under program control and controls the entire electronic device 10. For example, the CPU 11 executes processes based on programs of an OS (Operating System) and a BIOS (Basic Input Output System). The CPU 11 is an example of a processor.

[0021] The main memory 12 is a writable memory that is used as a loading area for the execution program of the CPU 11 or as a working area for writing the processing data of the execution program. The main memory 12 is composed of, for example, a plurality of DRAM (Dynamic Random Access Memory) chips. This execution program includes various drivers for operating the OS and peripheral devices, various services / utilities, and application programs, etc.

[0022] The video subsystem 13 is a subsystem for realizing functions related to image display and includes a video controller. The video controller processes drawing commands from the CPU 11, writes the processed drawing information to the video memory, reads the drawing information from the video memory, and outputs it as drawing data (display data) to the display unit 14.

[0023] The display unit 14 is, for example, a liquid crystal display or an organic EL display, and displays a display screen based on the drawing data (display data) output from the video subsystem 13.

[0024] The chipset 21 includes controllers such as USB (Universal Serial Bus), Serial ATA (AT Attachment), SPI (Serial Peripheral Interface) bus, PCI (Peripheral Component Interconnect) bus, PCI-Express bus, and LPC (Low Pin Count) bus, to which a plurality of devices are connected. For example, as the plurality of devices, there are included a BIOS memory 22 described later, a storage medium 23, an audio system 24, a WLAN card 25, a USB connector 26, and an embedded controller 31.

[0025] The BIOS memory 22 is composed of an electrically rewritable non-volatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory) or flash ROM, for example. The BIOS memory 22 stores a BIOS program and system firmware for controlling the embedded controller 31 and the like. The BIOS memory 22 is an example of a sub-memory.

[0026] The storage medium 23 includes an HDD (Hard Disk Drive) or an SSD (Solid State Drive), for example. The storage medium 23 stores an OS, various drivers, various services / utilities, application programs, and various data.

[0027] The audio system 24 has a microphone and a speaker (not shown) connected thereto, and records, plays back, and outputs audio data. Note that the microphone and the speaker are, as an example, built in the electronic device 10.

[0028] The WLAN (Wireless Local Area Network) card 25 connects to a network via a wireless LAN to perform data communication. When the WLAN card 25 receives data from the network, for example, it generates an event trigger indicating that the data has been received. The USB connector 26 is a connector for connecting peripheral devices using USB.

[0029] The input unit 32 collectively represents the input devices provided in the electronic device 10. The input devices included in the input unit 32 output the input information input by the user's operation to the embedded controller 31.

[0030] The power supply circuit 33 includes, for example, a DC / DC converter, a charge / discharge unit, and an AC / DC adapter. For example, the power supply circuit 33 converts the DC voltage supplied from an external power supply such as an AC adapter (not shown) or the battery 40 into a plurality of voltages required to operate the electronic device 10. Also, the power supply circuit 33 supplies power to each part of the electronic device 10 based on the control from the embedded controller 31.

[0031] The battery 40 is a secondary battery such as a lithium-ion battery, for example. When power is supplied to the electronic device 10 from an external power supply, the battery 40 is charged via the power supply circuit 33. When power is not supplied to the electronic device 10 from an external power supply, the battery 40 outputs the stored power as the operating power of the electronic device 10 via the power supply circuit 33.

[0032] The embedded controller 31 is a one-chip microcomputer that monitors and controls various devices (peripheral devices, sensors, etc.) regardless of the state of the system of the electronic device 10. The embedded controller 31 includes a CPU, a ROM, a RAM, A / D input terminals of multiple channels, D / A output terminals, a timer, and digital input / output terminals (not shown). An input unit 32, a power supply circuit 33, etc. are connected to the digital input / output terminals of the embedded controller 31, and the embedded controller 31 controls these operations. Also, the embedded controller 31 controls the change of the clock frequency of the CPU 11 via the chipset 21.

[0033] FIG. 2 shows an example of the configuration of the battery 40 according to this embodiment. The battery 40 has a battery 41, a BMU (Battery Management Unit) 42, and a battery capacity calculation device 43. The battery capacity calculation device 43 may be included in the BMU 42.

[0034] For example, the battery 41 is a lithium-ion battery. The BMU 42 monitors various states of the battery 41 and acquires information regarding the various states from the battery 41. For example, the BMU 42 acquires the voltage value, current value, and temperature of the battery 41 from the battery 41.

[0035] The battery capacity calculation device 43 has a controller 44 and a memory 45. The controller 44 has an MPU (Micro Processing Unit), etc. The memory 45 has a storage medium such as a RAM.

[0036] As a functional configuration of the processing executed by the MPU, the controller 44 has a state acquisition unit 440, an impedance value calculation unit 441, a battery capacity calculation unit 442, a memory control unit 443, and a charge control unit 444. The functions of the controller 44 may be implemented in the battery firmware.

[0037] The state acquisition unit 440 acquires information regarding various states of the battery 41 from the BMU 42. The impedance value calculation unit 441 calculates the impedance value of the battery 41 by using the information acquired from the BMU 42. The battery capacity calculation unit 442 calculates the full charge capacity of the battery 41 by using the information acquired from the BMU 42 and the impedance value calculated by the impedance value calculation unit 441. The memory control unit 443 controls the reading and writing of data between the controller 44 and the memory 45. The charge control unit 444 controls the charging of the battery 41 via the BMU 42.

[0038] Referring to FIG. 3, the impedance value calculation process executed by the controller 44 will be described. FIG. 3 shows an example of the impedance value calculation process according to the present embodiment. The controller 44 executes the impedance value calculation process shown in FIG. 3 during the charging of the battery 41.

[0039] (Step S100) The state acquisition unit 440 acquires information regarding the SoC (State of Charge) of the battery 41 from the BMU 42 every time a predetermined time elapses. The SoC indicates the charging state of the battery 41. When the battery 41 is in a fully charged state, the SoC is 100%, and when the battery 41 is in a fully discharged state, the SoC is 0%. The state acquisition unit 440 determines whether the charging state indicated by the SoC is a predetermined state. The predetermined state corresponds to a state in which the electronic device 10 is operating while receiving power from the battery 41 and the impedance of the battery 41 is stable. For example, the predetermined state corresponds to the SoC being 60%, 65%, 70%, 75%, or 80%.

[0040] When the charging state of the battery 41 is not the predetermined state, the controller 44 executes step S100 again. When the charging state of the battery 41 is the predetermined state, the controller 44 executes the following step S101.

[0041] When the SoC is 60%, 65%, 70%, 75%, or 80%, the controller 44 calculates the impedance value of the battery 41 as follows. Therefore, the controller 44 can calculate the impedance value of the battery 41 at high frequency.

[0042] (Step S101) The state acquisition unit 440 acquires information regarding the voltage value V1, current value I1, and temperature T of the battery 41 from the BMU 42.

[0043] (Step S102) After step S101 is executed, the charge control unit 444 stops the charging of the battery 41 for one minute. The time for which the charge control unit 444 stops charging is not limited to one minute.

[0044] (Step S103) After step S102 is executed, the state acquisition unit 440 acquires information regarding the voltage value V2 of the battery 41 from the BMU 42.

[0045] (Step S104) After step S103 is executed, the impedance value calculation unit 441 calculates the impedance value of the battery 41 by using the voltage value V1, voltage value V2, and current value I1. Further, the impedance value calculation unit 441 corrects the impedance value by using the temperature T to obtain a corrected impedance value.

[0046] Referring to FIGS. 4 and 5, a method by which the impedance value calculation unit 441 calculates the impedance value of the battery 41 will be described. FIG. 4 shows an example of the change in the voltage of the battery 41 during charging. FIG. 5 is an enlarged view of a part of FIG. 4.

[0047] The horizontal axis of the graph in FIG. 4 represents the SoC, and the vertical axis of the graph represents the voltage. Line L1 in FIG. 4 represents the closed circuit voltage (CCV) of the battery 41 during charging. Points P1 to P5 on line L2 in FIG. 4 represent the open circuit voltage (OCV) of the battery 41 after the charging of the battery 41 has stopped for one minute. When the SoC is 60%, the open circuit voltage of the battery 41 is at point P1. When the SoC is 65%, the open circuit voltage of the battery 41 is at point P2. When the SoC is 70%, the open circuit voltage of the battery 41 is at point P3. When the SoC is 75%, the open circuit voltage of the battery 41 is at point P4. When the SoC is 80%, the open circuit voltage of the battery 41 is at point P5.

[0048] FIG. 5 shows the voltage of the battery 41 around point P1 in FIG. 4. Point P0 on line L1 shown in FIG. 5 represents the voltage of the battery 41 in step S100. The state acquisition unit 440 acquires the voltage value V1 and the current value I1 at point P0. Point P1 on line L2 shown in FIG. 5 represents the voltage of the battery 41 in step S103. The state acquisition unit 440 acquires the voltage value V2 at point P1.

[0049] The impedance value calculation unit 441 calculates the impedance value of the battery 41 by dividing the difference between the voltage value V1 and the voltage value V2 (V1 - V2) by the current value I1. Further, the impedance value calculation unit 441 calculates a corrected impedance value by multiplying the impedance value by a correction coefficient according to the temperature T.

[0050] FIG. 6 shows an example of the impedance of a battery configured in the same manner as battery 41. The horizontal axis of the graph in FIG. 6 represents the voltage of the battery when the SoC is 60%, and the vertical axis of the graph represents the impedance of the battery. Line L3 in FIG. 6 represents the impedance at a temperature of 45°C. Line L4 in FIG. 6 represents the impedance at a temperature of 35°C. Line L5 in FIG. 6 represents the impedance at a temperature of 25°C. Line L6 in FIG. 6 represents the impedance at a temperature of 15°C.

[0051] For example, by using a battery configured in the same manner as battery 40, the same processes as steps S101 to S103 are executed, and an impedance value is calculated. Impedance values at various temperatures are calculated, and the data of the graph shown in FIG. 6 is obtained. By using that data, a correction coefficient corresponding to the temperature is calculated.

[0052] FIG. 7 shows an example of the correction coefficient. In this example, the reference temperature is 25°C, and the correction coefficient at the reference temperature is set to 1.00. The correction coefficient at each temperature other than the reference temperature is the ratio of the impedance value at each temperature to the impedance value at the reference temperature. The correction coefficient shown in FIG. 7 is pre-recorded in memory 45.

[0053] As the temperature increases, the correction coefficient increases. For example, when the temperature is the reference temperature (25°C), the impedance value calculation unit 441 multiplies the impedance value by a predetermined correction coefficient (1.00). When the temperature is lower than the reference temperature, the impedance value calculation unit 441 multiplies the impedance value by a correction coefficient smaller than the predetermined correction coefficient. When the temperature is higher than the reference temperature, the impedance value calculation unit 441 multiplies the impedance value by a correction coefficient larger than the predetermined correction coefficient.

[0054] (Step S105) After step S104 is executed, the memory control unit 443 records the corrected impedance value in the memory 45. The memory control unit 443 may update the corrected impedance value recorded in the memory 45 last time with the newly calculated corrected impedance value. The memory control unit 443 may record the newly calculated corrected impedance value in the memory 45 in a state distinguishable from the corrected impedance values calculated in the past. After that, the controller 44 executes step S100 again.

[0055] Referring to FIG. 8, the capacitance calculation process executed by the controller 44 will be described. FIG. 8 shows an example of the capacitance calculation process according to the present embodiment. The controller 44 executes the capacitance calculation process shown in FIG. 8 at an arbitrary timing. The controller 44 may execute the capacitance calculation process during charging of the battery 41, or may execute the capacitance calculation process when the battery 41 is not being charged.

[0056] (Step S200) Every time a predetermined time elapses, the memory control unit 443 determines whether a new corrected impedance value is recorded in the memory 45. If a new corrected impedance value is not recorded in the memory 45, the controller 44 executes step S200 again. If a new corrected impedance value is recorded in the memory 45, the controller 44 executes the following step S201.

[0057] (Step S201) The battery capacitance calculation unit 442 calculates the increase in corrected impedance. The increase in corrected impedance is the ratio of the corrected impedance value recorded in the memory 45 to the initial impedance value. The initial impedance value is the impedance value of the battery 41 before the use of the battery 41 (the first charge of the battery 41) is started. The impedance value of the battery 41 gradually increases from the initial impedance value over time. The initial impedance value is recorded in the memory 45 in advance.

[0058] (Step S202) The state acquisition unit 440 acquires information regarding the number of cycles and the high temperature and high pressure time from the BMU 42.

[0059] One cycle corresponds to the period from when the battery 41 is in a fully discharged state to a fully charged state and then back to a fully discharged state again. The battery 41 holds the number of cycles since the start of use of the battery 41 inside the battery 41.

[0060] The high temperature and high pressure time is the time (hour) during which the temperature of the battery 41 is within a predetermined temperature range and the output voltage value of the battery 41 is within a predetermined voltage range. For example, the predetermined temperature range is 45°C or higher and 70°C or lower. For example, the predetermined voltage range is 4.4V or higher and 4.5V or lower.

[0061] (Step S203) After step S202 is executed, the battery capacity calculation unit 442 calculates the full charge capacity of the battery 41 by using the number of cycles, the high temperature and high pressure time, and the corrected impedance increase. The memory control unit 443 records the full charge capacity in the memory 45. After that, the controller 44 executes step S200 again.

[0062] An example of a method for calculating the full charge capacity of the battery 41 will be described. FIG. 9 shows an example of the relationship between the number of cycles and the capacity retention rate and the relationship between the number of cycles and the impedance growth. As described above, the capacity retention rate is obtained by dividing the full charge capacity by the design capacity. The impedance growth is the ratio of the current impedance value to the initial impedance value.

[0063] In FIG. 9, the horizontal axis of the graph indicates the number of cycles, and the vertical axis of the graph indicates the capacity retention rate and the impedance increase. The line L10 shown in FIG. 9 indicates the relationship between the number of cycles and the capacity retention rate. The line L11 shown in FIG. 9 indicates the relationship between the number of cycles and the impedance increase. As shown in FIG. 9, as the number of cycles increases, the capacity retention rate decreases and the impedance increase increases. That is, when the impedance increases, the full charge capacity decreases. The battery capacity calculation unit 442 calculates the full charge capacity based on the relationship between the full charge capacity and the impedance.

[0064] FIG. 10 shows an example of the relationship between the impedance increase and the capacity retention rate of a battery configured in the same manner as the battery 41. The horizontal axis of the graph in FIG. 10 indicates the impedance increase, and the vertical axis of the graph indicates the capacity retention rate.

[0065] The graph in FIG. 10 is the measurement results of the impedance and the full charge capacity obtained by deteriorating the battery in three different test environments, and the respective test environment temperatures are 25° C., 45° C., and 60° C. As shown in FIG. 10, it is estimated that the relationship between the impedance and the full charge capacity can be approximated by a straight line.

[0066] FIG. 11 shows three straight lines that approximate the measurement results shown in FIG. 10. The straight line L7 approximates the measurement results in the degradation mode 1 (test environment temperature 25° C.). The straight line L8 approximates the measurement results in the degradation mode 2 (test environment temperature 45° C.). The straight line L9 approximates the measurement results in the degradation mode 3 (test environment temperature 60° C.).

[0067] As shown in FIG. 11, the relationship between the impedance and the full charge capacity can be approximated by a straight line, and the relationship depends on the temperature. Also, as shown in FIG. 9, the relationship between the number of cycles and the capacity retention rate can be approximated by a straight line. Considering these, the full charge capacity FCC of the battery 41 is represented by the following formula (1) using the number of cycles CYC, the high temperature and high pressure time HTVT, and the corrected impedance increase IMP. FCC = 1.0 + a * CYC + b * HTVT + c * IMP ···(1)

[0068] In formula (1), a, b, and c are predetermined coefficients. By using a battery configured in the same manner as battery 41, impedance values and full charge capacities at various temperatures are measured, and the number of cycles and the high temperature and high pressure time are obtained. For the results, for example, the least squares method is applied to calculate coefficient a, coefficient b, and coefficient c. These coefficients are stored in advance in memory 45. Controller 44 calculates the full charge capacity by using formula (1).

[0069] As described above, controller 44 acquires the first voltage value (V1) and the charging current value (I1) of battery 41 during charging of battery 41. Controller 44 acquires the second voltage value (V2) of battery 41 during the pause of charging of battery 41. Controller 44 calculates the impedance value of battery 41 by using the first voltage value, the second voltage value, and the charging current value. Controller 44 calculates an impedance increase, which is the ratio of the impedance value to the initial impedance value recorded in advance in memory 45. Controller 44 acquires the number of cycles of battery 41. Controller 44 acquires the time (high temperature and high pressure time) during which the temperature of battery 41 is included in a predetermined temperature range and the output voltage value of battery 41 is included in a predetermined voltage range. Controller 44 calculates the full charge capacity of battery 41 by using the number of cycles, the impedance increase, and the high temperature and high pressure time.

[0070] In this embodiment, the charging amount and the discharging amount of battery 41 required to calculate the full charge capacity are small. Therefore, controller 44 can calculate the full charge capacity at a high frequency.

[0071] Controller 44 calculates the full charge capacity according to the above formula (1). Controller 44 can calculate the full charge capacity by using a simple formula.

[0072] The controller 44 may calculate the full charge capacity without using the high temperature and high pressure time. In this case, the controller 44 does not need to obtain the high temperature and high pressure time from the BMU 42. The controller 44 calculates the full charge capacity by using the following formula (2) obtained by transforming formula (1). FCC = 1.0 + a*CYC + c*IMP ···(2)

[0073] The controller 44 corrects the impedance value according to the temperature during charging of the battery 41. The controller 44 calculates the full charge capacity by using the correction impedance increase according to the temperature. Therefore, the controller 44 can calculate the full charge capacity with high accuracy.

[0074] (Second Embodiment) The second embodiment of the present invention will be described. In the second embodiment, the battery 40a shown in FIG. 12 is used instead of the battery 40 shown in FIG. 2. FIG. 12 shows an example of the configuration of the battery 40a according to this embodiment. Only the configuration different from the configuration shown in FIG. 2 will be described, and the description of the same configuration as that shown in FIG. 2 will be omitted.

[0075] The battery capacity calculation device 43a shown in FIG. 12 is used instead of the battery capacity calculation device 43 shown in FIG. 2. In the battery capacity calculation device 43a, a controller 44a is used instead of the controller 44 shown in FIG. 2.

[0076] In addition to the state acquisition unit 440, impedance value calculation unit 441, battery capacity calculation unit 442, memory control unit 443, and charge control unit 444 shown in FIG. 2, the controller 44a has a life estimation unit 445. The life estimation unit 445 calculates the time until the full charge capacity of the battery 41 becomes equal to or less than a predetermined capacity.

[0077] The controller 44a executes the capacity calculation process shown in FIG. 13 instead of the capacity calculation process shown in FIG. 8. FIG. 13 shows an example of the capacity calculation process according to this embodiment. Only the process different from the process shown in FIG. 8 will be described, and the description of the same process as that shown in FIG. 8 will be omitted.

[0078] Steps S200 to S203 shown in FIG. 13 are the same as steps S200 to S203 shown in FIG. 8.

[0079] (Step S204) After step S203 is executed, the life estimation unit 445 determines whether the fully charged capacity (FCC) calculated in step S203 is less than 80%. If the fully charged capacity is 80% or more, the controller 44a executes step S200. If the fully charged capacity is less than 80%, the controller 44a executes the following step S205.

[0080] (Step S205) The fully charged capacity calculated in step S203 and the time information indicating the day on which the fully charged capacity was calculated are recorded in the memory 45. The life estimation unit 445 calculates the time until the fully charged capacity reaches the reference capacity by using the fully charged capacity and the time information recorded in the memory 45.

[0081] FIG. 14 shows an example of the time change of the fully charged capacity of a battery configured in the same manner as the battery 41. The horizontal axis of the graph in FIG. 14 indicates time, and the vertical axis indicates the fully charged capacity.

[0082] The fully charged capacity gradually decreases over time. The relationship between time and the fully charged capacity can be approximated by a straight line. On the day indicated by T1, the fully charged capacity becomes 80%. Thereafter, on the day indicated by T2, the fully charged capacity becomes 60%, which is the reference capacity. The life estimation unit 445 calculates the time between T1 and T2.

[0083] Specifically, the life estimation unit 445 calculates an approximate linear equation showing the relationship between time and the fully charged capacity by using the past fully charged capacities recorded in the memory 45. By using this equation, the life estimation unit 445 calculates the time until the fully charged capacity changes from 80% to 60%. This time serves as a guideline for when the user should replace the battery 41. The life estimation unit 445 may also calculate the number of cycles corresponding to this time.

[0084] In the above example, the threshold value in step S204 is 80%, but the threshold value may be a value other than 80%. In the above example, the reference capacity is 60%, but the reference capacity may be a value other than 60%.

[0085] The time calculated by the life estimation unit 445 may be output to the CPU 11. The CPU 11 may execute a notification process for notifying the user of that time. For example, the CPU 11 may display information indicating that time on the display unit 14. The CPU 11 may generate a voice corresponding to that information from a speaker not shown in FIG. 1. The CPU 11 may transmit that information to other devices via the WLAN card 25.

[0086] As described above, the controller 44 records the calculated fully charged capacity and the time information at the time when the fully charged capacity was calculated in the memory 45. By using the fully charged capacity and the time information recorded in the memory 45, the controller 44 calculates the time until the fully charged capacity of the battery 41 becomes equal to or less than a predetermined capacity. The controller 44 can predict the life of the battery 41.

[0087] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the above embodiments, and design changes and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0088] 10 Electronic device, 11 CPU, 12 Main memory, 13 Video subsystem, 14 Display unit, 21 Chipset, 22 BIOS memory, 23 Storage medium, 24 Audio system, 25 WLAN card, 26 USB connector, 31 Embedded controller, 32 Input unit, 33 Power supply circuit, 40, 40a Battery, 41 Battery, 42 BMU, 43, 43a Battery capacity calculation device, 44, 44a Controller, 45 Memory, 440 State acquisition unit, 441 Impedance value calculation unit, 442 Battery capacity calculation unit, 443 Memory control unit, 444 Charge control unit, 445 Life estimation unit

Claims

1. A controller is provided. The controller: obtaining a first voltage value and a charging current value of the battery while the battery is being charged; obtaining a second voltage value of the battery during a pause in charging the battery; calculating an impedance value of the battery using the first voltage value, the second voltage value, and the charging current value; Calculating an impedance increase, which is the ratio of the impedance value to an initial impedance value previously stored in memory; Obtaining a cycle count for the battery; obtaining a time during which the temperature of the battery is within a predetermined temperature range and the output voltage value of the battery is within a predetermined voltage range; Calculating the full charge capacity of the battery using the number of cycles, the impedance increase, and the time. Battery capacity calculation device.

2. The controller calculates the full charge capacity according to the formula: FCC=1.0+a*CYC+b*HTVT+c*IMP; In the above formula, FCC is the full charge capacity, CYC is the cycle number, HTVT is the time, IMP is the impedance increase, and a, b, and c are predetermined coefficients. The battery capacity calculation device according to claim 1 .

3. The controller corrects the impedance value according to the temperature during charging of the battery. The battery capacity calculation device according to claim 1 or 2.

4. The controller: Recording the calculated full charge capacity and time information at the time when the full charge capacity was calculated in a memory; Using the full charge capacity and the time information recorded in the memory, a time until the full charge capacity of the battery becomes equal to or less than a predetermined capacity is calculated. The battery capacity calculation device according to claim 1 or 2.

5. A controller is provided. The controller: obtaining a first voltage value and a charging current value of the battery while the battery is being charged; obtaining a second voltage value of the battery during a pause in charging the battery; calculating an impedance value of the battery using the first voltage value, the second voltage value, and the charging current value; Calculating an impedance increase, which is the ratio of the impedance value to an initial impedance value previously stored in memory; Obtaining a cycle count for the battery; Calculate the full charge capacity of the battery using the number of cycles and the impedance increase. Battery capacity calculation device.

6. obtaining a first voltage value and a charging current value of the battery while the battery is being charged; obtaining a second voltage value of the battery during a pause in charging the battery; calculating an impedance value of the battery by using the first voltage value, the second voltage value, and the charging current value; calculating an impedance increase which is a ratio between the impedance value and an initial impedance value previously stored in a memory; obtaining a cycle count of the battery; acquiring a time during which the temperature of the battery is within a predetermined temperature range and the output voltage value of the battery is within a predetermined voltage range; calculating a full charge capacity of the battery using the number of cycles, the impedance increase, and the time; A battery capacity calculation method comprising:

7. obtaining a first voltage value and a charging current value of the battery while the battery is being charged; obtaining a second voltage value of the battery during a pause in charging the battery; calculating an impedance value of the battery by using the first voltage value, the second voltage value, and the charging current value; calculating an impedance increase which is a ratio between the impedance value and an initial impedance value previously stored in a memory; obtaining a cycle count of the battery; calculating a full charge capacity of the battery using the number of cycles and the impedance increase; A battery capacity calculation method comprising:

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