Battery management device, battery pack, battery management method, and battery management program

Abstract

In a battery management device (11) according to an embodiment, a control unit (13) calculates, on the basis of the full charge capacity and the remaining capacity of a battery pack (10), the required charge capacity at the time of CV (Constant Voltage) charging of the battery pack (10). On the basis of the charging current at the start of CV charging and the charging current at the time of full charge of the battery pack (10), the control unit (13) generates a charging current transition assuming that the charging current decreases at a constant speed. Further, the control unit (13) estimates the charging time when performing CV charging on the basis of the required charging capacity and the charging current transition.

Description

Battery management device, battery pack, battery management method, and battery management program

[0001] The present disclosure relates to a battery management device, a battery pack, a battery management method, and a battery management program that manage charging of a battery.

[0002] The constant current constant voltage (CC-CV) charging method is widely used as a charging method for battery packs (see, for example, Patent Document 1). In typical CC-CV charging, the charging mode switches from CC charging to CV charging when the SOC (State Of Charge) is around 80% to 90%, and the charging current gradually decreases.

[0003] Charge capacity is calculated by multiplying the charge current by the time. The time until charging is complete during CC charging is calculated by dividing the charge capacity until full charge by the charge current. As mentioned above, with CC-CV charging, CC charging is performed when the battery voltage is low, but when the battery voltage exceeds a set voltage, it switches to CV charging and the charge current gradually decreases. Therefore, with CV charging, the time until charging is complete cannot be calculated by simply dividing the charge capacity until full charge by the charge current.

[0004] Therefore, it is conceivable to obtain in advance through experiments or simulations the relationship between the SOC and the time until the end of charging during CV charging and define the relationship in a table. Specifically, a table is created that describes relationships such as: time from SOC = 81% to the end of charging = 88 minutes, time from SOC = 82% to the end of charging = 86 minutes, ..., time from SOC = 99% to the end of charging = 3 minutes. It is also conceivable to obtain in advance through experiments or simulations the relationship between the charging current and the time until the end of charging during CV charging and define the relationship in a table.

[0005] However, during CV charging, the relationship between the SOC and the time to end of charge, or the relationship between the charging current and the time to end of charge, is affected by factors such as temperature and SOH (State of Health). For example, the lower the SOH (the more deterioration progresses), the greater the error in the relationship defined in the table, and the greater the discrepancy between the estimated time to end of charge and the actual time to end of charge. To reduce this discrepancy, it is necessary to create a multidimensional table that takes into account changes in temperature and SOH. In this case, the program size increases.

[0006] JP 2014-39400 A

[0007] The present disclosure provides a technique for easily estimating the time remaining until the end of charging during CV charging with a relatively high degree of accuracy.

[0008] A battery management device according to one aspect of the present disclosure includes a control unit that estimates a charging time required for fully charging a battery pack. The control unit calculates a required charging capacity for CV charging of the battery pack based on the fully charged capacity and remaining capacity of the battery pack. The control unit also generates a charging current trend that assumes that the charging current decreases at a constant rate based on the charging current at the start of CV charging and the charging current when the battery pack is fully charged. The control unit also estimates the charging time required for CV charging based on the required charging capacity and the charging current trend.

[0009] Any combination of the above components, and conversion of the expression of the present disclosure into an apparatus, system, method, computer program, etc., are also valid aspects of the present disclosure.

[0010] According to the present disclosure, the time until the end of charging during CV charging can be estimated easily with relatively high accuracy.

[0011] FIG. 1 is a diagram illustrating the configuration of a battery pack and a charger according to an embodiment. FIG. 2 is a diagram schematically illustrating the change over time of the charging current during CC-CV charging. FIG. 3 is a diagram illustrating the required charge capacity during the CV charging period. FIG. 4 is a diagram illustrating an example of calculating the required charge capacity during the CV charging period in FIG. 3 using trapezoidal area approximation. FIG. 5 is a diagram illustrating an example of the change over time of the charging current during CC-CV charging and the SOC of the battery pack.

[0012] 1 is a diagram illustrating the configuration of a battery pack 1 and a charger 2 according to an embodiment. In this embodiment, the battery pack 1 is assumed to be a battery pack 1 mounted on an electric mobility (for example, an electric bicycle, an electric motorcycle, an electric kick scooter, etc.). The battery pack 1 may be a detachable, portable battery pack 1, or may be fixed to the vehicle. In the former case, the battery pack 1 is charged by being inserted into a charging slot of a charger 2, and in the latter case, the battery pack 1 is charged by being connected to the charger 2 via a charging cable.

[0013] The battery pack 1 includes a battery assembly 10 and a battery management device 11. The battery assembly 10 includes multiple cells E1-En connected in series. The number of cells connected in series is determined by the load specifications. Lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, etc. can be used for the cells E1-En. In the following description, an example will be assumed in which lithium-ion battery cells (nominal voltage: 3.6-3.7 V) are used as the cells E1-En. Note that, in each series stage of cells, multiple cells may be connected in parallel to increase capacity.

[0014] A switch SW1 that switches between electrical continuity and non-conduction with the charger 2 is inserted in the power line connecting the battery pack 10 and the charger 2. A semiconductor switch or a relay can be used as the switch SW1.

[0015] The battery management device 11 includes a measurement unit 12 and a control unit 13. The measurement unit 12 is configured by an analog front end integrated circuit (AFEIC) or an application specific integrated circuit (ASIC), and the control unit 13 is configured by a microcontroller.

[0016] The measurement unit 12 is connected to each node of the multiple cells E1-En connected in series by multiple voltage measurement lines, and measures the voltage of each cell E1-En by measuring the voltage between each two adjacent voltage measurement lines.

[0017] The measurement unit 12 includes a multiplexer and an analog-to-digital (A / D) converter. The multiplexer outputs the voltages of the multiple cells E1-En to the A / D converter in a predetermined order. The A / D converter converts the analog voltages input from the multiplexer into digital values. The measurement unit 12 transmits the converted digital voltage values ​​of the cells E1-En to the control unit 13 via a communication interface.

[0018] The measurement unit 12 measures the current flowing through the battery pack 10. A shunt resistor Rs is connected to the power line connecting the battery pack 10 and the charger 2. A differential amplifier (not shown) amplifies the voltage across the shunt resistor Rs and outputs it to an A / D converter in the measurement unit 12. The A / D converter converts the analog voltage indicating the current flowing through the battery pack 10, which is input from the differential amplifier, into a digital value. The measurement unit 12 transmits the current value converted into a digital value to the control unit 13 via the communication interface.

[0019] A temperature sensor T1 (e.g., a thermistor) is installed on the surface of the battery pack 10. A divided voltage between the temperature sensor T1 and a voltage dividing resistor (not shown) is input to a measurement unit 12. An A / D converter in the measurement unit 12 converts the input analog voltage indicating the temperature into a digital value. The measurement unit 12 transmits the converted digital temperature value to the control unit 13 via a communication interface.

[0020] The control unit 13 manages the states of the cells E1-En based on the voltage values ​​of the cells E1-En, the current values ​​flowing through the battery pack 10, and the temperature values ​​of the battery pack 10 received from the measurement unit 12. When the control unit 13 detects overcharge, overdischarge, overcurrent, abnormally high temperature, or abnormally low temperature, it sends a shut-off signal for the switch SW1 to the measurement unit 12 to turn off the switch SW1.

[0021] The control unit 13 executes programs such as firmware within the microcontroller to achieve the following functions. The control unit 13 estimates the SOC by combining the OCV (Open Circuit Voltage) method and the current integration method. The OCV method is a method for estimating the SOC based on the measured cell OCV and the cell's SOC-OCV curve. The cell's SOC-OCV curve is created in advance by the battery manufacturer based on characteristic tests and is registered in the control unit 13 at the time of shipment.

[0022] The current integration method is a method for estimating the SOC based on the OCV at the start of cell charging and discharging and the integrated value of the measured current. With the current integration method, current measurement errors accumulate as the charging and discharging time increases. Therefore, it is preferable to use a weighted average of the SOC estimated by the current integration method and the SOC estimated by the OCV method.

[0023] The control unit 13 converts the SOC of each cell E1-En into an actual capacity, combines these actual capacities to calculate the actual capacity of the battery pack 1, and can estimate the SOC of the battery pack 1 based on the actual capacity and the current full charge capacity (FCC) of the battery pack 1.

[0024] The control unit 13 can estimate the current FCC of the battery pack 1 by dividing the current integrated value in the usable SOC range by the usable SOC range. The control unit 13 can estimate the SOH by dividing the current FCC by the initial FCC.

[0025] The charger 2 includes an alternating current (AC) / direct current (DC) converter 21, a DC / DC converter 22, a control unit 23, and a display unit 24. The AC / DC converter 21 converts AC power supplied from the commercial power system 3 into DC power. If the commercial power system 3 does not have a reverse power flow function, the AC / DC converter 21 can be configured by combining a rectifier and a filter. If the commercial power system 3 has a reverse power flow function, a bidirectional inverter is used for the AC / DC converter 21.

[0026] When the battery pack 1 and the charger 2 are connected, the DC / DC converter 22 controls the voltage or current of the DC power supplied from the AC / DC converter 21 and outputs it to the battery pack 10. If the commercial power system 3 does not have the function of reverse power flow, the DC / DC converter 22 may be a unidirectional DC / DC converter. If the commercial power system 3 has the function of reverse power flow, the DC / DC converter 22 is a bidirectional DC / DC converter.

[0027] The control unit 23 is composed of a microcontroller. The control unit 23 of the charger 2 and the control unit 13 of the battery pack 1 are connected by a signal line, and predetermined serial communication is performed between them. When the battery pack 1 is connected to the charger 2, the control unit 23 of the charger 2 receives the constant current value, constant voltage value, and current value at full charge (charge end current value) in CC-CV charging from the control unit 13 of the battery pack 1.

[0028] The control unit 23 of the charger 2 performs CC charging when the voltage of the battery pack 10 is lower than the received constant voltage value, and performs CV charging when the voltage is equal to or higher than the constant voltage value. The control unit 23 generates a current command value so that the measured output current of the DC / DC converter 22 maintains the received constant current value during CC charging. The control unit 23 generates a current command value to decrease the output of the DC / DC converter 22 when the measured output current of the DC / DC converter 22 is greater than the received constant current value, and generates a current command value to increase the output of the DC / DC converter 22 when the measured output current of the DC / DC converter 22 is smaller than the received constant current value.

[0029] Control unit 23 generates a voltage command value so that the measured output voltage of DC / DC converter 22 maintains the received constant voltage value during CV charging. If the measured output voltage of DC / DC converter 22 is higher than the received constant voltage value, control unit 23 generates a voltage command value for lowering the output of DC / DC converter 22, and if the measured output voltage of DC / DC converter 22 is lower than the received constant voltage value, control unit 23 generates a voltage command value for increasing the output of DC / DC converter 22. DC / DC converter 22 performs a switching operation in response to a drive signal based on the generated current command value or voltage command value.

[0030] 2 is a diagram showing a schematic diagram of the change in charging current over time during CC-CV charging. The charging period during CC-CV charging is determined by the sum of the CC charging period and the CV charging period. In this embodiment, the control unit 13 of the battery pack 1 has a function of estimating the charging time required to fully charge the battery pack 10.

[0031] When CC-CV charging the battery pack 10, the control unit 13 calculates the required charge capacity for the CC charging period and the required charge capacity for the CV charging period based on the FCC, remaining charge (RC) of the battery pack 10, and the capacity at the time of switching from CC charging to CV charging. The capacity at the time of switching from CC charging to CV charging may be set in advance as a fixed value (e.g., 80%) in a non-volatile memory area in the control unit 13. Alternatively, a value notified by the charger 2 may be used as the capacity at the time of switching from CC charging to CV charging.

[0032] The timing of the actual switch from CC charging to CV charging is determined when the voltage of the battery pack 10 reaches a preset constant voltage value during CC charging by the DC / DC converter 22 and the charging current drops by more than the tolerance. The control unit 13 of the battery pack 1 can store the capacity at the time of actual switching from CC charging to CV charging in a non-volatile memory area. The control unit 13 may use the capacity measured during the previous charging at the time of switching from CC charging to CV charging, which is stored in the non-volatile memory area, as the capacity at the time of switching from CC charging to CV charging.

[0033] The control unit 13 estimates the charging time of the CC charging period based on the required charging capacity and the constant current value for the CC charging period, as shown in the following (Equation 1).

[0034] CC charging time = required charge capacity during CC charging period / constant current value (Equation 1) Required charge capacity during CC charging period = (FCC × capacity when switching to CV charging (%) - RC) The control unit 13 estimates the charging time during the CV charging period based on the required charge capacity during the CV charging period and the change in charging current, as shown in the following (Equation 2). The control unit 13 generates the change in charging current during the CV charging period by linear approximation, assuming that the charging current decreases at a constant rate, based on the charging current at the start of CV charging and the charging current when the battery pack 10 is fully charged.

[0035] CV charging time = required charge capacity during CV charging period × 2 / (charge current at start of CV charging + charge current at full charge) (Equation 2) Required charge capacity during CV charging period = (FCC × (100 - capacity at switch to CV charging (%)) - RC) A constant current value is basically used as the charge current at the start of CV charging. The charge current at full charge of the battery pack 10 may be set in advance as a fixed value (e.g., 360 mA) in a non-volatile memory area in the control unit 13. The control unit 13 can store in the non-volatile memory area the charge current actually measured when the battery pack 10 reached full charge. The control unit 13 may use the charge current measured when the battery pack 10 reached full charge during the previous charging, which is stored in the non-volatile memory area, as the charge current at full charge of the battery pack 10.

[0036] If the SOC of the battery pack 10 at the start of charging is equal to or greater than the capacity (%) at which switching to CV charging is performed, the CC charging period is omitted and CV charging is performed from the start of charging. In this case, the charging current at the start of CV charging is basically the current measured at the start of CV charging.

[0037] Fig. 3 is a diagram showing the required charge capacity during the CV charging period. Fig. 4 is a diagram showing an example of calculating the required charge capacity during the CV charging period of Fig. 3 using trapezoidal area approximation. Figs. 3 and 4 show an example in which the capacity when switching from CC charging to CV charging is SOC = 80%.

[0038] As shown in Figure 3, the charge capacity is calculated by integrating the charge current over time. However, it is difficult to predict in advance the charge current at each point during the CV charging period, as it gradually decreases while being affected by temperature, cell degradation, etc. Therefore, in this embodiment, the charge capacity during the CV charging period is approximated by the area of ​​a trapezoid, as shown in the following (Equation 3).

[0039] Charge capacity during CV charging period=(charging current at start of CV charging+charging current at full charge)×CV charging time / 2 (Equation 3) From this (Equation 3), the above (Equation 2) can be derived.

[0040] The control unit 13 estimates the charging time for CC-CV charging by adding the charging time for the CC charging period and the charging time for the CV charging period. The control unit 13 estimates the charging time required to fully charge the battery pack 10 using CC-CV charging before charging starts. After charging starts, the control unit 13 calculates the remaining time until charging is completed.

[0041] For example, during CC charging, the control unit 13 acquires the RC of the battery pack 10 in real time and calculates (Equation 1) + (Equation 2) above to update the remaining time until the end of charging. For example, the control unit 13 recalculates the remaining time until the end of charging every time the SOC of the battery pack 10 is incremented. Note that the remaining time until the end of charging may be recalculated periodically (for example, once per minute or once per five minutes).

[0042] When charging is switched from CC charging to CV charging, the control unit 13 calculates the remaining required charge capacity by subtracting the RC at that time from the FCC of the battery pack 10. The control unit 13 sets the remaining required charge capacity to the required charge capacity for the CV charging period, calculates the above (Equation 2), and recalculates the remaining time until charging is completed.

[0043] During CV charging, the control unit 13 acquires the RC and charging current value of the battery pack 10 in real time. The control unit 13 recalculates the remaining required charge capacity by subtracting the RC at each time point from the FCC. The control unit 13 sets the remaining required charge capacity to the required charge capacity for the CV charging period, sets the current measured value of the charging current to the charging current at the start of CV charging, and calculates the above (Equation 2) to recalculate the remaining time until the end of charging. Note that during CV charging, the remaining time until the end of charging fluctuates greatly due to fluctuations in the charging current. Therefore, the control unit 13 may calculate the remaining time until the end of charging by subtracting the elapsed time from the time when CV charging was switched to CV charging from the CV charging time calculated at the time when CV charging was switched to.

[0044] If the specification does not recalculate the remaining time until the end of charging during charging, the control unit 13 subtracts the elapsed time from the start of charging from the charging time estimated before the start of charging to determine the remaining time until the end of charging.

[0045] The control unit 13 transmits the remaining time until the end of charging to the control unit 23 of the charger 2 via a signal line. The control unit 23 of the charger 2 displays the remaining time until the end of charging on the display unit 24. The display unit 24 can be a 7-segment display, a liquid crystal display, an organic EL (Electro Luminescence) display, or the like.

[0046] The control unit 13 can also display the remaining time until charging is complete on another user interface. For example, if the battery pack 1 itself is equipped with a display unit such as a 7-segment display, a liquid crystal display, or an organic EL display, the control unit 13 can display the remaining time until charging is complete on the display unit of the battery pack 1. The control unit 13 can also convert the ratio of the remaining time until charging is complete to the charging time into the number of lit LED lamps mounted on the battery pack 1, and change the number of lit LED lamps.

[0047] In addition, when the battery pack 1 is fixed to the vehicle and is connected to a meter installed on the steering wheel or the like of the vehicle by a signal line, the control unit 13 can cause the vehicle's meter to display the remaining time until charging is complete.

[0048] 5 is a diagram showing an example of the time transition of the charging current during CC-CV charging and the SOC of the battery pack 10. The battery pack 10 has an FCC of 16051 mAh, a constant current value of 4000 mA, a temperature of 25°C, an SOC of 80% when switching from CC charging to CV charging, a charging current value at full charge of 360 mA, and an RC of 0 mAh at the start of charging.

[0049] The CC charging period is calculated as (16051 x 0.8 - 0) / 4000 x 60 ≒ 193 minutes from the above formula (1). The CV charging period is calculated as (16051 x 0.2 - 0) x 2 / (4000 + 360) x 60 ≒ 88 minutes from the above formula (2). Therefore, the total charging time is 281 minutes.

[0050] As described above, according to this embodiment, by approximating the charge capacity during CV charging using the trapezoid area, it is possible to easily estimate the time to end of charging during CV charging with relatively high accuracy. Using the current FCC eliminates the influence of SOH degradation. Furthermore, using a constant current value and a current value at full charge minimizes the influence of current changes due to temperature changes and the like. In particular, when a value measured during the previous charge is used as the current value at full charge, it is possible to adapt the current value at full charge to the current state of the battery pack 10. Furthermore, since there is no need to prepare a multidimensional table that takes into account changes in temperature and SOH, an increase in program size can be suppressed. Furthermore, it is possible to flexibly respond to situations that are not defined in the multidimensional table.

[0051] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0052] In the above-described embodiment, an example was shown in which charging was controlled by the DC / DC converter 22 in the charger 2. However, if the battery pack 1 has a built-in DC / DC converter and an AC / DC converter, the battery pack 1 can be directly connected to an AC outlet of the commercial power system 3 with a cord equipped with an AC plug. In this case, charging is controlled by the DC / DC converter in the battery pack 1.

[0053] In the above-described embodiment, an example has been described in which the battery pack 1 according to the present disclosure is mounted on an electric mobility. In this regard, the battery pack 1 according to the present disclosure can also be mounted on consumer electronic devices (e.g., notebook PCs, smartphones, tablets), EVs (Electric Vehicles), multicopters (drones), and stationary power storage systems.

[0054] The embodiment may be specified by the following items.

[0055] [Item 1] The battery management device (11) of Item 1 includes a control unit (13) that estimates the charging time required to fully charge the battery pack (10). The control unit (13) calculates the charging capacity required to CV charge the battery pack (10) based on the full charge capacity and remaining capacity of the battery pack (10). The control unit (13) also generates a charging current trend that assumes the charging current decreases at a constant rate based on the charging current at the start of CV charging and the charging current when the battery pack (10) is fully charged. The control unit (13) also estimates the charging time required to CV charge based on the required charging capacity and the charging current trend.

[0056] This allows the time until charging is completed during CV charging to be estimated easily and with relatively high accuracy.

[0057] [Item 2] In the battery management device (11) of Item 2, in the battery management device (11) described in Item 1, the control unit (13) calculates the required charging capacity×2 / (charging current at the start of CV charging+charging current at full charge) to estimate the charging time during CV charging.

[0058] According to this, the charging time during CV charging can be estimated easily and with a relatively high degree of accuracy based on the approximation of the trapezoid area.

[0059] [Item 3] In the battery management device (11) of item 3, in the battery management device (11) described in item 1, the control unit (13) uses the charging current measured at the time of the previous full charge as the charging current at the time of full charge of the battery pack (10).

[0060] This allows the use of a charging current suitable for the current state of the battery pack (10) when fully charged.

[0061] [Item 4] In the battery management device (11) of Item 4, in the battery management device (11) described in Item 1, when the battery pack (10) is CC-CV charged, the control unit (13) calculates the required charge capacity for the CC charging period and the required charge capacity for the CV charging period based on the full charge capacity, remaining capacity, and capacity at the time of switching from CC charging to CV charging of the battery pack (10). The control unit (13) also estimates the charge time for the CC charging period based on the required charge capacity for the CC charging period and the constant current value. The control unit (13) also estimates the charge time for the CV charging period based on the required charge capacity for the CV charging period and a change in the charging current. The control unit (13) also estimates the charge time for CC-CV charging by adding the charge time for the CC charging period and the charge time for the CV charging period.

[0062] This allows the time until charging is completed during CC-CV charging to be estimated easily and with relatively high accuracy.

[0063] [Item 5] In the battery management device (11) of Item 5, in the battery management device (11) described in Item 4, the control unit (13) uses the capacity measured during the previous charging at the time of switching from CC charging to CV charging as the capacity when switching from CC charging to CV charging.

[0064] This allows the capacity to be used when switching from CC charging to CV charging, which is suited to the current state of the battery pack (10).

[0065] [Item 6] A battery pack (1) of item 6 includes a battery pack (10) and the battery management device (11) according to any one of items 1 to 5.

[0066] This makes it possible to realize a battery pack (1) that can easily estimate the time until the end of charging during CV charging with a relatively high degree of accuracy.

[0067] [Item 7] The battery management method of item 7 includes a step of calculating a required charge capacity when CV charging the battery pack (10) based on the full charge capacity and remaining capacity of the battery pack (10). The battery management method of item 7 also includes a step of generating a charge current trend assuming that the charge current decreases at a constant rate based on the charge current at the start of CV charging and the charge current when the battery pack (10) is fully charged. The battery management method of item 7 also includes a step of estimating a charge time when CV charging is performed based on the required charge capacity and the charge current trend.

[0068] This allows the time until charging is completed during CV charging to be estimated easily and with relatively high accuracy.

[0069] [Item 8] The battery management program of item 8 causes a computer to execute a process for calculating a required charge capacity when CV charging the battery pack (10) based on the full charge capacity and remaining capacity of the battery pack (10). The battery management program of item 8 also causes a computer to execute a process for generating a charge current trend assuming that the charge current decreases at a constant rate based on the charge current at the start of CV charging and the charge current when the battery pack (10) is fully charged. The battery management program of item 8 also causes a computer to execute a process for estimating a charge time when CV charging is performed based on the required charge capacity and the charge current trend.

[0070] This allows the time until charging is completed during CV charging to be estimated easily and with relatively high accuracy.

[0071] REFERENCE SIGNS LIST 1 battery pack 10 assembled battery 11 battery management device 12 measurement unit 13 control unit 2 charger 21 AC / DC converter 22 DC / DC converter 23 control unit 24 display unit 3 commercial power system E1 cell E2 cell En cell Rs shunt resistor SW1 switch T1 temperature sensor

Claims

1. A battery management device comprising a control unit that estimates a charging time for fully charging a battery pack, wherein the control unit calculates a required charging capacity for CV (Constant Voltage) charging of the battery pack based on the full charge capacity and remaining capacity of the battery pack, generates a charging current trend assuming that the charging current decreases at a constant rate based on the charging current at the start of CV charging and the charging current when the battery pack is fully charged, and estimates the charging time for CV charging based on the required charging capacity and the charging current trend.

2. The battery management device according to claim 1, wherein the control unit calculates the required charging capacity x 2 / (charging current at the start of CV charging + charging current at full charge) to estimate the charging time for CV charging.

3. The battery management device according to claim 1, wherein the control unit uses a charging current measured when the battery pack was previously fully charged as the charging current when the battery pack was fully charged.

4. The battery management device of claim 1, wherein when the battery pack is CC (Constant Current)-CV charged, the control unit calculates the required charge capacity for the CC charging period and the required charge capacity for the CV charging period based on the full charge capacity, remaining capacity and capacity when switching from CC charging to CV charging of the battery pack, estimates the charging time for the CC charging period based on the required charge capacity for the CC charging period and a constant current value, estimates the charging time for the CV charging period based on the required charge capacity for the CV charging period and the charging current trend, and estimates the charging time for CC-CV charging by adding the charging time for the CC charging period and the charging time for the CV charging period.

5. The battery management device according to claim 4, wherein the control unit uses the capacity measured during the previous charging at the time of switching from CC charging to CV charging as the capacity when switching from CC charging to CV charging.

6. A battery pack comprising: the assembled battery; and the battery management device according to any one of claims 1 to 5.

7. A battery management method comprising the steps of: calculating a required charging capacity for CV charging a battery pack based on the full charge capacity and remaining capacity of the battery pack; generating a charging current trend based on the charging current at the start of CV charging and the charging current when the battery pack is fully charged, assuming that the charging current decreases at a constant rate; and estimating a charging time for CV charging based on the required charging capacity and the charging current trend.

8. A battery management program that causes a computer to execute the following processes: a process for calculating the required charging capacity when CV charging a battery pack based on the full charge capacity and remaining capacity of the battery pack; a process for generating a charging current trend assuming that the charging current decreases at a constant rate based on the charging current at the start of CV charging and the charging current when the battery pack is fully charged; and a process for estimating the charging time when CV charging is performed based on the required charging capacity and the charging current trend.