Remaining battery capacity calculation device and remaining battery capacity calculation method

Abstract

When available output power of a battery (1) is the minimum power required to start a vehicle, a controller (20) calculates the remaining capacity of the battery (1) as zero.

Description

Battery Remaining Capacity Calculation Device and Battery Remaining Capacity Calculation Method

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

[0002] There is a known technique for controlling an instrument panel to display an icon that represents one of a first index indicating the SOC of a vehicle battery and a second index indicating the full charge capacity of the battery by an increase or decrease in a scale, and represents the other by an amount indicated by the size of the display area of the icon (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2023-168339

[0004] In the technique described in Patent Document 1, the remaining capacity of the displayed battery is calculated in association with the voltage of the battery. However, for example, when the remaining capacity of the battery is calculated in association with zero when the voltage of the battery is the minimum voltage, before the voltage of the battery reaches the minimum voltage, the battery may not be able to output the minimum power required to start the vehicle. In such a case, there is a problem that the remaining capacity of the battery is not calculated as zero even though the vehicle cannot start.

[0005] The problem to be solved by the present invention is to provide a battery remaining capacity calculation device and a battery remaining capacity calculation method that can calculate the remaining capacity of a vehicle battery as zero if the vehicle cannot start.

[0006] The present invention solves the above problems by calculating the remaining capacity of the battery as zero when the output power of the battery is the minimum power required for starting the vehicle.

[0007] According to the present invention, if the vehicle cannot start, the remaining capacity of the vehicle battery can be calculated as zero.

[0008] Figure 1 is a block diagram of a battery management system including a battery remaining capacity calculation device according to one embodiment of the present invention. Figure 2 is a map showing an example of the output characteristics of a battery according to this embodiment. Figure 3 is a map showing an example of the output characteristics of a battery according to this embodiment. Figure 4 is a flowchart showing the control flow of the battery remaining capacity calculation method executed by the battery remaining capacity calculation device according to this embodiment.

[0009] Hereinafter, an embodiment of the battery remaining capacity calculation device and battery remaining capacity calculation method according to the present invention will be described with reference to the drawings. Figure 1 is a block diagram of a battery management system including a battery remaining capacity calculation device according to an embodiment of the present invention. The battery management system 100 manages the remaining capacity of the battery 1. The battery management system 100 comprises a battery 1, a battery remaining capacity calculation device 2, and a display 3. In the battery management system 100, the battery remaining capacity calculation device 2 calculates the remaining capacity of the battery 1 and displays the calculated remaining capacity of the battery 1 on the display 3. The control processing performed by the battery remaining capacity calculation device 2 corresponds to the "battery remaining capacity calculation method" of the present invention. In this embodiment, the battery remaining capacity calculation device 2 is provided in the battery management system 100, but it is not an essential configuration to provide it in the battery management system 100, as long as it calculates the remaining capacity of the battery 1. For example, the display 3 can be set as appropriate as needed, and it is not an essential configuration for the battery remaining capacity calculation device 2 to display the calculated remaining capacity of the battery 1 on the display 3.

[0010] Battery 1 is a battery cell, or a battery module formed by connecting multiple battery cells in series or parallel. A battery cell is, for example, a lithium-ion secondary battery. An example of a battery cell is a flat laminate film lithium-ion secondary battery. A flat laminate film lithium-ion secondary battery has a power generation element in which electrode layers (positive electrode layer and negative electrode layer) and a separator are laminated and filled with electrolyte, a positive electrode tab connected to the positive electrode layer, a negative electrode tab connected to the negative electrode layer, and an outer casing member that houses and seals these. The battery cell charges and discharges by the movement of lithium ions between the positive electrode and the negative electrode. Battery 1 is a power source installed in vehicles such as electric vehicles and hybrid vehicles.

[0011] Battery 1 is connected to a voltage sensor 11 and a current sensor 12, and a temperature sensor 13 is installed. The voltage sensor 11 detects the voltage of each of the multiple battery cells contained in battery 1. The current sensor 12 detects the current flowing through the battery cells. The temperature sensor 13 detects the temperature of the battery cells. The detected values ​​from the voltage sensor 11, current sensor 12, and temperature sensor 13 are output to the battery remaining capacity calculation device 2.

[0012] The battery remaining capacity calculation device 2 comprises a controller 20 and a battery status acquisition unit 21. The battery status acquisition unit 21 is a unit that acquires the status of the battery 1. The battery status acquisition unit 21 acquires the voltage, current, and temperature of the battery 1 by acquiring detection values ​​from the voltage sensor 11, current sensor 12, and temperature sensor 13. In this embodiment, the battery status acquisition unit 21 acquires the status of the battery 1 at regular intervals.

[0013] The controller 20 calculates the remaining capacity of the battery 1. The controller 20 controls the display 3 to display the calculated remaining capacity of the battery 1 on the display 3. In the following explanation, the State of Charge (SOC) of the battery 1 is used as an example of the remaining capacity of the battery 1. SOC is expressed as a percentage from 0% to 100%, with 0% representing a remaining capacity of zero (completely discharged state) and 100% representing a remaining capacity of full charge (fully charged state). The indicator used to represent the remaining capacity is not limited to SOC; other indicators may also be used.

[0014] The controller 20 is a processor and includes a ROM in which a program is stored, a CPU that executes the program stored in the ROM, and RAM that functions as an accessible storage device. The controller 20 has an SOC calculation unit 201 and an SOC display unit 202 as functional blocks. The controller 20 executes the functions of the SOC calculation unit 201 and the SOC display unit 202 by having the CPU execute the program stored in the ROM. Details of each functional block will be described later. Note that there are not limited to two functional blocks, but there may be one or three or more functional blocks. The controller 20 does not necessarily have an SOC display unit 202.

[0015] The SOC calculation unit 201 performs calculation processing to calculate the State of Control (SOC) of battery 1 based on the voltage of battery 1 acquired by the battery state acquisition unit 21. The voltage of battery 1 is the cell voltage or the voltage of each of the multiple battery cells. The cell voltage and the SOC of battery 1 are associated. For example, the SOC calculation unit 201 has a voltage-SOC map that shows the correspondence between the cell voltage and the SOC of battery 1. The voltage-SOC map is also called the first map. For example, in the correspondence between the cell voltage and the SOC of battery 1, if the cell voltage is the lower limit voltage, the corresponding SOC is 0%. The lower limit voltage is a voltage greater than the lowest voltage at which battery 1 can no longer output power. Details of the lower limit voltage will be described later. In the calculation processing, the SOC calculation unit 201 calculates the corresponding SOC by referring to the first map according to the acquired cell voltage. The calculation processing is performed at regular intervals.

[0016] Furthermore, in this embodiment, in addition to a lower voltage limit, an upper voltage limit may be set for the cell voltage. In the correspondence between the cell voltage and the SOC of battery 1, the upper voltage limit is associated with an SOC of 100%. When the cell voltage is at the upper voltage limit, the SOC calculation unit 201 refers to the map and calculates the SOC as 100% as the SOC corresponding to the upper voltage limit. In the first map, the SOC corresponds to the voltage range from the lower voltage limit to the upper voltage limit, and the higher the cell voltage, the higher the calculated value. In this embodiment, if the cell voltage falls below the lower voltage limit, the SOC may be calculated as 0%. Also, although the state value of battery 1 that is associated with the SOC for SOC calculation is explained using the voltage of battery 1, in this embodiment the state value of battery 1 used for SOC calculation is not limited to the voltage of battery 1, but may be the current of battery 1, or a combination of multiple state values.

[0017] The SOC calculation unit 201 calculates the SOC of battery 1 as 0% when the output power of battery 1 is the minimum power required to start the vehicle. Output power is the maximum output power that battery 1 can output. Minimum power is the power limit at which the vehicle cannot start if the output power falls below the minimum power, for example, the lowest power that can output the torque required to start the vehicle from a standstill. In this embodiment, the lower limit voltage is set to the voltage at which the output power is the minimum power in the correspondence relationship between output power and voltage. The SOC calculation unit 201 calculates the SOC of battery 1 as 0% when the voltage of battery 1 is at the lower limit voltage. Specifically, in the map showing the correspondence between the voltage of battery 1 and the SOC, the lower limit voltage is associated with SOC 0%. Therefore, when the voltage of battery 1 is the lower limit voltage, i.e., the voltage at which the output power is at its minimum, the SOC calculation unit 201 refers to the map and calculates the SOC of battery 1 as 0%.

[0018] Here, we will explain the output power. The output power is determined by the state of battery 1, including the cell voltage and temperature of battery 1. In this embodiment, the cell voltage and temperature of battery 1 are associated with the output power of battery 1. For example, the output power is derived by the following formula (1): Output power = minimum voltage × (open circuit voltage - minimum voltage) / battery internal resistance ... (1) The minimum voltage is the voltage at which battery 1 can no longer output power. The open circuit voltage (OCV) is the value detected by the voltage sensor 11 when battery 1 is in an unloaded state. The battery internal resistance is calculated based on the temperature and open circuit voltage of battery 1. For example, the SOC calculation unit 201 has a map that shows the correspondence between the temperature and open circuit voltage of battery 1 and the battery internal resistance. This map is also called the second map. The SOC calculation unit 201 refers to the second map and calculates the battery internal resistance according to the temperature and open circuit voltage of battery 1.

[0019] Next, using Figure 2, an example of the correspondence between the voltage of the battery 1 and the temperature of the battery 1 according to this embodiment, and the output power of the battery 1, will be explained. Figure 2 is a map showing an example of the output characteristics of the battery according to this embodiment. The horizontal axis represents the cell voltage, and the vertical axis represents the output power. Graph A shows the output characteristics of the battery 1 when the temperature of the battery 1 is at room temperature (e.g., 25°C). Graph B shows the output characteristics of the battery 1 when the temperature of the battery 1 is at a low temperature (e.g., -10°C). The SOC calculation unit 201 has a map showing the correspondence between the cell voltage, the temperature of the battery 1, and the output power of the battery 1. This map is also called the third map. As shown in Figure 2, the output power increases as the cell voltage increases. Also, the correspondence between the cell voltage and the output power changes depending on the temperature of the battery 1. When the temperature of the battery 1 is low, the output power with respect to the cell voltage is smaller than when the temperature of the battery 1 is at room temperature. For example, assuming the cell voltage is the same, when the temperature of battery 1 is at the first temperature (low temperature), the output power is lower than when the temperature of battery 1 is at the second temperature (room temperature), which is higher than the first temperature.

[0020] The lower limit voltage of the battery 1 according to this embodiment will be explained using Figure 2. In the output characteristics (graph) of the battery 1 for each temperature, the cell voltage corresponding to the minimum power is set as the lower limit voltage. In the example in Figure 2, when the temperature of the battery 1 is at room temperature (graph A), the lower limit voltage corresponding to the minimum power Pm of the output power is voltage VLa. When the temperature of the battery 1 is at a low temperature (graph B), the lower limit voltage corresponding to the minimum power Pm of the output power is voltage VLb. That is, when the temperature of the battery 1 is at a first temperature (low temperature), the lower limit voltage is higher than when the temperature of the battery 1 is at a second temperature (room temperature), which is higher than the first temperature.

[0021] When the output power of battery 1 is at its minimum power, i.e., when the cell voltage is at the lower limit voltage, the SOC calculation unit 201 calculates the SOC of battery 1 as 0%. When the temperature of battery 1 is at room temperature (Graph A), the SOC calculation unit 201 calculates the SOC of battery 1 as 0% when the cell voltage becomes voltage VLa. When the temperature of battery 1 is at a low temperature (Graph B), the SOC calculation unit 201 calculates the SOC of battery 1 as 0% when the cell voltage becomes voltage VLb. In other words, as the temperature of battery 1 decreases from room temperature to a low temperature, the value of the lower limit voltage at which the SOC of battery 1 is calculated as 0% increases.

[0022] In conventional methods, when performing SOC calculations based on voltage, the lower limit voltage is set to the lowest voltage at which battery 1 can no longer output power. In the example in Figure 2, the lower limit voltage is set to the lowest voltage Vm. That is, when the cell voltage is the lowest voltage Vm, the SOC of battery 1 is calculated as 0%. The lowest voltage, as shown in Figure 2, is the voltage at which the output power is 0 kW, i.e., the voltage at which battery 1 can no longer output power. With such an SOC calculation method, for example, even if the output power of battery 1 becomes less than the minimum power before the cell voltage reaches the lowest voltage, and the vehicle becomes unable to start, the SOC of battery 1 is not calculated as 0%. In other words, even though there is still SOC remaining in battery 1, the vehicle becomes unable to start, so the SOC of battery 1 does not match the state of the vehicle where the vehicle cannot start. In the example shown in Figure 2, when the cell voltage falls within the voltage range where the output power is 0 kW or more and the minimum power is Pm or less (hatched area in Figure 2), the State of Charge (SOC) of battery 1 is calculated as greater than 0%, even though the vehicle is unable to start. Therefore, when the calculated SOC is displayed on the display 3, the vehicle occupants who see the SOC display may feel that the display is inconsistent. In contrast, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, as described above, the lower limit voltage at which the SOC of battery 1 is calculated as 0% is set to the voltage at which the output power is the minimum power. Therefore, if the vehicle is unable to start (the cell voltage is the voltage in the hatched area in Figure 2), the remaining capacity of battery 1 is calculated as 0%. As a result, a 0% SOC of battery 1 matches the vehicle's state of being unable to start. Thus, it is possible to reduce the feeling of incongruity that vehicle occupants may have when they see the displayed SOC.

[0023] The minimum power required to start a vehicle can vary depending on the gradient of the road on which the vehicle is traveling. For example, when a vehicle is traveling on an uphill road, it must be able to output more power than when it is traveling on a flat road in order to start. As shown in Figure 3, the minimum power that can be output is set according to the gradient of the road. Figure 3 is a map showing an example of the output characteristics of the battery according to this embodiment. The output characteristics of battery 1 are the same as in Figure 2, and the explanation of Figure 2 will be used as appropriate. When the road is uphill, the vehicle needs more torque to start on the road than it does on a flat road (a road with a 0% gradient). Therefore, when the road is uphill, the minimum power is greater than the minimum power when the road is flat. Conversely, when the road is downhill, the vehicle needs less torque to start on the road than it does on a flat road (a road with a 0% gradient). Therefore, when the road is on a downhill slope, the minimum power is lower than when the road is on a flat surface.

[0024] In the example in Figure 3, the minimum power Pm1 is the minimum power when the gradient of the road is 0%. The minimum power Pm2 is the minimum power when the gradient of the road is -10%. The minimum power Pm2 is less than the minimum power Pm1. The minimum power Pm3 is the minimum power when the gradient of the road is 10%. The minimum power Pm3 is greater than the minimum power Pm1. In the graph showing the output characteristics of battery 1, the lower limit voltage corresponding to the minimum power Pm1 is voltage VL1. That is, voltage VL1 is the lower limit voltage when the gradient of the road is 0%. The lower limit voltage corresponding to the minimum power Pm2 is voltage VL2. That is, voltage VL2 is the lower limit voltage when the gradient of the road is -10%. The lower limit voltage corresponding to the minimum power Pm3 is voltage VL3. That is, voltage VL3 is the lower limit voltage when the gradient of the road is 10%. Voltage VL2 is lower than voltage VL1. Voltage VL3 is higher than voltage VL1. In other words, the steeper the gradient of the road, the greater the minimum power and the higher the lower limit voltage.

[0025] When the gradient of the road changes in a direction that decreases, the minimum power is set to be lower than the minimum power before the change in the road's gradient. For example, when the gradient of the road changes from 0% to a value less than 0%, the minimum power is set to be lower than the minimum power when the road's gradient is 0%. When the gradient of the road changes in a direction that increases, the minimum power is set to be higher than the minimum power before the change in the road's gradient. For example, when the gradient of the road changes from 0% to a value greater than 0%, the minimum power is set to be higher than the minimum power when the road's gradient is 0%.

[0026] One method for setting the minimum power according to the gradient of the road is to apply a correction to the minimum power according to the gradient of the road. For example, the minimum power is calculated by multiplying the minimum power when the gradient of the road is 0% by a predetermined correction coefficient, with the minimum power when the gradient of the road is 0% being used as the reference minimum power. The predetermined correction coefficient is set according to the gradient of the road. When the gradient of the road is 0%, the predetermined correction coefficient is set to 1. When the gradient of the road is greater than 0%, the predetermined correction coefficient is set to a value greater than 1. When the gradient of the road is less than 0%, the predetermined correction coefficient is set to a value greater than 0 and less than 1.

[0027] In this embodiment, the lower limit voltage corresponds to the minimum power output. Therefore, the lower limit voltage fluctuates as the minimum power fluctuates according to the gradient of the road. Furthermore, since the SOC is calculated as 0% in accordance with the lower limit voltage, the SOC also fluctuates due to fluctuations in the lower limit voltage. In other words, the SOC also fluctuates due to fluctuations in the gradient of the road. For example, when the gradient of the road is 0%, the SOC is calculated as 0% when the cell voltage is VL1. When the gradient of the road is -10%, the SOC is calculated as 0% when the cell voltage is VL2. When the gradient of the road is 10%, the SOC is calculated as 0% when the cell voltage is VL3.

[0028] The SOC display unit 202 displays the State of Control (SOC) of battery 1, calculated by the SOC calculation unit 201, to the vehicle user. The user is, for example, the occupants of the vehicle, including the driver. The SOC display unit 202 transmits a control command to the display 3 to display the calculated SOC on the display 3. For example, the display of the SOC on the display 3 starts when the vehicle's ignition switch is turned on. The SOC display unit 202 updates the display on the display 3 according to the SOC calculated at regular intervals while the vehicle is running or in an active state.

[0029] The SOC display unit 202 may update the SOC displayed on the display 3 when the gradient of the road on which the vehicle is traveling changes. When the gradient of the road changes in a direction that increases, the SOC display unit 202 updates the SOC displayed on the display 3 to the SOC after the change in the road gradient. On the other hand, when the gradient of the road changes in a direction that decreases, the lower limit voltage corresponding to SOC 0% decreases, which can lead to a problem where the calculation results in an increase in SOC. Therefore, when the gradient of the road changes in a direction that decreases, the SOC display unit 202 maintains the SOC displayed on the display 3 at the SOC before the change in the road gradient. This prevents problems such as the SOC increasing due to a change in the road gradient while the vehicle is traveling. The SOC display unit 202 may, for example, obtain the gradient of the road from map information and determine the change in the road gradient.

[0030] Display 3 is a device that provides information to the vehicle user by displaying image information, and is composed of, for example, a liquid crystal display equipped with a touch panel. Examples of display 3 include an in-vehicle display such as an instrument panel display located in front of the driver's seat of the vehicle, or a display located on the vehicle's dashboard. Display 3 may also output audio information. In this embodiment, the display 3 displays the SOC calculated by the SOC calculation unit 201 in response to control commands transmitted from the SOC display unit 202.

[0031] Next, with reference to Figure 4, the procedure for the control processing performed by the battery remaining capacity calculation device according to this embodiment will be described. Figure 4 is a flowchart showing the control flow of the battery remaining capacity calculation method performed by the battery remaining capacity calculation device according to this embodiment. The control flow shown in Figure 4 is executed repeatedly at regular time intervals.

[0032] In step S1, the controller 20 acquires the voltage of battery 1. In step S2, the controller 20 calculates the State of Charge (SOC) of battery 1 according to the voltage of battery 1 acquired in step S1. For example, if the voltage of battery 1 is at the lower limit voltage, the SOC of battery 1 is calculated as 0%. The lower limit voltage is set to the voltage at which the output power of battery 1 is the minimum power required to start the vehicle, so when the vehicle cannot start, the SOC of battery 1 is calculated as 0%. In step S3, the controller 20 displays the SOC of battery 1 calculated in step S2 on the display 3. As a result, the display 3 shows that the SOC of battery 1 is 0% when the vehicle cannot start. In this embodiment, the flowchart shown in Figure 4 does not need to include all of steps S1 to S3, and some steps may be omitted, or additional steps may be added as appropriate. For example, step S3 may be omitted, or steps to acquire the temperature of battery 1, calculate the output power, and set the lower limit voltage according to the output power may be added. Furthermore, the processing order of each step in the control flow may be changed as appropriate.

[0033] As described above, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the controller that calculates the remaining capacity of the vehicle's battery calculates the remaining capacity of the battery as zero when the power that the battery can output is the minimum power required to start the vehicle. As a result, if the vehicle is in a state where it cannot start, the remaining capacity of the battery can be calculated as zero.

[0034] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the controller acquires the battery voltage and calculates the remaining battery capacity as zero when the battery voltage is at the lower limit voltage. The lower limit voltage is the voltage at which the output power is the minimum power in the correspondence relationship between the output power and voltage. As a result, when the battery voltage is such that the battery can no longer output the minimum power necessary to start the vehicle, the remaining battery capacity can be calculated as zero.

[0035] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the minimum power is the lowest power that can output the torque required to start the vehicle from a standstill. As a result, when the battery can no longer output the power required to output the torque required to start the vehicle from a standstill, the remaining capacity of the battery can be calculated as zero.

[0036] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the lower limit voltage is higher when the battery temperature is at a second temperature (higher than the first temperature) than when the battery temperature is at a first temperature. This allows the lower limit voltage to be changed according to the battery temperature.

[0037] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the output power is calculated by minimum voltage × (open circuit voltage - minimum voltage) / battery internal resistance, where the minimum voltage is the voltage at which the battery can no longer output power. This makes it possible to determine the output power based on the battery voltage.

[0038] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the battery's internal resistance is calculated based on the battery's temperature and open-circuit voltage. This makes it possible to determine the battery's internal resistance based on the battery's temperature and open-circuit voltage.

[0039] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the minimum power is set according to the gradient of the road on which the vehicle is traveling. As a result, if the vehicle is unable to start due to the gradient of the road on which the vehicle is traveling, the remaining battery capacity can be calculated as zero.

[0040] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the minimum power is set to be lower than the minimum power before the change in the gradient of the road when the gradient of the road changes in the direction of decreasing, and higher than the minimum power before the change in the gradient of the road when the gradient of the road changes in the direction of increasing. This prevents the remaining capacity of the battery from increasing in response to changes in the gradient of the road on which the vehicle is traveling.

[0041] Furthermore, in the battery remaining capacity calculation device and battery remaining capacity calculation method according to this embodiment, the controller displays the calculated battery remaining capacity to the vehicle user, and when the gradient of the road changes in a direction that decreases, it maintains the displayed battery remaining capacity at the battery remaining capacity before the change in the road gradient. This prevents the displayed battery remaining capacity from increasing due to changes in the road gradient while the vehicle is in motion.

[0042] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0043] 1...Battery 11 Voltage sensor 12 Current sensor 13 Temperature sensor 2...Battery remaining capacity calculation device 20...Controller 201...SOC calculation unit 202...SOC display unit 21...Battery status acquisition unit 3...Display 100 Battery management system

Claims

1. A battery remaining capacity calculation device comprising a controller for calculating the remaining capacity of a vehicle's battery, wherein the controller calculates the remaining capacity of the battery as zero when the output power of the battery is the minimum power required to start the vehicle.

2. A battery remaining capacity calculation device according to claim 1, wherein the controller acquires the voltage of the battery, calculates the remaining capacity of the battery as zero when the voltage of the battery is at the lower limit voltage, and the lower limit voltage is the voltage at which the output power is the minimum power in the correspondence relationship between the output power and the voltage.

3. A battery remaining capacity calculation device according to claim 1 or 2, wherein the minimum power is the lowest power among the powers capable of outputting torque that allows the vehicle to start moving from a stationary state.

4. A battery remaining capacity calculation device according to claim 2, wherein the lower limit voltage is higher when the battery temperature is a second temperature which is higher than the first temperature when the battery temperature is a first temperature.

5. A battery remaining capacity calculation device according to any one of claims 1 to 4, wherein the output power is calculated by the following formula (1), and the minimum voltage is the voltage at which the battery can no longer output power. Output power = minimum voltage × (open circuit voltage - minimum voltage) / battery internal resistance ... (1) 6. A battery remaining capacity calculation device according to claim 5, wherein the internal resistance of the battery is calculated based on the temperature and open-circuit voltage of the battery.

7. A battery remaining capacity calculation device according to any one of claims 1 to 6, wherein the minimum power is set according to the gradient of the road on which the vehicle travels.

8. A battery remaining capacity calculation device according to claim 7, wherein the minimum power is set to be smaller than the minimum power before the change in the gradient of the road when the gradient of the road changes in a direction that decreases, and is set to be larger than the minimum power before the change in the gradient of the road when the gradient of the road changes in a direction that increases.

9. A battery remaining capacity calculation device according to claim 8, wherein the controller displays the calculated remaining capacity of the battery to the user of the vehicle, and maintains the displayed remaining capacity of the battery at the remaining capacity of the battery before the change in the gradient of the road when the gradient of the road changes in a direction that decreases.

10. A battery remaining capacity calculation method performed by a controller that calculates the remaining capacity of a vehicle's battery, wherein the controller calculates the remaining capacity of the battery as zero when the output power of the battery is the minimum power required to start the vehicle.

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