Temperature control system for secondary batteries

Abstract

This technology provides a method for adjusting multiple secondary batteries to a suitable temperature. [Solution] The secondary battery temperature control system of the present disclosure comprises a plurality of secondary battery groups, each classified according to the trend of change in battery temperature during discharge; a temperature control device for each secondary battery group that adjusts the battery temperature of the secondary batteries belonging to each secondary battery group; and a control device that controls the temperature control device. The control device is configured to set a target temperature for each secondary battery group based on weather forecasts and power demand forecasts so that the battery temperature of the secondary batteries belonging to each secondary battery group during discharge falls within a reference range, and to adjust the battery temperature of the secondary batteries belonging to each secondary battery group to the target temperature set for each secondary battery group by the temperature control device before the discharge of the secondary batteries begins.

Description

Technical Field

[0001] The present disclosure relates to a temperature control system for secondary batteries.

Background Art

[0002] Patent Document 1 discloses a battery management device that adjusts the temperature of a vehicle-mounted battery. The battery management device in Patent Document 1 has a function of acquiring vehicle usage information that affects the state of the battery at the vehicle's destination before the start of the vehicle's usage schedule and changing the target battery temperature of the battery from the set initial value based on the acquired information.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of stationary secondary batteries, the degree of deterioration varies for each secondary battery depending on the use of the reused battery and the environment of the installation location. Therefore, since the thermal resistance is different for each secondary battery, the amount of heat generated during charge and discharge is also different. For this reason, in a control such as that in Patent Document 1 where a target battery temperature is set for one battery and temperature adjustment is performed, it is difficult to adjust each of a plurality of secondary batteries to an appropriate temperature.

[0005] One object of the present disclosure is to provide a technology capable of adjusting a plurality of secondary batteries to an appropriate temperature.

Means for Solving the Problems

[0006] One aspect of this disclosure is a temperature control system for secondary batteries, which has the following features. Specifically, the temperature control system comprises multiple secondary battery groups, each classified according to the trend of change in battery temperature during discharge; a temperature control device for each secondary battery group that adjusts the battery temperature of the secondary batteries belonging to each secondary battery group; and a control device that controls the temperature control device. The control device is configured to set a target temperature for each secondary battery group based on weather forecasts and power demand forecasts so that the battery temperature of the secondary batteries belonging to each secondary battery group during discharge falls within a reference range, and to adjust the battery temperature of the secondary batteries belonging to each secondary battery group to the target temperature set for each secondary battery group by the temperature control device before the discharge of the secondary batteries begins. [Effects of the Invention]

[0007] According to the temperature control system disclosed herein, a group of secondary batteries is classified into multiple secondary batteries according to the trend of changes in battery temperature during discharge, and a target temperature is set for each group of secondary batteries, and temperature control is performed. Therefore, each of the secondary batteries with different temperature change trends can be adjusted to a more appropriate temperature range. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the overall configuration of the temperature control system and its surroundings in Embodiment 1 of the present disclosure. [Figure 2] This flowchart shows the temperature control operation performed by the temperature control device of the present disclosure. [Figure 3] This figure illustrates the effects of temperature control by each temperature control device in this disclosure. [Figure 4] This figure illustrates the effects of temperature control by each temperature control device in this disclosure. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure will be described below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and their descriptions are simplified or omitted.

[0010] Embodiment 1. Figure 1 is a schematic diagram showing the overall configuration of the temperature control system and its surroundings in Embodiment 1 of the present disclosure. The temperature control system in Figure 1 (hereinafter also simply referred to as the "system") comprises a plurality of secondary battery groups 1A to 1C and temperature control devices 3A to 3C. Each of the plurality of secondary battery groups 1A to 1C belongs to a plurality of stationary secondary batteries 2A to 2C.

[0011] Temperature control devices 3A to 3C are installed in accordance with each of the secondary battery groups 1A to 1C. Temperature control device 3A is for adjusting the temperature of secondary battery 2A, which belongs to secondary battery group 1A; temperature control device 3B is for adjusting the temperature of secondary battery 2B, which belongs to secondary battery group 1B; and temperature control device 3C is for adjusting the temperature of secondary battery 2C, which belongs to secondary battery group 1C.

[0012] For the sake of simplicity, in the following, unless otherwise necessary, multiple secondary battery groups 1A-1C, secondary batteries 2A-2C, and temperature control devices 3A-3C will also be simply referred to as "secondary battery group 1," "secondary battery 2," and "temperature control device 3."

[0013] As shown in Figure 1, each temperature control device 3 is equipped with a hydrothermal circuit 4 through which a refrigerant flows to raise or lower the temperature of each secondary battery 2 belonging to the corresponding secondary battery group 1. There are no limitations on the refrigerant used in the hydrothermal circuit 4; for example, water can be used. Although not shown in the figure, the hydrothermal circuit 4 is equipped with a pump for circulating water within the circuit, and a heat exchanger, etc. Each temperature control device 3 may also be equipped with a valve 5 for switching the flow of refrigerant to each secondary battery 2 belonging to each secondary battery group 1. Each temperature control device 3 is equipped with a control device, which adjusts the temperature of each secondary battery 2 belonging to each secondary battery group 1 by controlling the operation of the pump, valve, etc. in the hydrothermal circuit 4.

[0014] In the system of this embodiment, multiple secondary batteries 2 are grouped together according to their similar temperature change trends during discharge, and classified into each secondary battery group 1. For example, secondary batteries 2 are considered to have similar temperature change trends depending on their respective installation environments. The "installation environment" here refers to an environment that can directly or indirectly affect the temperature change during charging and discharging of the secondary batteries 2.

[0015] In the example shown in Figure 1, secondary battery group 1C includes multiple secondary batteries 2C installed in a shaded area by the roof of house 10, secondary battery group 1A includes multiple secondary batteries 2A installed in a well-ventilated location, and secondary battery group 1B includes multiple secondary batteries 2B installed in a location that is exposed to direct sunlight and has poor ventilation. Among these secondary battery groups 1A to 1C, the battery temperatures of secondary battery groups 1A to 1C are expected to show different trends in change. In particular, since secondary batteries 2 are housed in containers or the like for each secondary battery group 1, heat tends to accumulate if they are in a poorly ventilated location. Therefore, for example, the degree of temperature rise in secondary batteries 2B in secondary battery group 1B, which is exposed to direct sunlight and has poor ventilation, and the resulting rate of battery degradation are expected to be higher than that of secondary batteries 2A and 2C in secondary battery groups 1A and 1C located in other locations.

[0016] Each temperature control device 3 controls the temperature of the secondary battery 2 belonging to each secondary battery group 1 so that its battery temperature falls within a reference range. Here, the reference range is the appropriate temperature range in which the secondary battery can be properly charged and discharged. The upper limit of the reference range is the output limit temperature X. The output limit temperature X is a limit temperature set for reasons such as preventing the progression of degradation of the secondary battery 2 and preventing thermal runaway. The system is configured to monitor the temperature of each secondary battery 2, and when the battery temperature reaches the output limit temperature X, it limits or stops the battery output of that secondary battery. The lower limit of the reference range is the output reduction temperature Y. When the temperature of the secondary battery 2 drops, its internal resistance increases and its charge and discharge performance decreases significantly. The output reduction temperature Y is a temperature near the temperature at which the performance of the secondary battery 2 deteriorates significantly.

[0017] FIG. 2 is a flowchart for explaining the control process executed by the control device of each temperature adjustment device 3. Hereinafter, referring to FIG. 2, the temperature adjustment control by the control device of each temperature adjustment device 3 will be described. The control in FIG. 2 is executed, for example, every day at the control start time. The control start time is preset at a fixed time (for example, 5:00 am) before the start of discharging in a day.

[0018] Each temperature adjustment device 3 calculates the current thermal resistance Rα according to the following formula (1) in step S102.

Equation

[0019] Next, in step S104, the maximum achievable temperature Tb_max of each secondary battery group 1 is calculated from the weather forecast information and the predicted power demand information according to the following formula (2).

Equation

[0020] Also, the minimum achievable temperature Tb_min of each secondary battery group 1 is calculated according to the following formula (3).

Equation

[0021] Furthermore, the predicted values ​​of the achievable temperature calculated using equations (2) and (3) should be set with a margin to allow for appropriate temperature adjustment. That is, for example, the maximum value of the predicted range of power demand will be used for the amount of electricity Q, and the highest and lowest predicted values ​​will be used for the maximum temperature Tb_maxtemp_time and minimum temperature Tb_mintemp_time.

[0022] Next, in step S106, it is determined whether the maximum temperature Tb_max is higher than the output limit temperature X. If, in step S106, it is determined that the maximum temperature Tb_max is less than or equal to the output limit temperature X, then in step S108, it is determined whether the minimum temperature Tb_min is lower than the output reduction temperature Y.

[0023] If it is determined in step S108 that the minimum temperature Tb_min reached is equal to or greater than the output drop temperature Y, then the temperature adjustment of the secondary battery 2 of the secondary battery group 1 is not performed, and the process is terminated.

[0024] On the other hand, if it is determined in step S106 that the maximum temperature Tb_max is higher than the output limit temperature X, then in step S110, the target temperature Tb_tag is calculated according to the following equation (4). The target temperature Tb_tag is the target temperature for pre-cooling the secondary battery 2 at a certain time before the start of discharge (for example, 6 a.m.).

number

number

[0025] If, in step S108, it is determined that the minimum achievable temperature Tb_min is lower than the output drop temperature Y, then in step S112, the target temperature is set. In this case, the target temperature is calculated according to the following equation (6).

number

number

[0026] After the target temperature Tb_tag is set in step S110 or step S112, the temperature control device 3 is activated at a certain time before the discharge starts (for example, 6:00 AM), and the temperature of the secondary battery 2 is adjusted until it reaches the set target temperature Tb_tag.

[0027] Figures 3 and 4 illustrate the effects of temperature control by each temperature control device 3. Figure 3 shows an example when the ambient temperature is high, and Figure 4 shows an example when the ambient temperature is low. In each figure, the solid line (a) shows the example when temperature control is performed, and the dashed line (b) shows the conventional example when temperature control is not performed.

[0028] As shown in Figure 3, when the daytime ambient temperature reaches a high temperature of nearly 40°C, without temperature control, the battery temperature may exceed the output limit temperature X during the period when daytime temperatures and power demand are high, resulting in insufficient power output (dashed line (b)). However, by pre-cooling each secondary battery 2 before the start of discharge through temperature control, the battery temperature can be kept below the output limit temperature X even during the daytime, ensuring sufficient power output to meet power demand (solid line (a)).

[0029] Furthermore, as shown in Figure 4, in extremely cold conditions (e.g., -20°C), if temperature control is not performed, the battery temperature may fall below the output reduction temperature Y, potentially resulting in insufficient output (dashed line (b)). However, by preheating each secondary battery 2 before the start of discharge through temperature control, the secondary batteries 2 can maintain a temperature higher than the output reduction temperature Y, ensuring sufficient output to meet power demand (solid line (a)).

[0030] The above temperature control is performed for each secondary battery group 1. The secondary battery groups 1 are classified into groups based on their similar temperature change trends, according to the installation environment that affects the secondary battery temperature. Therefore, the battery temperature can be effectively adjusted to an appropriate temperature range.

[0031] In this embodiment, the case in which secondary batteries 2 are classified into secondary battery groups 1 according to the installation environment has been described. However, the classification into secondary battery groups 1 in the temperature control system is not limited to this. For example, when many reused batteries are used as secondary batteries 2, the resistance of the secondary batteries will differ depending on the degree of degradation. Therefore, by classifying secondary batteries 2 into groups with similar degrees of degradation and setting up secondary battery groups 1 accordingly, more appropriate temperature control can be achieved. Alternatively, secondary batteries with similar degrees of degradation may be installed in similar installation environments, and secondary battery groups may be set up so that the temperature change trends and thermal resistance values ​​are similar.

[0032] The case where a temperature control device 3 is provided for each secondary battery group 1 has been described. However, any temperature control device 3 that can adjust the temperature for each secondary battery group 1 is acceptable. For example, the components of the temperature control device 3, such as the control device, heat exchanger, and pump, may be common to the entire system. [Explanation of Symbols]

[0033] 1, 1A~1C secondary battery group 2, 2A~2C secondary battery 3, 3A~3C temperature control device 4 Hydrothermal circuit 5 valves 10 companies

Claims

[Claim 1] Multiple secondary batteries are classified according to the trend of changes in battery temperature during discharge, forming multiple groups of secondary batteries, For each of the secondary battery groups, a temperature control device is provided to adjust the battery temperature of the secondary battery belonging to each of the secondary battery groups. The system comprises a control device for controlling the temperature control device, The control device is Based on weather forecasts and electricity demand forecasts, a target temperature is set for each secondary battery group so that the battery temperature during discharge of each secondary battery belonging to each secondary battery group falls within a standard range. Before the discharge of the secondary battery begins, the temperature control device is configured to adjust the battery temperature of each secondary battery belonging to each of the secondary battery groups to the target temperature set for each secondary battery group. Temperature control system.

Images