Battery system and its control method

Abstract

To provide a battery system with which it is possible to secure the maneuverability of a mobile entity by a secondary battery whose SOC is controlled so as to last long and remain stable and adapt to outside temperature.SOLUTION: Provided is a battery system comprising a power storage system having a plurality of battery cells and mounted to a mobile entity, and a charge rate control unit that controls the charge rate of the power storage system, the charge rate control unit controlling a charge from a charging facility to the power storage system when the operation of the mobile entity is terminated, on the basis of the temperature of the power storage system and the charge rate of the power storage system, a condition for charge control requiring that the charge rate of the power storage system is increased from a first charge rate threshold when the temperature of the power storage system is higher than a first temperature threshold, and the charge rate of the power storage system is reduced from a second charge rate threshold which is smaller than or equal to the first temperature threshold when the temperature of the power storage system is lower than a second temperature threshold which is smaller than or equal to the first temperature threshold. The temperature may be translated from the measured or predicted value of a storage battery temperature or from an environment temperature.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a battery system and a control method thereof.

Background Art

[0002] For a power storage system equipped with a secondary battery, managing it at an appropriate temperature and state of charge (SOC) is important for ensuring stable output characteristics of the secondary battery and suppressing battery degradation of the secondary battery. For example, in Patent Document 1, temperature information and state-of-charge information of a secondary battery are acquired, and based on these pieces of information, when the state of charge of the secondary battery is equal to or higher than a specific threshold value and the temperature of the secondary battery is equal to or lower than a specific threshold temperature, a power storage control device that switches the secondary battery to a discharged state is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power storage control device of Patent Document 1, since it is possible to suppress the secondary battery from being cooled and the temperature of the secondary battery from decreasing in a low-temperature environment, there is an effect of suppressing a decrease in the output characteristics of the secondary battery. However, Patent Document 1 does not mention control techniques and operation methods regarding the state of charge of the secondary battery in a high-temperature environment from the viewpoint of degradation suppression.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a battery system that enables stable long-term use of a secondary battery by appropriately controlling the SOC of the secondary battery according to the outside air temperature, and thereby ensures the mobility of a moving body.

Means for Solving the Problems

[0006] The present invention for solving the above problems is a battery system including a power storage system having a plurality of battery cells and mounted on a moving body, and a charging rate control unit for controlling the charging rate of the power storage system. The charging rate control unit controls the charging from a charging facility to the power storage system when the operation of the moving body ends, based on the temperature of the power storage system and the charging rate of the power storage system. As a condition for the charging control, when the temperature of the power storage system is higher than a first temperature threshold, the charging rate of the power storage system is made higher than a first charging rate threshold, and when the temperature of the power storage system is No. lower than a second temperature threshold which is lower than or equal to the first temperature threshold, the charging rate of the power storage system is made lower than a second charging rate threshold which is lower than or equal to the first charging rate threshold.

Advantages of the Invention

[0007] According to the present invention, by appropriately controlling the SOC of the secondary battery according to the outside air temperature, it is possible to enable stable long-term use of the secondary battery and provide a battery system capable of ensuring the mobility of the moving body thereby.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and the like. The following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in this specification. Also, in all the drawings for explaining the present invention, those having the same function are denoted by the same reference numerals, and the repeated description thereof is omitted. Further, hereinafter, the secondary battery (storage battery) may be simply abbreviated as "battery".

[0010] [Basic Example] FIG. 1 is a graph showing the temperature characteristics of the secondary battery output. The horizontal axis represents the temperature [°C], and the vertical axis represents the secondary battery output [W]. As shown in FIG. 1, it is known that the temperature characteristic is such that the secondary battery output rapidly decreases at temperatures below 10°C. Although this temperature characteristic has some differences depending on the type of secondary battery, most of the lithium-ion batteries used in this battery system 3, 6 (FIGS. 3 and 6) correspond to this.

[0011] FIG. 2 is a graph showing a rectangular wave applied to the warm-up process. The horizontal axis represents time [seconds], and the vertical axis represents the charge / discharge current. In the graph of FIG. 2, the charge current is shown in the positive direction, and the discharge current is shown in the negative direction. In the warm-up process, even if a certain amount of power consumption cannot be avoided, in order to efficiently heat and keep the battery warm with the minimum power consumption, as shown in FIG. 2, the secondary battery is repeatedly charged and discharged with a rectangular wave, and the secondary battery is heated by the Joule heat generated from the charge / discharge current and the internal resistance (battery resistance R). Specific examples of other warm-up processes will be described later.

[0012] FIG. 3 is a functional block diagram showing an overview of a battery system (this battery system) 3 according to an embodiment of the present invention. In FIG. 3, the control flow for a power storage system 40 which is the control target of this battery system 3 is also shown. A railway vehicle equipped with the power storage system 40 can travel even in a non-electrified section by the stored power of the power storage system 40. The power storage system 40 is configured to include a plurality of secondary batteries (battery cells) connected in series and in parallel, and a control function for equalizing the voltage and charge / discharge current of each of them.

[0013] The charge rate control unit (hereinafter also referred to as the "control unit") 61 has a function of controlling the timing of charging power to the power storage system 40 and the charge rate (SOC), and includes the control unit 61, the target charge rate data 62 of the battery, the temperature threshold 63 used for setting the charge rate target, and the time information (operation end information 64) when the operation of the railway vehicle equipped with the power storage system 40 ends.

[0014] The operation end information 64 is registered in the control unit 61 in advance based on the train schedule or the like. A data table is formed in the memory included in the control unit 61. At least the information on the operation end time of the railway vehicle and the charging facility that stops at the operation end time or a predetermined time before that is stored in the data table.

[0015] The control unit 61 is, for example, a control circuit formed by a computer that executes software or a hardware device. The control unit 61 performs predetermined calculations based on the information input from the outside (charge rate detection unit 70, temperature detection unit 71, and timing device 80) and the information held inside (target charge rate 62, temperature threshold 63). The control unit 61 controls to determine the charge rate of the power storage system 40 based on the calculation result. Alternatively, a form may be adopted in which a cell controller or the like (Cell controller) under the control unit 61 measures the battery cells constantly or periodically and appropriately delivers information to the control unit 61.

[0016] The control unit 61 determines the charge rate based on the charge rate information acquired by the charge rate detection unit 70 and the temperature information acquired by the temperature detection unit 71 regarding which of the first and second values are used for the target charge rate and the temperature threshold, respectively. The details of this control process will be described later. Note that at least one of the value pre-registered in the control unit 61 and the value sequentially input to the control unit 61 may be applied to the target charge rate 62 and the temperature threshold 63, or both may be combined.

[0017] The set values of the target charge rate 62 and the temperature threshold 63 adopted by the control unit 61 may be used separately according to the period. As an example, during a certain period, the values pre-registered in the internal memory of the control unit 61 may be used, and at other times, the values input from outside the control unit 61 may be used.

[0018] Two target charge rates, i.e., a first target charge rate and a second target charge rate, are set for the target charge rate 62. The first target charge rate is defined by the threshold value of the SOC value at which the deterioration of the secondary battery hardly progresses. The second target charge rate is set as the upper limit value of the SOC at which the warm-up process can be carried out with the assumed current value.

[0019] However, when the SOC value set by the second target charge rate is smaller than the SOC value (SOC*) at which the remaining capacity of the battery can become zero during the running of the railway vehicle, the SOC* is adopted as the value of the second target charge rate. In some cases, these two first and second target charge rates may be set to the same value. Similarly, two temperature thresholds, i.e., a first temperature threshold and a second temperature threshold, are set for the temperature threshold 63. In some cases, these two first and second temperature thresholds may be set to the same value.

[0020] The operation end information 64 has at least the time when the railway vehicle ends its operation, the information about the charging facility visited immediately before the end, and the time when it visits the charging facility. The charge rate detection unit 70 acquires the information about its charge state from the power storage system 40.

[0021] The temperature detection unit 71 acquires at least one or more temperature information items including the temperature of any one or more of the storage batteries provided in the power storage system 40 and the outside air temperature as the temperature information of the power storage system 40. When a plurality of temperature information items are measured, both the maximum value and the minimum value among them are applied.

[0022] In this way, the temperature information obtained by easily acquiring numerical values and simply summarizing them based on reasonable criteria is referred to as "the temperature information of the power storage system 40". Even if the temperature characteristics of the power storage system 40 are determined by the temperature of the internal electrodes located deeper inside the built-in battery cells, it is not easy to measure the true temperature. Therefore, the control unit 61 adopts the simply summarized temperature information for charge rate control so as to substitute for the true temperature.

[0023] Hereinafter, the process for the control unit 61 to control the charge rate of the power storage system 40 will be described by specifically classifying cases and exemplifying them. Based on the operation end information 64 of the railway vehicle, the control unit 61 starts the control process at the charging facility where it stops immediately before the operation ends. First, the control unit 61 acquires the temperature information of the power storage system 40 from the temperature detection unit 71.

[0024] At this time, the control unit 61 compares the acquired temperature value with the temperature threshold 63, and acquires the charge rate information of the power storage system 40 from the charge rate detection unit 70. The control unit 61 controls the charge rate of the power storage battery system 40 as follows based on the magnitude relationship of the obtained temperature and the charge rate information. Here, when a plurality of temperature values are measured from the temperature detection unit 71, only the maximum value among them may be used as the temperature information.

[0025] When the temperature value acquired from the temperature detection unit 71 (when a plurality are measured, their maximum value) is greater than the first temperature threshold and the charge rate acquired from the charge rate detection unit 70 is lower than the first target charge rate, the control unit 61 charges the power storage system 40 until the charge rate reaches the target charge rate.

[0026] When the temperature value acquired from the temperature detection unit 71 (if a plurality are measured, their maximum value) is greater than the first temperature threshold and the charge rate acquired from the charge rate detection unit 70 is higher than the first target charge rate, the control unit 61 does not perform control on the power storage system 40.

[0027] When the temperature value obtained from the temperature detection unit 71 (if multiple values are measured, the minimum value thereof) is less than the second temperature threshold value and the charge rate obtained from the charge rate detection unit 70 is lower than the second target charge rate, the control unit 61 charges the power storage system 40 until the charge rate reaches the second target charge rate.

[0028] When the temperature value obtained from the temperature detection unit 71 (if multiple values are measured, the minimum value thereof) is less than the second temperature threshold value and the charge rate obtained from the charge rate detection unit 70 is higher than the second target charge rate, the control unit 61 discharges the power storage system 40 until the charge rate reaches the second target charge rate. When the temperature and charge rate of the power storage system 40 do not fall under any of the above cases, the control unit 61 does not perform control processing on the power storage system 40.

[0029] By implementing the above charge rate control, it is possible to achieve both suppression of deterioration of the storage battery in a high temperature environment and improvement in the efficiency of warm-up processing in a low temperature environment. This will be illustrated by taking a secondary battery in which spinel type lithium manganate (LiMn2O4) is used as the positive electrode.

[0030] In the following, consider the case where the surface temperature and charge rate of the secondary battery are measured. At this time, the first temperature threshold value and the second temperature threshold value are preferably 30°C or higher and 30°C or lower, respectively, and more preferably 35°C or higher and 25°C or lower. Also, the first target charge rate and the second target charge rate are preferably 70% or higher and 70% or lower, respectively, and more preferably 75% or higher and 60% or lower. The reasons for these will be shown with reference to FIG. 4.

[0031] FIG. 4 is a graph showing the temperature characteristics of battery deterioration used for setting the temperature threshold value, with the temperature [°C] shown on the horizontal axis and the deterioration rate shown on the vertical axis. The solid line in FIG. 4 is the temperature characteristic of the deterioration rate of the secondary battery, and it can be confirmed that the deterioration rate of the secondary battery increases rapidly as the temperature rises. In this way, the deterioration rate gradually increases when exceeding around 20°C, and some countermeasures will be required when exceeding 40°C to 50°C.

[0032] Also, the one-dot chain line in FIG. 4 is the tangent line on the high-temperature side of 40° C. or higher in the temperature characteristic shown by the solid line, and the tangent line on the low-temperature side of 10° C. or lower in the temperature characteristic shown by the solid line. existing In this way, the intersection point of the tangent line on the low-temperature side and the tangent line on the high-temperature side is located at has a sharp increase in the deterioration rate around 30° C. Therefore, it is preferable that the first temperature threshold is set to a value (30° C.) or higher at which the increase in the deterioration rate occurs, and the second temperature threshold is preferably set to a value (30° C.) or lower.

[0033] Here, the case where the surface temperature of the secondary battery is measured as temperature information is exemplified. However, when the ambient temperature is measured, it is preferable to use a value about 5 to 10° C. lower than the above first and second temperature thresholds. This is because the surface temperature of the secondary battery is about 5 to 10° C. higher than the ambient temperature due to Joule heat generation during the use of the secondary battery.

[0034] Next, a method for determining the values of the first and second target charge rates is shown. These first target charge rate and second target charge rate are preferably set to 70% or more and 70% or less, and more preferably 75% or more and 60% or less, respectively. The reasons for this are shown with reference to FIG. 5.

[0035] FIG. 5 is a graph showing the charge rate dependence of battery deterioration used for setting the charge rate threshold, with the horizontal axis SOC showing [%] and the vertical axis showing the deterioration rate. The solid line in FIG. 5 shows the result at 40° C. (equal to or higher than the first temperature threshold), and the broken line shows the result at 10° C. (equal to or lower than the second temperature threshold). If the charge rate of the secondary battery is too low, the energy required for the running of the railway vehicle cannot be supplemented. Therefore, hereinafter, the region where the charge rate is 50% or more will be described.

[0036] As shown by the dashed line in FIG. 5, for the secondary battery, the charge rate dependence of the deterioration rate at or below the first temperature threshold is very small. However, as shown by the solid line in FIG. 5, for the secondary battery, above the first temperature threshold, the charge rate dependence of the deterioration rate becomes large. In particular, the deterioration rate changes significantly around charge rates of approximately 30% and 70%. Therefore, for the secondary battery, above the first temperature threshold, it is preferable that the first target charge rate is in the range of SOC (SOC 70% or higher) where the deterioration rate is small, and the second target charge rate is also in the range of SOC (SOC 30% or lower) where the deterioration rate is small.

[0037] When the battery system 3 uses the first and second temperature thresholds and the first and second target charge rates set as described above, it will be explained how the deterioration of the secondary battery is suppressed. As an example, first, consider the case where the temperature value acquired by the temperature detection unit 71 is 40°C and the SOC acquired from the charge rate detection unit 70 is 60%.

[0038] Since these temperature values are below the first temperature threshold and the SOC is also below the first target charge rate, the control unit 61 performs charge control so that the SOC of the secondary battery in the power storage system 40 becomes 70% or higher. As a result, the battery system 3 prevents the secondary battery in the power storage system 40 from being held in the medium SOC range (the range where the SOC is 40% to 70%, refer to the solid line in FIG. 5) for a long time at a high temperature such as 40°C. Consequently, the battery system 3 can suppress the accelerated deterioration progress of the secondary battery.

[0039] As another example, the case where the temperature value acquired by the temperature detection unit 71 is 10°C and the SOC acquired from the charge rate detection unit 70 is 60% will be explained. At this time, since the temperature value is below the second threshold temperature and the SOC is below the second target charge rate, the battery system 3 does not perform charge and discharge control on the secondary battery. The reason is that as shown by the dashed line in FIG. 5, at a low temperature below 10°C, the deterioration rate of the secondary battery has extremely low SOC dependence, so the influence of such control on the deterioration of the secondary battery is extremely small.

[0040] On the one hand, at low temperatures such as 10°C, it is desirable to perform a warm-up process on the secondary battery before using it for railway vehicle operation. At this time, according to this battery system 3, if the SOC value allows for warm-up processing (the range where SOC is 50% - 70%), the power storage system 40 can start the warm-up process earlier, thus minimizing the time required for the warm-up process before vehicle operation starts.

[0041] [Modification Example] FIG. 6 is a functional block diagram showing the outline of a battery system 6 (which is also this battery system) according to a modification example of this battery system. The battery system 6 in FIG. 6 is different in that it employs a temperature prediction unit 72 instead of the temperature detection unit 71 in the battery system 3 in FIG. 3.

[0042] Temperature prediction unit 72 Then, at the timing when the operation of the railway vehicle equipped with the power storage system 40 ends, it is good to have a function of obtaining a predicted value of the outside air temperature at the time when the railway vehicle will be operated next by referring to weather forecast information or the like. For example, when the operation of the railway vehicle ends at dusk on a certain date and time and the operation resumes the next morning, the temperature prediction unit 72 obtains the predicted value of the outside air temperature the next morning.

[0043] Hereinafter, the operation of the control unit 61 in the battery system 6 with respect to the information acquired by the temperature prediction unit 72 will be described. Based on the operation end information 64, that is, the train schedule, the railway vehicle often stops at a charging facility immediately before the operation ends. The control unit 61 starts control processing for charging the power storage system 40 at the charging facility where the railway vehicle stops. The temperature prediction unit 72 preferably has a function of predicting the outside air temperature at the next departure time or a little before that at the end of the railway vehicle operation. The control unit 61 acquires the predicted value from the temperature prediction unit 72.

[0044] At this time, the control unit 61 compares the temperature value acquired from the temperature prediction unit 72 with the temperature threshold value 63, and acquires the charging rate information of the power storage system 40 from the charging rate detection unit 70. Based on the obtained magnitude relationship of the temperature and the charging rate information, the control unit 61 controls the charging rate of the battery stem as follows.

[0045] When the temperature value acquired from the temperature prediction unit 72 is greater than the first temperature threshold value and the charging rate acquired from the charging rate detection unit 70 is lower than the first target charging rate, the control unit 61 charges the power storage system 40 until the charging rate reaches the First target charging rate.

[0046] When the temperature value acquired from the temperature prediction unit 72 is less than the second temperature threshold value and the charging rate acquired from the charging rate detection unit 70 is lower than the second target charging rate, the control unit 61 charges the power storage system 40 until the charging rate reaches the second target charging rate.

[0047] When the temperature value acquired from the temperature prediction unit 72 is less than the second temperature threshold value and the charging rate acquired from the charging rate detection unit 70 is higher than the second target charging rate, the control unit 61 discharges the power storage system 40 until the charging rate reaches the second target charging rate. When the temperature and charging rate of the power storage system 40 do not correspond to any of the above, the control unit 61 does not perform control processing on the power storage system 40.

[0048] When it is predicted that the environmental temperature will rise, the battery system 6 can control the charging rate of the battery by performing the above-described series of operations in the control unit 61 to suppress deterioration. Conversely, when it is predicted that the environmental temperature will drop, the battery system 6 can suppress the disruption of the train schedule by controlling the power storage system 40 to a charging rate at which warm-up processing can be efficiently performed.

[0049] From the above, according to the present battery system 3, 6, the mobility of the moving body can also be ensured by the secondary battery that is controlled to an appropriate SOC according to the outside air temperature so as to have a long life and be stabilized. That is, the present battery system 3, 6 controls the charging rate of the secondary battery to a predetermined value according to the secondary battery temperature or the outside air temperature, and suppresses the deterioration of the secondary battery in a high-temperature environment, so that the secondary battery can be stably used for a long time. In addition, the present battery system 3, 6 can prevent the delay of the train operation schedule even in a low-temperature environment.

[0050] [Supplementary Explanation] Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described present battery system 3, 6 has been described in detail for easy understanding of the invention, and is not necessarily limited to the one having all the configurations described.

[0051] Also, it is possible to replace a part of the configuration in one embodiment with the configuration in another embodiment, and it is also possible to add the configuration in another embodiment to the configuration in one embodiment. In addition, for a part of the configuration in each embodiment, it is possible to add, delete, or replace with other configurations.

[0052] Also, the configurations, functions, processing units, processing means, etc. shown in each embodiment may be realized in hardware by designing part or all of them, for example, by an integrated circuit. In addition, the above-described each configuration, function, etc. may be realized in software by a computer CPU (Central Processing Unit) interpreting and executing a program for realizing each function.

[0053] Information such as programs, tables, and files that implement each function can be stored in a recording device such as a hard disk or SSD (Solid State Drive) which is a memory, or in a recording medium such as an IC card, SD card, or DVD. Also, control lines and information lines show those considered necessary for explanation, and not all control lines and information lines are necessarily shown on the product. For implementation, it may be considered that almost all components are interconnected.

[0054] In recent years, in order to prevent global warming, reduction of carbon dioxide emissions has been demanded. For example, for automobiles using gasoline engines which are one of the major sources of carbon dioxide emissions, the substitution to hybrid electric vehicles, electric vehicles, etc. is progressing. As a rechargeable battery (secondary battery) suitable for them, there are lithium-ion secondary batteries, nickel-metal hydride batteries, lead batteries, and electric double layer capacitors, etc. Among them, a power storage system 40 having a plurality of battery cells with a high output density typified by lithium-ion batteries is widely adopted for industrial applications.

[0055] [Battery electric train] In recent years, a power storage system 40 with higher voltage and larger capacity has become widespread. This power storage system 40 is also widely used in the field of railway vehicles in order to achieve energy saving. In particular, for the purpose of reducing the environmental impact of railway vehicles running in non-electrified sections without overhead lines, battery electric trains equipped with a high-voltage and large-capacity power storage system 40 have begun to become popular.

[0056] A battery electric train can run not only using the overhead line power obtained in electrified sections with overhead lines as a power source, but also run using the power storage system 40 as a power source in non-electrified sections without overhead lines. Therefore, the large-scale power storage system 40 applied to the power source for the battery electric train is required to be high-voltage and high-output. Such a power storage system 40 for high-voltage and high-output applications is configured by connecting a plurality of battery cells in series and parallel.

[0057] [Temperature characteristics of output] Each of the above-configured battery cells commonly uses a unified lithium-ion battery. The output of secondary batteries represented by lithium-ion batteries has temperature characteristics that strongly depend on the outside air temperature. Regarding this point, as described above with reference to FIG. 1, particularly in the low temperature range from 10°C or lower to 0°C, the temperature characteristic of a sharp output drop becomes a problem in use.

[0058] This temperature characteristic is presumably caused by, for example, an increase in the resistance of the secondary battery in a low temperature environment. Due to this temperature characteristic, as a phenomenon where the secondary battery voltage deviates from the upper and lower limit ranges set in the specifications, the overvoltage during energization increases. In response to this phenomenon, the power storage system 40 operates its self-defense control function, and the energization with the secondary battery is stopped. Due to the stop of energization of the power storage system 40, not only is it impossible to discharge for driving the railway vehicle, but it also becomes impossible to charge the power storage system 40.

[0059] Therefore, when using a secondary battery in a low temperature environment, a warming process (warming-up process) is required in advance so that the temperature of the secondary battery becomes 0°C or higher, preferably 10°C or higher. As such a warming-up process, in addition to the method of warming up in advance with a heater installed in the power storage system 40, as described above with reference to FIG. 2, the secondary battery is repeatedly charged and discharged with a rectangular wave, and the secondary battery is warmed up by the Joule heat generated from the charge and discharge current and the internal resistance. to Examples include a method of warming the secondary battery with the Joule heat generated from the charge and discharge current and the internal resistance.

[0060] [Dependence of Deterioration on SOC] The environmental temperature when using a secondary battery affects not only the above-described output characteristics but also the deterioration characteristics of the secondary battery. Generally, secondary batteries have the characteristic that deterioration progresses more easily when used at a high temperature of 30°C or higher, or 45°C or higher. In addition to temperature, the state of charge (SOC) is one of the factors that affect the deterioration of secondary batteries.

[0061] The state of charge (SOC), also known as the charge state, is generally expressed with the fully discharged state specified in the specifications as 0% and the fully charged state as 100%, although there is also an inverse display. Generally, for secondary batteries, a range of SOC within which the operation is guaranteed as a safe product is defined in the specifications. Operating the secondary battery beyond the upper and lower limits of the SOC range according to this specification will cause the power storage system 40 to malfunction and will also shorten the life of the power storage system 40, so it must be avoided.

[0062] Also, even within the specified SOC range, it is widely known that in a specific SOC band, deterioration accelerates, the battery capacity decreases, the internal resistance increases, and the output fluctuates beyond the allowable range. The deterioration of the secondary battery tends to progress SOC in a band that is known to depend on the active material used for the electrodes.

[0063] For example, a secondary battery using spinel-type lithium manganate as the positive electrode active material has the characteristic that deterioration tends to progress in the medium SOC band of about 30% to 60% in a high-temperature environment. Therefore, in order to use the secondary battery stably for a long time, it is necessary to avoid using it in a high-temperature environment and in the medium SOC band.

[0064] When the deterioration of the secondary battery progresses, a decrease in battery capacity and an increase in internal resistance occur. Therefore, as the battery deteriorates, the power amount and output of the power storage system 40 gradually decrease and eventually become unusable. In addition, if the output of the power storage system 40 decreases during the running of the railway vehicle, it will cause the vehicle to stop.

[0065] To prevent such problems, it is necessary to appropriately replace the power storage system 40 in which the deterioration of the secondary battery has progressed. However, a large number of secondary batteries are used in the power storage system 40 for battery electric vehicles so as to be suitable for vehicle running, and the cost ratio of the secondary batteries in the entire vehicle system is high. Therefore, control technology for suppressing the deterioration of secondary batteries is also emphasized from the viewpoint of suppressing the running cost of the vehicle system.

[0066] As an example of a measure to suppress the progress of deterioration, it is considered effective to keep the charge rate of the secondary battery at a low SOC or a high SOC, avoiding the medium SOC range. However, when using at a low SOC (low charge rate), depending on the running section of the railway vehicle, there is a concern that the capacity of the secondary battery may be exhausted during running. Also, when using at a high SOC while appropriately observing the train schedule, it may be difficult to perform the warm-up process of the secondary battery under low temperature conditions. The reasons are shown below. As described above, since the battery resistance R increases in a low temperature environment, the battery voltage V during charging is approximately expressed as follows.

[0067] V = V_OCV + IR·····(1)

[0068] Here, V_OCV (Open Circuit Voltage) is the open circuit voltage (battery voltage when not energized), and I represents the charging current value. Generally, upper and lower limit voltages at which the secondary battery can be used safely are set, and when the secondary battery voltage deviates from this value, the amount of electricity conducted is often limited. In that case, in order to efficiently perform warm-up under low temperature, it is necessary to increase the charging current value to increase joule heat generation.

[0069] Therefore, in order to increase the charging current value and prevent the secondary battery voltage V from exceeding the upper limit voltage of the voltage, it is necessary to reduce the open circuit voltage V_OCV in the above formula (1). If this corresponds to an operation of keeping the charge rate (SOC) of the secondary battery low, the warm-up process may become difficult when using at a high SOC.

[0070] [Relationship with train schedule] When the current value that can be applied to the secondary battery becomes small, the time required for warm-up becomes long, which causes a delay in the train schedule of the railway vehicle. Although it is also possible to warm up the secondary battery by discharging, in this case, after discharging to warm up the secondary battery, it is necessary to recharge the secondary battery again in preparation for vehicle running, and it takes a long time until a series of processes are completed. Therefore, there is also a concern of causing a train schedule delay in this case.

[0071] Therefore, the present battery system 3,6 controls the charging and discharging of the power storage system 40 mounted on a railway vehicle as follows. First, it collects the information necessary for control. That is, in the power storage system 40, among the plurality of components it is equipped with, the charging rate for any one or more of the battery cells and, similarly, the temperature for any of the battery cells are constantly or periodically measured by a cell controller or the like. Also, the ambient temperature of the power storage system 40 is constantly or periodically measured so that the control unit 61 can acquire it.

[0072] Next, when the operation of the vehicle ends, the control unit 61 performs charge and discharge control based on the following control rules. When the measured temperature is higher than a predetermined temperature, it charges so that the charging rate of the battery cell becomes larger than a predetermined value. Conversely, when the measured temperature is lower than a predetermined temperature, it charges so that the charging rate of the battery becomes smaller than a predetermined value. Note that, as the temperature information applied as this control rule, at least any one of the surface temperature of the battery cell that is easy to measure, the ambient temperature, and the estimated battery temperature based on predetermined information and calculation formulas may be used.

[0073] The present battery system 3,6 will be supplemented and explained separately in the following [1] to [8] from the viewpoints of configuration, operation, and effects. [1] The present battery system 3,6 shown in FIGS. 3 and 6 includes a power storage system 40 having a plurality of battery cells and a control unit 61 that can control at least the charging rate and the timing of charging with respect to the power storage system 40, and is applied to a moving body. The power storage system 40 has a cell controller that manages the state of each of the plurality of battery cells, or has an equivalent function.

[0074] The control unit 61 is capable of acquiring at least information on the ambient temperature, the battery temperature, and the charging rate, and has a function of appropriately controlling the charging rate based on the information and adapting it to the ambient temperature. As the ambient temperature, either the measured value or the predicted value may be adopted. As the predicted value, in addition to calculation, different numerical values may be set for each season. In the main battery system 3 of FIG. 3, the temperature detection unit 71 acquires the measured value. In the main battery system 6 of FIG. 6, the temperature prediction unit 72 generates the predicted value based on weather information or the like. The battery temperature may be obtained or calculated from any one or more of the battery cells provided in the power storage system 40 via a cell controller or the like. The charging rate may also be measured by a cell controller or the like from any one or more of the battery cells provided in the power storage system 40.

[0075] The control unit 61 performs charging control by applying the conditions based on the information acquired at the following timing. The timing is when the moving body is immediately before or at the end of operation within the substantial management period. For example, in the case of a railway operation managed by a timetable, it may be considered as immediately before or at the end of the operation of the last train in the daily management period.

[0076] Note that a railway vehicle, that is, an electric multiple unit, may arrive at a charging facility immediately before the end of the operation of the last train and charge, and the operation may be considered to end when it arrives at a garage or the like away from the charging facility. On the other hand, there may be a case where a charging facility is attached to the garage. The electric multiple unit may also be charged with the power received from the overhead line without using the charging facility. In any of these cases, the main battery systems 3 and 6 are applicable.

[0077] The control unit 61 of the main battery systems 3 and 6 executes charging according to the charging control conditions based on the information acquired at the above timing. The control unit 61 specifically sets the charging control conditions as follows to adapt to the ambient temperature.

[0078] · When the battery temperature is higher than a predetermined first temperature threshold, charge at a charging rate greater than the first charging rate threshold. · When the ambient temperature is lower than a predetermined second temperature threshold, charge at a charging rate smaller than the second charging rate threshold.

[0079] The battery system 3, 6 can stably utilize the secondary battery for a long time by appropriately controlling the charging rate and charging timing so as to adapt to the environmental temperature. That is, in the battery system 3, 6, if the control unit 61 charges according to the above charging control conditions, it can be adapted to the environmental temperature, so that the life of a plurality of battery cells constituting the power storage system 40 can be extended, and the resource energy efficiency can be improved. Moreover, according to the battery system 3, 6, the mobility of the moving body can also be ensured by the secondary battery controlled to an appropriate SOC according to the outside air temperature.

[0080] [2] In the above [1], the temperature of the power storage system 40 is at least one of the battery temperatures of a plurality of battery cell , or the measured value thereof, or the predicted value thereof, and may be further converted from the environmental temperature. Also, the charging rate is the measured value or calculated value of at least one of a plurality of battery cell batteries. Such a battery system 3, 6 can be easily realized with a simple configuration. Although the temperature characteristics of the battery are considered to depend on the temperature of the electrode, it is difficult to actually measure the temperature near the electrode in a non-destructive state, so a practical temperature is estimated by a simple alternative means. That is, if the charging rate control unit 61 controls the charging rate using the current temperature at an easily measurable location or the predicted temperature based on weather data, the object of the present invention of achieving both the extension of the battery life and the effective utilization of the battery output can be achieved.

[0081] [3] In the above [1], the battery system 3, 6 may conveniently substitute the surface temperature or environmental temperature of the battery cell instead of the internal temperature of the battery cell. More precisely, an estimated temperature using a combination of various correction means may be adopted. Also, by setting the following charging control conditions based on the battery characteristics shown in FIGS. 4 and 5, good results were obtained for the battery system 3, 6. The battery characteristics are preferably applied based on the battery specifications stored in the memory of the control unit 61.

[0082] · When applying the battery temperature to the temperature information, the first temperature threshold is set to 30°C or higher, and the second temperature threshold is set to 30°C or lower. · When applying the ambient temperature to the temperature information, the first temperature threshold is set to 25°C or higher, and the second temperature threshold is set to 25°C or lower.

[0083] [4] In the present battery system 3, 6 of [1] above, even if the control unit 61 specifically sets the charging control conditions as follows, good results adaptable to the ambient temperature are obtained. The following charging control conditions may also be applied based on the battery specifications stored in the memory of the control unit 61. That is, it is a setting based on the battery characteristics shown in FIGS. 4 and 5. · The first charging rate threshold is set to 70% or higher of the charging rate, and the second charging rate threshold is set to 70% or lower of the charging rate.

[0084] [5] In the present battery system 3, 6 of [1] above, even if the control unit 61 specifically sets the charging control conditions as follows, good results adaptable to the ambient temperature are obtained. The following charging control condition settings may also be applied based on the battery specifications stored in the memory of the control unit 61. That is, it is a setting based on the battery characteristics shown in FIGS. 4 and 5. · When applying the battery temperature to the temperature information, the first temperature threshold is set to 35°C or higher, and the second temperature threshold is set to 20°C or lower. · When applying the ambient temperature to the temperature information, the first temperature threshold is set to 30°C or higher, and the second temperature threshold is set to 10°C or lower.

[0085] [6] In the present battery system 3, 6 of [1] above, even if the control unit 61 specifically sets the charging control conditions as follows, good results adaptable to the ambient temperature are obtained. The following charging control condition settings may also be applied based on the battery specifications stored in the memory of the control unit 61. That is, it is a setting based on the battery characteristics shown in FIGS. 4 and 5. · The first threshold of the charging rate is set to 75% - 85% of the charging rate, and the second threshold of the charging rate is set to 50% - 60% of the charging rate.

[0086] [7] In the main battery systems 3 and 6 described above in [1] to [6], the charging control conditions were easily implemented in the following form and good results were obtained. That is, the main battery systems 3 and 6 are equipped with a computer, various hardware devices that make up the electric circuit, and sensors. Also, many of the functions of the control unit 61 are realized by the CPU of the computer executing a program stored in the memory. The computer may be a one-chip microcomputer or a personal computer, and further, a part of a computer being used for other purposes may be used in combination.

[0087] The control unit 61 forms a data table in the memory included in the control unit 61. At least information on the operation end time of the moving body and the charging facility where the moving body stops at the operation end time or a predetermined time before that is stored in the data table. When the operation end time or a predetermined time before that arrives, the control unit 61 starts charging the power storage system 40.

[0088] [8] In the above [7], the moving body is a railway vehicle, and a battery electric vehicle is preferable, but it is also applicable to a hybrid train. These railway vehicles, in the manner described above, at the charging facility where they stop at the operation end time or a predetermined time before that, the control unit 61 starts charging the power storage system 40 at a charging rate adapted to the environmental temperature. Since the railway vehicle is well charged at the start of the first operation, it can run in a section without overhead lines with high energy efficiency. Also, when spinel-type lithium manganate is used as the positive electrode active material of the battery cell, good results are obtained.

Description of symbols

[0089] 3,6 Battery system (this battery system), 40 Power storage system, 61 Charge rate control unit (Specification), 62 Target charge rate, 63 Temperature threshold, 64 Service end information, 70 Charge rate detector, 71 Temperature detector, 72 Temperature prediction unit

Claims

1. A power storage system having a plurality of battery cells and mounted on a mobile body, a charging rate control unit that controls the charging rate of the power storage system, A battery system comprising: The charging rate control unit controls charging of the power storage system from a charging facility when operation of the mobile body ends, based on the temperature of the power storage system and the charging rate of the power storage system, As conditions for charging control, when the temperature of the power storage system is greater than a first temperature threshold, the charging rate of the power storage system is made greater than a first charging rate threshold, when the temperature of the power storage system is less than a second temperature threshold that is less than or equal to the first temperature threshold, the charging rate of the power storage system is made less than a second charging rate threshold that is less than or equal to the first charging rate threshold, Battery system.

2. The temperature of the power storage system is the storage battery temperature of at least one of the plurality of battery cells, its measured value, or its predicted value, and may further be converted from the ambient temperature, The charging rate is a measured value of at least one storage battery of the plurality of battery cells, The battery system according to claim 1.

3. As conditions for the charging control, when applying the battery temperature to the temperature information, the first temperature threshold is set to 30°C or higher, and the second temperature threshold is set to 30°C or lower, when applying the ambient temperature to the temperature information, the first temperature threshold is set to 25°C or higher, and the second temperature threshold is set to 25°C or lower, The battery system according to claim 1.

4. As conditions for the charging control, the first charging rate threshold is set to 70% or higher of the charging rate, and the second charging rate threshold is set to 70% or lower of the charging rate, The battery system according to claim 1.

5. As conditions for the charging control, when applying the battery temperature to the temperature information, the first temperature threshold is set to 35°C or higher, and the second temperature threshold is set to 20°C or lower, when applying the ambient temperature to the temperature information, the first temperature threshold is set to 30°C or higher, and the second temperature threshold is set to 10°C or lower, The battery system according to claim 1.

6. As conditions for the charging control, the first charging rate threshold is set to 75% to 85% of the charging rate, and the second charging rate threshold is set to 50% to 60% of the charging rate, The battery system according to claim 1.

7. The charging rate control unit in a memory included in the charging rate control unit, the operation end time of the mobile body, the charging facility where the mobile body stops immediately before operation ends, The time of approaching the charging equipment, and stores the information of starts charging at or before the predetermined time of the operation end time, The battery system according to any one of claims 1 to 6.

8. The moving body is a railway vehicle, and spinel-type lithium manganate is used as the positive electrode active material of the battery cell. The battery system according to claim 7.

9. A power storage system having a plurality of battery cells and mounted on a moving body, A charging rate control unit that controls the charging rate of the power storage system, A battery system control method using The charging rate control unit controls the charging of the power storage system from the charging equipment to the power storage system when the operation of the moving body ends, based on the temperature of the power storage system and the charging rate of the power storage system, As conditions for charging control, when the temperature of the power storage system is higher than the first temperature threshold, the charging rate of the power storage system is made higher than the first charging rate threshold, when the temperature of the power storage system is lower than the second temperature threshold which is below the first temperature threshold, the charging rate of the power storage system is made lower than the second charging rate threshold which is below the first charging rate threshold, Battery system control method.

10. The temperature of the power storage system is at least one battery temperature of the plurality of battery cells, its measured value, or its predicted value, and may also be converted from the environmental temperature. The charging rate is the measured value of at least one battery of the plurality of battery cells. The battery system control method according to claim 9.

11. As conditions for the charging control, when applying the battery temperature to the temperature information, the first temperature threshold is set to 30 °C or higher, and the second temperature threshold is set to 30 °C or lower. when applying the environmental temperature to the temperature information, the first temperature threshold is set to 25 °C or higher, and the second temperature threshold is set to 25 °C or lower. The battery system control method according to claim 9.

12. As conditions for the charging control, the first charging rate threshold is set to 70% or higher of the charging rate, and the second charging rate threshold is set to 70% or lower of the charging rate. The battery system control method according to claim 9.

13. As conditions for the charging control, when applying the battery temperature to the temperature information, the first temperature threshold is set to 35 °C or higher, and the second temperature threshold is set to 20 °C or lower. when applying the environmental temperature to the temperature information, the first temperature threshold is set to 30 °C or higher, and the second temperature threshold is set to 10 °C or lower. The battery system control method according to claim 9.

14. As the conditions for the charging control, the first charging rate threshold is set to a charging rate of 75% to 85%, and the second charging rate threshold is set to a charging rate of 50% to 60%. The battery system control method according to claim 9.

15. The charging rate control unit stores in the memory provided in the charging rate control unit the operation end time of the moving body, the charging facility where the moving body stops immediately before the operation ends, and the time when it stops at the charging facility, and starts charging at the operation end time or a predetermined time before that. The battery system control method according to any one of claims 9 to 14. ​

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