JP6883852B2 - Power supply unit equipped with lithium ion secondary battery and its control method - Google Patents

Description

The present invention relates to a power supply device including a lithium ion secondary battery and a control technique thereof, and more particularly to a power supply device provided with a lithium ion secondary battery and which can be used at a low temperature and a control technique thereof.

Lithium-ion secondary batteries are small and lightweight, and have a large energy density per unit volume. For this reason, it is being widely used, and its demand is expected to increase further in the future. Lithium-ion secondary batteries have a range of operating temperature because they only move lithium ions in the electrolyte during charge / discharge operation and do not store power by using chemical changes like many other secondary batteries. It has a relatively wide range of advantages.

However, in the charged / discharged state, the characteristics of the lithium ion move electrolyte change depending on the temperature. In a lithium ion secondary battery, the performance of the lithium ion secondary battery changes depending on the movement characteristics of the lithium ions moving in the electrolyte. When the temperature decreases, the state of the electrolyte changes, and the lithium ion transfer characteristics in the electrolyte deteriorate. As a result, the performance of the lithium ion secondary battery deteriorates as the temperature decreases in the environment in which the lithium ion secondary battery is placed.

Lithium-ion secondary batteries are superior in performance to other secondary batteries, and there is a demand for using lithium-ion secondary batteries even at low temperatures. However, in a low temperature state of −20 ° C. or −30 ° C., for example, the viscosity of the electrolyte of the lithium ion secondary battery increases, the mobility of lithium ions decreases, and the performance as a secondary battery deteriorates. Therefore, a technique has been proposed for improving the above-mentioned electrolyte and suppressing an increase in the viscosity of the electrolyte of the lithium ion secondary battery in a low temperature state.

Japanese Unexamined Patent Publication No. 2016-134261 Japanese Unexamined Patent Publication No. 2015-5426

Patent Document 1 and Patent Document 2 propose an electrolyte for a lithium ion secondary battery in which the decrease in the mobility of lithium ions is small even in a low temperature state. However, it cannot be said that sufficient performance has been obtained.

An object of the present invention is to provide a power supply device including a lithium ion secondary battery capable of improving the performance of the lithium ion secondary battery in a low temperature state, or a control method thereof.

The first invention includes a lithium ion secondary battery, a control circuit, a discharge circuit, and a measurement circuit for measuring the state of the lithium ion secondary battery, and the control circuit is the lithium ion secondary battery. The power supply device is characterized in that a discharge current is passed from the lithium ion secondary battery to the discharge circuit in order to raise the temperature.

In the second invention, in the first invention, the maximum value of the discharge current flowing from the lithium ion secondary battery to the discharge circuit in order to raise the temperature of the lithium ion secondary battery is the maximum value of the lithium ion secondary battery. It is a power supply device characterized in that the current value is larger than the maximum current value of the lithium ion secondary battery in normal operation.

In the third invention, in the first invention, a display device is further provided, and the control circuit transmits a discharge current from the lithium ion secondary battery to the discharge circuit in order to raise the temperature of the lithium ion secondary battery. The power supply device is characterized in that, when flowing, the display device indicates that the operation mode is for raising the temperature of the lithium ion secondary battery.

A fourth aspect of the present invention is characterized in that, in the third invention, the display device further displays information relating to the scheduled time until the end of the operation mode for raising the temperature of the lithium ion secondary battery. It is a power supply device.

The fifth invention is the control method of the power supply device of the first invention, in which the control circuit raises the temperature of the lithium ion secondary battery based on the measurement result of the measurement circuit, so that the temperature rise operation mode The power supply device is characterized in that it determines whether or not the operation is necessary, and controls the flow of current from the lithium ion secondary battery to the discharge circuit when it is determined that the operation in the temperature rise operation mode is necessary. It is a control method.

A sixth aspect of the present invention is the control method of the power supply device of the fifth aspect, wherein the control circuit obtains the current value or energization time to be passed through the discharge circuit from the measurement result of the measurement circuit, and the control circuit is the discharge circuit. It is a control method of a power supply device characterized by controlling the current flowing through the power supply.

According to the present invention, it is possible to obtain a power supply device capable of improving the performance of a lithium ion secondary battery in a low temperature state, or a control method thereof.

It is explanatory drawing explaining the concept of the power supply device provided with the lithium ion secondary battery to which this invention is applied. It is explanatory drawing explaining the relationship between the temperature of a lithium ion secondary battery and an operation mode. It is a flowchart explaining the control of the power supply device provided with the lithium ion secondary battery. It is explanatory drawing explaining the display content of the display device 160 in a temperature rise operation mode 20. It is explanatory drawing explaining the relationship between the temperature of a lithium ion secondary battery 110 and the magnitude of a temperature rise current A1, the pulse width, or the number of pulses.

1. 1. Configuration of Power Supply Device 100 and Description of Basic Operation of Power Supply Device 100 FIG. 1 shows a configuration of a power supply device 100 according to an embodiment of the present invention. The power supply device 100 includes a lithium ion secondary battery 110. In order to store electric power in the lithium ion secondary battery 110, electric power is supplied from the charging power supply 190 to the lithium ion secondary battery 110 via the external connection circuit 180 and the internal connection circuit 140, and the lithium ion secondary battery 110 is supplied with electric power. Electric power is stored at 110. Since the lithium ion secondary battery 110 stores direct current power, when the charging power supply 190 supplies alternating current power, AC / which converts alternating current between the charging power supply 190 and the lithium ion secondary battery 110 to direct current. A DC conversion circuit is provided.

When the electric power stored in the lithium ion secondary battery 110 is supplied to the electric load 182, the electric power stored in the lithium ion secondary battery 110 is transferred to the electric load 182 via the internal connection circuit 140 and the external connection circuit 180. Be supplied. When the electric load 182 requires AC power, a DC / AC conversion circuit for converting DC to AC is provided between the lithium ion secondary battery 110 and the electric load 182.

Charging control for storing electric power in the lithium ion secondary battery 110 and electric power supply control for supplying electric power to the electric load 182 are performed by a control circuit 150 provided with a computer. When the operator directly operates the lithium ion secondary battery 110, it can be operated from the operation unit 142, and the lithium ion secondary battery 110 can be charged and the electric load 182 can be supplied with electric power from the operation unit 142. It can be carried out. Further, it is possible to charge the above-mentioned lithium ion secondary battery 110 with electric power and supply electric power to the electric load 182 based on the information from the external device. Such a command can be issued from an external device, and the command is sent from the external device to the control circuit 150 via the information terminal 144.

The power supply device 100 includes a current measuring circuit 152 that measures the entire input or output current of the lithium ion secondary battery 110, the entire terminal voltage of the lithium ion secondary battery 110, and each cell constituting the lithium ion secondary battery 110. It is equipped with a voltage measuring circuit 154 that measures the terminal voltage and a temperature measuring device 156 that measures the surface and internal temperature of the lithium ion secondary battery 110, and constantly detects the state of the power supply device 100 and diagnoses the abnormal state. Is always done. The diagnosis history and measurement data are stored in the storage device 158, and can be read and confirmed at the time of maintenance and inspection, for example. The display device 160 is provided and can be used not only for input / output of information but also for displaying the operation mode and status of the power supply device 100.

2. Temperature rise operation mode When the power supply device 100 is placed in a low temperature environment, the internal temperature of the lithium ion secondary battery 110 also decreases, and as described above, the state of the electrolyte in each cell of the lithium ion secondary battery 110 changes. , The mobility of lithium ions in the electrolyte is reduced. As a result, the performance of the lithium ion secondary battery 110 deteriorates. The control circuit 150 can detect the temperature of the lithium ion secondary battery 110 by the temperature measuring device 156, and can detect the deterioration of the performance of the lithium ion secondary battery 110 due to the temperature decrease. Alternatively, the deterioration in the performance of the lithium ion secondary battery 110 due to the temperature decrease can also be detected from the detection values of the current measurement circuit 152 and the voltage measurement circuit 154.

The deterioration in the performance of the lithium ion secondary battery 110 due to the temperature decrease can be improved by raising the internal temperature of the lithium ion secondary battery 110. The power supply device 100 includes a discharge circuit 146 that allows the discharge current of the lithium ion secondary battery 110 to flow. By passing the current from the lithium ion secondary battery 110 through the discharge circuit 146, the internal temperature of the lithium ion secondary battery 110 can be raised. A temperature rise operation mode for raising the internal temperature of the lithium ion secondary battery 110 will be described with reference to FIG.

When the internal temperature of the lithium ion secondary battery 110 decreases, the performance of the lithium ion secondary battery 110 decreases accordingly. However, as an example, when it is desired to operate the lithium ion secondary battery 110 at −t1 ° C. or higher, the control circuit 150 first uses the temperature measuring device 156 to reduce the lithium ion 2 It is detected that the next battery 110 is in a state of −t1 ° C. or lower. Based on this detection, the control circuit 150 enters the temperature rise operation mode, and supplies a current from the lithium ion secondary battery 110 to the discharge circuit 146 via the internal connection circuit 140. The discharge circuit 146 is a circuit for passing a current for raising the temperature of the lithium ion secondary battery 110, and temporarily exceeds the maximum discharge current of the lithium ion secondary battery 110, or the maximum discharge of the lithium ion secondary battery 110. It is possible to pass a current several times, or even tens of times, the current. When such a large current is passed for a long time, there is a great danger, but when a large current is passed only for an extremely short period of time, it is dangerous because the internal temperature of the lithium ion secondary battery 110 is originally low. There is no sex.

Since the temperature of the lithium ion secondary battery 110 is lower than −t1 ° C. in FIG. 2, the temperature rise operation mode 20 is controlled, and the temperature rise current A1 that exceeds the maximum discharge current A0 of the lithium ion secondary battery 110. Is supplied from the lithium ion secondary battery 110 to the discharge circuit 146. As shown in Graph 1 of FIG. 2, the temperature of the lithium ion secondary battery 110 rises due to the flow of the temperature rise current A1. As a result, the temperature of the lithium ion secondary battery 110 becomes higher than −t1 ° C., and the normal operation mode 30 is controlled instead of the temperature rise operation mode 20. The discharge circuit 146 is separated from the lithium ion secondary battery 110 by the internal connection circuit 140, and the operating current A2 is supplied from the lithium ion secondary battery 110 to the electric load 182 via the internal connection circuit 140 and the external connection circuit 180. .. The operating current A2 changes according to the request from the electric load 182, but does not exceed the maximum discharge current A0.

As described above, the purpose of the temperature rise current A1 is to positively raise the internal temperature of the lithium ion secondary battery 110 in a short time, and in this embodiment, the maximum discharge current A0 of the lithium ion secondary battery 110 is used. The current exceeds. In order to pass such a large current, an electric load having a small resistance value is required, and a discharge circuit 146 is provided.

In FIG. 2, the current supply mode to the electric load 182 is illustrated as the normal operation mode 30, but the power supply mode from the charging power source 190 to the lithium ion secondary battery 110 may be used. In that case, the operating current A2 is a current in the direction opposite to the current shown in FIG.
3. 3. Explanation of Operation of Control Circuit 150 The operation of the control circuit 150 in the temperature rise operation mode 20 in the power supply device 100 will be described with reference to the control flowchart S500 shown in FIG. When the power supply device 100 itself is not used, it is not necessary to raise the temperature even if the temperature of the lithium ion secondary battery 110 is as low as -30 ° C, for example. Therefore, it is not necessary to operate the lithium ion secondary battery 110 based on the temperature rise operation mode 20 for raising the temperature of the lithium ion secondary battery 110. If there is no command from the information terminal 144 and there is no input related to the operation from the operation unit 142, the state is waiting for a command. In this state, the control circuit 150 confirms the presence or absence of an operation command to the control circuit 150 at regular intervals. If there is no special operation command, the temperature rise operation mode 20 is not performed in this embodiment.

When an operation command is input by the operator from the operation unit 142 or an operation command is received from another device via the information terminal 144, the control circuit 150 operates using the lithium ion secondary battery 110. Judge as necessary. The control circuit 150 determines in step S510 that there is an operation command, and the execution of the control circuit 150 shifts to step S512. In order to start the operation using the lithium ion secondary battery 110, it is necessary to detect the state of the lithium ion secondary battery 110, and in step S512, the state of the lithium ion secondary battery 110 is detected. .. Specifically, as an example, the current measurement circuit 152, the voltage measurement circuit 154, and the temperature measurement device 156 measure the state of the lithium ion secondary battery 110.

The measurement result in step S512 is recorded in the storage device 158. As described above, the storage device 158 stores not only the measurement data but also the past diagnosis results, and stores the history of the state of the lithium ion secondary battery 110 and the history of the measurement results. Therefore, it is possible to confirm the state change of the lithium ion secondary battery 110. Based on the measurement result in step S512, the measurement result before that, the change in the state, and the like, the safety determination of the lithium ion secondary battery 110 is made in step S514. If an abnormality is detected, step S515 is executed, the content of the abnormal state is displayed on the display device 160, and the control circuit 150 further controls to avoid the danger. Issue an alarm if necessary. As a control for avoiding danger, for example, the internal connection circuit 140 is operated to disconnect the lithium ion secondary battery 110 from other devices and circuits. As a result, there is a possibility that the above state of the lithium ion secondary battery 110 can be avoided.

When the control circuit 150 determines that the lithium ion secondary battery 110 is in a safe state from the measurement results and the previously measured data regarding the lithium ion secondary battery 110 in step S512, the execution of the control circuit 150 shifts to step S516. .. In step S516, it is determined whether or not the state of the lithium ion secondary battery 110 is in a low temperature state. To determine the low temperature state of the lithium ion secondary battery 110, for example, it is determined whether the temperature of the lithium ion secondary battery 110 is −t1 ° C. or lower as described in FIG. 2, and the lithium ion is determined in the state of −t1 ° C. or lower. It may be determined that the state of the secondary battery 110 is a low temperature state. Alternatively, it may be determined by another method.

When it is determined that the state of the lithium ion secondary battery 110 is a low temperature state, the performance of the lithium ion secondary battery 110 is deteriorated, and the control circuit 150 is connected to the control circuit 150 via the operation unit 142 and the information terminal 144. The control circuit 150 determines that the supported operation cannot be performed, and controls the temperature rise operation mode 20 for raising the temperature of the lithium ion secondary battery 110.

On the other hand, when the control circuit 150 determines that the state of the lithium ion secondary battery 110 is not a low temperature state, the execution operation of the control circuit 150 shifts from step S516 to step S517 and is supported via the operation unit 142 and the information terminal 144. , The operation using the lithium ion secondary battery 110 is performed. As this operation, for example, power is supplied from the lithium ion secondary battery 110 to the electric load 182, and the charging operation of the lithium ion secondary battery 110 that supplies the power from the charging power source 190 to the lithium ion secondary battery 110 is performed. is there.

When it is determined in step S516 that the state of the lithium ion secondary battery 110 is a low temperature state, the operation of the control circuit 150 shifts to step S520. In step S520, the display device 160 indicates that the temperature rise operation mode 20 is to be executed. As a result, the operator can know that the temperature rise operation mode 20 is executed before executing the normal operation mode 30, and further, when the temperature rise operation mode 20 ends, the normal operation mode 30 is executed. You can know. Further, the display device 160 also displays the scheduled execution time of the temperature rise operation mode 20.

FIG. 4 is a display screen of the display device 160, in which "the temperature rise operation mode 20 of the lithium ion secondary battery 110 is being executed" is displayed in the display column 162 as the execution mode, and the scheduled execution time is further displayed in the display column 164. To. Next, in step S520, the magnitude of the temperature rise current A1 is determined. When the temperature of the lithium ion secondary battery 110 is low, the temperature of the lithium ion secondary battery 110 can be raised in a short time by increasing the value of the temperature raising current A1. In step S522, the magnitude of the temperature rise current A1 is determined based on the measurement result. The scheduled end time of the temperature rise operation mode 20 in the display field 164 may be displayed in characters, but may also be displayed in a graph. In this case, the relationship between the executed time and the remaining time with respect to the scheduled time is displayed in a graph state.

The relationship between the temperature of the lithium ion secondary battery 110 and the temperature rise current A1 is shown in Graph 30 of FIG. The lower the temperature of the lithium ion secondary battery 110, the larger the value of the temperature rise current A1. Graph 20 shows the energization time of the temperature rise current A1 once. The lower the temperature of the lithium ion secondary battery 110, the longer the energization time of the temperature rise current A1. Graph 10 shows the number of pulses to be supplied. A current may be continuously passed during the energization time of the temperature rise current A1 shown in the graph 20, but a current pulse for a unit time is generated and the number of pulses corresponds to the energization time of the temperature rise current A1. May be good.

The relationship between the graph 30, the graph 20, and the graph 10, which are the data shown in FIG. 5, is stored in the storage device 158 in advance. Based on the data stored in the storage device 158 in advance in step S522, the current value of the temperature rising current A1, the energization time, or the number of pulse generations is determined, and the process is executed in step S524. For example, the discharge circuit 146 has a resistor, a semiconductor switching element, and a current control circuit, and the semiconductor switching element and the current control circuit of the discharge circuit 146 operate based on a command from the control circuit 150, and the determination is made in step S522. Control is executed.

The execution of the control circuit 150 returns to step S512 again, the state of 110 during the execution of the temperature rise operation mode 20 is measured in step S512, the safety is confirmed in step S514, and the temperature rise operation mode 20 is set in step S516. It is determined whether it should be terminated. Further, in step S522, the control content in the temperature rise operation mode 20 is determined in a state of reflecting the new measurement result regarding the lithium ion secondary battery 110, and is executed in step S524.

4. Effect of Example According to this embodiment, there is an effect that the temperature of the lithium ion secondary battery 110 can be raised in a short time. In addition, it has the effect of ensuring safety. The control contents of the graph 30, the temperature rise operation mode 20, and the graph 10 of FIG. 5 may be selectively executed or may be executed in combination. When the power supply device 100 is used in a cold region, in this embodiment, the lithium ion secondary battery 110 can be raised to a temperature at which the lithium ion secondary battery 110 normally operates in a short time. Therefore, there is an effect that it can be used as a power source for a lithium ion secondary battery even in a cold region.

10 ... Graph, 20 ... Graph, 30 ... Graph, 100 ... Power supply, 110 ... Lithium ion secondary battery, 140 ... Internal connection circuit, 142 ... Operation unit, 144 ... Information terminal, 146 ... Discharge circuit, 150 ... Control circuit, 152 ... Current measurement circuit, 154 ... Voltage measurement circuit, 156 ... Temperature measurement device, 158 ... Memory Device, 160 ... Display device, 162 ... Display column, 164 ... Display column, 180 ... External connection circuit, 182 ... Electric load, 190 ... Power supply for charging.

Claims (6)

The state of a lithium ion secondary battery that stores power supplied from the outside and supplies power by supplying a discharge current based on the stored power, a control circuit, and the lithium ion secondary battery is measured. It is a power supply device that includes a measurement circuit and operates so that the discharge current of the lithium ion secondary battery does not exceed a predetermined maximum discharge current value A0 from the viewpoint of safety in the normal operation mode. ,
The control circuit determines whether or not the state of the lithium ion secondary battery is lower than a predetermined temperature t1 based on the measurement result of the measurement circuit.
When the state of the lithium ion secondary battery is higher than the predetermined temperature t1, the control circuit selects the normal operation mode, and the maximum discharge from the lithium ion secondary battery based on the normal operation mode. A discharge current that does not exceed the current value A0 is supplied,
When the control circuit determines that the state of the lithium ion secondary battery is lower than the predetermined temperature t1, the control circuit selects the temperature rise operation mode and does not flow in the normal operation mode. A power supply device characterized in that a discharge current having a value exceeding the maximum discharge current value A0 is supplied from the lithium ion secondary battery. The power supply device according to claim 1 is provided with a storage device that stores the relationship between the temperature of the lithium ion secondary battery and the discharge current of the lithium ion secondary battery in the temperature rise operation mode.
When the temperature rise operation mode is selected by the control circuit, the temperature rise is based on the relationship between the temperature of the lithium ion secondary battery stored in the storage device and the discharge current of the lithium ion secondary battery. the value of the discharge current of the lithium ion secondary battery definitive the operation mode is determined, the power supply apparatus characterized by. The power supply device according to claim 1 or 2, wherein a discharge circuit including a current control circuit for passing a discharge current in the temperature rise operation mode is provided inside the power supply device. A power supply that is characterized by that. The power supply device according to claim 1 is provided with a storage device that stores the relationship between the temperature of the lithium ion secondary battery and the discharge time for flowing the discharge current of the lithium ion secondary battery in the temperature rise operation mode.
When the temperature rise operation mode is selected by the control circuit, it is based on the relationship between the temperature of the lithium ion secondary battery stored in the storage device and the discharge time for flowing the discharge current of the lithium ion secondary battery. The power supply device is characterized in that the discharge time for passing the discharge current of the lithium ion secondary battery in the temperature rise operation mode is determined. The power supply device according to claim 1 or 4, characterized in that a discharge circuit including a semiconductor switching element for passing a discharge current in the temperature rise operation mode is provided inside the power supply device. Power supply. In the power supply device according to any one of claims 1 to 5, when a display device is provided and the temperature rise operation mode is selected by the control circuit, the display device executes the temperature rise operation mode. A power supply that is characterized by being displayed as.

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