JP6540998B2 - Vehicle secondary battery system - Google Patents

Description

  The present invention relates to a vehicle secondary battery system.

  JP-A-2013-149471 discloses a method of repeatedly charging and discharging mutually among a plurality of secondary batteries to raise the temperature of the secondary battery. In this method, it is supposed that the temperature of the secondary battery is raised while the power loss is suppressed.

JP, 2013-149471, A

  By the way, the secondary battery is widely used in vehicle applications. Examples of vehicle applications include hybrid vehicles, plug-in hybrid vehicles, electric vehicles and fuel cell vehicles. In such a vehicle application, a secondary battery is used as a power supply which electrically stores energy, outputs it to a drive motor, and applies a driving force to wheels. In such applications, since it is mainly used outdoors, it may be used in a cryogenic environment such as below -30 ° C. in cold regions and the like. Under a very low temperature environment where the temperature is lower than -30 ° C, the viscosity of the electrolyte of the secondary battery is high, and the output of the secondary battery tends to decrease rapidly as the temperature decreases. Furthermore, in a very low temperature environment where the temperature is lower than -30.degree. C., the secondary battery is likely to be deteriorated due to high rate charging and discharging. Moreover, in the said vehicle use, a large output is calculated | required especially at the time of start to the secondary battery used as a power supply output to a drive motor.

  In view of the specific problems in such vehicle applications, the present inventor is useful if it is possible to raise the temperature early while suppressing the power loss when it can be used in a very low temperature environment below -30 ° C. I believe there is. In the case of adopting a method in which the temperature of the secondary battery is raised by repeatedly charging and discharging each other among a plurality of secondary batteries, the temperature of the secondary battery rises more rapidly as the charging current value and the discharging current value are increased. Do. For this reason, it is desirable to repeat charging and discharging with a current value as large as possible. On the other hand, in a very low temperature environment where the temperature is lower than -30.degree. C., the secondary battery is likely to be deteriorated if charging and discharging at high rates where the charging current value and the discharging current value are large are repeated. For this reason, in the case of adopting a method in which the temperature of the secondary battery is raised by repeatedly charging and discharging mutually among a plurality of secondary batteries, in particular, the temperature should be rapidly raised from a very low temperature environment such as -30.degree. And, there is a trade-off relationship between minimizing deterioration of the secondary battery.

  The vehicle secondary battery system proposed herein includes a plurality of secondary batteries to be controlled, a temperature sensor, a voltmeter or an SOC detector, a charge / discharge device, and a control device. Here, the temperature sensor is a sensor that acquires temperature information on a plurality of secondary batteries. The voltmeter is a device that detects the voltage of each of the plurality of secondary batteries. The SOC detection unit is a device that detects an SOC of each of a plurality of secondary batteries. Here, SOC is an abbreviation of State of Charge, and means a remaining capacity. The charge and discharge device is a device that is electrically connected to a plurality of secondary batteries, and charges another secondary battery with power discharged from a part of the plurality of secondary batteries. When the temperature of the plurality of secondary batteries detected based on the temperature information acquired by the temperature sensor is lower than a predetermined temperature of -30.degree. A process S1 of setting a charging current value at the time of charging the secondary battery and a process S2 of performing charging and discharging between a plurality of secondary batteries by the charge / discharge device are performed. Here, in the process S1, the temperature sensor obtains the relationship between the temperature, the voltage or the SOC, and the maximum current value at which lithium is not deposited as charging is performed by the temperature sensor based on a predetermined map. The maximum current value corresponding to the temperatures of the plurality of secondary batteries detected based on the stored temperature information and the voltage obtained by the voltmeter or the SOC obtained by the SOC detection unit is obtained, and the maximum current value As the charging current value.

  By such control, the charge current value at the time of charge can be appropriately controlled, and the temperature rise from a very low temperature environment such as -30.degree. C. can be quickly raised while suppressing the deterioration of the secondary battery small. The output of the battery can be improved.

FIG. 1 is a schematic view schematically showing a vehicle secondary battery system proposed here. FIG. 2 is a schematic view showing a configuration example of the map M. As shown in FIG. FIG. 3 is a flowchart showing an example of the control flow of the control device. FIG. 4 is a graph schematically showing the transition of the temperature and voltage of the plurality of secondary batteries A and B and the charge and discharge operation. FIG. 5 is a graph schematically showing the transition of the temperature and voltage of the plurality of secondary batteries A and B and the charge and discharge operation.

  Hereinafter, one embodiment will be described for the vehicle secondary battery system proposed here. The embodiments described herein are, of course, not intended to limit the present invention. Further, each drawing is schematically drawn, and for example, dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

  FIG. 1 is a schematic view schematically showing a vehicle secondary battery system proposed here. The vehicle secondary battery system 100 proposed here includes a plurality of secondary batteries A and B to be controlled, temperature sensors A1 and B1, voltmeters A2 and B2, a charge / discharge device C, and a control device. It has D and. In the following description, FIG. 1 is appropriately referred to for each member of the vehicle secondary battery system 100, and the reference numerals of FIG. 1 are appropriately given and described.

  The plurality of secondary batteries A and B to be controlled are, for example, non-aqueous electrolyte secondary batteries, and typically, lithium ion secondary batteries. Each of the plurality of secondary batteries A and B may be a single battery, or may be an assembled battery in which a plurality of cells are combined into one set. Furthermore, the plurality of secondary batteries A and B may be a battery group (not limited to the assembled battery) formed of a plurality of single batteries, or may be a assembled battery group formed of a plurality of assembled batteries.

  In such a non-aqueous electrolyte secondary battery, the viscosity of the electrolyte solution of the secondary battery is high in a low temperature environment below -30 ° C., and the output of the secondary battery is difficult to increase. Furthermore, the secondary battery is likely to deteriorate due to high rate charging and discharging. For example, in a lithium ion secondary battery, under a very low temperature environment lower than -30 ° C., an event of precipitation of lithium in an electrolyte solution is likely to occur during high rate charging and discharging. When lithium is deposited and part of it is immobilized, lithium ions contributing to the battery reaction are reduced, and the battery capacity is reduced. For this reason, the deposition of lithium is one of the factors that degrade the battery capacity. Here, according to the findings of the present inventor, lithium is likely to be deposited on the negative electrode surface in a very low temperature environment below -30 ° C., particularly when charging at a high rate.

  In a vehicle application, the plurality of secondary batteries A and B are used as a power supply that electrically stores energy generated in the vehicle and outputs the energy to a drive motor that applies a driving force to the wheels. As shown in FIG. 1, in a vehicle application, a plurality of secondary batteries A and B are connected to a generator and an electric motor (not shown) via a power supply control device E. Moreover, although illustration is abbreviate | omitted, the generator and the electric motor are further connected to the driving wheel through a power distribution mechanism and a reduction gear.

  The temperature sensors A1 and B1 are sensors for acquiring temperature information on the plurality of secondary batteries A and B. Here, the temperature sensors A1 and B1 may be attached to predetermined positions of the plurality of secondary batteries A and B (for example, predetermined positions on the battery side surfaces), or a plurality of secondary batteries A , B may be arranged at the arranged positions. The temperature sensors A1 and B1 are connected to the control device D by signal lines A1a and B1a, respectively.

  The voltmeters A2 and B2 are devices that respectively detect voltages of a plurality of secondary batteries A and B. For example, the voltage may be detected based on a voltmeter electrically connected in parallel to the plurality of secondary batteries A and B. The voltmeters A2 and B2 are connected to the control device D by signal lines A2a and B2a, respectively. Here, secondary batteries A and B have a correlation between voltage (open circuit voltage: OCV) and SOC (remaining capacity).

  In the example shown in FIG. 1, although voltmeters A2 and B2 are adopted, the processing units that detect voltage based on voltmeters A2 and B2 and voltmeters A2 and B2 are secondary battery A in control device D, respectively. , And B can be replaced by SOC detection units A3 and B3. Here, various methods that can infer the SOC of the plurality of secondary batteries A and B can be employed as the SOC detection units A3 and B3. For example, the SOC may be inferred from a map prepared in advance based on voltage, temperature, capacity deterioration rate and the like detected based on the voltmeters A2 and B2. Also, the secondary battery may be adjusted to a predetermined SOC, and the remaining capacity may be calculated based on the difference between the amount of current input thereafter and the amount of current output based on the SOC. Good. It should be noted that if an appropriate correlation is not found between the open circuit voltage and the SOC in the use range of a plurality of secondary batteries A, B (in other words, it is difficult to infer the SOC from the open circuit voltage) ) May adopt the SOC detected by the SOC detection units A3 and B3.

  The charge / discharge device C is electrically connected to the plurality of secondary batteries A and B, respectively, and the other secondary batteries are discharged by the power discharged from some of the plurality of secondary batteries A and B. To charge. For example, when the secondary battery A is discharged from the plurality of secondary batteries A and B, for example, the charge / discharge device C charges the secondary battery B with the electric power. When the charge and discharge device C is discharged from the secondary battery B, the charge and discharge device C charges the secondary battery A with the electric power. About the structural example of such a charge / discharge apparatus C, it is disclosed as "the charge / discharge means 12" in the paragraph 0015 of the patent document 1, the paragraph 0016, and FIG. 2, for example. Therefore, the structure of the charge / discharge device C is not disclosed in detail. As described above, the charge / discharge device C is electrically connected to the plurality of secondary batteries A and B, respectively, and is discharged from some of the plurality of secondary batteries A and B. It is only necessary to realize the function of charging other secondary batteries by electric power, and is not necessarily limited to the structure disclosed by Patent Document 1.

  The control device D is a computer that includes an arithmetic device and a storage device and performs electrical processing in accordance with a predetermined program. Each process performed by control device D may be embodied by such a computer. Here, the control device D is illustrated separately from the power control device E, but may not necessarily be separate from the power control device E. For example, the control device D may be incorporated in the power control device E such that the process embodied by the control device D is embodied as one function of the power control device E. Further, the control device D may be incorporated into another control unit mounted on the vehicle besides the power supply control device E.

  Here, the control device D detects the temperatures of the plurality of secondary batteries A and B based on the temperature information acquired by the temperature sensors A1 and B1. And temperature T1 of a plurality of detected rechargeable batteries A and B is memorized by control device D with time when temperature information was detected. Further, the voltages of the plurality of secondary batteries A and B are detected based on the voltage information obtained by the voltmeters A2 and B2. And voltage V1 of a plurality of detected rechargeable batteries A and B is memorized by control device D with time when voltage information was detected.

The control device D determines whether or not the detected temperatures T1 of the plurality of secondary batteries A and B are lower than a predetermined temperature Xt of -30 ° C or less (T1 < Xt). And when temperature T1 of several secondary batteries A and B is lower than predetermined temperature Xt below -30 degreeC, the following processes S1 and S2 are performed.

  Here, the process S1 is a process of setting the charging current value when the charge / discharge device C charges another secondary battery. The process S2 is a process of causing the charge and discharge device C to perform charging and discharging between the plurality of secondary batteries A and B. Here, process S2 is suitably called "a temperature rising process."

  The control device D is provided with a map M in which the relationship among the temperature, the voltage or the SOC, and the maximum current value at which lithium is not deposited with charging is predetermined for the plurality of secondary batteries A and B. Then, based on the map M, based on the temperature information obtained by the temperature sensors A1 and B1, the maximum corresponding to the temperatures of the plurality of secondary batteries A and B and the voltages obtained by the voltmeters A2 and B2. The current value is obtained, and the maximum current value is taken as the charging current value.

  FIG. 2 is a schematic view showing a configuration example of the map M. As shown in FIG. In the map M illustrated in FIG. 2, the SOC and the voltage are set on the vertical axis, and the temperature is set on the horizontal axis. A predetermined maximum current value is stored in each square of the map M defined by the voltage (or SOC) and the temperature. Here, the maximum current value is the maximum value found by a test previously performed on the basis of the temperature specified by the grid and the voltage or the SOC, in which lithium does not reliably precipitate with charging. The current value may be stored. For example, in consideration of the safety factor (for example, 80%), a current value slightly lower than the maximum current value at which lithium deposition was not found by the previously performed test is set as “maximum current value” in Map M. It may be stored. By setting the "maximum current value" in this manner, it is possible to set a current value at which lithium is not more reliably deposited as charging is performed. Note that FIG. 2 schematically shows a configuration example of the map M, and in practice, it is preferable that grids be set more finely with respect to the SOC, the voltage, and the temperature. Further, the vertical axis may be defined by either SOC or voltage.

  Under the control of the control device D, the above-described processes S1 and S2 are performed in a very low temperature environment where the outputs of the secondary batteries A and B may fall below -30 ° C. Under the present circumstances, in process S1, the current value according to temperature and voltage is set so that lithium may not precipitate certainly with charge. Then, when the charge and discharge device C mutually charges and discharges the plurality of secondary batteries A and B in the processing S2, the charging is performed with the charging current value set in the processing S1. As described above, in the secondary batteries A and B, charging and discharging are repeated between the plurality of secondary batteries A and B, depending on the maximum current value and to the extent that lithium does not precipitate. As a result, it is possible to quickly discontinue the plurality of secondary batteries A and B from a very low temperature state where the output falls below -30 ° C while suppressing the deposition of lithium.

  FIG. 3 is a flowchart showing an example of the control flow of the control device. The control device D detects the temperatures and voltages of the plurality of secondary batteries A and B as shown in FIG. 3 (S101). Here, the temperature is detected based on the temperature information obtained by the temperature sensors A1 and B1. The voltage is detected based on the voltage information obtained by the voltmeters A2 and B2.

  In the flowchart of FIG. 3, it is determined whether the detected voltage V1 (OCV) of the plurality of secondary batteries A and B is higher than a predetermined voltage Xv (S102). In this determination process, when the open circuit voltages of the plurality of secondary batteries A and B are not higher (lower) than the predetermined voltage Xv (No), the plurality of secondary batteries A and B are charged with one another. After all, even if the temperature is raised, the output of the secondary battery is limited due to the power loss due to the discharge. When the detected voltage V1 is different among the plurality of secondary batteries A and B, the highest voltage among the detected voltages may be adopted as the “voltage V1” in the determination process S102. That is, although there is no margin in the capacity of one secondary battery among the plurality of secondary batteries A and B, when there is a margin in the other secondary battery, it is possible to start with the battery having the spare capacity. It is preferable to start control to repeat charging and discharging mutually among a plurality of secondary batteries so that a battery which is discharged and can not be spared is charged.

  Further, when the highest voltage V1 among the detected voltages is not higher than the predetermined voltage Xv (No), charging and discharging are repeated mutually between the plurality of secondary batteries A and B. Even if the temperature of the secondary battery is raised, the outputs of the secondary batteries A and B are limited. Therefore, the control may be ended as shown by the solid arrows in FIG. Further, as shown by the broken arrow in FIG. 3, the process may be returned to the process S101 again. When the process returns to step S101, the voltages of the plurality of secondary batteries A and B are detected (S101), and it is determined whether the detected voltage V1 is higher than a predetermined voltage Xv (S102). In this manner, the secondary batteries A and B may be charged and wait for the capacity of the secondary batteries A and B to recover.

  Then, if the detected voltage V1 is higher than the predetermined voltage Xv (Yes), it is determined whether the detected temperature T1 is lower than the predetermined temperature Xt (S103). The threshold value Xt can be arbitrarily set at a temperature of -30 ° C or less. The temperature Xt (threshold value) may be set, for example, to a temperature at which a sharp drop in output due to the temperature is recognized in the plurality of secondary batteries A and B to be controlled. If the temperature detected in the processing S101 varies among the plurality of secondary batteries A and B, the lowest temperature among the detected temperatures may be used as the temperature T1 used in the determination processing. Thus, based on the temperature of the secondary battery having the lowest temperature among the plurality of secondary batteries A and B, it is determined whether the temperature raising process (S2) is to be performed. For example, when there is a secondary battery whose output does not easily increase at a very low temperature of about -30.degree. C. among the plurality of secondary batteries A and B, the process (S2) of raising the temperature of the secondary battery is performed. Can be controlled to

  If it is determined in the process S103 that the detected temperature T1 is lower than the predetermined temperature Xt (Yes), as described above, the process of setting the charging current value C1 (S1), and the temperature raising process ( S2) is performed in order. If it is determined in the process S103 that the detected temperature T1 is not lower than the predetermined temperature Xt (No), it is determined whether the present control is to be ended (S104). Then, when it is determined that the control is not ended (No), the process may be returned to the process S101 of detecting the temperature and the voltage. If it is determined that the control is to be ended (Yes), this control may be ended. Here, as a determination condition for determining whether or not to end the present control, it is preferable to arbitrarily set a condition appropriate for ending the present control.

  FIG. 4 is a graph schematically showing the transition of the temperature and voltage of the plurality of secondary batteries A and B and the charge and discharge operation. In FIG. 4, the plurality of secondary batteries A and B are left in a very low temperature environment lower than −30 ° C. in a state where they have a required remaining capacity. In this case, the temperatures of the plurality of secondary batteries A and B gradually decrease with time. Then, at timing P1 at which the detected temperature T1 is determined to be lower than the predetermined temperature Xt, the maximum charging current value C1 is set in a range in which lithium is not deposited by charging (S1). Then, temperature increase processing (S2) is performed in which the charge and discharge device C repeatedly charges and discharges each other between the plurality of secondary batteries A and B to raise the temperature of the secondary battery. In the charging of the temperature rising process (S2), charging is performed with the charging current value C1 set in the process S1. As a result, even when the battery is left in a very low temperature environment lower than -30.degree. C., the temperature of the plurality of secondary batteries A and B is raised at an early stage while suppressing the deposition of lithium, and the output It can be improved.

  Moreover, FIG. 5 is a graph which shows typically transition of the temperature of the some secondary batteries A and B, a voltage, and charging / discharging operation | movement. In FIG. 5, initially, the plurality of secondary batteries A and B are left in a cryogenic environment such as below -30 ° C. without having the required remaining capacity. For this reason, the temperature T1 detected in the plurality of secondary batteries A and B gradually decreases. Thereafter, charging is started at the timing of Q1. Here, a state of being connected to a charging power source is estimated as in a plug-in hybrid vehicle. By this charging, the capacities of the plurality of secondary batteries A and B gradually recover. Then, at timing Q2 at which the capacities of the plurality of secondary batteries A and B exceed a certain voltage Xv (threshold value), the maximum charging current value C1 is set in a range in which lithium is not deposited by charging (S1). Then, temperature increase processing (S2) is performed in which the charge and discharge device C repeatedly charges and discharges each other between the plurality of secondary batteries A and B to raise the temperature of the secondary battery. In the charging of the temperature rising process (S2), charging is performed with the charging current value C1 set in the process S1. As a result, even when the battery is left in a very low temperature environment lower than -30.degree. C., the temperature of the plurality of secondary batteries A and B is raised at an early stage while suppressing the deposition of lithium, and the output It can be improved.

According to a test conducted by the inventor, the following results were confirmed by adopting the vehicle secondary battery system proposed here.
Test: From the state of the battery temperature of -32 ° C at an ambient temperature of -33 ° C, the plurality of secondary batteries are mutually charged by an appropriate charge current value C1 set in the process S1 of setting the charge current value And the discharge was repeated to perform a temperature raising process S2 for raising the temperature of the secondary battery.
Result: At an ambient temperature of -33 ° C, the battery temperature reached -27 ° C. Here, the battery temperature rose by about 5 ° C. in a relatively short time of about 1000 seconds. At this time, the output of the secondary battery was approximately 96 W when the battery temperature was -32 ° C, but the output of the secondary battery improved to approximately 116 W when the battery temperature was -27 ° C. Thus, the output improvement can be confirmed by performing the temperature rising process S2 with the appropriate charging current value C1. Further, in the control, in the temperature raising process (S2), the charging current value C1 is appropriately managed so as to suppress the deposition of lithium. Therefore, the capacity retention rates of the secondary batteries A and B hardly deteriorate before and after the temperature raising process (S2).

  As mentioned above, although one Embodiment was described about the secondary battery system for vehicles proposed here, the secondary battery system for vehicles proposed here is not limited to embodiment mentioned above unless it mentions in particular.

100 Vehicle secondary battery system A, B Secondary battery A1, B1 Temperature sensor A2, B2 Voltmeter A3, B3 Detection part C Charge / discharge device D Control device E Power supply control device

Claims (1)

Several secondary batteries to be controlled,
A temperature sensor for acquiring temperature information on the plurality of secondary batteries;
A voltmeter for detecting a voltage of each of the plurality of secondary batteries ;
An SOC detection unit that detects an SOC of each of the plurality of secondary batteries;
A charge / discharge device electrically connected to each of the plurality of secondary batteries and charging another secondary battery by the electric power discharged from a part of the plurality of secondary batteries;
Equipped with a control unit,
The controller is
Of the voltages of the plurality of secondary batteries detected by the voltmeter, the highest voltage is higher than a predetermined voltage Xv, and among the temperatures of the plurality of secondary batteries detected by the temperature sensor If the lowest temperature is lower than a predetermined temperature Xt below -30.degree. C.,
A step S1 that pre KiTakashi discharge device sets the charge current value in charging the other battery,
By the rechargeable device, have rows and step S2 to perform the charge and discharge between said plurality of secondary batteries, and,
When the lowest temperature among the temperatures of the plurality of secondary batteries detected by the temperature sensor is not lower than the temperature Xt, the present control is ended under a predetermined condition.
Is configured as
Here, in the process S1,
The relationship between the temperature, the voltage or the SOC, and the maximum current value at which lithium does not precipitate with charging for the plurality of secondary batteries is predetermined based on a map.
Depending on the temperature of the plurality of secondary batteries detected based on the temperature information obtained by the temperature sensor and the voltage obtained by the voltmeter or the SOC obtained by the SOC detection unit , along with charging Obtain the maximum current value that lithium does not precipitate ,
Let the maximum current value be the charging current value,
Vehicle secondary battery system.

Images