Charging and discharging control method of secondary battery

Abstract

To safely and efficiently control a voltage range to be used according to a state of a battery.SOLUTION: A charging and discharging control method of a secondary battery, comprises: a step (S1) of measuring a lithium ion secondary battery, to acquire information on a measurement current AM[A], a measurement voltage VM[V], and measurement temperature TM[°C]; a step (S2) of estimating an estimated voltage VES[V] by a battery model; a step (S3) of correcting the battery model; a step (S4) of, in a case where a current flows in a range of a constant current I [A] for a predetermined set time t1 [s], collecting samples of a combination of an input / output power amount P[Wh] for the set time t1[s] and a charge / discharge end voltage VE [V] at the end for each SOC of S [%]; steps (S6 and S7) of deriving an actual relationship between the input / output power amount P[Wh] and the charge / discharge end voltage VE [V] for each SOC of S [%]; and steps (S8 and S9) of setting an allowable maximum discharge power amount PDmax[Wh] based on the actual power relationship as an input / output power limit value.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for controlling charge and discharge of a secondary battery, and more particularly to a method for controlling charge and discharge of a secondary battery that safely and efficiently controls the voltage range to be used according to the state of the battery.

Background Art

[0002] In secondary batteries, particularly in driving lithium-ion secondary batteries mounted on electric vehicles or hybrid vehicles, charge and discharge are performed with a large current during sudden acceleration, regenerative current due to braking, rapid charging, etc. At the design stage of such secondary batteries, the manufacturer estimates the actual capacity or actual capacity value representing the approximate usage time and service life under the assumed conditions. The upper and lower limit voltages are set according to the actual capacity of the secondary battery assumed by the manufacturer, and based on these upper and lower limit voltages, a power limit, which is a limit on power in charge and discharge, is provided to control charge and discharge.

[0003] However, in the case of a secondary battery with a usage history, it may be used under conditions different from those assumed by the manufacturer, and the actual capacity at that time is also unknown. If charge and discharge are controlled based on the initially set upper and lower limit voltages and power limit when the actual capacity is unknown, it may not be appropriate control in terms of battery life and efficiency.

[0004] Therefore, for example, in Patent Document 1, in a charging power limit value calculation device that obtains a charging power limit value for a battery for supplying vehicle driving power, a battery state quantity is obtained based on the detection result of a usage state detection unit that detects the power transfer state of the battery. Further, the chargeable power when the battery is charged with the charging current limit value is obtained based on the battery state quantity. Further, the chargeable power when the battery is charged with the charging voltage limit value is obtained based on the battery state quantity. At the same time, the chargeable power is selected according to the comparison result between the output voltage and the charging voltage limit value, and a chargeable power characteristic indicating the time change of the chargeable power is obtained based on the selection result. With such an invention, the charging power limit value can be optimally obtained according to the usage conditions of the battery.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the invention disclosed in Patent Document 1, the discharge power limit value is estimated based on the battery state estimated from the measured values, but the limit value is not calculated from the error between the estimated value and the measured value of the battery model, so the versatility is low.

[0007] The problem to be solved by the charge and discharge control method of the secondary battery of the present invention is to safely and efficiently control the charge and discharge according to the state of the battery within the range of the voltage used.

Means for Solving the Problems

[0008] To solve the above problems, in the charge and discharge control method of the secondary battery of the present invention, it is a charge and discharge control method of the secondary battery by a control device, and the control device measures and acquires the measured current A M [A], measured voltage V M [V], measured temperature T M [°C] in the information acquisition step of acquiring information, and based on the measured current A M [A], measured temperature T M [°C] information, the estimated voltage V ES [V] is estimated by the battery model in the battery voltage estimation step, and the measured voltage V M [V] acquired in the information acquisition step and the estimated voltage V ESA step of correcting the battery model of the secondary battery by comparing with [V], and when a current I [A] flows through the secondary battery within a set time t1 [s] and within a range of a constant current I [A], the input / output power amount P [Wh] during the set time t1 [s] and the charge / discharge cut-off voltage V at the end E A step of collecting samples by dividing samples of the combination of [V] for each SOC: S [%] of the secondary battery, and a plurality of the input / output power amounts P [Wh] and the charge / discharge cut-off voltage V collected in the step of collecting samples E From [V] and the SOC: S [%], a step of deriving an actual power relationship between the input / output power amount P [Wh] and the charge / discharge cut-off voltage V for each SOC: S [%] E From the actual power relationship, a maximum allowable discharge power amount PD that can be tolerated without falling below a set allowable lower limit voltage V [V] when the secondary battery is at a specific SOC: S [%] L [Wh], or a maximum allowable charge power amount PC that can be tolerated without exceeding a set allowable upper limit voltage V [V] max [Wh], and a step of determining an input / output power limit value by setting it as an input / output power limit value H [V] max Characterized by executing the steps described above.

[0009] Based on the maximum allowable discharge power amount PD [Wh] determined in the step of determining the input / output power limit value, the allowable lower limit voltage V [V] is set by the battery model, or based on the maximum allowable charge power amount PC [Wh], an allowable upper and lower limit voltage value setting step of setting the allowable upper limit voltage V [V] by the battery model can be further provided. max [Wh] L [V], or max [Wh] H [V]

[0010] In the step of estimating the battery voltage, the battery model may estimate the estimated voltage V [V] by an equivalent circuit. ES [V] In the step of correcting the battery model, the measured voltage V [V] obtained in the step of obtaining information and the estimated voltage V estimated in the step of estimating the battery voltage M [V]ES Based on the voltage difference ΔV [V] with [V], the battery model of the secondary battery may be corrected by correcting the set value of the battery model so as to eliminate the voltage difference ΔV [V].

[0011] In the step of sample collection, the set time t1 [s] for measuring the current I [A] in the secondary battery may be 5 [s] or more. In the step of sample collection, the range of the current I [A] in the secondary battery may be in the range of ±10 [%].

[0012] In the step of sample collection, the SOC: S [%] of the secondary battery may collect samples by dividing the band of SOC [%] assumed to be used into a plurality of bands. In the step of deriving the strength relationship, the plurality of input / output power amounts P [Wh] collected in the step of sample collection and the charge / discharge cut-off voltage V E [V] and the SOC: S [%] may be plotted on a double logarithmic graph.

[0013] In the step of determining the input / output power limit value, the input / output power amount P [Wh] is estimated from the charge / discharge cut-off voltage V E [V] by an approximate straight line obtained by the least squares method for the points plotted on the double logarithmic graph.

[0014] When the secondary battery is at the SOC: S [%], the maximum power amount P L [Wh] that can be tolerated without falling below the set allowable lower limit voltage V max [V] or the maximum power amount P H [Wh] that can be tolerated without exceeding the set allowable upper limit voltage V max [V] may be set as the input / output power limit value.

[0015] The approximate straight line is the allowable lower limit voltage V L [V] or the allowable upper limit voltage V HIt preferably includes [V], and the estimation of the input / output power amount P [Wh] is calculated by interpolation. The usage range of the secondary battery is such that the allowable upper limit voltage V H [V] is not exceeded, and the allowable lower limit voltage V L [V] is not fallen below. When this is done, the allowable upper limit voltage V H [V] < allowable lower limit voltage V L In order to ensure the preset minimum charge / discharge voltage range [V] so that it does not become the allowable upper limit voltage V H [V] + minimum charge / discharge voltage range [V], the steps of the usage charge / discharge voltage range guard for correcting the allowable upper limit voltage V L [V] and the allowable lower limit voltage V

[0016] In the step of sample collection, for each SOC: S [%] of the secondary battery, the input / output power amount P [Wh] of the collected time t1 and the charge / discharge termination voltage V E [V] of the combination of samples do not satisfy the specified dispersibility. When this is the case, the estimated voltage V ES [V] and the measured voltage V M [V] collect the voltage difference ΔV [V] between them. When the voltage difference ΔV [V] is greater than the set threshold V th [V], add the voltage difference ΔV [V] to the allowable lower limit voltage V L [V], and further provide a step of setting the allowable voltage range to change so as to subtract the voltage difference ΔV [V] from the allowable upper limit voltage V H [V].

[0017] The secondary battery can be preferably implemented when it is a lithium-ion secondary battery. Further, the secondary battery can be preferably implemented when it is mounted on a stationary power storage system or a vehicle and used for driving.

Effect of the Invention

[0018] According to the charge / discharge control method of the secondary battery of the present invention, the charging and discharging can be safely and efficiently controlled according to the state of the battery within the range of the voltage to be used.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0020] (Outline of this embodiment) Hereinafter, a charge / discharge control method for a secondary battery of the present invention will be described with reference to FIGS. 1 to 8 by way of an example of a charge / discharge control method for a lithium-ion secondary battery 1 mounted on a vehicle. In this embodiment, an example of an in-vehicle lithium-ion secondary battery 1 will be used for the description, but the present invention is not limited thereto.

[0021] <Principle of the Invention of this Embodiment> When controlling the charge and discharge of the lithium-ion secondary battery 1 according to this embodiment, when charging and discharging the lithium-ion secondary battery 1 with unknown usage history or the like, there may be a case where the allowable limit of the input / output power amount P [Wh] that can be used is unknown. For example, the currently set maximum allowable discharge power amount PD max [Wh] may be set higher than the actual capacity. Or, the currently set maximum allowable charge power amount PC max [Wh] may be set higher than the actual capacity. Note that the maximum allowable discharge power amount PD max [Wh] and the maximum allowable charge power amount PC max [Wh] may be collectively referred to as the maximum allowable power amount P max [Wh].

[0022] Here, the "capacity" refers to the charge and discharge performance that can be expected at that time in the case of the normal usage mode set by this lithium-ion secondary battery 1. If this capacity is overestimated, when discharging up to the currently set maximum allowable discharge power amount PD max [Wh], the allowable lower limit voltage V of the lithium-ion secondary battery 1 L [V] may be exceeded. Similarly, when charging up to the currently set maximum allowable charge power amount PC max [Wh], the allowable upper limit voltage V of the lithium-ion secondary battery 1 H [V] may be exceeded.

[0023] Here, the "allowable lower limit voltage V L [V]" is the lowest battery voltage V [V] set including a predetermined margin to protect the lithium-ion secondary battery 1 from over-discharge or the like. In this embodiment, it is set to 3.0 [V]. Also, the "allowable upper limit voltage V H [V]" is the highest battery voltage V [V] set including a predetermined margin to protect the lithium-ion secondary battery 1 from over-charge or the like. In this embodiment, it is set to 4.2 [V]. Therefore, the charge and discharge control method of the lithium-ion secondary battery 1 according to this embodiment is to safely and efficiently control the charge and discharge by controlling the range of the battery voltage V [V] used according to the state of the battery.

[0024] <Overview of this embodiment> Therefore, in the method for controlling charging and discharging of the lithium-ion secondary battery 1 by the control device 18 of this embodiment, control is performed according to the following general procedure. First, in the information acquisition step (FIG. 8: S1), the control device 18 measures the lithium-ion secondary battery 1 to obtain the measured current A M [A], the measured voltage V M [V], and the measured temperature T M [°C]. Next, in the battery voltage estimation step (S2), based on the measured current A M [A] and the measured temperature T M [°C] obtained in the information acquisition step (S1), the estimated voltage V ES [V] is estimated by the battery model M (FIG. 3). In the battery model correction step (S3), the measured voltage V M [V] obtained in the information acquisition step (S1) is compared with the estimated voltage V ES [V] estimated in the battery voltage estimation step (S2) to correct the battery model M of the lithium-ion secondary battery 1. That is, the calibration of the battery model M is always performed here. In the sample collection step (S4), it is executed when a current I [A] flows through the lithium-ion secondary battery 1 within a certain current I [A] range for a set time t1 [s]. Samples of the combination of the input / output power P [Wh] at the set time t1 [s] and the charge / discharge cut-off voltage V E [V] at the end are collected separately for each state of charge SOC: S [%] of the lithium-ion secondary battery 1.

[0025] In the actual performance relationship derivation steps (S6, S7), the actual sample points are output to a double logarithmic graph (S6), and an internal and external interpolation formula is calculated from the plot of the graph (S7). From the data of the plurality of input / output power amounts P [Wh], charge / discharge cut-off voltages V E [V], and SOC: S [%] collected in the sample collection step (S4), the actual performance relationship between the input / output power amount P [Wh] and the charge / discharge cut-off voltage V E [V] for each SOC: S [%] is derived.

[0026] In the steps of determining the input / output power limit values (S8, S9), at the end of charging (discharging), the power reaching the minimum voltage (3V in the representative diagram) within the usable range of the battery is obtained (S8), and the power is restored using the formula "exp{In(power)} = power" (S9). From the actual power relationship, the maximum allowable discharge power amount PD L [Wh] of the lithium-ion secondary battery 1 at its SOC: S [%] does not fall below the set allowable lower limit voltage V max [V], and the maximum allowable charge power amount PC H [Wh] that does not exceed the set upper limit voltage V max [V] are set. Such a maximum allowable power amount P max [Wh] is set as the input / output power limit value.

[0027] In the steps of setting the allowable upper and lower limit voltage values (Fig. 8: S10, Fig. 9: S11), the calculated power is input to the current battery model, the voltage at the end of charging (discharging) is calculated (S10), and the calculated voltage is set as the upper (lower) limit (S11). Based on this maximum allowable power amount P max [Wh], the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] are set using the battery model M calibrated in the battery model correction step (S3). In this case, the maximum allowable power amount P max [Wh], which is a so-called power limit, can be adjusted to an appropriate value in the operation of the vehicle. That is, based on the maximum allowable power amount P max [Wh] corresponding to the actual situation of the vehicle operation, the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] are set. In this embodiment, such correction is always performed using the battery model M calibrated in the battery model correction step (S3), so it can be adjusted immediately, flexibly, and with high accuracy.

[0028] (Configuration of this embodiment) <Configuration of the lithium-ion secondary battery 1> FIG. 4 is a perspective view showing an outline of the external configuration of the lithium-ion secondary battery 1 of the present embodiment. First, the configuration of the lithium-ion secondary battery 1 of the present embodiment, which is an example of the present invention, will be described.

[0029] The lithium-ion secondary battery 1 shown in FIG. 4 is a cell battery, and a battery module 1M is constituted by the cell battery (see FIG. 6). The lithium-ion secondary battery 1 which is a cell battery includes a plate-shaped rectangular parallelepiped battery case 11 having an opening on the upper side. An electrode body 12 is housed inside the battery case 11. The battery case 11 is filled with a non-aqueous electrolyte 13 from a liquid injection hole. The battery case 11 is made of a metal such as an aluminum alloy, and forms an electrolytic cell sealed by a lid body. Further, the lithium-ion secondary battery 1 includes a positive electrode external terminal 14 and a negative electrode external terminal 15 used for charging and discharging electric power. The positive electrode external terminal 14 is electrically connected to a positive electrode current collecting terminal 16 inside the battery case 11 via the lid body. Also, the negative electrode external terminal 15 is electrically connected to a negative electrode current collecting terminal 17 inside the battery case 11 via the lid body. The positive electrode current collecting terminal 16 is electrically connected to the positive electrode current collecting portion 33 (see FIG. 5) of the electrode body 12. Also, the negative electrode current collecting terminal 17 is electrically connected to the negative electrode current collecting portion 23 (see FIG. 5) of the electrode body 12.

[0030] <Electrode body 12> FIG. 5 is a schematic diagram showing the configuration of the wound electrode body 12. The electrode body 12 is formed by laminating a large number of negative electrode plates 2, positive electrode plates 3, and separators 4 disposed therebetween. The laminated negative electrode plates 2, positive electrode plates 3, and separators 4 are wound to form a flat shape. The negative electrode plate 2 has a negative electrode composite material layer 22 formed on a negative electrode current collector 21 made of a copper foil as a base material. A negative electrode current collecting portion 23 is provided on one end side in the width direction W (winding axis direction) orthogonal to the winding direction L. The negative electrode current collecting portion 23 has a configuration in which the negative electrode composite material layer 22 is not formed and the negative electrode current collector 21 is exposed.

[0031] The positive electrode plate 3 has a positive electrode mixture layer 32 formed on a positive electrode current collector 31 made of an aluminum foil serving as a base material. As shown in FIG. 4, a positive electrode current collector portion 33 is provided on the other end side (the side opposite to the negative electrode current collector portion 23) in the width direction W (the winding axis direction) orthogonal to the direction (winding direction L) in which the positive electrode current collector 31 is wound. In the positive electrode current collector portion 33, the positive electrode mixture layer 32 is not formed and the metal of the positive electrode current collector 31 is exposed.

[0032] <Laminated structure of the electrode body 12> As shown in FIG. 4, the basic configuration of the electrode body 12 of the lithium-ion secondary battery 1 includes a negative electrode plate 2, a positive electrode plate 3, and a separator 4.

[0033] The negative electrode plate 2 includes negative electrode mixture layers 22 on both surfaces of a negative electrode current collector 21 serving as a negative electrode base material. One end portion of the negative electrode current collector 21 is a negative electrode current collector portion 23 where the metal is exposed. The positive electrode plate 3 includes positive electrode mixture layers 32 on both surfaces of a positive electrode current collector 31 serving as a positive electrode base material. The other end portion of the positive electrode current collector 31 is a positive electrode current collector portion 33 where the metal is exposed.

[0034] The negative electrode plate 2 and the positive electrode plate 3 are overlapped via a separator 4 to form a laminate. As shown in FIG. 3, this laminate is wound in the longitudinal direction around a winding axis to form a wound-type electrode body 12 that is shaped flat as shown in FIG. 5.

[0035] <Non-aqueous electrolyte 13> The non-aqueous electrolyte 13 of the lithium-ion secondary battery 1 according to the present embodiment shown in FIG. 3 permeates the electrode body 12. The non-aqueous electrolyte 13 is a composition in which a lithium salt is dissolved in an organic solvent. As the lithium salt, LiClO4, LiPF6, LiAsF6, LiBF4, LiSO3CF3, etc. can be used. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran, and dimethoxyethane; sulfur compounds such as ethyl methyl sulfone and butane sultone; or phosphorus compounds such as triethyl phosphate and trioctyl phosphate. As the non-aqueous electrolyte 13, these can be used by mixing one or more of them. Note that the composition of the non-aqueous electrolyte 13 is not limited to this.

[0036] <Components of the electrode body 12> Next, the negative electrode plate 2, the positive electrode plate 3, and the separator 4, which are the components constituting the electrode body 12, will be described.

[0037] <Negative electrode plate 2> As shown in FIG. 4, negative electrode composite layers 22 are formed on both surfaces of a negative electrode current collector 21, which is a negative electrode substrate, to form the negative electrode plate 2. The negative electrode composite layer 22 is formed by coating the negative electrode current collector 21 with a negative electrode composite paste 22a. Thereafter, the negative electrode plate 2 is completed through a drying process, a pressing process, and a cutting process.

[0038] <Negative electrode current collector 21> The negative electrode current collector 21 is composed of a Cu foil in the present embodiment. The negative electrode current collector 21 serves as a base as an aggregate of the negative electrode composite layer 22 and has a function of a current collecting member that collects electricity from the negative electrode composite layer 22. One end portion of the negative electrode current collector 21 is a negative electrode current collecting portion 23 where the metal surface is exposed without the formation of the negative electrode composite layer 22. That is, the negative electrode active material particles are electrically connected to the negative electrode external terminal 15 through the negative electrode current collector 21, the negative electrode current collecting portion 23, and the negative electrode current collecting terminal 17.

[0039] <Negative electrode composite material layer 22> In this embodiment, the negative electrode active material is a powdery carbon material made of graphite (graphite) having a layered structure or the like, and is a material capable of occluding and releasing lithium ions Li + and is a material capable of occluding and releasing lithium ions Li.

[0040] <Positive electrode plate 3> As shown in FIG. 4, the positive electrode plate 3 is composed of a positive electrode current collector 31 which is a positive electrode substrate, and a positive electrode composite material layer 32 coated thereon. The positive electrode composite material layer 32 is coated with a positive electrode composite material paste on the positive electrode current collector 31. Thereafter, the positive electrode plate 3 is completed through a drying process, a pressing process, and a cutting process.

[0041] <Positive electrode current collector 31> The positive electrode plate 3 is formed by forming the positive electrode composite material layer 32 on both sides of the positive electrode current collector 31 which is a positive electrode substrate. In the embodiment, the positive electrode current collector 31 is composed of an Al foil. The positive electrode current collector 31 serves as a base as an aggregate of the positive electrode composite material layer 32 and has a function of a current collecting member for collecting electricity from the positive electrode composite material layer 32.

[0042] First, the positive electrode substrate constituting the positive electrode current collector 31 is exemplified by an Al foil. However, for example, it may be composed of a conductive material made of a metal having good conductivity. As a material having good conductivity, for example, in addition to an Al foil, a material containing an Al alloy can be used. The configuration of the positive electrode current collector 31 is not limited to this.

[0043] <Positive electrode composite material layer 32> The positive electrode composite material layer 32 is formed by coating and drying a positive electrode composite material paste on the positive electrode current collector 31. The positive electrode composite material layer 32 contains, in addition to positive electrode active material particles, additives such as a conductive auxiliary material, a binder, and a dispersant.

[0044] <Composition of the positive electrode active material> The positive electrode active material particles contain a lithium transition metal oxide having a layered crystal structure. The lithium transition metal oxide contains one or more predetermined transition metal elements in addition to Li. The transition metal element contained in the lithium transition metal oxide is preferably at least one of Ni, Co, and Mn. The positive electrode active material of the present embodiment exemplifies a ternary system called so-called NCM having a lithium transition metal oxide containing all of Ni, Co, and Mn.

[0045] Note that the positive electrode active material of the present embodiment is not limited to those having a lithium transition metal oxide containing all of Ni, Co, and Mn. Further, for example, a composition containing Al other than these may be used. Also, the positive electrode active material may be LiMnO4, LiFePO4, or the like.

[0046] <Separator 4> Separator 4 is a highly insulating non-woven fabric made of polypropylene or the like, which is a porous resin for holding the non-aqueous electrolyte 13 between the negative electrode plate 2 and the positive electrode plate 3. Further, as the separator 4, a porous polymer film such as a porous polyethylene film, a porous polyolefin film, and a porous polyvinyl chloride film, or a lithium ion or ion conductive polymer electrolyte film can be used alone or in combination.

[0047] <Overall configuration of a vehicle equipped with a secondary battery> FIG. 6 is a block diagram showing an example of the configuration of a vehicle using the lithium ion secondary battery 1 at the implementation stage. The vehicle exemplified in FIG. 6 is a hybrid vehicle. The vehicle includes a control device 18 that also functions as a charge and discharge control device for the lithium ion secondary battery 1, a power control unit (PCU), a motor generator 41, 42, an engine 50, a power split device 60, a drive shaft 70, and drive wheels 80. The control device 18 of the lithium ion secondary battery 1 of the present embodiment includes a battery module 10A, a monitoring unit 40, and an ECU (electronic control unit) 100.

[0048] The engine 50 is an internal combustion engine that outputs power by converting the combustion energy generated when a mixture of air and fuel burns into the kinetic energy of moving elements such as pistons and rotors.

[0049] The power split device 60 includes, for example, a planetary gear mechanism (not shown) having three rotating shafts of a sun gear, a carrier, and a ring gear. The power split device 60 splits the power output from the engine 50 into the power for driving the motor generator 41 and the power for driving the drive wheels 80.

[0050] Each of the motor generators 41 and 42 is an AC rotating electric machine, for example, a three-phase AC synchronous motor in which a permanent magnet (not shown) is embedded in the rotor. The motor generator 41 is mainly used as a generator driven by the engine 50 via the power split device 60. The electric power generated by the motor generator 41 is supplied to the motor generator 42 or the lithium-ion secondary battery 1 via the PCU 30.

[0051] The motor generator 42 mainly operates as an electric motor and drives the drive wheels 80. The motor generator 42 is driven by receiving at least one of the electric power from the lithium-ion secondary battery 1 and the generated electric power of the motor generator 41, and the driving force of the motor generator 42 is transmitted to the drive shaft 70. On the other hand, during braking of the vehicle or when reducing acceleration on a downhill slope, the motor generator 42 operates as a generator to perform regenerative power generation. The electric power generated by the motor generator 42 is supplied to the battery module 1M via the PCU 30.

[0052] The battery module 1M is configured to include the lithium-ion secondary battery 1 which is a plurality of cell batteries. The lithium-ion secondary battery 1 stores electric power for driving the motor generators 41 and 42 and supplies electric power to the motor generators 41 and 42 through the PCU 30. Further, the lithium-ion secondary battery 1 is charged by receiving the generated electric power through the PCU 30 during the power generation of the motor generators 41 and 42.

[0053] The monitoring unit 20 includes a voltage measurement device 40a, a current measurement device 40b, and a temperature measurement device 40c. The voltage measurement device 40a of the present embodiment detects, for example, the battery voltage V [V] of each cell of the lithium-ion secondary battery 1. However, the battery voltage V [V] of the entire battery module 1M composed of a plurality of cells of the lithium-ion secondary battery 1 connected in parallel to each other may be detected. In this case, the battery voltage V [V] of each cell battery is estimated from the overall voltage. The current measurement device 40b detects the current I [A] input to and output from the lithium-ion secondary battery 1. The temperature measurement device 40c detects the temperature T [°C] for each block. Each measurement device outputs a signal indicating the detection result to the ECU 100.

[0054] Note that the monitoring units of the voltage measurement device 40a and the temperature measurement device 40c are basically for each cell of the lithium-ion secondary battery 1. However, it is not limited to this, and it may be for each block.

[0055] The PCU 30 performs bidirectional power conversion between the lithium-ion secondary battery 1 and the motor generators 41 and 42 according to a control signal from the ECU 100. The PCU 30 is configured to be able to control the states of the motor generators 41 and 42 separately. For example, the motor generator 41 can be set in the regeneration state (power generation state) while the motor generator 42 is set in the power running state. The PCU 30 is provided corresponding to the motor generators 41 and 42, for example, and includes two inverters and a converter (neither shown) that boosts the DC voltage supplied to each inverter to be equal to or higher than the output voltage of the lithium-ion secondary battery 1.

[0056] <ecu100> In this embodiment, the ECU 100 of the control device 18 serves as the part that controls the charging and discharging of this embodiment.

[0057] The ECU 100 includes a CPU (Central Processing Unit) 101, a memory 102, and an input / output port (not shown) for inputting and outputting various signals. <Memory 102> The memory 102 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). It also includes a storage medium, such as an EPROM (erasable programmable read only memory), an SSD (Solid State Drive), or an HDD (Hard Disc Drive), in which programs, maps, etc. are stored.

[0058] The ECU 100 controls the charging and discharging of the lithium-ion secondary battery 1 by controlling the engine 50 and the PCU 30 based on the signals received from each measuring device and the programs and maps stored in the memory 102.

[0059] Figure 7 is a block diagram showing the details of the configuration of the memory of the ECU of the full charge capacity estimation device of this embodiment. As shown in Figure 7, the memory 102 stores a program that causes the CPU 101 to function as a current measurement unit 102a. Similarly, a voltage estimation unit 102b, an SOC estimation unit 102c, a voltage measurement unit 102d, a sample storage unit 102e, an actual power relationship derivation unit 102f, an upper and lower limit voltage setting unit 102g, an input / output limit value setting unit 102h, and a battery model correction unit 102i are stored. The memory 102 can store programs for performing respective processes and their results, etc.

[0060] <Method for Controlling Charging and Discharging of Lithium-Ion Secondary Battery 1 of this Embodiment> FIG. 8 and FIG. 9 are flowcharts showing the procedure of the charge / discharge control method of the lithium-ion secondary battery 1 according to the present embodiment. Note that the flowcharts of FIG. 8 and FIG. 9 are connected by connector 1 and connector 2. Hereinafter, the procedure of the charge / discharge control method of the lithium-ion secondary battery 1 according to the present embodiment will be described with reference to the flowcharts of FIG. 8 and FIG. 9.

[0061] <Step of information acquisition (S1)> In the step of information acquisition (FIG. 8: S1), the control device 18 measures the measurement current A of the lithium-ion secondary battery 1 with the current measurement device 40b M [A]. The measurement voltage V is measured with the voltage measurement device 40a M [V]. The measurement temperature T is measured with the temperature measurement device 40c M [°C]. Then, the acquired information is stored in the memory 102.

[0062] <Step of battery voltage estimation (S2)> Next, in the step of battery voltage estimation (S2), based on the information of the measurement current A M [A] and the measurement temperature T M [°C] obtained in the step of information acquisition (S1), the estimated voltage V is estimated by the battery model M (FIG. 3) ES [V].

[0063] <Step of battery model correction (S3)> In the step of battery model correction (S3), the battery model M is corrected by comparing the measurement voltage V M [V] obtained in the step of information acquisition (S1) with the estimated voltage V ES [V] estimated in the step of battery voltage estimation (S2).

[0064] <Battery model M> FIG. 3 is a block diagram showing the equivalent circuit of the battery model M of the lithium-ion secondary battery 1 according to the present embodiment.

[0065] Here, the "battery model M" in this embodiment will be described. As shown in FIG. 5, in the lithium-ion secondary battery 1, the positive electrode plate 3 and the negative electrode plate 2 face each other with the separator 4 interposed therebetween, and the non-aqueous electrolyte 13 is filled therein. For this reason, since the facing positive electrode plate 3 and negative electrode plate 2 act as a capacitor, it can be conceptually regarded as the capacitor C1 shown in FIG. 3. Further, the non-aqueous electrolyte 13 and the like can be conceptually regarded as resistance components R0 and R1. Therefore, as the simplest battery model M, it can be represented as an equivalent circuit using a CR circuit as shown in FIG. 3. More specifically, it can be analyzed by dividing it into a negative electrode model, a positive electrode model, a liquid phase model, a DC resistance model, etc., considering the Li ion concentration, salt concentration, error of the current sensor, etc. However, in this embodiment, for the sake of explanation, the simplest equivalent circuit as shown in FIG. 3 will be exemplified and described as the battery model M.

[0066] The battery model M quantifies each element using complex impedance analysis or the like. In this embodiment, when a current I [A] flows through the lithium-ion secondary battery 1, the battery voltage V [V] can be calculated according to the resistance values [mΩ] of the resistance component R0, the resistance component R1, and the capacitor C1. In the lithium-ion secondary battery 1, since the resistance value [mΩ] and the like change depending on the temperature T [°C] of the battery, correction is performed according to the temperature T [°C].

[0067] <Correction of Battery Model M> As described above, when the battery model M is constructed, the battery voltage V [V] can be estimated from the current I [A]. In this embodiment, the battery voltage V [V] estimated by the battery model M is referred to as the "estimated voltage V ES [V]". On the other hand, the battery voltage V [V] actually measured for the lithium-ion secondary battery 1 is referred to as the "measured voltage V M [V]". If the internal resistance [mΩ] assumed by the battery model M is different, a voltage difference ΔV [V] will occur between the estimated voltage V ES [V] and the measured voltage V M [V].

[0068] Therefore, in this embodiment, in the "step of correcting the battery model (S3)", the estimated voltage V ES [V] is made to match the measured voltage V M [V], and the resistance value set in the battery model M is corrected so that the voltage difference ΔV[V] = 0.

[0069] <Estimation of SOC[%]> The estimation of SOC[%] can be simply obtained from a conversion table with temperature correction from the battery voltage V[V]. In this embodiment, in order to more accurately estimate SOC[%], the battery model M is used to estimate SOC[%]. Here, as shown in the formula in FIG. 3, the change in SOC[%] is obtained from the integrated value of integrating the current I[A], and the amount of current [Ah] is obtained. Then, the increased or decreased SOC[%] is obtained from the ratio of the amount of current [Ah] to the FCC (Full Charge Capacity of the battery) [Ah].

[0070] <Step of sample collection (S4)> FIG. 2 is a time chart showing the procedure of the step of sample collection during discharge. The horizontal axis is the elapsed time t[s], and the time elapses in the direction from the measurement start time t S [s] to the measurement end time t E [s]. Here, the graph G1 is a graph showing the change in the battery voltage V[V] by the battery model M. Also, the graph G2 is based on the actually measured voltage V M [V].

[0071] As shown in FIG. 2, in the step of sample collection (S4), a current I[A] is applied to the lithium-ion secondary battery 1 from the measurement start time t S [s] to the measurement end time t E [s] for the set time t1[s], and samples are collected when the change in the current I[A] is small. If this condition is satisfied, samples are collected at any time during charging and discharging, respectively.

[0072] The set time t1 [s] is desirably 5 [s] or more, and is set to 10 [s] in this embodiment. Also, the change in the current I [A] is desirably within ±10 [%], and is set to a range of ±5 [%] in this embodiment.

[0073] The collection of samples records the SOC [%] at the start of measurement. When the measurement starts at the start time t S [s], the power [W] is integrated from the battery voltage V [V] and the current I [A] until the measurement end time t E [s]. The integrated input / output power amount P [Wh] and the charge / discharge end voltage V E at the measurement end time t E [V] are stored in the sample storage unit (Fig. 7: 102e). In this way, if the conditions of the set time t1 [s] and the change in the current I [A] are satisfied, samples are collected at any time.

[0074] In the example shown in Fig. 2, the measurement starts at the start time t S [s], and the measured current A M [A] of the discharge at that time is measured and integrated. Then, when the time has elapsed by the set time t1 [s] and the measurement end time t E [s] is reached, the measurement is terminated. And at the measurement end time t E [s], the battery voltage V [V] is recorded as the charge / discharge end voltage V E [V]. Also, the current I [A] integrated from the start time t S [s] is recorded as the input / output power amount P [Ah].

[0075] The samples collected in this way are separated and collected for each SOC: S [%] at the start time t E of the input / output power amount P [Wh] for the set time t1 [s] and the charge / discharge end voltage V E [V] at the measurement end time t S [s]. The SOC: S [%] is classified into bands, for example, every 10 [%]. The collected samples are stored in the sample storage unit (Fig. 7: 102e).

[0076] The example shown in FIG. 2 shows the collection of samples during discharge, but samples are also collected during charging. During charging, the measurement start time is t E [s], and the measurement end time t S [s] will be swapped, and time will elapse in the leftward direction in FIG. 2. The set time t1 [s] is common for the set time. And in FIG. 2, the measurement start time is t E [s], and the charging measurement current A M [A] is measured and integrated. Then, when the time has elapsed by the set time t1 [s] and the measurement end time t S [s] is reached, the measurement is terminated. And at the measurement end time t S [s], the battery voltage V [V] is recorded as the charge / discharge end voltage V E [V]. Also, the integrated current I [A] from the measurement start time t E [s] is recorded as the input / output power amount P [Ah].

[0077] <Steps for deriving the actual performance relationship (S6, S7)> When a predetermined number of samples with a specified variance are collected for the input / output power amount P [Wh] and the charge / discharge end voltage V E [V] (S5: YES), the steps for deriving the actual performance relationship (S6, S7) are executed. The predetermined number is, for example, 6 samples.

[0078] FIG. 1 is a double logarithmic graph showing the relationship between the charge / discharge end voltage V E [V] at SOC 60 [%], and the input / output power amount P [Wh]. Here, the plot points PL1 to PL6 of 6 samples are shown.

[0079] In the steps for deriving the actual performance relationship (S6, S7), the actual performance relationship is derived from a plurality of input / output power amounts P [Wh], the charge / discharge end voltage V E [V], and SOC: S [%]. Here, the "actual performance relationship" refers to the ability to determine how much the battery voltage V [V] will decrease when a certain amount of input / output power amount P [Wh] is used when at a specific SOC [%]. In other words, from the state of that SOC: S [%], the maximum allowable discharge power amount PD, which is the dischargeable power amount [Wh], max [Wh], and the maximum allowable charge power PC which is the chargeable energy [Wh] max [Wh] are shown. In this embodiment, these are collectively referred to as "the maximum allowable energy P max [Wh]".

[0080] First, the actual sample points are output to a double-logarithmic graph (S6). That is, in the graph of SOC:S[%] shown in FIG. 1 (here 60 [%]), the input / output energy P [Wh] and the charge / discharge cut-off voltage V E [V] are plotted on a double-logarithmic graph in combination. Here, a double-logarithmic graph is used for the graph.

[0081] Next, an internal and external interpolation formula indicated by a straight line L is calculated from the plot points PL1 to PL6 in the graph of FIG. 1 (S7). The relationship indicated by these plot points PL1 to PL6 is approximated to the straight line L by, for example, the least squares method. In this embodiment, a double-logarithmic graph is used, but if the approximation formula is a straight line, it can be implemented in a graph showing either the x or y coordinates in real numbers. Even in this case, an approximate straight line can be shown.

[0082] <Regarding the internal and external interpolation formula> In the estimation from data, "interpolation" or "interpolation" refers to obtaining an output within that range in a relationship derived using certain data. Also, "extrapolation" refers to obtaining an output outside that range based on the relationship recognized within that range. In other words, "extrapolation" is to predict outside the data region beyond the known values. Here, in this embodiment, the charge / discharge cut-off voltage V E [V] and the approximate line showing the relationship with the input / output energy P [Wh] is called the "internal and external interpolation formula".

[0083] The internal and external interpolation formula in this embodiment is obtained as a straight line using the least squares method from each plot point. It becomes the straight line L shown by a broken line on the graph shown in FIG. 1. In this embodiment, the charge / discharge cut-off voltage V collected in the sample collection step E Interpolation is to predict the input / output power amount P [Wh] between the maximum and minimum values of [V]. It is known that the prediction by interpolation is more accurate than the prediction by extrapolation. Therefore, the charge / discharge cut-off voltage V E [V] of the samples to be collected is preferably lower than the assumed allowable lower limit voltage V L [V].

[0084] <Steps for determining the input / output power limit value (S8, S9)> In the steps for determining the input / output power limit value (S8, S9), first, at the end of charging (discharging), the power reaching the allowable lower limit voltage V L [V] (true value 3.00 [V], logarithmic value 1.1 in this embodiment) within the usage range of the battery is obtained (S8). In FIG. 1, it can be read that the logarithmic value of the point on the straight line L indicating the internal / external interpolation method corresponding to 3 [V] of the allowable lower limit voltage V L [V] is approximately 6.84. Therefore, when obtaining the true value of the power using the formula exp{In(power)} = power [Ah] (S9), it can be seen that the allowable maximum discharge power amount PD max [Wh] is approximately 934 [Wh].

[0085] It can be derived from this that if the SOC [%] of the lithium-ion secondary battery 1 is 60 [%], the allowable maximum discharge power amount PD max [Wh] that can be discharged from here is 934 [Wh].

[0086] <Steps for setting the allowable upper and lower limit voltage values (FIG. 8: S10, FIG. 9: S11)> In the steps for setting the allowable upper and lower limit voltage values (S10, S11), based on the allowable maximum discharge power amount PD max [Wh] determined in the steps for determining the input / output power limit value (S8, S9), the allowable lower limit voltage V L [V] is set by the battery model M. Or based on the allowable maximum charge power amount PC max [Wh], the allowable upper limit voltage V H [V] is set by the battery model M.

[0087] First, the input / output power amount P [Wh] is restored by the equation exp{ln(power)} = power [Ah] (S9), and the input / output power amount P [Wh] calculated here is input into the battery model M in the current state to calculate the voltage at the end of charging or discharging (S10). The calculated voltage is set as the allowable upper limit voltage V H [V], and the allowable lower limit voltage V L [V] (S11).

[0088] That is, in the steps of deriving the actual performance relationship (S6, S7), the actual performance relationship of the lithium-ion secondary battery 1 has already been derived from the sample. Also, in the step of correcting the battery model (S3), the calibration of the battery model M is always performed. Therefore, for any power limit, that is, the allowable maximum discharge power amount PD max [Wh], the allowable maximum charge power amount PC max [Wh], when set, the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] can be accurately estimated and set. As a result, within the range ensuring smooth operation of the vehicle, the range of the battery voltage V [V] using the lithium-ion secondary battery 1 can be determined.

[0089] Also, by using the battery model M, the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] can be set first, and the power limit, that is, the allowable maximum discharge power amount PD max [Wh] and the allowable maximum charge power amount PC max [Wh] can also be set.

[0090] <Step of using the charge / discharge voltage range guard (Fig. 9: S12, S13)> In the step of using the charge / discharge voltage range guard, it is guarded so that the upper limit (lower limit) does not exceed the voltage within the usage range of the battery (S12), and it is guarded so that "upper limit voltage < lower limit voltage + minimum charge / discharge voltage range" is not satisfied (S13). The "guarding process" mentioned here refers to the allowable lower limit voltage V restricted by the procedures of the above S1 to 11 and the procedures of S15 to 18 described later L [V], and the allowable upper limit voltage V H According to [V], the range of the battery voltage V [V] that allows the use of the lithium-ion secondary battery 1 may become narrow. In this case, it is a procedure to secure a certain range of the battery voltage V [V] so that the range of the usable battery voltage V [V] does not become too narrow in practice. First, guard so that the lower limit (upper limit) does not exceed the voltage within the use range of the battery (S12). Here, for example, when the allowable upper limit voltage V H [V] becomes 3.00 [V], the practically usable range will be lost. Similarly, when the allowable lower limit voltage V L [V] becomes 4.20 [V], the range of the practically usable battery voltage V [V] will be lost. Therefore, for example, when the allowable upper limit voltage V H [V] becomes 3.00 [V], the allowable upper limit voltage V H [V] is forcibly raised to, for example, 3.50 [V]. Similarly, when the allowable lower limit voltage V L [V] becomes 4.20 [V], the allowable lower limit voltage V L [V] is forcibly lowered to, for example, 3.50 [V].

[0091] Also, make sure that the allowable upper limit voltage V H < the allowable lower limit voltage V L + the minimum charge-discharge voltage range does not hold (S13). Here, the "minimum charge-discharge voltage range" refers to the range of the battery voltage V [V] that enables the minimum necessary charge and discharge for the operation of the vehicle. For example, the allowable upper limit voltage V H [V] = 3.500 [V], the allowable lower limit voltage V L [V] = 3.400 [V], and the minimum charge-discharge voltage range is 1.00 V [V]. In this case, when applying to "the allowable upper limit voltage V H < the allowable lower limit voltage V L + the minimum charge-discharge voltage range", it becomes 3.500 <3.400 + 1.00 [V], and the relationship of "the allowable upper limit voltage V H < the allowable lower limit voltage V L + the minimum charge-discharge voltage range" does not hold. Also in this case, it is necessary to expand the "minimum charge-discharge voltage range" to 1.00 [V] by raising the "allowable upper limit voltage V H [V]" or lowering the "allowable lower limit voltage V L [V]".

[0092] In this way, the guard process enhances the practicality and effectiveness of control. Here, if there is a charge / discharge end request (S14: YES), the process ends. If there is no charge / discharge end request (S14: NO), the process returns to S1 again to collect samples (S2 to S4).

[0093] <When the number of scattered data that can be collected is less than a predetermined number (S5: NO)> Here, there may be a case where the number of scattered data that can be collected is less than a predetermined number (S5: NO). If the number of scattered data that can be collected is less than a predetermined number, a valid power relationship cannot be obtained. Therefore, when the current I [A] is at the measurement start time t S ~measurement end time t E If the change in the current I [A] is not small during the set time t1 [s] from the measurement start time t to the measurement end time t (S15: NO), the process returns to S1 again to continue collecting samples (S2 to S4). On the other hand, when the current I [A] is at the measurement start time t S ~measurement end time t E If the change in the current I [A] is small during the set time t1 [s] from the measurement start time t to the measurement end time t (S15: YES), it is determined whether the data of the voltage difference ΔV [V] is equal to or greater than a predetermined value (S17). If it is determined that the data of the voltage difference ΔV [V] is not equal to or greater than a predetermined value (S17: NO), the process returns to S1 again to collect samples (S2 to S4). On the other hand, if it is determined that the data of the voltage difference ΔV [V] is equal to or greater than a predetermined value (S17: YES), the voltage difference ΔV [V] is added to the allowable lower limit voltage V L [V] within the usage range of the lithium-ion secondary battery 1. Alternatively, the upper and lower limit voltages are set by subtracting from the allowable upper limit voltage V H [V] (S18). Then, it is stored in the upper and lower limit voltage setting unit 102g of the memory 102 (S11).

[0094] (Operation of this embodiment) In the method for controlling the charge and discharge of the lithium-ion secondary battery 1 by the control device 18 of this embodiment, control is performed in the following procedure. In the battery voltage estimation step (S2) based on the information acquired in the information acquisition step (FIG. 8: S1), the estimated voltage V is obtained by the battery model M (FIG. 3). ES Estimate [V]. Next, in the battery model correction step (S3), correct the battery model M of the lithium-ion secondary battery 1. For this reason, even if deterioration or the like occurs, the battery model M can always be calibrated to accurately estimate the battery voltage V [V] and the SOC [%].

[0095] In the sample collection step (S4), when the current I [A] flows within a fixed set time t1 [s] and within a certain current I [A] range, collect samples. The samples are the input / output power amount P [Wh] for the set time t1 and the charge / discharge cut-off voltage V E [V] combinations are collected separately for each SOC: S [%] of the secondary battery. Then, in the actual capacity relationship derivation steps (S6, S7), from the input / output power amount P [Wh], the charge / discharge cut-off voltage V E [V], and the SOC: S [%], derive the actual capacity relationship between the input / output power amount P [Wh] and the charge / discharge cut-off voltage V E [V] for each SOC: S [%]. Since the actual capacity relationship is derived based on the actual samples, the actual capacity of the lithium-ion secondary battery 1 can be measured very accurately.

[0096] Then, in the input / output power limit value determination steps (S8 to S9), from the actual capacity relationship, ensure that the lithium-ion secondary battery 1 does not fall below the set allowable lower limit voltage V L [V] and does not exceed the allowable upper limit voltage V H [V] at its SOC: S [%]. In this way, set the allowable maximum discharge power amount PD max [Wh] as the input / output power limit value.

[0097] In the allowable upper and lower limit voltage value setting steps (S10, S11), based on this allowable maximum power amount P max [Wh], set the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] using the battery model M calibrated in the battery model correction step (S3). In this case, the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] can be adjusted. Also, the allowable maximum power amount P, which is the so-called power limit max [Wh] can also be adjusted and corrected to an appropriate value in the operation of the vehicle. That is, the maximum allowable power consumption P according to the actual situation of vehicle operation max [Wh], based on this, the lower allowable voltage V L [V] and the upper allowable voltage V H [V] are set. In this embodiment, such correction is always performed by the battery model M calibrated in the step (S3) of battery model correction, so it can be adjusted immediately, flexibly and with high accuracy.

[0098] (Effect of this embodiment) (1) In the control method of the lithium-ion secondary battery 1 of this embodiment, the range of the battery voltage V [V] used is set according to the state of the lithium-ion secondary battery 1, and there is an effect that charging and discharging can be controlled safely and efficiently.

[0099] (2) The control device 18 measures the lithium-ion secondary battery 1 in the information acquisition step (S1) to obtain the measured current A M [A], the measured voltage V M [V], the measured temperature T M [°C] information. Based on the measured current A M [A] and the measured temperature T M [°C] information, the estimated voltage V ES [V] is estimated by the battery model M.

[0100] Then, in the battery model correction step (S3), the measured voltage V M [V] and the estimated voltage V ES [V] are compared to correct the battery model M of the lithium-ion secondary battery 1. Therefore, the battery model M is always calibrated to an accurate model, and there is an effect that the estimation by the battery model M can be made accurate.

[0101] (3) In the sample collection step (S4), the control device 18 collects samples when the current I [A] flows within a fixed current I [A] range for a fixed set time t1 [s]. This sample collects the combination of the input / output power amount P [Wh] at the set time t1 and the charge / discharge cut-off voltage V E [V] for each battery SOC: S [%]. For this reason, there is an effect that a plurality of distributed samples can be collected under substantially the same conditions.

[0102] (4) In the input / output power limit value determination step (S11), the control device 18 derives the actual power relationship between the input / output power amount P [Wh] and the charge / discharge cut-off voltage V E [V] for each SOC: S [%] from the samples collected in the sample collection step (S4). For this reason, there is an effect that the actual power of the actual lithium ion secondary battery 1 can be accurately reflected in charge / discharge.

[0103] (5) From the actual power relationship derived in this way, at that SOC: S [%], the allowable maximum power amount P L [Wh] that does not fall below the set allowable lower limit voltage V max [V] is set. Or, the allowable maximum power amount P H [Wh] that does not exceed the set allowable upper limit voltage V max [V] is set as the input / output power limit value. For this reason, there is an effect that charge / discharge control according to the actual power of this lithium ion secondary battery 1 can be performed by the allowable lower limit voltage V L [V] and the allowable upper limit voltage V H [V] that reflect the actual power relationship.

[0104] (6) In the allowable upper and lower limit voltage value setting steps (S10, S11), based on the allowable maximum discharge power amount PD max [Wh] determined in the input / output power limit value determination steps (S8, S9), the battery model M sets the allowable lower limit voltage V L [V]. Also, based on the allowable maximum charge power amount PC max [Wh], the battery model M sets the allowable upper limit voltage V H Set [V]. For this reason, there is an effect that the allowable upper and lower voltage values can be set simply and accurately based on the maximum allowable power amount P max [Wh].

[0105] (7) In the battery voltage estimation step (S2), the battery model M estimates the voltage V ES [V] by an equivalent circuit. For this reason, there is an effect that the battery model M can be easily calibrated by comparing it with the actually measured measurement voltage V M [V].

[0106] (8) Based on the voltage difference ΔV [V] between the measurement voltage V M [V] obtained in the information acquisition step (S1) and the estimated voltage V ES [V] estimated in the battery voltage estimation step (S2), correct the set value of the battery model M. For this reason, based on the always calibrated battery model M, the estimation of SOC: S [%] etc. can be accurately performed.

[0107] (9) In the sample collection step (S4), the set time t1 [s] for measuring the current I [A] is 5 [s] or more. For this reason, there is an effect that sudden noise can be excluded and samples can be collected.

[0108] (10) In the sample collection step (S4), the range of the current I [A] is set to the range of ± 10 [%]. For this reason, there is an effect that samples correctly reflecting the relationship between the input / output power amount P [Wh] and the charge / discharge termination voltage V E [V] can be collected.

[0109] (11) In the sample collection step (S4), SOC: S [%] collects samples by dividing the band of SOC [%] assumed to be used into a plurality of bands. For this reason, there is an effect that the maximum allowable power amount P max [Wh] corresponding to the SOC: S [%] at that time can be set.

[0110] (12) In the step of deriving the power relationship (S6, S7), plot the samples on a double logarithmic graph. Thus, the relationship between the input / output power amount P [Wh] and the charge / discharge end voltage V E [V] over a wide range can be verified.

[0111] (13) In the step of determining the input / output power limit value (S11), estimate the input / output power amount P [Wh] from the charge / discharge end voltage V E [V] based on the approximate straight line obtained by the least squares method for the points plotted on the double logarithmic graph. Thus, there is an effect that a more accurate power relationship with less noise can be derived from a plurality of samples.

[0112] (14) Based on the derived power relationship, the allowable maximum power amount P L [Wh] that allows the secondary battery not to fall below the set allowable lower limit voltage V max [V] at its SOC: S [%] can be set. Or, the allowable maximum power amount P H [Wh] that does not exceed the set allowable upper limit voltage V max [V] can be set as the input / output power limit value.

[0113] (15) The approximate straight line includes the allowable lower limit voltage V L [V] or the allowable upper limit voltage V H [V], and the estimation of the input / output power amount P [Wh] is by interpolation. There is an effect that accurate estimation can be performed by interpolation, and wide-range estimation can be performed by extrapolation.

[0114] (16) In the step of using the charge / discharge voltage range guard (S12, S13), guard so that the upper limit does not exceed the battery voltage V [V] within the usage range of the battery, and the lower limit does not fall below the battery voltage V [V] within the usage range of the battery. Also, guard so that the upper limit voltage < lower limit voltage + minimum charge / discharge voltage range is not satisfied. Thus, there is an effect that the charge / discharge of the lithium ion secondary battery 1 can be controlled so as not to interfere with the operation of the vehicle.

[0115] (17) In the step of sample collection (S4), the input / output power amount P [Wh] for the set time t1 and the charge / discharge cut-off voltage V E [V] at the end, collected separately for each state of charge (SOC) of the secondary battery: S [%], may not satisfy the specified dispersibility. In such a case, since the reliability of the sample is low, the steps of allowable voltage range setting (S15 to S18) are executed. Here, instead of collecting samples, the voltage difference ΔV [V] between the estimated voltage V ES [V] and the measured voltage V M [V] is collected. And when the voltage difference ΔV [V] is larger than the set threshold voltage V th [V], the voltage difference ΔV [V] is added to the allowable lower limit voltage V L [V]. Or, the voltage difference ΔV [V] is subtracted from the allowable upper limit voltage V H [V]. Therefore, even when appropriate samples cannot be collected, there is an effect that the charge / discharge control can be optimized by the steps of allowable voltage range setting (S15 to S18).

[0116] (18) In this embodiment, the lithium-ion secondary battery 1 is used as the secondary battery. Thus, there is an effect that a charge / discharge control method suitable for the lithium-ion secondary battery 1 can be achieved. Further, the lithium-ion secondary battery 1 is mounted on a vehicle and used for driving. In this embodiment, there is an effect that it can be suitably implemented as a charge / discharge control method suitable for the lithium-ion secondary battery 1 mounted on such a vehicle.

[0117] (Alternative example) ○ The charge / discharge control method suitable for the lithium-ion secondary battery 1 of this embodiment is not limited to in-vehicle use. For example, it can also be implemented in ships, trains, airplanes, etc. Further, it can also be implemented as a stationary or portable power source. For example, it can also be suitably applied to a stationary power storage system that charges and stores excess power generated by solar power generation, etc. in factories and homes.

[0118] ○ In this embodiment, the lithium-ion secondary battery 1 is exemplified as the secondary battery, but the type is not limited, and other non-aqueous electrolyte secondary batteries, alkaline secondary batteries such as NiMH, all-solid-state batteries, etc. are also applicable.

[0119] ○ The battery model M shown in Fig. 3 is an example of a simplified model, and a more complex model may also be used. ○ In this embodiment, the lithium-ion secondary battery 1 as the cell battery constituting the battery module 1M which is a battery pack is exemplified, but it may also be in a form such as controlling a single cell battery or a battery pack equipped with a plurality of battery modules. In this case, the measured current A M [A] and the measured voltage V M [V] can be measured directly for each cell battery or for the battery pack.

[0120] ○ In this embodiment, in the guard process (S12, S13), the range of the battery voltage V [V] that can be used for control is set to 3.00 to 4.20 [V], but this is appropriately optimized by those skilled in the art according to the characteristics of the secondary battery.

[0121] ○ The numerical values, numerical ranges, etc. of this embodiment are given as examples and are not limited thereto. Those skilled in the art can appropriately optimize and implement them according to the characteristics of the battery. The number of exemplified samples, the time for sample acquisition, etc. are examples and are appropriately optimized by those skilled in the art.

[0122] ○ The flowchart shown in Fig. 8 is an example of implementation for explanation and is not limited thereto. Those skilled in the art can add, delete, replace, and change the procedures for implementation. ○ Needless to say, the present invention can be implemented by those skilled in the art by adding, deleting, or changing its configuration without departing from the scope of the claims.

Explanation of Reference Numerals

[0123] M... Battery model L... Approximate straight line (indicating the internal and external interpolation type) G1... Graph G2... Graph PL1~PL6… Plot points A M [A]… Measured current T M [°C]… Measured temperature V[V]… Battery voltage V M [V]… Measured voltage V ES [V]… Estimated voltage V S [V]… Starting voltage of measurement V E [V]… Charge / discharge termination voltage V L [V]… Allowable lower limit voltage V H [V]… Allowable upper limit voltage ΔV[V]… Voltage difference I[A]… Current t1[s]… Set time t S [s]… Starting time of measurement t E [s]… Ending time of measurement P[Wh]… Input / output electric energy P max [Wh]… Allowable maximum electric energy PC max [Wh]… Allowable maximum charge electric energy PD max [Wh]… Allowable maximum discharge electric energy S[%]… SOC 1… Lithium-ion secondary battery (cell battery) 1M… Battery module 11… Battery case 12… Electrode body 13… Non-aqueous electrolyte 14… Positive electrode external terminal 15… Negative electrode external terminal 16… Positive electrode current collecting terminal 17… Negative electrode current collecting terminal 2… Negative electrode plate 21… Negative electrode current collector 22… Negative electrode composite material layer 23… Negative electrode current collecting part 3… Positive electrode plate 31… Positive electrode current collector 32… Positive electrode composite material layer 33…Positive current collector 4…Separator 18…Control device 30…PCU 40…Monitoring unit 40a…Voltage measurement device 40b…Current measurement device 40c…Temperature measurement device 100…ECU (Computer) 101…CPU 102…Memory 102a…Current measurement section 102b…Voltage estimation section 102c…SOC estimation section 102d…Voltage measurement section 102e…Sample storage section 102f…Derivation section of actual power relationship 102g…Upper and lower limit voltage setting section 102h…Input / output limit value setting section 102i…Battery model correction section

Claims

1. A method for controlling charging and discharging of a secondary battery by a control device, wherein the control device Measured current A obtained by measuring the secondary battery Ｍ [A], measured voltage V Ｍ [V], measured temperature T Ｍ A step of information acquisition for acquiring information of [°C], and The measured current A obtained in the step of obtaining the information Ｍ [A], the measured temperature T Ｍ Based on the information of [°C], the estimated voltage V ＥＳ [V] is estimated by a battery model, and the step of estimating the battery voltage The measured voltage V obtained in the step of obtaining the information Ｍ [V] and the estimated voltage V estimated in the step of estimating the battery voltage ＥＳ [V] are compared, and a step of correcting the battery model of the secondary battery When a current I [A] flows through the secondary battery within a set time t １ [s] and within a certain current I [A] range, the set time t １ [s], a sample collection step of collecting samples of the combination of the input / output power amount P [Wh] and the charge / discharge termination voltage V Ｅ [V] for each SOC: S [%] of the secondary battery is performed. A plurality of the input / output electric energy amounts P [Wh] and the charge / discharge end voltage V collected in the step of the sample collection Ｅ From the [V], the SOC: S [%], derive the actual power relationship between the input / output electric energy amount P [Wh] and the charge / discharge end voltage V for each of the SOC: S [%] in the step of deriving the actual power relationship Ｅ And a step of deriving the actual power relationship Based on the above power relationship, when the secondary battery is at a specific SOC: S [%], the maximum allowable discharge energy PD Ｌ [Wh] that can be tolerated without falling below the set allowable lower limit voltage V max [V], or the maximum allowable charge energy PC Ｈ [Wh] that can be tolerated without exceeding the set allowable upper limit voltage V max [V] is set as the input / output power limit value, and a step of determining the input / output power limit value is performed executes the method for controlling charging and discharging of a secondary battery, characterized in that.

2. The maximum allowable discharge energy amount PD max [Wh] determined in the step of determining the input / output power limit value, the allowable lower limit voltage V Ｌ [V] is set, or the maximum allowable charge energy amount PC max [Wh] determined in the step of determining the input / output power limit value, the allowable upper limit voltage V Ｈ [V] is set, and the method for controlling charge and discharge of a secondary battery according to claim 1, further comprising a step of setting an allowable upper and lower limit voltage value.

3. The battery model in the step of estimating the battery voltage estimates the estimated voltage V by an equivalent circuit ＥＳ The method for controlling charge and discharge of a secondary battery according to claim 1, characterized in that [V] is estimated.

4. In the step of correcting the battery model, The measured voltage V obtained in the step of obtaining the information Ｍ [V], and the estimated voltage V estimated in the step of estimating the battery voltage ＥＳ [V], based on the voltage difference ΔV [V] between them, correct the battery model of the secondary battery by correcting the set value of the battery model so as to eliminate the voltage difference ΔV [V]. The method for controlling charge and discharge of the secondary battery according to claim 3, characterized in that

5. In the step of sample collection, The set time t １ [s] for measuring the current I [A] in the secondary battery is 5 [s] or more, and the method for controlling charge and discharge of the secondary battery according to claim 1.

6. In the step of sample collection, The method for controlling charging and discharging of a secondary battery according to claim 1, characterized in that the range of the current I [A] in the secondary battery is in the range of ±10 [%].

7. In the step of sample collection, The method for controlling charging and discharging of a secondary battery according to claim 1, characterized in that the SOC: S [%] of the secondary battery divides the band of the SOC [%] assumed to be used into a plurality of bands and collects samples.

8. In the step of deriving the strength relationship, A plurality of input / output power amounts P [Wh], the charge / discharge termination voltage V Ｅ and the SOC: S [%] collected in the step of the sample collection are plotted on a double logarithmic graph, and the method for controlling charge and discharge of the secondary battery according to claim 1 is characterized in that.

9. In the step of determining the input / output power limit value, The input / output power amount P [Wh] is estimated from the charge / discharge end voltage V Ｅ [V]by an approximate straight line obtained by the least squares method for the points plotted on the two logarithmic graphs, and the control method for charging and discharging of the secondary battery according to claim 8 is characterized by this.

10. When the secondary battery is at the SOC: S [%], the maximum allowable power amount P Ｌ [Wh] that can be tolerated without falling below the set allowable lower limit voltage V max [V] or the maximum allowable power amount P Ｈ [Wh] that can be tolerated without exceeding the set allowable upper limit voltage V max [V] is set as the input / output power limit value, and the method for controlling charging and discharging of the secondary battery according to claim 9 is characterized by this.

11. The approximate straight line includes the lower allowable voltage V Ｌ [V] or the upper allowable voltage V Ｈ [V], and the estimation of the input / output power amount P [Wh] is by interpolation. The method for controlling charge and discharge of a secondary battery according to claim 10, characterized in that.

12. The usage range of the secondary battery is such that it does not exceed the allowable upper limit voltage V Ｈ [V], and when it does not fall below the allowable lower limit voltage V Ｌ [V], Allowable upper limit voltage V Ｈ [V] < Allowable lower limit voltage V Ｌ [V] + Minimum charge-discharge voltage range [V] To ensure the preset minimum charge-discharge voltage range [V] so as not to fall below, the allowable upper limit voltage V Ｈ [V], the allowable lower limit voltage V Ｌ The method for controlling charge and discharge of a secondary battery according to claim 2, further comprising steps of a use charge-discharge voltage range guard for correcting [V].

13. In the step of sample collection, The time t collected separately for each SOC: S [%] of the secondary battery １ and the input / output power amount P [Wh] and the charge / discharge cut-off voltage V Ｅ [V] of the combination of samples do not satisfy the specified dispersibility, the estimated voltage V ＥＳ [V] and the measured voltage V Ｍ [V] to collect the voltage difference ΔV [V], When the voltage difference ΔV [V] is greater than the set threshold voltage V ｔｈ [V], adding the voltage difference ΔV [V] to the allowable lower limit voltage V Ｌ [V], and further providing a step of setting an allowable voltage range to change by subtracting the voltage difference ΔV [V] from the allowable upper limit voltage V Ｈ The method for controlling charge and discharge of a secondary battery according to claim 2, further characterized in that.

14. The method for controlling charging and discharging of a secondary battery according to any one of claims 1 to 13, characterized in that the secondary battery is a lithium-ion secondary battery.

15. The method for controlling charging and discharging of a secondary battery according to claim 14, characterized in that the secondary battery is mounted on a stationary power storage system or a vehicle and used for driving.

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