Battery evaluation device, battery protection system, battery evaluation method, and battery manufacturing method

Abstract

The objective of the present invention is to evaluate a battery with high accuracy using a simple method. A battery evaluation device (100) is provided with an impedance real part measuring unit for measuring the real part of the impedance of a battery, for each of a first frequency and a second frequency. The battery evaluation device (100) obtains an evaluation value indicating the state of the battery on the basis of the real part of the impedance of the battery obtained for each of the first frequency and the second frequency, a temperature coefficient and a capacity deterioration coefficient acquired in advance for the first frequency, and a temperature coefficient and a capacity deterioration coefficient acquired in advance for the second frequency. The evaluation value is at least one of a metal deposition amount and a temperature.

Description

Battery evaluation device, battery protection system, battery evaluation method, and battery manufacturing method

[0001] The present invention relates to a battery evaluation device, a battery protection system, a battery evaluation method, and a battery manufacturing method, and in particular to a technique for measuring the internal impedance of a battery.

[0002] Electric vehicles and hybrid vehicles are equipped with secondary batteries (hereinafter simply referred to as batteries) that can be repeatedly charged and discharged. Solar power generation systems also include batteries for storing the generated electrical energy. These batteries are evaluated for their performance and for defects during the manufacturing process. Evaluation indices include, for example, internal impedance and the amount of metal deposition.

[0003] As a technique for evaluating a battery, Patent Document 1 describes a technique for measuring a change in impedance with respect to a change in frequency. Patent Document 2 describes a technique for estimating the amount of lithium deposition based on the voltage output from a battery or the current flowing through a battery when both ends of the battery are short-circuited.

[0004] JP 2018-179652 A JP 2023-95745 A

[0005] One method for measuring the internal impedance of a battery is to determine the internal impedance from the relationship between the sinusoidal voltage applied to the battery and the sinusoidal current flowing through the battery. This method requires a highly accurate sinusoidal wave generator, which can lead to complex measurement equipment. Furthermore, the battery temperature is sometimes used to evaluate the battery. However, because the battery temperature is affected by the environment, it can be difficult to measure with high accuracy.

[0006] An object of the present invention is to evaluate a battery with high accuracy using a simple method.

[0007] The battery evaluation device according to the present invention includes an impedance real part measurement unit that measures the impedance real part of a battery for each of a first frequency and a second frequency, and calculates an evaluation value that indicates the state of the battery based on the impedance real part of the battery calculated for each of the first frequency and the second frequency, a temperature coefficient and a capacity degradation coefficient that are previously obtained for the first frequency, and a temperature coefficient and a capacity degradation coefficient that are previously obtained for the second frequency.

[0008] Preferably, the evaluation value is at least one of the amount of metal deposition and the temperature.

[0009] Preferably, the temperature coefficients for the first frequency and the second frequency are determined based on the relationship between the temperature of the battery, the frequency of the current flowing through the battery, and the real part of the impedance of the battery.

[0010] Preferably, the capacity degradation coefficients for the first frequency and the second frequency are calculated based on the relationship between the amount of capacity degradation of the battery, the frequency of the current flowing through the battery, and the amount of change in the real part of the impedance of the battery.

[0011] Preferably, the impedance real part measuring unit includes a damped oscillation circuit that causes a current flowing through the battery to oscillate in a damped manner, acquires damped oscillation data on the damped oscillation current of the battery from the damped oscillation circuit, and determines the impedance real part of the battery based on the damped oscillation data, and the damped oscillation circuit includes a plurality of capacitive circuits each including a capacitive element, an inductive circuit including an inductive element, and a selection circuit that selects at least one of the plurality of capacitive circuits and connects it to the inductive circuit, and causes the current flowing through the battery to oscillate in a damped manner at a plurality of frequencies.

[0012] Preferably, the impedance real part measuring unit includes a damped oscillation circuit that damps oscillates the current flowing through the battery, acquires damped oscillation data on the damped oscillation current of the battery from the damped oscillation circuit, and calculates the impedance real part of the battery based on the damped oscillation data, and the damped oscillation circuit includes an inductive circuit including an inductive element, a variable capacitance element connected to the inductive circuit, and a control unit that changes the capacitance of the variable capacitance element to damp oscillate the current flowing through the battery at a plurality of frequencies.

[0013] Preferably, the battery evaluation device includes an electric circuit connected to the battery, and the battery evaluation device controls the electric circuit based on the evaluation value to adjust the voltage applied to the battery or the current flowing through the battery.

[0014] A battery evaluation method according to the present invention includes measuring first battery characteristics indicating a relationship between a temperature of a battery, a frequency of a current flowing through the battery, and a real part of an impedance of the battery; determining a temperature coefficient of the battery for each of a first frequency and a second frequency based on the first battery characteristics; measuring second battery characteristics indicating a relationship between an amount of capacity degradation of the battery, a frequency of a current flowing through the battery, and a change in the real part of the impedance of the battery; determining a capacity degradation coefficient of the battery for each of the first frequency and the second frequency based on the second battery characteristics; measuring the real part of the impedance of the battery for each of the first frequency and the second frequency; and determining an evaluation value indicating a state of the battery based on the temperature coefficient and capacity degradation coefficient determined for the first frequency, the temperature coefficient and capacity degradation coefficient determined for the second frequency, and the real part of the impedance of the battery measured for each of the first frequency and the second frequency.

[0015] Preferably, the evaluation value is at least one of the amount of metal deposition and the temperature.

[0016] The battery evaluation method according to the present invention includes a step of evaluating the battery by the battery evaluation method.

[0017] According to the present invention, a battery can be evaluated with high accuracy by a simple method.

[0018] FIG. 1 is a diagram showing the configuration of a battery evaluation device according to a first embodiment; FIG. 2 is a diagram showing an example of a time waveform of a damped oscillation voltage; FIG. 3 is a diagram showing the configuration of a battery evaluation device according to a second embodiment; FIG. 4 is a diagram showing the configuration of a battery evaluation device according to a third embodiment; FIG. 5 is a diagram showing the impedance real part frequency characteristics; FIG. 6 is a diagram showing the impedance real part temperature characteristics; FIG. 7 is a diagram showing the impedance real part change frequency characteristics; FIG. 8 is a diagram showing the configuration of a battery protection system according to an application embodiment;

[0019] Each embodiment of the present invention will be described with reference to the drawings. Identical components shown in multiple drawings will be assigned the same reference numerals, and their description will be omitted. Furthermore, in the specification and drawings of this application, to simplify the description, alphabetical reference numerals indicating circuit elements will also be used to indicate the element constants of those circuit elements.

[0020] 1 shows the configuration of a battery evaluation device 100 according to a first embodiment of the present invention. The battery evaluation device 100 includes a primary inductor L ｓ , the first capacitive circuit 12-1, the first selection switch S １ , the second capacitive circuit 12-2, the second selection switch S2, the secondary inductor L ｓｓ , an amplifier 14, a peak hold circuit 16, and a control unit 18. The battery 10 to be evaluated may be, for example, a lithium ion battery. The battery 10 includes a battery capacitor C ｂ , internal resistor R ｂ and the internal inductor L ｂ The internal resistor R ｂ The resistance value of the battery capacitor C corresponds to the real part of the impedance of the battery 10. ｂ and the internal inductor L ｂ The imaginary part of the impedance of the circuit in which these are connected in series corresponds to the imaginary part of the internal impedance of the battery 10.

[0021] The positive electrode of the battery 10 is connected to the primary inductor L ｓ is connected to one end of the primary inductor L ｓThe other end of the first capacitive circuit 12-1 is connected to one end of the first capacitive circuit 12-1 and one end of the second capacitive circuit 12-2. The first capacitive circuit 12-1 includes a first capacitor C ｓ１ and a discharge resistor R ｓ１ The second capacitive circuit 12-2 is a circuit in which the second capacitor C ｓ２ and a discharge resistor R ｓ２ The first capacitor C ｓ１ and the capacitance of the second capacitor C ｓ２ The capacitances of the capacitors are different.

[0022] The other end of the first capacitive circuit 12-1 is connected to a first selection switch S １ is connected to one end of the first selection switch S １ The other end of the second capacitive circuit 12-2 is connected to the negative terminal of the battery 10. The other end of the second capacitive circuit 12-2 is connected to the second selection switch S ２ and a second selection switch S ２ The other end is connected to the negative electrode of the battery 10 .

[0023] That is, the first capacitive circuit 12-1 and the first selection switch S １ The first capacitive block 20-1 is connected in series with the second capacitive circuit 12-2 and the second selection switch S ２ The second capacitive block 20-2, which is formed by connecting the first capacitive block 20-1 and the second capacitive block 20-2 in series, is connected in parallel. One end of the capacitive block formed by connecting the first capacitive block 20-1 and the second capacitive block 20-2 in parallel is connected to the primary inductor L ｓ The other end of the capacitive block is connected to the negative terminal of the battery 10.

[0024] Secondary inductor L ｓｓ is the primary inductor L ｓ and a secondary inductor L ｓｓ The primary inductor L ｓ An induced electromotive force is generated according to the change in the current flowing through the secondary inductor L. ｓｓ The two ends of the amplifier 14 are connected to a pair of input terminals of the amplifier 14. The output terminal of the amplifier 14 is connected to a peak hold circuit 16.

[0025] The control unit 18 may include a processor as hardware that executes a program to control the battery evaluation device 100. The control unit 18 is configured to １ and the second selection switch S ２ The first selection switch S １ is on, and the second selection switch S ２ When is off, the battery 10, the primary inductor L ｓ and the first capacitive circuit 12-1 form a first series resonant circuit. １ and the second selection switch S ２ are both off, the first selection switch S １ When only the battery capacitor C is turned on in a pulsed manner, a damped oscillatory current flows through the first series resonant circuit. ｂ , internal resistor R ｂ , internal inductor L ｂ , primary inductor L ｓ The first capacitive circuit 12-1 is connected in series to a first series resonant circuit, and the output voltage V ｂ Here, turning on in a pulsed manner refers to an operation in which the switch turns from off to on, maintains the on state for a predetermined time, and then turns from on to off.

[0026] First selection switch S １ and the second selection switch S ２ are both off, the second selection switch S ２ When only the battery 10 and the primary inductor L ｓ A damped oscillatory current flows through the second series resonant circuit formed by the second capacitive block 20-2. ｂ , internal resistor R ｂ , internal inductor L ｂ , primary inductor L ｓ The second capacitive circuit 12-2 is connected in series to a second series resonant circuit, and the output voltage V ｂ A second damped oscillation current corresponding to

[0027] First capacitor C ｓ１and the capacitance of the second capacitor C ｓ２ Since the capacitances of the first and second damped oscillatory currents are different, the resonant frequency f1 of the first damped oscillatory current is different from the resonant frequency f2 of the second damped oscillatory current.

[0028] Primary inductor L ｓ The damped oscillatory current flowing through the secondary inductor L ｓｓ A damped oscillatory voltage is generated as an induced electromotive force across the primary inductor L ｓ The damped oscillation voltage has a time waveform similar to that of the damped oscillation current flowing in the amplifier 14. The amplifier 14 amplifies the damped oscillation voltage and outputs it to the peak hold circuit 16.

[0029] The peak hold circuit 16 extracts two maximum values ​​from the damped oscillation voltage under the control of the control unit 18. For example, it extracts the n1th maximum value and the n2th maximum value after the damped oscillation voltage is input, and outputs them to the control unit 18. The control unit 18 stores the n1th maximum value in association with the time tn1 at which the maximum value occurred. The control unit 18 also stores the n1th maximum value in association with the time tn1 at which the maximum value occurred.

[0030] FIG. 2 shows an example of the time waveform of the damped oscillation voltage V. Here, the primary inductor L ｓ 2, the integer n1 is 1 and the integer n2 is 7. In a state where the first selection switch S1 and the second selection switch S2 are off, at time t0, the first selection switch S １ is turned on in a pulsed manner, and at time t0, the secondary inductor L ｓｓ A damped oscillation voltage of frequency f1 is generated at the output of the amplifier 14, and the amplified damped oscillation voltage V is output to the peak hold circuit 16.

[0031] The peak hold circuit 16 extracts the first maximum value Vn1 and the seventh maximum value Vn2 under the control of the control unit 18 and outputs them to the control unit 18. The control unit 18 stores the maximum value Vn1(f1) in association with the time tn1(f1) at which the maximum value Vn1(f1) occurred. The control unit 18 also stores the maximum value Vn2(f1) in association with the time tn2(f1) at which the maximum value Vn2(f1) occurred. Here, the f1 in parentheses indicates the value when the frequency of the damped oscillation current is f1.

[0032] The control unit 18 calculates the real part Zreal(f1) of the impedance of the battery 10 for the first frequency f1 based on the set of the maximum value Vn1(f1) and the time tn1(f1) obtained for the first frequency f1 and the set of the maximum value Vn2(f1) and the time tn2(f1).

[0033] Specifically, the control unit 18 calculates the impedance real part Zreal(f1) according to the following (Equation 1). Note that the process of deriving (Equation 1) will be described later. Here, L ｓ is the primary inductor L ｓ In the process of deriving (Equation 1), the primary inductor L ｓ The inductance of the battery 10 is the internal inductance L ｂ is sufficiently larger than the inductance of the battery capacitor C ｂ The capacitance of the first capacitor C ｓ１ The capacitance of the first capacitive circuit 12-1 is set to be sufficiently larger than the capacitance of the first capacitive circuit 12-2. ｓ is the internal resistor R in the battery 10 ｂ The resistance value is set to be sufficiently larger than the resistance value of the

[0034]

[0035] The control unit 18 also performs the same process on the second damped oscillation current as it did on the first damped oscillation current. １ and the second selection switch S ２ is off, the second selection switch S ２By turning on the primary inductor L ｓ As a result, at time t0, the secondary inductor L ｓｓ A damped oscillation voltage of frequency f2 is generated at the output of the amplifier 14, and the amplified damped oscillation voltage V is output to the peak hold circuit 16.

[0036] The peak hold circuit 16 extracts the first maximum value Vn1 and the seventh maximum value Vn2 under the control of the control unit 18 and outputs them to the control unit 18. The control unit 18 stores the maximum value Vn1(f2) and the time tn1(f2) at which the maximum value Vn1(f2) occurred in association with each other. The control unit 18 also stores the maximum value Vn2(f2) and the time tn2(f2) at which the maximum value Vn2(f2) occurred in association with each other.

[0037] The control unit 18 calculates the impedance real part Zreal(f2) of the battery 10 for the second frequency f2 based on the set of the maximum value Vn2(f2) and the time tn1(f2) obtained for the second frequency f2 and the set of the maximum value Vn2(f2) and the time tn2(f2). Specifically, the control unit 18 calculates the impedance real part Zreal(f2) according to the following Equation 2.

[0038]

[0039] In this way, the battery evaluation device 100 has the function of an impedance real part measurement unit that measures the impedance real part of the battery 10 for each of the first frequency f1 and the second frequency f2.

[0040] The impedance real part measuring unit configured in the battery evaluation device 100 includes a damped oscillation circuit that damps oscillation of the current flowing through the battery 10. The damped oscillation circuit includes the battery 10 and a primary inductor L ｓ and a first capacitive circuit 12-1, or a first series resonant circuit including a battery 10 and a primary inductor L ｓ and a second series resonant circuit including a second capacitive circuit 12-2.

[0041] The control unit 18 realizes the function of an impedance real part measuring unit. That is, the control unit 18 acquires damped oscillation data on the damped oscillation current of the battery 10 from the damped oscillation circuit, and calculates the impedance real part of the battery 10 based on the damped oscillation data. Here, the damped oscillation data includes data associating the maximum value Vn1(f2) with the time tn1(f2) at which the maximum value Vn1(f2) occurred. The damped oscillation data also includes data associating the maximum value Vn2(f2) with the time tn2(f2) at which the maximum value Vn2(f2) occurred. The damped oscillation circuit includes a plurality of capacitive circuits 12-1 and 12-2 and an inductive circuit including an inductive element. Here, the inductive circuit includes a primary inductor L as the inductive element. ｓ The impedance real part measuring unit includes a selection switch S as a selection circuit that selects at least one of the plurality of capacitive circuits and connects it to the inductive circuit, and causes the current flowing through the battery to oscillate at damped oscillation at a plurality of frequencies. １ and S ２ Includes.

[0042] The derivation process of (Equation 1) and (Equation 2) is shown below. The damped oscillation voltage V shown in Fig. 2 is expressed as the following (Equation 3) with t as the time variable. α, ω, and β in (Equation 3) are expressed by (Equation 4), (Equation 5), and (Equation 6), respectively.

[0043]

[0044]

[0045]

[0046]

[0047] where M is the primary inductor L ｓ and secondary inductor L ｓｓ mutual inductance, V ｂ is the output voltage of the battery 10, L ｓ is the primary inductor L ｓ inductance, R ｂ is the internal resistance of the battery 10, C ｓ is the first capacitor C ｓ１ or C ｓ２ is the capacitance of Rｓ is the first capacitor C ｓ１ or C ｓ２ is the discharge resistance.

[0048] The n-th maximum value V(tn) is expressed by (Equation 7), where tn is the time when the maximum value appears.

[0049]

[0050] Substituting tn = tn2 into (Equation 7) and dividing both sides of the equation by substituting tn = tn1 into (Equation 7), we solve the equation for α and substitute it into (Equation 4), and then we get R ｂ By solving the above equation, we obtain (Equation 8). However, the second term on the right side of (Equation 4) is omitted since it is sufficiently smaller than the first term.

[0051]

[0052] Substituting Vtn1(f1), Vtn2(f1), tn1(f1), and tn2(f1) into V(tn1), V(tn2), tn1, and tn2, respectively, in (Equation 8) results in (Equation 1). Substituting Vtn1(f2), Vtn2(f2), tn1(f2), and tn2(f2) into V(tn1), V(tn2), tn1, and tn2, respectively, in (Equation 8) results in (Equation 2).

[0053] As shown in (Equation 5), the resonant frequency of the damped oscillatory current and the damped oscillatory voltage is ｓ Inductance L ｓ and the capacitance C of the first capacitive circuit 12-1. ｓ１ In other words, the resonant angular frequency is the reciprocal of the square root of the product of the inductance L ｓ and the primary inductor L ｓ It is determined by the reciprocal of the square root of the product of the capacitance of the capacitive circuit connected in series with the capacitance of the inductor.

[0054] The control unit 18 operates the first selection switch S １ and the second selection switch S ２ are both off, the second selection switch S ２ When only the inductance L is turned on in a pulsed manner, the resonant angular frequency is ｓ and capacitance Cｓ２ It is the reciprocal of the square root of the product of

[0055] In addition, the control unit 18 operates the first selection switch S １ and the second selection switch S ２ are both off, the first selection switch S １ and the second selection switch S ２ When both are turned on in a pulsed manner, the resonant angular frequency is ｓ and capacitance (C ｓ１ +C ｓ２ ) is the reciprocal of the square root of the product of

[0056] Therefore, in the battery evaluation device 100 according to this embodiment, the first selection switch S １ and the second selection switch S ２ By controlling ｓ ・C ｓ１ ), 1 / √(L ｓ ・C ｓ２ ) and 1 / √[L ｓ ・(C ｓ１ +Cs2)] may be passed through the battery 10.

[0057] 3 shows the configuration of a battery evaluation device 102 according to the second embodiment. In the battery evaluation device 102, the first capacitive block 20-1 and the second capacitive block 20-2 in the battery evaluation device 100 are replaced with first capacitive block 20-1 to n-th capacitive block 20-n connected in parallel. The j-th capacitive block 20-j, where j is an integer from 1 to n, includes a capacitive circuit 12-j connected in series and a j-th selection switch Sj. The capacitive circuit 12-j includes a j-th capacitor C connected in parallel. ｓｊ and discharge resistor R ｓｊ Includes.

[0058] First selection switch S １ ~nth selection switch S ｎ When all of the first selection switch S １ ~nth selection switch S ｎWhen the control unit 18 turns on at least one of the selection switches in a pulsed manner, the resonance angular frequency is determined by the sum of the capacitances of the capacitors connected to the selection switches that are turned on in a pulsed manner and the inductance L ｓ The resonant angular frequency is the reciprocal of the square root of the product of the first selection switch S １ ~ ｎ Selection switch S ｎ The control unit 18 selects at least one of the first selection switch S １ ~nth selection switch S ｎ By determining which of the inductors to turn on in a pulsed manner, the primary inductor L ｓ The frequency (angular frequency) of the damped oscillatory current flowing through the

[0059] 4 shows the configuration of a battery evaluation device 104 according to the third embodiment. In the battery evaluation device 104, the first capacitive block 20-1 and the second capacitive block 20-2 in the battery evaluation device 100 are replaced with a variable capacitance circuit 20v. The variable capacitance circuit 20v includes a capacitive circuit 12v and a switch S ｖ The capacitive circuit 12v includes a variable capacitance element C ｓｖ and discharge resistor R ｓｖ The variable capacitance element C ｓｖ may be a variable capacitance diode, a variable capacitor that mechanically changes the area where adjacent conductive plates face each other, or the like.

[0060] The control unit 18 turns on the switch S ｖ is turned off, the switch S ｖ When the primary inductor L ｓ The resonant angular frequency of the damped oscillatory current flowing through ｓ ・C ｓｖ The control unit 18 controls the variable capacitance element C ｓｖ The variable capacitance element C in ｓｖ By adjusting the capacitance of the primary inductor L ｓ Determine the frequency of the damped oscillatory current flowing through the

[0061] As described below, the control unit 18 calculates an evaluation value indicating the state of the battery 10. The evaluation value of the battery 10 may be at least one of the amount of metal deposition and the temperature. If the battery 10 is a lithium ion battery, the amount of metal deposition is the amount of lithium deposition.

[0062] The process by which the control unit 18 determines the temperature T of the battery 10 and the amount of metal deposition ΔD is described below. The relationship between the impedance real part Zreal(f1) at frequency f1, the amount of metal deposition ΔD, and the temperature change ΔT of the battery is shown in Equation 9. The relationship between the impedance real part Zreal(f2) at frequency f2, the amount of metal deposition ΔD, and the temperature change ΔT of the battery is shown in Equation 10.

[0063]

[0064]

[0065] Here, A1 and A2 are capacity degradation coefficients for frequencies f1 and f2, respectively, and are determined in advance using a derivation method described below. The capacity degradation coefficient indicates the degree to which a decrease in battery capacity contributes to the impedance real part. Furthermore, B1 and B2 are temperature coefficients for frequencies f1 and f2, respectively, and are determined in advance using a derivation method described below. The temperature coefficient indicates the degree to which a temperature change in the battery contributes to the impedance real part. The temperature change ΔT represents the increase from the reference temperature T0 when deriving the temperature coefficients B1 and B2, as described below. When the battery 10 to be evaluated is a lithium-ion battery, the first frequency f1 and the second frequency f2 may be 10 kHz or higher.

[0066] By eliminating the temperature change ΔT from (Equation 9) and (Equation 10) and solving for the amount of metal deposition ΔD, (Equation 11) can be obtained.

[0067]

[0068] By eliminating the amount of metal deposition ΔD from (Equation 9) and (Equation 10) and solving for the temperature change ΔT, (Equation 12) can be obtained.

[0069]

[0070] The control unit 18 calculates the amount of metal deposition ΔD and the temperature change ΔT based on the impedance real parts Zreal(f1) and Zreal(f2) calculated according to (Equation 1) and (Equation 2), and (Equation 11) and (Equation 12). The control unit 18 further calculates the temperature T of the battery 10, T=T0+ΔT, by adding the temperature change ΔT to the reference temperature T0.

[0071] The method for deriving the temperature coefficients B1 and B2 is described below. When deriving the temperature coefficients, as shown in FIG. 5 , the temperature T of the battery 10 is used as a parameter to determine the characteristic of the impedance real part Zreal with respect to frequency f (the impedance real part frequency characteristic). That is, the temperature of the battery 10 is varied in multiple ways, and the characteristic of the impedance real part Zreal with respect to frequency f is determined for each temperature. The impedance real part frequency characteristic may be determined statistically, for example, by averaging measured values ​​for multiple batteries.

[0072] Furthermore, as shown in FIG. 6 , the characteristic of the impedance real part dZreal with respect to the temperature T of the battery 10 (the impedance real part temperature characteristic) is obtained using frequency f as a parameter. The impedance real part temperature characteristic may also be obtained statistically by, for example, averaging measured values ​​for multiple batteries. In the example shown in FIG. 6 , the impedance real part dZreal indicates the increase in the impedance real part Zreal from when the temperature T is a reference temperature T0 = 20°C. The impedance real part temperature characteristic shown in FIG. 6 may be obtained from the impedance real part frequency characteristic shown in FIG. 5 . Similarly, the impedance real part frequency characteristic shown in FIG. 5 may be obtained from the impedance real part temperature characteristic shown in FIG. 6 .

[0073] When deriving the temperature coefficient, the impedance real part change frequency characteristic 30T shown in Fig. 7 is also obtained. That is, the impedance real part change ΔZreal at a constant temperature change ΔT with respect to frequency f is obtained. The impedance real part change frequency characteristic 30T shown in Fig. 7 is a characteristic that associates the impedance real part change ΔZreal when the temperature changes from 20°C to 60°C with frequency f.

[0074] The temperature coefficient B1 at frequency f1 is calculated by dividing the change in the real part of impedance ΔZreal(f1) when the frequency is f1 in the impedance real part change frequency characteristic of 30T by ΔT = 60-20°C. That is, B1 is calculated as B1 = ΔZreal(f1) / ΔT.

[0075] Similarly, the temperature coefficient B2 at frequency f2 is calculated as ΔZreal(f2) / ΔT, which is the value obtained by dividing the change in the real part of impedance ΔZreal(f2) when the frequency is f2 in the impedance real part change frequency characteristic of 30T by ΔT = 60-20°C. That is, the temperature coefficient B2 is calculated as B2 = ΔZreal(f2) / ΔT.

[0076] In this way, the temperature coefficient B1 for the first frequency f1 and the temperature coefficient B2 for the second frequency f2 are calculated based on the impedance real part frequency characteristic ( FIG. 5 ) or the impedance real part change frequency characteristic ( FIG. 7 ) derived from the impedance real part temperature characteristic ( FIG. 6 ). The impedance real part frequency characteristic and the impedance real part temperature characteristic are characteristics (first battery characteristics) that indicate the relationship between the temperature of the battery 10, the frequency of the current flowing through the battery 10, and the impedance real part of the battery.

[0077] Next, the method for deriving the capacity degradation coefficients A1 and A2 is described below. To derive the capacity degradation coefficients, the impedance real part change frequency characteristic 30M shown in FIG. 7 is obtained. That is, the impedance real part change ΔZreal at a certain capacity degradation amount X with respect to frequency is obtained as the impedance real part change frequency characteristic 30M. Here, the capacity degradation amount indicates how much the full charge capacity [mAh] has deteriorated from when the battery was new. The impedance real part change frequency characteristic 30M shown in FIG. 7 is a characteristic that associates the impedance real part change ΔZreal when the capacity degradation amount is 10% with frequency f. The impedance real part change frequency characteristic 30M may be obtained statistically, for example, by averaging measured values ​​for multiple batteries.

[0078] The capacity degradation coefficient A1 at frequency f1 is calculated by dividing the change in the real part of impedance ΔZreal(f2) when the frequency is f1 in the impedance real part change frequency characteristic 30M by the capacity degradation X=10[%]. That is, the capacity degradation coefficient A1 is calculated as A1=ΔZreal(f1) / X.

[0079] Similarly, the capacity degradation coefficient A2 at frequency f2 is calculated by dividing the change in the real part of impedance ΔZreal(f2) at frequency f2 in the impedance real part change frequency characteristic 30M by the capacity degradation X=10[%]. That is, the capacity degradation coefficient A2 is calculated as A2=ΔZreal(f2) / X.

[0080] In this way, the capacity degradation coefficient A1 for the first frequency f1 and the capacity degradation coefficient A2 for the second frequency f2 are calculated based on the impedance real part change frequency characteristic (second battery characteristic) that indicates the relationship between the capacity degradation amount X of the battery 10, the frequency f of the current flowing through the battery 10, and the change amount of the impedance real part of the battery 10.

[0081] In each embodiment of the present invention, a battery evaluation method is performed, which includes the following steps. This battery evaluation method may be included in the steps of a manufacturing method for battery 10. (i) Measuring first battery characteristics indicating the relationship between the temperature of battery 10, the frequency of the current flowing through battery 10, and the real part of the impedance of battery 10. (ii) Calculating temperature coefficients B1 and B2 of battery 10 for the first frequency f1 and the second frequency f2, respectively, based on the first battery characteristics. (iii) Measuring second battery characteristics indicating the relationship between the amount of capacity degradation of battery 10, the frequency of the current flowing through battery 10, and the amount of change in the real part of the impedance of battery 10. (iv) Calculating capacity degradation coefficients A1 and A2 of battery 10 for the first frequency f1 and the second frequency f2, respectively, based on the second battery characteristics. (v) Measuring the real part of the impedance of battery 10 for each of the first frequency f1 and the second frequency f2. (vi) Calculating an evaluation value indicating the state of the battery 10 based on the temperature coefficient B1 and capacity degradation coefficient A1 calculated for the first frequency f1, the temperature coefficient B2 and capacity degradation coefficient A2 calculated for the second frequency f2, and the impedance real parts measured for each of the first frequency and the second frequency.

[0082] According to each embodiment of the present invention, a battery evaluation value is calculated based on a temperature coefficient and a capacity degradation coefficient that are previously acquired. Because the evaluation value is calculated based on the real part of the battery's impedance calculated at two frequencies, the process of measuring the evaluation value is simpler than, for example, a process of calculating the internal impedance from the relationship between the sinusoidal voltage applied to the battery and the sinusoidal current flowing through the battery while changing the frequency. Furthermore, because the temperature coefficient is calculated in advance, there is no need to measure the temperature during evaluation, and the process of measuring the evaluation value is simplified.

[0083] In the battery evaluation devices 100, 102, and 104 according to the embodiments of the present invention, a damped oscillatory current is passed through the battery 10 by a damped oscillatory circuit in order to evaluate the battery 10. Therefore, there is no need to use a device that generates a sinusoidal voltage or sinusoidal current, and the configuration of the device is simplified.

[0084] 8 shows the configuration of a battery protection system 106 according to an application embodiment of the present invention. The battery protection system 106 is a system in which a battery evaluation device 100 is connected to a battery 10 connected to an electric circuit 40. The electric circuit 40 may be a load circuit for the battery 10, or a charging circuit for charging the battery 10. The battery evaluation device 100 may be replaced with the battery evaluation device 102 or 104.

[0085] The control unit 18 controls the electric circuit 40 according to the evaluation value of the battery 10 to adjust the voltage applied to the battery 10 or the current flowing through the battery 10. The control unit 18 executes the following control, for example: When the temperature of the battery 10 exceeds a predetermined temperature threshold, the control unit 18 controls the electric circuit 40 so that the voltage applied to the battery 10 does not exceed a predetermined threshold voltage. Furthermore, when the temperature of the battery 10 exceeds the predetermined temperature threshold, the control unit 18 may control the electric circuit 40 so that the magnitude of the current flowing through the battery 10 does not exceed a predetermined threshold current.

[0086] When the amount of metal deposition in battery 10 exceeds a predetermined deposition amount threshold, control unit 18 controls electric circuit 40 so that the voltage applied to battery 10 does not exceed a predetermined threshold voltage. Furthermore, when the amount of metal deposition exceeds the predetermined deposition amount threshold, control unit 18 may control electric circuit 40 so that the current flowing through battery 10 does not exceed a predetermined threshold current.

[0087] [Configurations of the Invention] Configuration 1: A battery evaluation device including an impedance real part measurement unit that measures the impedance real part of a battery for each of a first frequency and a second frequency, and that calculates an evaluation value indicating the state of the battery based on the impedance real part of the battery calculated for each of the first frequency and the second frequency, a temperature coefficient and a capacity degradation coefficient previously obtained for the first frequency, and a temperature coefficient and a capacity degradation coefficient previously obtained for the second frequency. Configuration 2: The battery evaluation device according to Configuration 1, wherein the evaluation value is at least one of an amount of metal deposition and a temperature. Configuration 3: The battery evaluation device according to Configuration 1 or Configuration 2, wherein the temperature coefficients for the first frequency and the second frequency are calculated based on the relationship between the temperature of the battery, the frequency of a current flowing through the battery, and the impedance real part of the battery. and a selection circuit that selects and connects at least one of the plurality of capacitive circuits to the inductive circuit, thereby causing the current flowing through the battery to oscillate at a plurality of frequencies.and a control unit that changes the capacitance of the variable capacitance element to cause the current flowing through the battery to oscillate at a plurality of frequencies.Configuration 6: The battery evaluation device according to any one of configurations 1 to 4, wherein the impedance real part measurement unit comprises a damped oscillation circuit that causes a current flowing through the battery to oscillate at a damped oscillation, acquires damped oscillation data on the damped oscillation current of the battery from the damped oscillation circuit, and calculates the impedance real part of the battery based on the damped oscillation data, the damped oscillation circuit comprises: an inductive circuit including an inductive element, a variable capacitance element connected to the inductive circuit, and a control unit that changes the capacitance of the variable capacitance element to cause the current flowing through the battery to oscillate at a plurality of frequencies.Configuration 7: A battery protection system comprising: the battery evaluation device according to any one of configurations 1 to 6, and an electric circuit connected to the battery, wherein the battery evaluation device controls the electric circuit based on the evaluation value to adjust the voltage applied to the battery or the current flowing through the battery. A battery evaluation method comprising: measuring first battery characteristics indicating a relationship between a battery temperature, a frequency of a current flowing through the battery, and a real part of an impedance of the battery; determining a temperature coefficient of the battery for each of a first frequency and a second frequency based on the first battery characteristics; measuring second battery characteristics indicating a relationship between an amount of capacity degradation of the battery, a frequency of a current flowing through the battery, and a change in the real part of the impedance of the battery; determining a capacity degradation coefficient of the battery for each of the first frequency and the second frequency based on the second battery characteristics; measuring the real part of the impedance of the battery for each of the first frequency and the second frequency; and determining an evaluation value indicating a state of the battery based on the temperature coefficient and capacity degradation coefficient determined for the first frequency, the temperature coefficient and capacity degradation coefficient determined for the second frequency, and the real part of the impedance of the battery measured for each of the first frequency and the second frequency. A battery evaluation method according to A1, wherein the evaluation value is at least one of an amount of metal deposition and a temperature. Configuration 10: A battery manufacturing method comprising the step of evaluating the battery by the battery evaluation method according to Configuration 8 or Configuration 9.

[0088] 10 Battery, 12-1 to 12-n, 12v Capacitive circuit, 14 Amplifier, 16 Peak hold circuit, 18 Control unit, 20-1 to 20-n 1st to nth capacitive blocks, 20v Variable capacitance circuit, 30T, 30M Impedance real part change amount frequency characteristic, 40 Electric circuit, 100, 102, 104 Battery evaluation device, 106 Battery protection system, Cb Battery capacitor, Rb Internal resistor, Lb Internal inductor, L ｓ Primary inductor, L ｓｓ Secondary inductor, R ｓ , R ｓ１ ~R ｓｎ Discharge resistor, Cs, C ｓ１ ~Csn first and second capacitors, S １ ~S ｎ Selection switch, S ｖ switch.

Claims

1. A battery evaluation device comprising an impedance real part measurement unit that measures the impedance real part of a battery for each of a first frequency and a second frequency, and that calculates an evaluation value that indicates the state of the battery based on the impedance real part of the battery calculated for each of the first frequency and the second frequency, a temperature coefficient and a capacity degradation coefficient that are obtained in advance for the first frequency, and a temperature coefficient and a capacity degradation coefficient that are obtained in advance for the second frequency.

2. A battery evaluation device according to claim 1, wherein the evaluation value is at least one of the amount of metal deposition and the temperature.

3. A battery evaluation device according to claim 1, wherein the temperature coefficients for the first frequency and the second frequency are determined based on the relationship between the temperature of the battery, the frequency of the current flowing through the battery, and the real part of the impedance of the battery.

4. A battery evaluation device according to claim 1, wherein the capacity degradation coefficients for the first frequency and the second frequency are calculated based on the relationship between the amount of capacity degradation of the battery, the frequency of the current flowing through the battery, and the amount of change in the real part of the impedance of the battery.

5. A battery evaluation device according to claim 1, wherein the impedance real part measurement unit comprises a damped oscillation circuit that causes a current flowing through the battery to oscillate at a damped oscillation; obtains damped oscillation data on the damped oscillation current of the battery from the damped oscillation circuit and calculates the impedance real part of the battery based on the damped oscillation data; and the damped oscillation circuit comprises: a plurality of capacitive circuits each including a capacitive element; an inductive circuit including an inductive element; and a selection circuit that selects at least one of the plurality of capacitive circuits and connects it to the inductive circuit, thereby causing the current flowing through the battery to oscillate at a damped oscillation at a plurality of frequencies.

6. A battery evaluation device according to claim 1, wherein the impedance real part measurement unit comprises a damped oscillation circuit that causes a current flowing through the battery to oscillate at a damped oscillation; damped oscillation data on the damped oscillation current of the battery is acquired from the damped oscillation circuit, and the impedance real part of the battery is determined based on the damped oscillation data; and the damped oscillation circuit comprises an inductive circuit including an inductive element, a variable capacitance element connected to the inductive circuit, and a control unit that changes the capacitance of the variable capacitance element to cause the current flowing through the battery to oscillate at a plurality of frequencies.

7. A battery protection system comprising: a battery evaluation device according to any one of claims 1 to 6; and an electric circuit connected to the battery, wherein the battery evaluation device controls the electric circuit based on the evaluation value to adjust the voltage applied to the battery or the current flowing through the battery.

8. A battery evaluation method comprising: measuring first battery characteristics indicating the relationship between the temperature of a battery, the frequency of a current flowing through the battery, and the real part of the impedance of the battery; determining a temperature coefficient of the battery for each of a first frequency and a second frequency based on the first battery characteristics; measuring second battery characteristics indicating the relationship between an amount of capacity degradation of the battery, the frequency of a current flowing through the battery, and an amount of change in the real part of the impedance of the battery; determining a capacity degradation coefficient of the battery for each of the first frequency and the second frequency based on the second battery characteristics; measuring the real part of the impedance of the battery for each of the first frequency and the second frequency; and determining an evaluation value indicating the state of the battery based on the temperature coefficient and capacity degradation coefficient determined for the first frequency, the temperature coefficient and capacity degradation coefficient determined for the second frequency, and the real part of the impedance of the battery measured for each of the first frequency and the second frequency.

9. A battery evaluation method according to claim 8, wherein the evaluation value is at least one of the amount of metal deposition and the temperature.

10. A battery manufacturing method comprising the step of evaluating the battery by the battery evaluation method according to claim 8 or 9.

Images