JP2012220344A - Cell voltage measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that each of cell voltages cannot be correctly measured when a contact resistance is present between each cell and a connection terminal of a cell voltage measurement circuit.SOLUTION: The cell voltage measurement device of the present invention includes a plurality of terminals (qto q) which are arranged corresponding to a plurality of connecting parts for electrically connecting a plurality of cells which are connected in series; a voltage measurement unit (6) for sequentially measuring voltage values of cells from the plurality of terminals; a contact resistance calculation unit (5) for sequentially calculating contact resistance values generated in the terminals; and a cell voltage calculation unit (8) for calculating voltage values of cells by using the contact resistance values and voltage values.

Description

  The present invention relates to a cell voltage measurement device, and more particularly to a cell voltage measurement device that measures the voltage of individual cells constituting a battery in which a plurality of cells are connected in series.

  In electric vehicles and hybrid vehicles, a stack type battery in which a plurality of cells made of secondary batteries such as lithium ion batteries are connected in series to obtain a desired voltage is used as a motor power source. . In such a stack type battery, electric power supplied to the automobile from a power supply facility installed outside the automobile or electric power regenerated by the motor can be stored in each cell. Moreover, the voltage of each cell fluctuates by charging or discharging.

  Here, if the cell is overdischarged or overcharged, it adversely affects the characteristics of the cell, and as a result, the ability to drive the battery motor is reduced. Therefore, it is important to monitor the voltage of each cell constituting the stack type battery, and a cell voltage measuring device capable of measuring the voltage of each cell is known (for example, Patent Document 1). .

  FIG. 1 shows the configuration of a conventional cell voltage measuring apparatus. In the conventional cell voltage measurement device, the switch switching circuit 102 connects both ends of any one cell constituting the battery pack 101 and the capacitor 103 to select the one cell, and the measurement circuit 107 selects both ends of the capacitor 103. Measure the voltage. With this configuration, the cell voltage can be measured in units of individual cells.

JP 2001-86656 A

  Here, in order to measure the voltage of each cell, it is necessary to provide a connection terminal in order to connect the connection part which connects each cell, and a voltage measuring device. At this time, there is a problem that contact resistance exists in the connection terminal, and the voltage of each cell cannot be accurately measured as described below.

A method for measuring voltages of individual cells constituting a stack type battery will be described with reference to FIG. Here, a case where the cell voltage is measured using a differential amplifier circuit will be described as an example. In the stack type battery 1, cells C _{1 to} C _N are connected in series, and individual cells are connected to each other by j _{2 to} j _N among connection portions j _{1 to} j _{N + 1} provided at both ends of the cell. Has been. Cell-side terminals p _{1 to} p _{N + 1} for measuring cell voltages V _{1 to} V _N are provided at the respective connection portions j _{1 to} j _{N + 1} . When measuring the voltage V _n of the _nth cell C _n , the cell side terminals _pn and _{pn + 1} and the terminals q _a and q _{b of the} voltage measuring circuit 21 are connected to output voltage Vout _n. Measure the value of. Here, the output voltage Vout _n is obtained by the following equation.

ここで、ｒ_n、ｒ_n+1はそれぞれ、ｐ_nとｑ_bとの間の接触抵抗、ｐ_n+1とｑ_aとの間の接触抵抗を表している。なお、図２において接触抵抗を便宜的に接続部と端子間に記載する。Ｒ_a、Ｒ_b、Ｒ_c、Ｒ_dは、電圧測定回路２１に設けられた抵抗、ΣＶ_mはオフセット電圧と呼ばれ、セルＣ₁〜Ｃ_n-1の電圧Ｖ₁〜Ｖ_n-1の総和である。

Here, it represents the contact resistance between the r _n, respectively r n _{+ 1,} the contact resistance between the p _n and q _b, p n _{+ 1} and q _a. In FIG. 2, the contact resistance is shown between the connection portion and the terminal for convenience. _{R a, R b, R c} , R d , the resistance provided to the voltage measuring circuit 21, [sigma] v _m is called the offset voltage, the cell C ₁ ~C _n-1 of the voltage V ₁ ~V _n-1 It is the sum.

From the equation (1), the error ΔV _n between the cell voltage (cell voltage) V _n and the measured voltage Vout _n is given by the following equation.

As can be seen from the equation (2), if the contact resistances r _n and r _{n + 1} are both 0 [Ω], ΔV _m is also 0 [V]. However, when the contact resistances r _n and r _{n + 1} are 10 [Ω] and 1 k [Ω], for example, R _a and R _c are 510 k [Ω], R _b and R _d are 360 k [Ω], If the cell voltage V _n is 2 [V] and the offset voltage ΣV _m is 60 [V], the error ΔV _n is 50.86 [mV]. If the allowable measurement error of the voltage of each cell is 50 [mV], an error exceeding the allowable measurement error may occur when measuring the cell voltage due to the presence of the contact resistance.

Here, in order to reduce the contact resistance, it is also conceivable to configure the cell side terminals p _{1 to} p _{N + 1} using expensive components. However, in this case, there is a problem that the price of the stack type battery becomes expensive.

  Therefore, in the present invention, each cell constituting a stack type battery including a plurality of cells and the voltage of each cell, such as when the cell side terminal is configured using low-cost parts having relatively high contact resistance, An object of the present invention is to provide a cell voltage measuring device capable of accurately measuring the voltage of a cell even when a contact resistance exists between the terminal and the terminal for measuring the voltage.

  The cell voltage measuring device according to the present invention sequentially includes a plurality of terminals provided corresponding to a plurality of connection portions that electrically connect a plurality of cells connected in series, and a cell voltage value sequentially from the plurality of terminals. A voltage measuring unit for measuring, a contact resistance calculating unit for sequentially calculating a value of contact resistance generated at the terminal, a cell voltage calculating unit for calculating a voltage value of the cell using the value of the contact resistance and the value of the voltage; It is characterized by having.

  According to the present invention, even when contact resistance exists between individual cells constituting a stack type battery including a plurality of cells and terminals for measuring voltages of the individual cells, The cell voltage can be accurately measured.

It is a block diagram of the conventional cell voltage measuring apparatus. FIG. 3 is a configuration diagram of a stack type battery and a cell voltage measurement circuit that measures voltages of individual cells constituting the stack type battery. It is a figure which shows the structure of the cell voltage measuring apparatus which concerns on Example 1 of this invention. It is a flowchart which shows the cell voltage calculation method by the cell voltage measuring apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the cell voltage measurement apparatus at the time of using the RC circuit for the contact resistance calculation part in the cell voltage measurement apparatus which concerns on Example 1 of this invention. 5 is a flowchart illustrating a contact resistance calculation method when an RC circuit is used for the contact resistance calculation unit in the cell voltage measurement device according to Embodiment 1 of the present invention. 5 is a flowchart illustrating a method for calculating a time constant when an RC circuit is used for the contact resistance calculation unit in the cell voltage measurement device according to Embodiment 1 of the present invention. In the cell voltage measuring apparatus which concerns on Example 1 of this invention, it is a figure which shows the relationship between the voltage charged to the capacitor | condenser at the time of using RC circuit for a contact resistance calculation part, and charging time. In the cell voltage measuring device according to Example 1 of the present invention, it is a diagram showing the configuration of the cell voltage measuring device when a differential amplifier circuit is used for the voltage measuring unit. It is a figure which shows the structure of the cell voltage measuring apparatus which concerns on Example 2 of this invention. It is a flowchart which shows the calculation method of the contact resistance by the cell voltage measuring apparatus which concerns on Example 2 of this invention. It is a figure which shows the structure of the cell voltage measuring apparatus which concerns on Example 3 of this invention. It is a flowchart which shows the calculation method of the contact resistance by the cell voltage measuring apparatus which concerns on Example 3 of this invention.

  Hereinafter, a cell voltage measuring apparatus according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

FIG. 3 shows a cell voltage measuring apparatus according to Embodiment 1 of the present invention. The cell voltage measurement device 2 includes a cell changeover switch 3, a circuit changeover switch 4, a contact resistance calculation unit 5, a voltage measurement unit 6, a changeover switch control unit 7, a cell voltage calculation unit 8, a control unit 9, A storage unit 10 and a data transmission unit 11. The battery 1 includes a plurality of cells C _{1 to} C _N stacked (stacked), and each cell has j ₂ to j _N out of connection portions j _{1 to} j _{N + 1} provided at both ends of the cell. Connected through. The connecting portion j ₁ ~j N + ₁ of the cell, the cell-side terminal p ₁ ~p N + ₁ for measuring the voltage of the individual cells is provided, the cell-side terminal p ₁ ~p N + ₁ Are respectively connected to the terminals q _{1 to} q _{N + 1} of the cell changeover switch 3 of the cell voltage measuring device 2. That is, the plurality of terminals q _{1 to} q _{N + 1} are provided corresponding to the plurality of connection portions j _{1 to} j _{N + 1} that electrically connect the plurality of cells C _{1 to} C _N connected in series. ing. A contact resistance is generated between the cell side terminals p _{1 to} p _{N + 1} and the terminals q _{1 to} q _{N + 1} , which are r _{1 to} r _{N + 1} , respectively. In FIG. 3, are described between the contact resistance r ₁ ~r N + connection ₁ the convenience section j ₁ to j N + ₁ and the cell terminal p ₁ ~p N + _1.

  The cell changeover switch 3 switches a switch (not shown) in order to measure the contact resistance or voltage of a specific cell among the plurality of cells constituting the battery 1. The circuit changeover switch 4 switches the connection between the cell selected by the cell changeover switch 3 and the contact resistance calculation unit 5 or the voltage measurement unit 6. The changeover switch control unit 7 controls the switches of the cell changeover switch 3 and the circuit changeover switch 4.

The control unit 9 controls the changeover switch control unit 7 to switch between the cell changeover switch 3 and the circuit changeover switch 4, calculates the contact resistance by the contact resistance calculation unit 5, and measures the voltage by the voltage measurement unit 6. Execute. Contact resistance calculating unit 5, the contact resistance generated terminal, i.e., a plurality of cells C ₁ -C _N, the connecting portion j ₁ to j N + terminal q ₁ provided corresponding to ₁ to q N + ₁ The values of the contact resistances r _{1 to} r _{N + 1} generated during the period are sequentially calculated. The voltage measuring unit 6 sequentially measures cell voltage values from a plurality of terminals q _{1 to} q _{N + 1} . Specifically, the voltage between two terminals connected to both ends of each cell is measured.

  The cell voltage calculation unit 8 calculates the voltage value of each cell using the contact resistance value calculated by the contact resistance calculation unit 5 and the voltage value measured by the voltage measurement unit 6. The storage unit 10 stores the value of the contact resistance calculated by the contact resistance calculation unit 5 and the value of the voltage measured by the voltage measurement unit 6, and transmits these values to the cell voltage calculation unit 8 as well as the control unit. The program for controlling 9 is stored.

  The data transmission unit 11 transmits the value of the cell voltage calculated by the cell voltage calculation unit 8 to the battery ECU 12 outside the cell voltage measurement device 2, and the battery ECU 12 performs charging and discharging of each cell based on the value of the cell voltage. Take control.

Next, an outline of a method for calculating a cell voltage value using the cell voltage measuring apparatus of the present invention will be described. FIG. 4 is a flowchart showing a cell voltage calculation method. First, in step S101, the contact resistance calculating unit 5, a plurality of cells C ₁ -C _N, the terminal q ₁ ~q _{N + 1} provided corresponding to the connecting portion j ₁ ~j _{N + 1} cell The values r _{1 to} r _{N + 1} of the contact resistance generated during the period are calculated. Detailed description of the method of calculating the value of contact resistance will be described later.

Next, in step S102, the voltage measurement unit 6 measures a voltage between two terminals (for example, q _n and q _{n + 1} ) provided corresponding to each cell. A method for measuring the voltage will be described later. Next, in step S103, the cell voltage calculation unit 8 calculates the voltage (cell voltage) V _n of each cell using the value of the contact resistance and the voltage measured by the voltage measurement unit 6. A method for calculating the cell voltage V _n will be described later.

  According to the present invention, the value of the contact resistance generated between each cell and the cell voltage measurement terminal is calculated, and the cell voltage is calculated using the calculated contact resistance value and the measured voltage value between the terminals. Therefore, the cell voltage can be accurately measured even when contact resistance exists.

  Next, in the cell voltage measurement method using the cell voltage measurement device of the present invention, the value of contact resistance generated between a plurality of cells and terminals provided corresponding to the connection portions of the plurality of cells is calculated. How to do will be described. FIG. 5 shows a battery 1 composed of stack type cells, and a cell voltage measuring device 2 when an RC circuit is used for the contact resistance calculation unit 5.

  The contact resistance calculation unit 5 includes a capacitor C, a resistor R for discharging the voltage charged in the capacitor C, and a voltmeter 51 for measuring the voltage charged in the capacitor C. The size of the capacitor C is preferably determined according to the measured contact resistance.

The configuration of the battery 1 is the same as the configuration shown in FIG. In FIG. 5, the cell side terminals p _n−1 , p _n , and p _{n + 1 of the} two cells C _n−1 and C _n and the terminals q _n−1 , q _n , and q _{n of the} cell voltage measuring device 2 are shown. _In order to describe a method of calculating the values of contact resistances r _n−1 , r _n , and r _{n + 1 that} occur between ₊₁ and ₊₁ , only a part of the cells is displayed. In FIG. 5, the contact resistances r _n−1 , r _n , r _{n + 1} are connected to the connection parts j _n−1 , j _n , j _{n + 1} and the cell side terminals p _n−1 , p _n , It is described between _{pn + 1} . Cell selector switch 3, lines a, has a b, terminal q ₁ ~q _{N + 1} and the wiring a, the switch switches the connection between the b SWa ₁ ~SWa _N + _1, the SWb ₁ ~SWb _{N +} 1 I have. FIG. 5 shows only the switches SWa _n−1 , SWa _n , SWa _{n + 1} and SWb _n−1 , SWb _n , SWb _{n + 1} connected to the terminals q _n−1 , q _n , q _{n + 1.} Yes. The circuit changeover switch 4 includes SW _{1 to} SW _4, and includes wirings a and b of the cell changeover switch 3, terminals 5 a and 5 b of the contact resistance calculation unit 5, and terminals 6 a and 6 b of the voltage measurement unit 6. Switch the connection.

Next, a method for measuring contact resistance will be described with reference to the flowchart of FIG. First, in step S201, as shown in FIG. 5, when the switches SWa _n−1 , SWa _n , SWa _{n + 1} and SWb _n−1 , SWb _n , SWb _{n + 1} are turned off, SW ₁ , SW ₂ is turned on to connect the wirings a and b of the cell changeover switch 3 and the terminals 5 a and 5 b of the contact resistance calculation unit 5. Next, in step S202, it turns on the SWa _n, and a terminal 5a of the contact resistance calculation unit 5 and the terminal q _n connected via the wiring a, turns on the SWb _n-1, the terminal q _n-1 And the terminal 5b of the contact resistance calculation unit 5 are connected via the wiring b. As a result, the (n−1) th cell C _n−1 of the battery 1 and the contact resistance calculation unit 5 are connected. Next, in step S203, the SW of the contact resistance calculation unit 5 is temporarily switched to the resistance R side to discharge the capacitor C, and then switched to the cell side (SW ₁ side) to charge the capacitor C. As described below, determine the time constant from the charge characteristic of the capacitor C, and calculates the two values is the sum of the contact resistance r _n-1 + r _n from the time constant determined. Assuming that the time constant is τ ₁ and the capacitance of the capacitor C is C ₀ , r _n−1 + r _n is obtained by the following equation.

Next, in step S _< b _> 204, SWa _{n + 1} and SWb _n are turned on to connect the contact resistance calculation unit 5 and the nth cell C _{n in the} battery 1. Next, in step S205, the SW of the contact resistance calculation unit 5 is temporarily switched to the resistance R side to discharge the capacitor C, and then switched to the cell side (SW ₁ side) to charge the capacitor C. As will be described later, a time constant is obtained from the charging characteristics of the capacitor C, and a value of r _n + r _{n + 1} which is the sum of two contact resistances is calculated from the obtained time constant. Assuming that the time constant is τ ₂ and the capacitance of the capacitor C is C ₀ , r _n + r _{n + 1} is obtained by the following equation.

Next, in step S206, SWa _{n + 1} and SWb _n-1 are turned on, and the (n-1) th and nth cells Cn _-1 and Cn of the contact resistance calculation unit 5 and the battery 1 are set. Connect _n . Next, in step S207, the SW of the contact resistance calculation unit 5 is temporarily switched to the resistance R side to discharge the capacitor C, and then switched to the cell side (SW ₁ side) to charge the capacitor C. As will be described later, a time constant is obtained from the charging characteristics of the capacitor C, and a value of r _n-1 + r _{n + 1} which is the sum of two contact resistances is calculated from the obtained time constant. Assuming that the time constant is τ ₃ and the capacitance of the capacitor C is C ₀ , r _n−1 + r _{n + 1} is obtained by the following equation.

Next, in step S208, contact resistances r _n−1 , r _n , r _{n + 1} are calculated. The contact resistances r _n−1 , r _n and r _{n + 1} are calculated as follows using equations (3) to (5).

By repeating the above steps S202~S208 in n = 2~N-1, it is possible to sequentially calculate a contact resistance r ₁ ~r _N. First, r ₁ , r ₂ , and r ₃ are calculated as described above, and r ₄ to r _N can be calculated using only equation (3). This is based on the fact that r ₄ is obtained from τ ₁ / C and r ₃ in the equation (3), for example, when r ₄ is obtained, r ₃ is known.

Next, a method for calculating a time constant in the contact resistance calculation unit will be described with reference to the flowchart of FIG. Here, a method of calculating the time constant τ ₁ in step S203 described above will be described. That is, SW ₁ and SW ₂ are turned on to connect the terminals 5a and 5b of the contact resistance calculation unit 5 to the wirings a and b of the cell changeover switch 3, and SWa _n and SWb _n-1 are turned on to calculate contact resistance. terminals 5a parts 5, the terminal q _n with 5b, and the q _n-1 is connected. First, in step S301, the capacitor C is discharged by connecting the SW of the contact resistance calculator 5 to the resistor R.

Next, in step S302, SW is switched to the cell side (SW ₁ side) to charge the capacitor C, and the voltage Vc (t) of the capacitor is measured by the voltmeter 51. The voltage Vc (t) charged in the capacitor C changes with time as shown in FIG. 8, and is expressed by the following equation.

ここで、Ｖ_n-1はセルＣ_n-1の電圧であり、τ₁は時定数である。

Here, V _n−1 is the voltage of the cell C _n−1 , and τ ₁ is a time constant.

Next, in step S < _b > 303, the capacitor voltages Vc (t ₁ ) and Vc (t ₂ ) after the times t ₁ and t ₂ are measured and stored in the storage unit 10. Vc (t ₁ ) and Vc (t ₂ ) are given by the following equations.

Next, in step S304, τ ₁ is calculated. Specifically, the following relational expressions are obtained from the expressions (10) and (11).

式(１２)からτ₁を算出することができる。上述のステップＳ２０５及びＳ２０７における時定数τ₂、τ₃も上記と同様にして算出することができる。

Τ ₁ can be calculated from equation (12). The time constants τ ₂ and τ ₃ in steps S205 and S207 described above can also be calculated in the same manner as described above.

In the above description, the example in which the time constant τ ₁ is calculated using the capacitor voltages Vc (t ₁ ) and Vc (t ₂ ) at the times t ₁ and t ₂ has been described. This is not a limitation. For example, when the capacitor charging time t is sufficiently long and the capacitor voltage Vc (t) can be regarded as substantially equal to the cell voltage V _n , the capacitor as shown in FIG. voltage Vc (t) may be calculated constant τ time from the time when 63.2% of the V _n.

Next, a method for measuring the cell voltage will be described. FIG. 9 shows the configuration of the cell voltage measuring apparatus according to Embodiment 1 of the present invention. FIG. 9 shows an example in which a differential amplifier circuit is used for the voltage measuring unit 6. Here, a method for measuring the voltage V _n of the _nth cell C _n will be described. First, the connection in order to select the n-th cell, and on the SWa n + _1, SWb _n cell selector switch 3, q _n, wire a of q n _{+ 1} and the cell selector switch 3, respectively and b To do. Next, in order to connect the voltage measuring unit 6 and the cell side, SW ₃ and SW ₄ are turned on, and q _n and q _{n + 1} and the terminals 6a and 6b of the voltage measuring unit 6 are respectively connected to the wirings a and b. Connect through.

At this time, the voltage Vout _n of the output terminal of the voltage measuring unit 6 is represented by the above formula (1), from equation (1), the cell voltage V _n is expressed as follows.

ここで、Ｒ_a、Ｒ_b、Ｒ_c、Ｒ_dは電圧測定部６の抵抗、ΣＶ_mはｍ＝１〜（ｎ−１）における電圧Ｖ_mの総和である。式（１４）に接触抵抗算出部５によって算出された接触抵抗の値ｒ_n、ｒ_n+1を代入することにより、接触抵抗の値を考慮したセル電圧Ｖ_nを算出することができる。
セル電圧演算部８は、記憶部１０に記憶されている、接触抵抗算出部５が算出した接触抵抗ｒ₁〜ｒ_N+1の値と、電圧測定部６が測定した端子間の電圧Ｖout₁〜Ｖout_Nとを用いて、式（１４）に従って、セルの電圧Ｖ₁〜Ｖ_Nを算出する。

Here, R _a , R _b , R _c , and R _d are the resistance of the voltage measuring unit 6, and ΣV _m is the sum of the voltages V _m in m = 1 to (n−1). By substituting the contact resistance values r _n and r _{n + 1} calculated by the contact resistance calculator 5 into the equation (14), the cell voltage V _n considering the contact resistance value can be calculated.
The cell voltage calculation unit 8 stores the values of the contact resistances r _{1 to} r _{N + 1} calculated by the contact resistance calculation unit 5 and the voltage Vout ₁ between the terminals measured by the voltage measurement unit 6, which are stored in the storage unit 10. by using the to Vout _N, according to equation (14), calculates the voltage V ₁ ~V _N cell.

  As described above, according to the present invention, the value of the contact resistance generated between the plurality of cells and the terminals provided corresponding to the connection portions connecting the plurality of cells is calculated, and the individual cells are calculated. Since the voltage of each cell is calculated using the voltage measured between the two connected terminals and the value of the contact resistance, there is no contact resistance between the cell and the voltage measurement terminal. Even if it exists, the cell voltage can be calculated accurately.

Next, a cell voltage measuring apparatus according to Embodiment 2 of the present invention will be described. FIG. 10 shows the configuration of the cell voltage measuring apparatus according to the second embodiment. The difference from the cell voltage measuring apparatus according to the first embodiment is that a contact failure determination unit 13 is further provided. The contact failure determination unit 13 compares the contact resistance value calculated by the contact resistance calculation unit 5 with a predetermined threshold value and compares the cell side terminals p _{1 to} p _{N + 1} and the terminals q _{1 to} q _{N + 1} . The presence or absence of poor contact between the two is determined. Since other configurations are the same as those of the cell voltage measuring apparatus according to the first embodiment, detailed description thereof is omitted.

Next, a contact failure detection method by the cell voltage measurement device according to the second embodiment will be described with reference to the flowchart of FIG. First, in step S401, the contact resistance calculation unit 5 calculates the contact resistance r _n. The method of calculating the r _n is the same as the method shown in step S201~S208 of FIG. Next, in step S402, the contact failure judging unit 13 checks the magnitude relationship between the value r _n of the contact resistance contact resistance calculating unit 5 is calculated and a predetermined threshold r _TH. Here, the threshold value r _TH is a resistance value used as a criterion for contact failure. Threshold r _TH may be stored in advance in the storage unit 10, the contact failure judging unit 13, stored in examining the magnitude relationship between the value r _n of the contact resistance with a predetermined threshold value r _TH Reference is made to part 10.

In step S403 if the contact resistance r _n is greater than the threshold value r _TH, poor contact determination unit 13 determines that the contact failure occurs in the terminal. On the other hand, if the contact resistance _{rn is} less than or _equal to the threshold value r _TH , in step S404, the contact failure determination unit 13 determines that there is no contact failure.

Next, in step S <b> 405, the contact failure determination unit 13 transmits information about the presence or absence of contact failure regarding the terminal with the terminal number n to the battery ECU 12 via the data transmission unit 11. When the contact failure occurs, the contact failure determination unit 13 transmits the terminal number of the terminal where the contact failure occurs to the battery ECU 12 via the data transmission unit. The battery ECU 12 can display the position of the terminal where the contact failure has occurred, for example, by displaying the terminal number where the contact failure has occurred. By sequentially performing steps S401 to S405 with n = 1 to _N , it is possible to determine whether or not there is a contact failure between the terminals of the _N cells C _{1 to} C _N.

  As described above, according to the cell voltage measurement device according to the second embodiment of the present invention, it is possible to detect a contact failure simultaneously with the calculation of the contact resistance, and therefore it is possible to easily detect a contact failure.

Next, a cell voltage measuring apparatus according to Embodiment 3 of the present invention will be described. FIG. 12 shows the configuration of the cell voltage measurement device according to the third embodiment. The difference from the cell voltage measuring apparatus according to the first embodiment is that a temperature measuring unit 14 is further provided. The temperature measurement unit 14 measures the temperature of the capacitor C of the contact resistance calculation unit 5, corrects the capacitance value C ₀ of the capacitor C based on the temperature measured by the temperature measurement unit 14, and corrects the corrected capacitance value of the capacitor. It is characterized in that the value of contact resistance is calculated using C ′.

  Next, a contact resistance calculation method using the cell voltage measurement device according to the third embodiment will be described with reference to the flowchart of FIG. The procedure from step S501 to S504 is the same as step S301 to S304 of the contact resistance calculation method in the first embodiment shown in FIG. In step S <b> 505, the temperature measurement unit 14 measures the temperature T of the capacitor C of the contact resistance calculation unit 5. As a means for measuring the temperature T, for example, a thermistor can be used.

Next, in step S506, the contact resistance calculation unit 5 corrects the capacitance value C ₀ of the capacitor C from the temperature T of the capacitor C measured by the temperature measurement unit 14 and the temperature characteristics of the capacitor C. For example, when the temperature characteristic of the capacitor is expressed by a function f (T) of the temperature T, the corrected capacitance value C ′ can be obtained as C ′ = C ₀ × f (T). Data relating to temperature characteristics can be stored in the storage unit 10 in advance, and the contact resistance calculation unit 5 refers to the storage unit 10 to calculate the corrected capacitance value C ′. Next, in step S507, the contact resistance calculation unit 5 obtains a contact resistance value (= τ / C ′) using the calculated time constant τ and the corrected capacitance value C ′.

  As described above, the cell voltage measurement device according to the third embodiment of the present invention further includes a temperature measurement unit that measures the temperature of the capacitor, and calculates the capacitance value of the capacitor based on the temperature measured by the temperature measurement unit. Since the contact resistance value is calculated using the corrected capacitor capacitance value, the contact resistance value can be accurately measured even when the capacitor capacitance value varies with temperature. The cell voltage can be calculated accurately. In addition to the configuration including the contact failure determination unit as in the cell voltage measurement device according to the second embodiment, a temperature measurement unit may be provided.

  In the above description, an example in which an RC circuit is used as an example of the contact resistance calculation unit is shown, but the present invention is not limited to this, and other circuits may be used. For example, the time constant may be calculated using an RL circuit. Moreover, although the example using a differential amplifier circuit was shown as an example of a voltage measurement part, you may make it measure a voltage using another circuit.

  In the description of the present invention, an example is shown in which individual cells constituting a battery are selected by a cell changeover switch, and the selected cell is connected to a contact resistance calculation unit or a voltage measurement unit. A plurality of contact resistance calculation units and voltage measurement units may be provided corresponding to individual cells without providing the cell changeover switch.

  In the description of the present invention, the voltage measurement unit has shown an example of measuring the voltage between the terminals connected to the cell, but when the contact resistance calculation unit includes a voltmeter, the voltage measurement unit You may make it also serve as the said voltmeter.

In the description of the present invention, a battery used in a vehicle such as an electric vehicle has been described as an example. However, the present invention can be similarly applied even when used in another device such as a mobile phone. .
The battery constituted by the cells may be a secondary battery such as a fuel battery, lithium ion, nickel metal hydride, or nickel-cadmium battery that can be charged and used any number of times.

DESCRIPTION OF SYMBOLS 1 Battery 2 Cell voltage measuring device 3 Cell changeover switch 4 Circuit changeover switch 5 Contact resistance calculation part 6 Voltage measurement part 7 Changeover switch control part 8 Cell voltage calculation part 9 Control part 10 Storage part 11 Data transmission part 12 Battery ECU
13 contact failure judging section 14 temperature measurement section C ₁ -C _N cell V ₁ ~V _N cell voltage j ₁ ~j _{N + 1} connection part p ₁ ~p _{N + 1} cell terminal q ₁ ~q _{N + 1} terminal r _{1 to} r _{N + 1} contact resistance

Claims (4)

A plurality of terminals provided corresponding to a plurality of connection portions for electrically connecting a plurality of cells connected in series;
A voltage measuring unit that sequentially measures the voltage value of the cell from the plurality of terminals;
A contact resistance calculation unit that sequentially calculates a value of contact resistance generated in the terminal;
A cell voltage calculator that calculates a voltage value of the cell using the value of the contact resistance and the voltage value;
A cell voltage measuring device comprising: The contact resistance calculation unit includes a capacitor,
The cell voltage measuring device according to claim 1, wherein the value of the contact resistance is calculated using a time constant at the time of charging the capacitor and a value of the capacitance of the capacitor. A temperature measuring unit for measuring the temperature of the capacitor;
The cell voltage measurement device according to claim 2, wherein the capacitance value of the capacitor is corrected based on the temperature measured by the temperature measurement unit, and the value of the contact resistance is calculated using the corrected capacitance value of the capacitor. . A plurality of terminals provided corresponding to a plurality of connection portions for electrically connecting a plurality of cells connected in series;
A voltage measuring unit that sequentially measures the voltage value of the cell from the plurality of terminals;
A contact resistance calculation unit that sequentially calculates a value of contact resistance generated in the terminal;
A contact failure determination unit that compares the calculated value of the contact resistance with a predetermined threshold value to determine whether there is a contact failure of the terminal;
A cell voltage measuring device comprising:

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