JP2012019577A - Battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery system capable of easily determining the looseness of connection of a battery pack or the occurrence of device failures.SOLUTION: The battery system comprises: the battery pack in which electrode terminals and conductive members of a plurality of secondary batteries are connected and fixed by fixing members; a first voltage meter measuring an electric power load connected to the battery pack and voltage between the terminals of the plurality of the secondary batteries; a second voltage meter measuring the voltage of the battery pack; a current meter measuring a current flowing in the electric power load; a control device receiving voltage parameter values of the plurality of the terminals corresponding to the voltage between the terminals from the first voltage meter, a whole voltage parameter value from the second voltage meter, and a current parameter value from the current meter; and a memory portion storing a contact resisting value of the battery back, an error value of the control device, and a threshold value of the current. The control device determines the looseness of connection when the current parameter value is more than the threshold value, and determines the occurrence of device failures when the current parameter value is less than the threshold value.

Description

  The present invention relates to a battery system that manages an assembled battery composed of a plurality of secondary batteries.

Conventionally, an assembled battery including a plurality of secondary batteries is used in an electric vehicle or the like. The assembled battery is configured, for example, by connecting electrode terminals of a plurality of secondary batteries with a conductor called a bus bar. More specifically, when a plurality of secondary batteries are connected by a bus bar, the bus bar is fixed to the electrode terminal by fastening the electrode terminal of the secondary battery and the bus bar with a bolt.
Patent Document 1 discloses a technique related to an assembled battery in which a plurality of secondary batteries are connected by a bus bar.

JP 2010-33913 A

In this way, the secondary batteries that make up the assembled battery are generally connected by a metal member (conductive member) such as a bus bar. Looseness may occur and contact resistance may increase due to poor electrical connection between a metal member such as a bus bar and an electrode terminal (hereinafter also referred to as “connection loosening”). If this loose connection is left unattended, the electrical path between the assembled battery and the power load to which power is supplied may be unintentionally interrupted. If the electric path is interrupted unintentionally, for example, if the electric vehicle is suddenly decelerated, there will be a problem with the safety of the battery system, so it is necessary to find loose connection early.
On the other hand, in a battery system, a control circuit for monitoring the characteristics of each secondary battery constituting the assembled battery is generally used. However, the control circuit that performs the monitoring may also fail, and if this failure is left unattended, there will still be a problem with the safety of the battery system, so it is necessary to find a device failure at an early stage.

  Therefore, an object of the present invention is to provide a battery system with improved safety by early determination of loose connection and device failure.

In order to achieve the above object, a battery system of the present invention includes an assembled battery in which electrode terminals and conductive members of a plurality of secondary batteries are connected and fixed by a fixing member, and a power load connected to the assembled battery. A first voltmeter that measures a voltage between terminals of each of the plurality of secondary batteries, a second voltmeter that measures a voltage of the assembled battery, and an ammeter that measures a current flowing through the power load A plurality of terminal voltage parameter values corresponding to the respective terminal voltages from the first voltmeter, an overall voltage parameter value from the second voltmeter, and a current parameter from the ammeter A control device that receives a value, and a storage unit that stores a contact resistance value of the assembled battery, an error value of the control device, and a threshold value of the current,
When the current parameter value is larger than the threshold, the control device uses the overall voltage parameter value, the plurality of terminal voltage parameter values, the current parameter value, and the contact resistance value to loosen the connection. If the current parameter value is smaller than the threshold value, the control device fails using the overall voltage parameter value, the plurality of terminal voltage parameter values, and the error value. It is characterized by determining whether or not a device failure has occurred.

  According to the present invention, cases can be classified using the current threshold value, and it is possible to easily determine the occurrence of loose connection or device failure, thereby providing a battery system with excellent safety.

It is a block diagram which shows the structure of a battery system. It is a figure which shows the connection relation of an assembled battery and BMS. It is a figure which shows the connection relationship between BMS, a high-order control apparatus, etc. It is a figure which shows states, such as a connection with a bus-bar and an electrode terminal. It is the figure which showed an example of the relationship between a differential voltage and an electric current.

Hereinafter, a battery system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the battery system according to the embodiment.
In the present embodiment, the battery system 1 is, for example, an electric vehicle. The battery system 1 includes an assembled battery 10, a host control device 30, a display device 40, a power load 50, and a BMS (Battery Management System) 20. The assembled battery 10 and the BMS 20 that is a monitoring control device for the assembled battery 10 form one battery module, and is fitted from the outside of the battery system 1 to the inside of the battery system 1. By using the battery module, the battery system 1 can be easily replaced from the outside. Note that the power load 50, the host controller 30, and the display device 40 are incorporated in the battery system 1 in advance. Further, the host control device 30 and the BMS 20 in the battery system may be simply referred to as a control device.
Here, the battery system 1 of the present invention is not only an electric vehicle but also a mobile body such as an industrial vehicle such as a forklift or a train, an airplane or a ship in which a propeller or a screw is connected to an electric motor that is a power load 50. May be. Furthermore, the battery system 1 may be a stationary system such as a home power storage system or a grid-connected smoothing power storage system combined with a natural energy power generation such as a windmill or sunlight. That is, the battery system 1 is a system that uses power charging / discharging by a plurality of secondary batteries constituting the assembled battery 10.

The assembled battery 10 supplies power to the power load 50 of the battery system 1, and a plurality of secondary batteries 11a to 11f (hereinafter collectively referred to as a secondary battery 11) are connected in series. Composed. As the assembled battery 10, a plurality of secondary batteries connected in parallel may be used. Various sensors for measuring temperature, voltage, current, etc. are attached to each of the secondary batteries 11 constituting the assembled battery 10, and the measurement information measured and output by these sensors will be described in detail later. Input to BMS 20.
The host control device 30 controls the power load 50 in accordance with a user instruction (for example, the amount of accelerator depression by the user), and also related information about the assembled battery 10 transmitted from the BMS 20 (information related to the measurement information). Yes, including the charging rate of each secondary battery 11 calculated by the BMS 20 and the determination results of the connection looseness determination processing and device failure determination processing described later), and the display device 40 is controlled appropriately. The relevant information is displayed on the display device 40. Further, when the host control device 30 determines that the related information is an abnormal value, it turns on an abnormal lamp 401 built in the display device 40 or the like (it may be an optical display. The display screen 40 may indicate that there is an abnormality), and a sound device 402 such as a buzzer built in the display device 40 is operated to sound an alarm, and the visual and auditory senses are stimulated by light and sound. Call the user's attention. The host control device 30 outputs a determination start signal to the BMS 20 at a predetermined timing in order to cause the BMS 20 to perform connection looseness determination processing and device failure determination processing described later. The predetermined timing may be, for example, every predetermined time such as every 5 minutes, or the current value flowing through the power load 50 in the related information becomes larger than a threshold value Ith described later or becomes smaller than the threshold value Ith. It may be a case. If it is every predetermined time, one of the two determination processes may not be performed easily. However, in the related information, when the value of the current flowing through the power load 50 is larger than a threshold value Ith described later and smaller than the threshold value Ith. If this is the case, it is desirable because the above two determination processes are performed almost equally.
The display device 40 is a monitor such as a liquid crystal panel provided with the acoustic device 402, for example, and displays the related information of the secondary battery 11 constituting the assembled battery 10 based on the control from the host control device 30. .
The power load 50 is, for example, a power converter such as an electric motor or an inverter connected to the wheels of the electric vehicle. The power load 50 may be an electric motor that drives a wiper or the like.

Next, after briefly reviewing the BMS 20, its operation and the like will be described in detail.
As shown in FIG. 1, the BMS 20 of the battery system 1 includes a CMU (Cell Monitor Unit) 21 and a BMU (Battery Management Unit) 22.
Here, the CMU 21 includes an ADC (Analog Digital Converter) (not shown), receives a plurality of the measurement information detected and output by the various sensors as analog signals, and the analog signals correspond to the ADCs, respectively. After being converted into a digital signal, it is output to the BMU 22 as a plurality of parameters for calculating the related information. And in this embodiment, as shown in FIG. 1, CMU21 is connected with the six secondary batteries 11a-11f by the signal wire | line.
In addition, the BMU 22 performs connection looseness determination processing, which will be described later, each time the determination start signal is input from the host control device 30 based on the parameters of the assembled battery 10 and the secondary batteries 11 input from the CMU 21. Device failure determination processing is performed, and the determination result is output to the host control device 30.
Here, only one CMU 21 is shown, and the CMU 21 is connected to the six secondary batteries 11, but is not limited to this mode. For example, a plurality of CMUs 21 may be provided, and four secondary batteries 11 may be connected to each CMU 21, or the CMUs 21 may be provided in a one-to-one relationship with the plurality of secondary batteries 11. That is, the number of CMUs 21 may be any number as long as the BMU 22 can acquire a plurality of parameters necessary for performing the above two determination processes from the CMU 21. If the BMU 22 is configured including the CMU 21, the BMS 20 may be configured only by the BMU 22.

  Now, the internal configuration and operation of the BMS 20 will be described in detail with reference to FIGS. The connection between the electrode terminals of one secondary battery 11 (single cell) and the assembled battery 10 and the measurement lines of the bus bar 12 and the voltmeter will be described with reference to FIG. An example of the relationship between the differential voltage and the current in the process and the apparatus failure determination process will be described with reference to FIG.

As shown in FIG. 2, each of the secondary batteries 11a to 11f is provided with each of the voltmeters 3a to 3f in a one-to-one correspondence. Specifically, the voltmeters 3a to 3f are connected between the positive terminal and the negative terminal of the corresponding secondary battery 11, respectively. The CMU 21 includes a parameter value detection unit 211, and the parameter value detection unit 211 acquires each voltage value as measurement information measured and output by each voltmeter 3a to 3f as an analog signal (the analog signal is Input to the parameter value detector 211).
Further, in order to measure the maximum voltage that can be applied to the power load 50, a voltmeter 3g is connected between the positive terminal and the negative terminal of the assembled battery 10. Here, a voltmeter 3g is provided between the positive terminal of the secondary battery 11a and the negative terminal of the secondary battery 11f present at both ends of the assembled battery 10 (a configuration in which a plurality of secondary batteries 11 are connected in series by the bus bar 12). Is connected. The parameter value detection unit 211 acquires a voltage value as measurement information measured and output by the voltmeter 3g as an analog signal (the analog signal is input to the parameter value detection unit 211). Hereinafter, the voltmeters 3a to 3g are collectively referred to as a voltmeter 3.
Further, the ammeter 2 is connected between the assembled battery 10 and the power load 50 in order to measure the current flowing through the power load 50. The parameter value detection unit 211 acquires a current value as measurement information measured and output by the ammeter 2 as an analog signal (the analog signal is input to the parameter value detection unit 211).
The parameter detection unit 211 incorporates the ADC, converts an analog signal that is a current value and a voltage value acquired from the ammeter 2 and the voltmeter 3 into a digital signal, and corresponds to each parameter. Is output to the BMU 22 as the value of.

The ammeter 2 and the voltmeter 3 are examples of the various sensors.
Further, the assembled battery 10 may be configured by connecting a plurality of units including a plurality of secondary batteries 11 connected in series in parallel. In this case, the units adjacent to each other in parallel are connected to each other via a disconnecting means such as a switch, for example, and in performing a connection looseness determination process and a device failure determination process described later, a process specifying unit 233 in the BMU 22 described later. However, it is preferable to perform one determination for each unit by removing the columns as appropriate in order to eliminate the influence of other columns.

As shown in FIG. 3, the BMU 22 includes a parameter acquisition unit 23 (including a battery pack parameter acquisition unit 231 and a secondary battery parameter acquisition unit 232), a process specification unit 233, a connection looseness determination processing unit 234, and a device failure. A determination processing unit 235 and a storage unit 236 are provided.
First, the secondary battery parameter acquisition unit 232 in the parameter acquisition unit 23 has voltage values between terminals of all the secondary batteries 11a to 11f connected in series in the assembled battery 10 (the positive terminal in each secondary battery 11 and The value of the parameter corresponding to the voltage value between the negative terminals (the corresponding parameter of each of the secondary batteries 11a to 11f is referred to as the inter-terminal voltage parameter Va to Vf, and these values are referred to as the inter-terminal voltage parameter values). , Input from the CMU 21 and obtained respectively.
Also, the battery pack parameter acquisition unit 231 in the parameter acquisition unit 23 refers to the entire value (the parameter of the battery pack 10 parameter corresponding to the voltage value applied to the entire voltage parameter V _all the measurement by the voltmeter 3g, this Value is referred to as an overall voltage parameter value), and a parameter value corresponding to a current value flowing through the assembled battery 10 measured by the ammeter 2 (this parameter is referred to as a current parameter I, and this value is referred to as a current parameter value). Are respectively input from the CMU 21 and acquired.

Then, the assembled battery parameter acquisition unit 231 and the secondary battery parameter acquisition unit 232 output parameter values corresponding to the acquired voltage value and current value to the processing specifying unit 233, respectively. Then, the process specifying unit 233 determines the voltage applied to each secondary battery 11 input from the secondary battery parameter acquisition unit 232 from _{all the} voltage values V applied to the entire assembled battery 10 input from the assembled battery parameter acquisition unit 231. The difference voltage value α is calculated by subtracting the sum of the values (Va to Vf). That is, the process specifying unit 233, alpha = V _total - performs the operation of (Va + Vb + Vc + Vd + Ve + Vf), calculates the difference voltage value alpha.

Here, there are two reasons why the differential voltage value α is generated, one of which is as follows.
As shown in FIG. 4, the bus bar 12 is disposed on the electrode terminals 14 a (positive terminal) and 14 b (negative terminal) of each secondary battery 11, and the bus bar 12 is fixed on each electrode terminal by the bolt 13. Yes. In addition, the connection between the measurement lines 15 of the voltmeters 3a to 3f connected to the secondary battery 11 and the electrode terminals is greater than that of the connection points of the bus bar 12 to the electrode terminals 14a and 14b. Connected to the side closer to the electrical path of the electrode plate contained in the container (here, the above-mentioned connection in the region of the electrode terminal directly above the insulator 16 that insulates between the battery can as the battery container and each electrode terminal) Has been made). Therefore, the voltage parameter value between terminals is measured in a state where there is almost no influence of contact resistance (voltage drop due to contact resistance) on the electrode terminals 14a and 14b of the bus bar 12. On the other hand, the overall voltage parameter value becomes a large voltage value by the amount obtained by multiplying the sum of the contact resistances of the bus bars 12 connected to each secondary battery 11 by the current parameter value. For this reason, the differential voltage value α is obtained.
In addition, let R be the contact resistance value of the assembled battery 10 in the initial state in which the bus bar 12 is firmly fixed to each electrode terminal with a fixing member such as a bolt 13 without looseness. Further, when the assembled battery 10 is used, a fixing member such as a bolt is loosened due to vibration or the like, and the resistance value may increase from the initial value R of the contact resistance. Let r. The sum of R and r is the contact resistance Rerr due to loose connection. That is, Rerr = R + r (where R> 0Ω, r ≧ 0Ω).
The connection looseness determination process described later uses the fact that when the tightening of the bus bar 12 to the electrode terminals 14a and 14b is loosened, the contact resistance increases, so that the overall voltage parameter value increases, and as a result, the differential voltage value α increases. Is. That is, the looseness of the bus bar 12 is determined by determining the degree of increase in r from the initial state in the contact resistance Rerr due to loose connection.

Another reason why the differential voltage value α occurs is as follows.
The overall voltage parameter value acquired by the BMU 22 and the voltage parameter value between the terminals of each secondary battery 11 include a conversion error, an assembled battery parameter acquisition unit 231, and a secondary battery parameter that are generated during analog-digital conversion performed by the CMU 21. A voltage error due to a processing error or the like that occurs when the acquisition unit 232 acquires the overall voltage parameter value and the terminal voltage parameter value transmitted from the CMU 21 is included. Here, the voltage measurement error including the conversion error and the processing error is called an error value.
The value of the voltage measurement error, that is, the error value is a voltage value in consideration of an error from the true voltage value, and is processed in the CMU 21 or BMU 22 of the analog signal measured and output by each voltmeter. Since this error is caused by the hardware inside the BMS 20, etc., for example, unless the hardware fails, the rate of change is considered to be substantially constant even if the value of the current flowing through the assembled battery 10 fluctuates. .
For example, in a process in which each voltage value measured and output by each voltmeter 3a to 3f is processed in the BMS 20, at least data corresponding to each voltage value input to the processing specifying unit 233 is a ± 30 mV voltmeter. When side error occurs, the value of the total voltage parameter V _all included error values ± 30 mV is already also be included error values ± 30 mV is already in the respective voltage values Va~Vf Will be.
Therefore, the processing specification unit 233, alpha = V _total - when performing the calculation of (Va + Vb + Vc + Vd + Ve + Vf), in the case where the contact resistance Rerr is assumed that there at all, voltmeter side error Verr predetermined range becomes the difference voltage value alpha Will appear. That is, in this case, α = Verr (where Verr ≠ 0V), and in this case, −210 mV ≦ Verr ≦ + 210 mV.
Note that this Verr is a range of error values in the initial state in which there is no failure in the BMS 20 or the like (both ends of the range are set to ± β. Β> 0 and β = 210 mV in this case) May or may begin to occur, the range may deviate from the Verr range. If the deviation is ± γ, −β−γ ≦ Verr ≦ + β + γ is satisfied (assuming that γ ≧ 0).
The device failure determination process described later uses the fact that the value of the voltage measurement error Verr, which should be in a substantially constant range, deviates from the fixed range, and as a result, the differential voltage value α increases. That is, the possibility of failure of a device such as the BMS 20 is determined by determining the degree of increase of γ.

As described above, if the value of the current parameter I at a certain time point that is output from the assembled battery parameter acquisition unit 231 and input to the processing specifying unit 233 is Ip (that is, I = Ip), Using the absolute value, it can be expressed as α = Verr + (| Ip | × Rerr). Here, the current parameter I as shown in the example of FIG. 5 is recognized so that the control device including the BMS 20 can recognize that discharging is performed when the value of Ip is positive and charging is performed when the value of Ip is negative. It is assumed that the value of can be positive or negative.
Therefore, the smaller the absolute value of the current value Ip at a certain time point, the smaller the contact resistance can be substantially ignored because α≈Verr. Also, the absolute value of the current value Ip at a certain time point becomes smaller. The larger the value, αα | Ip | × Rerr, and the voltage measurement error can be substantially ignored.
Therefore, the device failure determination process described later is performed in a region where α≈Verr because the current value Ip at a certain point is small, and later described in a region where α≈ | Ip | × Rerr because the current value Ip at a certain point is large. It is effective to perform the connection looseness determination process in order to accurately perform these two determination processes.
For this reason, in the present embodiment, a constant threshold value Ith (where Ith> 0A) is set, and the current parameter is -Ith << I << Ith in view of the current direction that reverses between charging and discharging. Device failure determination processing is performed in the region, and connection looseness determination processing is performed in the region of I <<-Ith or Ith << I.

Now, the apparatus failure determination process and the connection looseness determination process will be described.
First, in the process specifying unit 233, when the determination start signal is input to the BMS 20 and a signal corresponding to the determination start signal is input to the process specifying unit 233, the calculation is performed to calculate the differential voltage value α, and the storage unit 236 Is used to compare the input value Ip of the current parameter I with the threshold value Ith. If the comparison result is −Ith << Ip << Ith, the process specifying unit 233 transmits the differential voltage value α to the device failure determination processing unit 235, and the device failure determination processing unit 235 that has received them transmits the difference voltage value α. Device failure determination processing is performed. When Ip <<-Ith or Ith << Ip, the process specifying unit 233 transmits the differential voltage value α to the connection looseness determination processing unit 234, and the connection looseness determination processing unit 234 that receives them transmits the connection looseness. Judgment processing is performed.
Here, regarding the determination of -Ith << Ip << Ith and the determination of Ip <<-Ith or Ith << Ip in the process specifying unit 233, specifically, Itha << Ith << Ithb (however, 0A <Itha And two auxiliary threshold values Itha and Ithb satisfying 0A <Ithb) are used. That is, when -Itha <Ip <Itha, the process specifying unit 233 transmits the differential voltage value α to the device failure determination processing unit 235, and when Ip <−Ithb or Ithb <Ip, the process specifying unit 233 Transmits the differential voltage value α to the connection looseness determination processing unit 234. These auxiliary threshold values are stored in advance in the storage unit 236, and are appropriately read from the storage unit 236 as the threshold value Ith or together with Ith and used in the process specifying unit 233 in the above determination.

Note that the current value Ip input to the processing specifying unit 233 includes a measurement error by the apparatus, that is, a current measurement error, as with the voltage value. If this current measurement error is ± 250 mA when Ip = 5 A, for example, the BMS 20 also performs processing for determining charging and discharging by the positive and negative values of the current value. Therefore, the auxiliary threshold value Itha is at least the current measurement. The absolute value of the error needs to be larger than 250 mA. That is, if current measurement error θ (where 0A <θ), θ <Itha needs to be satisfied. On the other hand, from the viewpoint of safety of the assembled battery 10, the maximum current value allowed to be output from the assembled battery 10, that is, the maximum allowable current value is also determined. If this maximum allowable current value is, for example, 300 A, the threshold value Ithb needs to be at least smaller than 300 A, which is the maximum allowable current value. That is, assuming that the maximum allowable current value Im (however, 0 A <Im), it is necessary to satisfy Ithb <Im.
In addition, the differential voltage value increases as the connection looseness increases, and the maximum differential voltage value is thought to occur immediately before the bus bar is disconnected from the electrode terminal and the current path is interrupted, but the voltmeter occupies the maximum differential voltage value. The ratio of the side error Verr is generally very small although it depends on the configuration of the apparatus. For example, β which is the upper limit of the error value of the voltmeter side error Verr is, for example, 0 <β ≦ 210 mV in the configuration of FIG. 1, and even if γ is added to this, the maximum value of Verr is about 300 mV. On the other hand, the contact resistance value R in the initial state is, for example, about 5 mΩ in the configuration of FIG. 1, and the value of Verr and the value of (| Ip | × R) in the differential voltage value α is a ratio of about 1: 3. If the current value is the auxiliary threshold value Ithb, it can be considered as a temporary guide for determining the looseness of the connection. Therefore, {(maximum value of Verr) × 3 ÷ R} ≦ Ithb <Im may be satisfied. Therefore, here, it is set as Ithb = 180A.
Furthermore, the auxiliary threshold value Itha needs to have a current value as small as possible and be less affected by current measurement errors. Since at least the influence of the current measurement error is considered to be practical when suppressed to 10% or less, the current value may be about 10 times the current measurement error. Therefore, it is sufficient if θ <Itha ≦ (current measurement error) × 10. Therefore, Itha = 2A is set here.

Next, connection looseness determination processing in the connection looseness determination processing unit 234 will be described. As described above, this determination process is performed when I <<-Ith or Ith << I.
First, the connection looseness determination processing unit 234 calculates the absolute values of the input differential voltage value α and current value Ip, and the contact resistance value R of the entire assembled battery 10 in the initial state stored in the storage unit 236. And a contact resistance increment threshold r _th described later are read out. Note that R> 0Ω and r _th > 0Ω.
A contact resistance-induced voltage value Vz that is a potential difference resulting from the contact resistance is set to Vz = | α |.
Furthermore, the connection looseness determination processing unit 234 calculates Rerr by dividing the contact resistance-induced voltage value Vz by the absolute value of the calculated current value Ip. That is, Rerr = Vz ÷ | Ip | is calculated.
As described above, since Rerr = R + r, the connection looseness determination processing unit 234 calculates the value r of the increase in contact resistance by subtracting the read R from the calculated Rerr. That is, r = Rerr−R is calculated.
Thereafter, the already read contact resistance increment threshold r _th is compared with the calculated r, and when the value of r is larger than the value of r _th , that is, when r> r _th , it is determined that the connection is loose. On the other hand, when the value of r is smaller than the value of r _th , that is, when r <r _th , it is determined that there is no loose connection.
Here, in the above description, the order of operations for calculating r is specified, but any order and operation method may be adopted as long as a value corresponding to r is obtained. Further, although r and the contact resistance increment threshold r _th are compared, Rerr and R may be compared and the presence / absence of loose connection may be determined based on the increment.
If the contact resistance increment threshold r _th exceeds this value, the fixing member such as a bolt loosens and the contact between the bus bar and the electrode terminal is not in a desired state, that is, loose connection occurs. This is a threshold value for determining that the value is determined, and is set after a numerical value is obtained in advance by experiments or the like and stored in the storage unit 236 (here, for example, r _th = 36 mΩ). Further, the contact resistance value R of the entire assembled battery 10 in the initial state is also set after a numerical value is obtained in advance by experiments or the like, and is stored in the storage unit 236 (here, R = 5 mΩ, for example). .
When the connection looseness occurrence determination processing unit 234 determines that the connection is loosened, the connection looseness occurrence determination processing unit 234 outputs a connection looseness occurrence signal to the host controller 30. If it is determined that there is no loose connection, a connection loose signal is output to the host controller 30.

Next, device failure determination processing in the device failure determination processing unit 235 will be described. As described above, this determination process is performed when -Ith << I << Ith.
First, the apparatus failure determination processing unit 235 calculates the absolute value of the input differential voltage value α, and also the upper limit value β of the voltage measurement error Verr in the initial state stored in the storage unit 236 and the error increment threshold γ _th. And read. If there is an increase in voltage exceeding this value, the error increment threshold γ _th is determined that the error in the processing of the BMS 20 or the like exceeds the allowable range, that is, the failure of the device such as the BMS 20 has occurred. And is set after a numerical value is obtained in advance through experiments or the like and stored in the storage unit 236 (where γ _th > 0V, where, for example, an error when there is no device failure) The same value as the upper limit value β of the value, that is, β = γ _th = 210 mV).
When a failure occurs in a device such as the BMS 20 or starts to occur, the range deviates from the range of Verr in the initial state, and the value γ of the deviation is added, so that 0 <| Verr | ≦ β + γ Yes, and | α | ≈ | Verr |. Therefore, the device failure determination processing unit 235 subtracts the upper limit value β of the range of the voltage measurement error Verr in the initial state from the absolute value of the differential voltage value α to calculate a deviation value γ. That is, the calculation of γ = | α | −β is performed.
Thereafter, the voltmeter-side error determination processing unit 235 compares the calculated γ with the read γ _th and determines that there is a device failure when γ is greater than γ _th , that is, when γ> γ _th . On the other hand, when γ is smaller than γ _th , that is, when γ <γ _th , it is determined that there is no device failure.
Here, in the above description, the order of operations for calculating γ is specified, but any order and operation method may be adopted as long as a value corresponding to γ is obtained. Further, although γ is compared with the error increment threshold γ _th , | Verr | may be compared with β to determine the presence or absence of a device failure based on the increment.
The voltmeter-side error determination processing unit 235 outputs a device failure occurrence signal to the host control device 30 when determining that there is a device failure. If it is determined that there is no device failure, a device failure no signal is output to the host control device 30.

In the above connection looseness determination process, a characteristic of α≈ | Ip | × Rerr is used in the region of I << − Ith or Ith << I. In the apparatus failure determination process, −Ith << Ip << Ith In the region, the characteristic that α≈Verr is used. However, when processing is performed more strictly, the fact that α = Verr + (| Ip | × Rerr) may be used.
In this case, since Verr or (| Ip | × Rerr) is excluded from α as will be described later, a stricter calculation is performed. Therefore, the region of I << − Ith or Ith << I and −Ith << Ip << It is not necessary to determine the region of <Ith, and the above two determination processes can be sufficiently performed as the determination of the region of I <-Ith or Ith <I and the region of -Ith <Ip <Ith. Therefore, without using the two auxiliary threshold values Itha and Ithb, for example, the value of Ith may be set in advance as Ith = Itha, and the following operation may be performed. The reason why Itha having a small value is selected as the Ith among the two auxiliary threshold values is that, as described above, in the apparatus failure determination process, the smaller the current parameter value, the more accurate the determination can be made. In this case, the corresponding Ith value is stored in the storage unit 236 in advance.
First, the process specifying unit 233 performs the above-described calculation to calculate the differential voltage value α, and reads the threshold value Ith stored in the storage unit 236 for the input current parameter I value Ip and compares it with this. . When the comparison result is −Ith <Ip <Ith, the process specifying unit 233 transmits the differential voltage value α and the current value Ip to the device failure determination processing unit 235, and Ip <−Ith or Ith < In the case of Ip, the process specifying unit 233 transmits the differential voltage value α and the current value Ip to the connection looseness determination processing unit 234.
The connection looseness determination processing unit 234 calculates the absolute values of the input differential voltage value α and current value Ip, and the upper limit value β of the voltage measurement error Verr in the initial state stored in the storage unit 236 and the initial state. The value R of the contact resistance of the entire assembled battery 10 and the contact resistance increment threshold r _th are read out.
Then, a voltage value Vz which is a potential difference caused by the contact resistance is calculated by calculating Vz = | α | + β. Here, β is added because −β−γ ≦ Verr ≦ + β + γ, as described above, and it is determined that the connection is loosened more quickly when calculation is performed assuming that Verr is negative. This is because the safety of the battery system can be further increased as a result. Here, γ = 0 is ignored because γ = 0, but this is a small value of γ from the viewpoint of the safety of the battery system even if the connection looseness determination is made because there is no device failure. This is because it is considered sufficient.

Furthermore, the connection looseness determination processing unit 234 calculates Rerr by dividing the calculated voltage value Vz by the absolute value of the calculated current value Ip. That is, Rerr = Vz ÷ | Ip | is calculated.
As described above, since Rerr = R + r, the connection looseness determination processing unit 234 calculates the value r of the increase in contact resistance by subtracting the read R from the calculated Rerr. That is, r = Rerr−R is calculated.
Thereafter, the already read contact resistance increment threshold r _th is compared with the calculated r, and when the value of r is larger than the value of r _th , that is, when r> r _th , it is determined that the connection is loose. On the other hand, when the value of r is smaller than the value of r _th , that is, when r <r _th , it is determined that there is no loose connection.
Here, in the above description, the order of operations for calculating r is specified, but any order and operation method may be adopted as long as a value corresponding to r is obtained. Further, although r and the contact resistance increment threshold r _th are compared, Rerr and R may be compared and the presence / absence of loose connection may be determined based on the increment.
When the connection looseness occurrence determination processing unit 234 determines that the connection is loosened, the connection looseness occurrence determination processing unit 234 outputs a connection looseness occurrence signal to the host controller 30. If it is determined that there is no loose connection, a connection loose signal is output to the host controller 30.

In this case, the device failure determination processing in the device failure determination processing unit 235 is as follows.
First, the device failure determination processing unit 235 calculates the absolute values of the input differential voltage value α and current value Ip, respectively, and sets the upper limit value β of the voltage measurement error Verr in the initial state stored in the storage unit 236. The error increment threshold γ _th and the contact resistance value R of the assembled battery 10 in the initial state are read out.
Then, a voltage value Vy, which is a potential difference caused by a device failure, is calculated by performing an operation of Vy = | α | − | Ip | × R. Here, even though Rerr = R + r, r = 0 and r is ignored because, strictly speaking, even if r exists, the current value Ip is smaller than the threshold value Ith and the influence thereof is This is because it is considered relatively small.
Further, the device failure determination processing unit 235 calculates the absolute value of Vy, subtracts the upper limit value β of the range of the voltage measurement error Verr in the initial state from the calculated absolute value of Vy, and calculates the deviation value γ. To do. That is, the calculation of γ = | Vy | −β is performed.
Thereafter, the device failure determination processing unit 235 compares the calculated γ with the read γ _th and determines that there is a device failure when γ is greater than γ _th , that is, when γ> γ _th . On the other hand, when γ is smaller than γ _th , that is, when γ <γ _th , it is determined that there is no device failure.
Here, in the above description, the order of operations for calculating γ is specified, but any order and operation method may be adopted as long as a value corresponding to γ is obtained. Further, although γ is compared with the error increment threshold γ _th , | Verr | may be compared with β to determine the presence or absence of a device failure based on the increment.
The device failure determination processing unit 235 outputs a device failure occurrence signal to the host control device 30 when it is determined that there is a device failure. When it is determined that there is no device failure, a device failure no signal is output to the upper control device 30.

The host controller 30 operates as follows when a connection looseness occurrence signal, a connection looseness absence signal, a device failure occurrence signal, or a device failure noness signal is input.
That is, when a connection looseness occurrence signal or a device failure occurrence signal is input to the host control device 30, the host control device 30 recognizes that a series of processing based on the determination start signal output by itself has ended, and displays An optical display corresponding to each of the connection looseness occurrence signal or the device failure occurrence signal is performed by controlling the device 40 (for example, the abnormal lamp 401 corresponding to each of them is turned on), or an alarm corresponding to each of them by the acoustic device 402 To alert the user. On the other hand, when a connection looseness-free signal or a device failure-free signal is input, the host control device 30 recognizes that a series of processes based on the determination start signal output by itself has been completed.
As a result, for example, when the battery system is an electric vehicle, a user who is a driver can easily grasp the occurrence of loose connection or device failure, that is, the abnormality of the battery system, and request a repair request from a repair shop or the like. Thus, the safety of the battery system can be improved.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the current path is formed by wiring between the secondary batteries of the assembled battery 10 by the bus bar 12. A metal member (conductive member) having a fixed connection terminal may be used. For example, the secondary battery may be connected by wiring with a cable or the like to form the current path. In this case, loosening of the connection terminal with respect to the electrode terminal also results in loose connection.

DESCRIPTION OF SYMBOLS 1 ... Battery system 10 ... Assembly battery 11 ... Secondary battery 20 ... BMS
21 ... CMU
22 ... BMU
23 ... Parameter acquisition unit 30 ... Host control device 40 ... Display device 50 ... Power load 211 ... Parameter value detection unit 231 ... Battery pack parameter acquisition unit 232 ... Secondary battery Parameter acquisition unit 233... Processing specification unit 234... Connection looseness occurrence determination processing unit 235... Device failure determination processing unit 401.

Claims (4)

An assembled battery in which electrode terminals and conductive members of a plurality of secondary batteries are connected and fixed by a fixing member;
A power load connected to the assembled battery;
A first voltmeter for measuring a voltage between terminals of each of the plurality of secondary batteries;
A second voltmeter for measuring the voltage of the assembled battery;
An ammeter for measuring the current flowing through the power load;
A plurality of terminal voltage parameter values corresponding to the respective terminal voltages are received from the first voltmeter, an overall voltage parameter value is received from the second voltmeter, and a current parameter value is received from the ammeter. Receiving control device,
A storage unit storing the contact resistance value of the assembled battery, the error value of the control device, and the threshold value of the current;
When the current parameter value is larger than the threshold, the control device uses the overall voltage parameter value, the plurality of terminal voltage parameter values, the current parameter value, and the contact resistance value to loosen the connection. If the current parameter value is smaller than the threshold value, the control device fails using the overall voltage parameter value, the plurality of terminal voltage parameter values, and the error value. A battery system for determining whether or not a device failure has occurred. The storage unit further stores a contact resistance increment threshold value and an error increment threshold value,
The controller is
When the connection looseness occurrence determination is performed, the contact resistance value is further subtracted from the absolute value of a value obtained by dividing the difference between the total voltage parameter value between the plurality of terminals and the overall voltage parameter value by the current parameter value. When the value corresponding to the value is larger than the contact resistance increment threshold, it is determined that the connection is loose,
When performing the apparatus failure occurrence determination, a value corresponding to a value obtained by further subtracting the error value from the absolute value of the difference between the sum of the plurality of terminal voltage parameter values and the overall voltage parameter value is the error increment threshold value. 2. The battery system according to claim 1, wherein the battery system is determined to have a failure in the control device when larger. The threshold value of the current includes a first auxiliary threshold value and a second auxiliary threshold value greater than the first auxiliary threshold value,
The control device performs the connection looseness determination when the current parameter value is larger than the second auxiliary threshold, and the device failure occurs when the current parameter value is smaller than the first auxiliary threshold. The battery system according to claim 2, wherein the determination is performed. A display device;
When it is determined that the connection is loose, the control device controls the display device to cause the display device to perform an optical display corresponding to the determination, and when it is determined that the control device is defective. The battery system according to claim 3, wherein the display device is controlled to cause the display device to perform an optical display corresponding to the determination.

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