Method for detecting defects of a module group of a battery

Abstract

x = |kAVj - AVi| (I) The present invention relates to a detection method for detecting a defect of a battery comprising a first and a second set of modules (Ei, Ej) connected in series and a first and a second measuring means for respectively measuring a first and a second voltage (Vi, Vj) of each set (Ei, Ej), each module (1) comprising at least one cell (2) and a measuring means for measuring a voltage (VCz, VMc) of said cell (2), the method comprising the following successive steps: - determining a value x according to formula I: (I) in which: * Vi and Vj are respectively the first and second voltage of the first and second set of modules (Ei, Ej), * AVi and AVj are respectively the difference between the sum of each voltage (VCz, VMc) of the cells (2) of the first (Ei) and second (Ej) set and the voltage Vi and Vj, * k is a correction coefficient, - comparing this value x to a threshold value, and - confirming that one of the set of modules (Ei, Ej) has a defect when this value x exceeds the threshold value.

Description

Technical Field

[0001] This invention claims priority to French application 2010870, filed on October 22, 2020, the contents of which (text, drawings and claims) are incorporated herein by reference.

[0002] This invention relates to a battery monitoring method for detecting defects in a battery module assembly. The battery comprises a series of modules connected in pairs by a busbar system (or busbar system) typically fastened to each electrical terminal of the module. Background Technology

[0003] Throughout this document, a battery is understood as a collection comprising at least two battery modules connected in series, each of the battery modules comprising at least one electrochemical cell. Optionally, the battery includes electrical or electronic components for managing the electrical energy of the modules. When multiple modules are present, they are assembled in a pack or housing to form a battery pack, typically expressed as a "pack batteries," the housing typically including mounting joints and connection terminals.

[0004] In addition, throughout this document, electrochemical cells are understood to be cells of, for example, lithium-ion (or Li-ion) type, Ni-Mh type, Ni-Cd type, or lead type that generate current through a chemical reaction.

[0005] The fastener participates in maintaining the bus system and also in ensuring good electrical contact between the terminal and the bus system.

[0006] Unfortunately, this fastening can loosen, for example, due to vibrations transmitted to the battery. This increases the electrical contact resistance between the terminals and the bus system. This is very harmful because current flowing through this contact resistance can cause a temperature rise that could eventually ignite the battery.

[0007] An analytical apparatus for analyzing contact resistance is known from patent document FR3051558A1. Unfortunately, this apparatus is expensive because it requires measuring the temperature at the location of the contact resistance. More importantly, however, the apparatus lacks accuracy in determining the resistance because it uses complex electrothermal models that take temperature as input data. This necessitates applying a safety margin to the determined values ​​to avoid erroneous detection of contact resistance defects, ultimately leading to delayed detection that cannot rule out ignition. Summary of the Invention

[0008] The purpose of this invention is to remedy this shortcoming by providing a method for improving the accuracy of detecting the resistor when a clamping defect occurs.

[0009] Therefore, the objective of this invention is to provide a method for detecting defects in a module assembly of a battery, the battery comprising:

[0010] A first assembly of battery modules connected in series, and a first measuring component, the first measuring component being used to measure a first voltage of the first assembly of modules.

[0011] - A second assembly of battery modules connected in series, and a second measuring component, the second measuring component being used to measure a second voltage of the second assembly of modules.

[0012] Each module includes at least one battery cell and a measuring component for measuring the voltage of the battery cell. The first set and the second set are connected in series. The method includes the following sequential steps:

[0013] - Determine the value x according to the formula:

[0014] [Equation 1]

[0015] x = |k△Vj - △Vi|

[0016] in:

[0017] *Vi is the first voltage of the first module set.

[0018] *Vj is the second voltage of the second module set.

[0019] *ΔVi is the sum of the voltages of each cell in the first set minus the voltage Vi.

[0020] *ΔVj is the sum of the voltages of each cell in the second set minus voltage Vj.

[0021] *k is the correction factor.

[0022] - Compare this value x with a threshold, and

[0023] - When the value x exceeds the threshold, it is confirmed that one of the modules in the set is defective.

[0024] Therefore, this method directly compares the first set and the second set based on the following evaluation criteria:

[0025] These collections within the same group are subjected to the same environment and therefore undergo the same cell aging under the same thermal conditions.

[0026] - The probability of having multiple faults of the same degree in the set simultaneously is zero.

[0027] Therefore, unless there is indeed an anomaly in one of the sets, there cannot be a deviation between the sets.

[0028] This method is extremely simple and is naturally immune to natural variations in internal resistance, such as those caused by aging and temperature, which affect the assembly in the same way. Therefore, this method requires neither temperature measurements nor electrothermal models.

[0029] This also allows for a lower threshold (i.e., a detection threshold) and the detection of more subtle damage, avoiding adverse effects with high repair costs. Furthermore, it reduces the risk of false detections due to confusion between natural variations and assumed local anomalies.

[0030] According to an embodiment of the present invention, the battery comprises n module sets connected in series, where n is greater than or equal to 2. For each combination of two voltages from two different sets among the n sets, the method is performed, and the method confirms that the combination of the sets is defective when the value x of at least one combination exceeds the threshold.

[0031] Therefore, this method can be easily adapted to groups that include more than two sets. The term "combination" should be understood in its mathematical sense.

[0032] According to an embodiment of the present invention, n is greater than or equal to 3, and the method includes:

[0033] - Steps for determining the common set shared by combinations that have been detected as defective.

[0034] - Confirmation steps used to verify that the common set is a defective set.

[0035] Therefore, this method not only detects defects, but also, when n is greater than or equal to 3, it can locate which set contains defects.

[0036] According to an embodiment of the invention, during the determination step for determining the value x, the method makes the value x dimensionless by dividing the value by a voltage, in particular by ΔVi or by the average value between ΔVi and ΔVj.

[0037] According to an embodiment of the invention, when the value x is dimensionless, particularly when x is divided by ΔVi or by the average value between ΔVi and ΔVj, the threshold is less than or equal to 0.05. This range of values ​​for the threshold is an example and can be adapted to the desired accuracy target.

[0038] Of course, "the value x after being divided by voltage" should be understood as a new dimensionless value x to be considered.

[0039] According to an embodiment of the present invention, the confirmation step for identifying a defective module in the module set includes sub-steps employed individually or in combination from the following steps:

[0040] - The steps for issuing visual or audible alarms.

[0041] - A circuit disconnection step for disconnecting the battery from the circuit.

[0042] - A loop-breaking step for breaking each loop in the module.

[0043] - A disconnection step for disconnecting each of the battery cells from the circuit.

[0044] - A limiting step for limiting the current flowing through the battery cell.

[0045] Another objective of the present invention is to provide a computer comprising an acquisition and processing component for acquiring and processing via software instructions stored in a memory, and a control component required for implementing the methods described above.

[0046] Another objective of this invention is to provide a battery system comprising:

[0047] A first assembly of battery modules connected in series, and a first measuring component, the first measuring component being used to measure a first voltage of the first assembly of modules.

[0048] - A second assembly of battery modules connected in series, and a second measuring component, the second measuring component being used to measure a second voltage of the second assembly of modules.

[0049] Each module includes at least one battery cell and a measuring component for measuring the voltage of the battery cell. The first set and the second set are connected in series. The system also includes a computer as described above.

[0050] According to an embodiment of the present invention, each set of modules is identical.

[0051] In the full text of this document, the same set is understood as a set of pre-distributed components (capacitance, nominal voltage, internal resistance) with the same electrical characteristics to be updated and the same architecture: the same number and type of modules, each module comprising the same number of cells, and all cells being identical in themselves and connected to each other in the same way.

[0052] Another objective of the present invention is to provide a vehicle comprising a battery system and a drive motor powered by the battery system as described above. Attached Figure Description

[0053] Other features and advantages of the invention will become more apparent from the following detailed description and accompanying drawings of non-limiting specific embodiments, in which:

[0054] Figure 1 A simplified battery system according to the invention is shown; a computer is not shown. Detailed Implementation

[0055] It should be noted that the accompanying drawings are given as examples and do not limit the invention. The drawings constitute a schematic diagram for facilitating understanding of the principles of the invention. Reference numerals for elements that are unchanged or have the same function are common to each repeating element.

[0056] The present invention therefore relates to a method for detecting defects in a module 1 group of a battery, the battery comprising:

[0057] - A first assembly of battery modules Ei connected in series, and a first measuring component for measuring a first voltage Vi of the first assembly of battery modules Ei.

[0058] - A second assembly of battery modules Ej connected in series, and a second measuring component for measuring a second voltage Vj of the second assembly of modules.

[0059] Each module 1 includes at least one battery cell 2 and a measuring component, the measuring component being used to measure the voltage VCz and VMc of the battery cell 2. A first set Ei and a second set Ej are connected in series. The method includes the following sequential steps:

[0060] - Determine the value x according to the formula:

[0061] [Equation 2]

[0062] x = |k△Vj - △Vi|

[0063] in:

[0064] *Vi is the first voltage of the first module set Ei.

[0065] *Vj is the second voltage of the second module set Ej.

[0066] *ΔVi is the sum of the voltages VCz and VMc of each cell 2 in the first set Ei, minus the first voltage Vi.

[0067] *ΔVj is the sum of the voltages VCz and VMc of each cell 2 in the second set Ej, minus the second voltage Vj.

[0068] *k is the correction factor.

[0069] - Compare this value x with a threshold, and

[0070] - When the value x exceeds the threshold, it is confirmed that one of the modules in the set is defective.

[0071] The term |ΔV1-ΔV2| is the absolute value.

[0072] The terms Vi, Ei, Vj, Ej, VCz, and VMc respectively include the subscripts i, j, z, and c.

[0073] The subscripts i and j (i is different from j) evolve between 1 and n, where n is the number of module sets Ei and Ej in the module group. For example, for a module group consisting of two module sets E1 and E2, there exist set pairs E1 and E2 or equivalent set pairs E2 and E1, where the value x is unaffected by the order of the items E1 and E2. For example, for a module group consisting of three module sets E1, E2, and E3, there exist set pairs E1 and E2 or E2 and E1, set pairs E1 and E3 or E3 and E1, set pairs E2 and E3 or E3 and E2, i.e., the number of combinations is three.

[0074] The subscript z evolves according to the number of cells 2 in the module group, while the subscript c evolves according to the number of modules 1 in the module group. In fact, in Figure 1 Six modules 1 are shown above, forming a single module group. These modules 1 are symmetrically distributed in two identical module sets E1 and E2. Only one module is marked with reference numeral 1, which is not repeated for clarity. The module marked 1 schematically includes two cells 2 (e.g., the two first cells of the module group), and therefore VC1 and VC2 are the voltages measured at the terminals of each of the two first cells 2. However, in the context of the invention, cells equivalent to these two cells 2 can be considered, which leads back to measuring the voltage of the first module VM1 at the terminals of this equivalent cell. However, by using VCz (i.e., the voltage at the terminals of each cell 2), the value x has better accuracy because the method can also detect the internal contact resistance of the module 1 in this case. It will be noted that a cell 2 with voltage VCz can be equivalent to a cell of multiple sub-cells connected in parallel.

[0075] As mentioned above, this method directly compares the first set and the second sets E1 and E2 based on the following evaluation criteria:

[0076] - These sets E1 and E2 in the same group are subjected to the same environment, and therefore undergo the same aging of cell 2 under the same thermal conditions and therefore at the same temperature.

[0077] - The probability that multiple faults of the same degree exist simultaneously in the sets E1 and E2 is zero.

[0078] but:

[0079] -ΔV1 is in fact the sum of the first voltage change due to the aging and temperature of cell 2 in set E1 and the second voltage change related to the contact resistance of set E1, similarly:

[0080] -ΔV2 is actually the sum of the third voltage change, which depends on the aging and temperature of cell 2 in set E2, and the fourth voltage change, which is related to the contact resistance of set E2.

[0081] Taking the above assessment into account, when based on Figure 1 When comparing ΔV1 and ΔV2 in the example, the first change and the third change are the same and cancel each other out, one of the second change and the fourth change is zero, and therefore, |ΔV1-ΔV2| directly characterizes the contact resistance defect on one of the two module sets E1 and E2.

[0082] The coefficient k is, for example, equal to Vi / Vj, or equal to a predetermined fixed value, the purpose of which is to correct the value x for embodiments in which the module sets Ei and Ej are not the same (and therefore do not have the same number of modules or cells, and therefore there is no structural voltage difference between sets Ei and Ej). Thus, in Figure 1 In the example, the two module sets E1 and E2 are symmetrical and have the same voltage in construction, and therefore, the coefficient k is equal to V1 / V2, or for example, equal to a predetermined fixed value of 1. In a variation, if in construction the first set E1 comprises three modules and the second set E2 comprises a single module, and each of these four modules is identical, the coefficient k is equal to V1 / V2, or for example, equal to a predetermined fixed value of 3, and so on. This coefficient k is therefore adapted to each voltage pair Vi, Vj, for which the method determines the value x. Of course, when... Figure 1 When all the module sets Ei and Ej shown are the same, for example, for all determinations of the value x, the coefficient k can be pre-determined to be a single fixed value of 1.

[0083] Of course, the battery may include multiple module groups, such as three module groups, which are connected in parallel, in a delta configuration, or in a star configuration, so as to generate three-phase current, for example, by means of a pulsation device, which may or may not be integrated into the battery. To detect defects in the battery, the method is performed on each of the three module groups.

[0084] The battery, for example, comprises n module sets Ei and Ej of the same module group, which are connected in series, and n is greater than or equal to 2. For each combination of two voltages Vi and Vj of two different sets Ei and Ej among the n sets E1 to En, the previous step is performed, and when the value x of at least one combination exceeds the threshold, the method confirms that the combination of sets Ei and Ej is defective.

[0085] For example, for a module group comprising three sets of modules, there exist set pairs E1, E2 or E2, E1, set pairs E1, E3 or E3, E1, set pairs E2, E3 or E2, E3, i.e., the number of combinations is three, and thus three determinations are made for the value x. These combinations need to be taken in the mathematical sense of the term, and the number of combinations and therefore the number of determinations for the value x is equal to:

[0086] [Equation 3]

[0087]

[0088] When n is greater than or equal to 3, the method also includes:

[0089] - Steps for determining the common set shared by combinations that have been detected as defective.

[0090] - Confirmation steps used to verify that the common set is a defective set.

[0091] This method is thus able to locate defective sets.

[0092] During the determination step for determining the value x, the method makes the value x dimensionless by dividing it by the voltage, in particular by ΔVi or by the average value between ΔVi and ΔVj. It will be noted that it is impossible for ΔVi or ΔVj to be equal to zero, because there is always contact resistance at the terminals of each module 1. Similarly, ΔVi and ΔVj are always positive.

[0093] The threshold is thus dimensionless, for example, less than or equal to 0.05.

[0094] For example, dividing |kΔVj-ΔVi| by ΔV1 makes the value x dimensionless and thus can be expressed as a percentage. For example, a value of x of 0.04 provides 4%.

[0095] Therefore, the value x can be expressed in multiple forms, as mentioned above, for example:

[0096] [Equation 4]

[0097]

[0098] Or for example:

[0099] [Equation 5]

[0100]

[0101] Or:

[0102] [Equation 6]

[0103]

[0104] The confirmation step for identifying a defective module in the set includes, for example, sub-steps taken individually or in combination from the following steps:

[0105] - The steps for issuing visual or audible alarms.

[0106] - A circuit disconnection step for disconnecting the battery from the circuit.

[0107] - A loop-breaking step for breaking each loop in the module (especially modules of a defective set),

[0108] - A disconnection step for disconnecting each of the cells (especially cells from a defective assembly) from the circuit.

[0109] - A limiting step for limiting the current flowing through the battery cell.

[0110] The computer advantageously includes acquisition and processing components for acquiring and processing via software instructions stored in memory, and control components necessary for implementing the method according to the invention. The computer is, for example, a battery management system called a BMS (an acronym for "battery management system").

[0111] Figure 1 A battery system is shown, the battery system comprising:

[0112] - A first assembly of battery modules Ei connected in series, and a first measuring component, the first measuring component being used to measure a first voltage Vi of the first assembly of battery modules Ei.

[0113] - A second set of battery modules Ej connected in series, and a second measuring component, the second measuring component being used to measure a second voltage Vj of the second set of battery modules Ej.

[0114] Each module 1 includes at least a battery cell 2 and a measuring component, the measuring component being used to measure the voltages VCz and VMc of the battery cell 2, with a first set Ei and a second set Ej connected in series. The system also includes a computer (not shown) according to the invention.

[0115] exist Figure 1 Above, each module set Ei and Ej is the same.

[0116] Figure 1 The diagram also shows a general line forming a circuit for collecting the positive and negative terminals of the module groups (all of which are connected in series). This busbar includes multiple elements 4, which connect the modules 1 to each other, for example, via fastening members 3 for securing these elements of the busbar 4 to the positive and negative terminals of each module 1. Each module set Ei, Ej is defined and bounded between two electrical laps 7 capable of measuring voltages Vi, Vj. Therefore, in this example, a central lap 7 is present to separate the three modules of the first set Ei from the three modules of the second set Ej. It will be noted that this lap 7 is employed on the elements 4 of the busbar and between two fastening members 3 of two different and adjacent modules 1 to effectively account for the contact resistance of the clamping members 3 in the measurement of Vi and Vj. The busbar includes a safety fuse 5 and a converter 6 assembled in series, which, for example, allows the battery to be disconnected from the circuit during a disconnection step.

[0117] The battery system, for example (not shown), includes:

[0118] - A emitting or visualizing component used to detect defects, such as a speaker or a signal light positioned in a control panel (or a dashboard for a vehicle).

[0119] - A circuit disconnection component for disconnecting battery cell 2 one by one from the circuit, for example by isolating the battery cell 2 and by replacing the battery cell with a shunt.

[0120] - A disconnection component for disengaging module 1 from the circuit one by one, for example by isolating the module 1 and by replacing the cell with a shunt.

[0121] - A limiting component for limiting the current through each module group, which limits the current passing through the module group and therefore each module 1.

[0122] This method is advantageously capable of detecting defects (i.e., excessively high contact resistance at each connection between element 4 and the terminal of module 1), such defects being caused, for example, by a loosening of one of the fasteners 3.

[0123] The battery system includes, for example, a measuring component for measuring the current flowing through the group of modules 1. This allows the battery system to determine the internal resistance of each set Ei, Ej in proportion to the number of modules in each set Ei, Ej, with the defective set being the set with the highest internal resistance. This identification of the defective set is advantageously applied when the sets Ei, Ej are structurally identical.

[0124] Specifically, the invention is particularly applicable to a vehicle comprising a battery system according to the invention and a drive motor powered by the battery system. However, the invention is particularly suitable for applications in fixed electrical energy storage sites or mobile sites of the construction site type, especially for battery systems used in generator sets.

Claims

1. A method for detecting defects in a module (1) assembly of a battery, the battery comprising: A first module assembly (Ei) of battery modules connected in series, and a first measuring component, the first measuring component being used to measure a first voltage (Vi) of the first module assembly (Ei). A second module assembly (Ej) of battery modules connected in series, and a second measuring component, the second measuring component being used to measure the second voltage (Vj) of the second module assembly. Each module (1) includes at least one battery cell (2) and a measuring component for measuring the voltage (VCz, VMc) of the battery cell (2). The first module set (Ei) and the second module set (Ej) are connected in series. The detection method is characterized by the following sequential steps: Determine the value x using the formula: in: Vi is the first voltage of the first module set (Ei). Vj is the second voltage of the second module set (Ej). Vi is the sum of the voltages (VCz, VMc) of each cell in the first module set (Ei) minus the first voltage Vi. Vj is the sum of the voltages (VCz, VMc) of each cell in the second module set (Ej) minus the second voltage Vj. k is the correction factor. The value x is compared with a threshold, and When the value x exceeds the threshold, it is confirmed that one of the modules in the set is defective.

2. The detection method according to claim 1, wherein the battery comprises n module sets (Ei, Ej), these module sets are connected in series, n is greater than or equal to 2, characterized in that, For each combination of two voltages from two different module sets among the n module sets, the detection method is performed, and when the value x of at least one combination exceeds the threshold, the detection method confirms that the combination of the module sets is defective.

3. The detection method according to claim 2, characterized in that, When n is greater than or equal to 3, the detection method includes: The steps for determining the common set shared by combinations that have been detected as defective. A confirmation step used to confirm that the common set is a defective set.

4. The detection method according to any one of claims 1 to 3, characterized in that, During the determination step for determining the value x, the detection method divides the value by Vi or divided by Vi and The average value between Vj makes the value x dimensionless.

5. The detection method according to any one of claims 1 to 3, characterized in that, The confirmation step for identifying a defective module in the set includes sub-steps, taken individually or in combination from the following steps: The steps for issuing visual or audible alarms. The circuit disconnection step for disconnecting the battery from the circuit. A loop-breaking step for disengaging each of the modules from the loop. Disconnection step for disconnecting each of the battery cells from the circuit Limiting steps for limiting the current flowing through the battery cell.

6. A computer, characterized in that, The computer includes an acquisition and processing component for acquiring and processing via software instructions stored in a memory, and a control component required for implementing the detection method according to any one of claims 1 to 5.

7. A battery system, the battery system comprising: A first module assembly (Ei) of battery modules connected in series, and a first measuring component, the first measuring component being used to measure a first voltage (Vi) of the first module assembly (Ei). A second module assembly (Ej) of battery modules connected in series, and a second measuring component, the second measuring component being used to measure the second voltage (Vj) of the second module assembly (Ej). Each module (1) includes at least one battery cell (2) and a measuring component for measuring the voltage (VCz, VMc) of the battery cell (2), the first module set (Ei) and the second module set (Ej) are connected in series, characterized in that the battery system includes a computer according to claim 6.

8. The battery system according to claim 7, characterized in that, Each module set (Ei, Ej) is identical.

9. A vehicle comprising a battery system and a drive motor powered by the battery system, characterized in that, The battery system is as described in claim 7 or 8.

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