Detection device for an electrical energy storage means of a motor vehicle, having an analysis of the

Abstract

The invention relates to a detection device (7) for an electrical energy store (1) of a motor vehicle for detecting a fault (6) of at least one energy store cell (5) in an electrical circuit (4) comprising energy store cells (5) of the energy store (1), comprising: a current sensor device (9) for detecting a current value of the electrical circuit (4), -a voltage sensor device (8) for detecting a cell voltage value of each energy storage cell (5), and-a storage and evaluation device (12) which is designed to receive the current value and the cell voltage value and to temporarily store the current value and the cell voltage value over a predetermined period of time ([delta] t1, [delta] t2, [delta] t3), the respective dynamics of the cell voltage curve (U1, U2, U2 ') obtained from the temporarily stored cell voltage values of a time period ([delta] t1, [delta] t2, [delta] t3) is compared with the dynamics of the current curve (I) obtained from the temporarily stored current values of the time period ([delta] t1, [delta] t2, [delta] t3), and a fault (6) of the at least one energy storage cell (5) is detected by means of the comparison.

Description

Technical Field

[0001] The invention relates to a detection device for an electrical energy accumulator of a motor vehicle, the detection device being used to detect a fault in at least one energy accumulator cell in an electrical circuit comprising energy accumulator cells of the energy accumulator. The detection device comprises a current sensor device for detecting a current value of the electrical circuit and a voltage sensor device for detecting a cell voltage value of each energy accumulator cell. The invention also relates to a method for detecting a fault in an energy accumulator cell, an electrical energy accumulator and a motor vehicle. Background Art

[0002] Currently, interest is focused on electrical energy storage devices that can be used as traction batteries for electrified motor vehicles. Such electrical energy storage devices usually have at least one circuit including individual energy storage cells, which is arranged in the interior of the energy storage housing of the electrical energy storage device. In the event of a fault in an energy storage cell, such as an internal short circuit in the cell, the energy storage cell may be vented, through which heat and particles are transported into the interior of the energy storage housing. As a result, other energy storage components, such as other energy storage cells, may be damaged. It is therefore desirable to be able to detect such faults or cell damage.

[0003] For this purpose, the energy storage device is usually equipped with a detection device for monitoring each energy storage cell, and the detection device has a sensor device for detecting the characteristic parameters of the electrical energy storage device. Such a sensor device is, for example, a current sensor device for detecting the current value of the energy storage cell and a cell voltage sensor for detecting the cell voltage value of the energy storage cell. For example, a damaged energy storage cell can be identified by comparing the detected cell voltage value with a predetermined voltage theoretical value. In particular, in a parallel circuit of each energy storage cell, the voltage characteristics of a damaged energy storage cell in an unloaded state are balanced by other energy storage cells. Therefore, it may not be possible or may not always be possible to identify a fault with the help of the comparison. In addition, it may happen that the voltage variation curve of each energy storage cell changes due to aging, so that the voltage theoretical value must be adapted to prevent erroneous diagnosis over time.

[0004] Therefore, other sensor devices are usually provided, such as temperature sensor devices for detecting the temperature in the interior of the accumulator housing and / or the accumulator cells, pressure sensor devices for detecting the pressure in the interior of the accumulator housing, light sensor devices for detecting the light in the interior of the accumulator housing, etc. These other sensor devices are mainly used to observe the following fault characteristics, which indicate obvious damage to the accumulator cells. However, such additional sensor devices increase the cost and weight of the electrical accumulator. Summary of the invention

[0005] The object of the present invention is to provide a simple and cost-effective solution for detecting a malfunction of an energy storage cell of an electrical energy storage device for a motor vehicle.

[0006] According to the invention, this object is achieved by a detection device, a method, an electrical energy storage device and a motor vehicle having the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the drawings.

[0007] The detection device for an electrical energy accumulator of a motor vehicle according to the invention is used to detect a fault in at least one energy accumulator cell in an electrical circuit comprising energy accumulator cells of the energy accumulator. The detection device has a current sensor device for detecting a current value of the electrical circuit and a voltage sensor device for detecting a cell voltage value of each energy accumulator cell. In addition, the detection device has a storage and analysis device, which is designed to: receive current values ​​and cell voltage values ​​and temporarily store them over a predetermined time period, compare the corresponding dynamics of a cell voltage variation curve obtained from the temporarily stored cell voltage values ​​of a time period with the dynamics of a current variation curve obtained from the temporarily stored current values ​​of the time period, and identify a fault in at least one energy accumulator cell by means of the comparison.

[0008] Furthermore, the invention relates to a method for detecting a fault in at least one energy storage cell in a circuit of energy storage cells comprising electrical energy storage cells. In the method, current values ​​of the circuit and cell voltage values ​​of the energy storage cells are detected. The current values ​​and cell voltage values ​​are received and temporarily stored over a predetermined time period. The corresponding dynamics of the cell voltage curve obtained from the temporarily stored cell voltage values ​​for a time period are then compared with the dynamics of the current curve obtained from the temporarily stored current values ​​for the time period, and a fault in the at least one energy storage cell is detected by means of the comparison.

[0009] The electrical energy accumulator according to the invention has a circuit including electrical energy accumulator cells and a detection device according to the invention. The electrical energy accumulator is in particular a high-voltage energy accumulator and is used as a rechargeable traction battery for an electrified motor vehicle. The electrical energy accumulator has a plurality of energy accumulator cells or battery cells, for example prismatic cells, round cells or soft-pack cells, which are interconnected and arranged in the interior of an energy accumulator housing of the electrical energy accumulator. Preferably, the circuit including the energy accumulator cells has at least one parallel circuit or parallel connection including at least two energy accumulator cells.

[0010] In order to monitor each energy storage cell, the electrical energy storage device has a detection device. The detection device is designed to identify a fault of at least one energy storage cell, that is, a cell damage, by means of the measured current value of each energy storage cell and the measured cell voltage value of each energy storage cell. In particular, the detection device is designed to identify a fault only by means of the measured current value and the measured cell voltage value, without using sensor data of other sensor devices and without comparing the measured values ​​with predetermined theoretical values. For this purpose, the detection device has a voltage sensor device and a current sensor device, wherein the voltage sensor device has a voltage sensor for each energy storage cell for measuring a cell-specific cell voltage value, and the current sensor device has at least one current sensor for each circuit for measuring the current flowing through the circuit. The current flowing through the circuit corresponds to the corresponding current passing through each energy storage cell.

[0011] The current value and the cell voltage value detected by the current sensor device and the voltage sensor device are transmitted to the storage and analysis device of the detection device and are temporarily stored or cached there for a predetermined time period, for example, for a maximum of several seconds. The storage and analysis device can be integrated into the control device inside the energy storage device and connected to the current sensor device and the voltage sensor device in communication technology, for example, wired connection. The storage and analysis device has a buffer or a temporary memory in particular for temporarily storing the current value and the cell voltage value, and the buffer is designed to continuously store the current value and the cell voltage value over a predetermined time period. Therefore, the current and the cell voltage value are continuously temporarily stored in the buffer over a predetermined time period, wherein the oldest value can be deleted again for each newly arrived current value. The buffer therefore has a fixed window width in particular, wherein the window width corresponds to the time period. The buffer therefore has the current current and the cell voltage value and a predetermined number of current and cell voltage values ​​that have occurred in the past.

[0012] With the help of the current values ​​and cell voltage values ​​temporarily stored over the time period, a current curve or current signal and a cell voltage curve or cell voltage signal can be determined. The cell voltage curve is now compared with the current curve. The present invention is based on the following understanding, that is, the dynamics of the cell voltage curve should follow the dynamics of the current curve in a fault-free energy storage cell. If the dynamics of the cell voltage curve deviates from the dynamics of the current curve, this indicates damage to the associated energy storage cell. Therefore, in order to monitor the cell, the dynamics of the cell voltage curve is analyzed for plausibility with the help of the dynamics of the current curve.

[0013] For example, the storage and analysis device is designed to determine the gradients of the cell voltage curve and the current curve in order to determine and compare the dynamics, and to detect a fault in at least one energy storage cell if the gradient of the associated cell voltage curve is at least partially oriented oppositely to the gradient of the current curve. Thus, in the absence of a fault, a positive gradient of the cell voltage signal caused by an increasing cell voltage value should follow a positive gradient of the current signal caused by an increasing current value. Conversely, in the absence of a fault, a negative gradient of the cell voltage signal caused by a decreasing cell voltage value should follow a negative gradient of the current signal caused by a decreasing current value. If the gradient of the cell voltage signal deviates at least partially in sign from the gradient of the current signal, a fault in the associated energy storage cell is detected.

[0014] Particularly advantageous is a method implemented with the aid of the detection device in which only the dynamics of the current profile and the cell voltage profile are subjected to a plausibility analysis for fault detection, since this is independent of changes in the voltage profile of the energy storage cell caused by aging. It is therefore not necessary to provide a target value and to constantly calibrate it. Furthermore, with the aid of the method, damages can also be detected which could not be detected with the aid of the voltage profile alone due to the damage-compensated parallel connection of the individual energy storage cells.

[0015] The invention also includes a motor vehicle having an electrical energy storage device according to the invention. The motor vehicle is an electrically drivable motor vehicle in the form of an electric or hybrid vehicle and has an electrical energy storage device as a traction battery.

[0016] The embodiments described with reference to the detection device and their advantages apply correspondingly to the method according to the invention, the electrical energy storage device according to the invention and the motor vehicle according to the invention.

[0017] Further features of the invention are apparent from the claims, the drawings and the description of the drawings. The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the drawings and / or shown only in the drawings can be used not only in the respectively indicated combination but also in other combinations or individually. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will now be described in more detail with the aid of preferred embodiments and with reference to the accompanying drawings.

[0019] Figure 1 A schematic diagram of an electrical energy storage device of a motor vehicle is shown,

[0020] Figure 2a-2c showing the current and cell voltage profiles of individual, fault-free energy storage cells of the electrical energy storage device; and

[0021] Figure 3 The current and cell voltage profiles of a non-defective and a defective energy storage cell are shown. DETAILED DESCRIPTION

[0022] In the figures, identical elements and elements having the same function are provided with the same reference symbols.

[0023] Figure 1 An electrical energy storage device 1 for a motor vehicle is shown. The electrical energy storage device 1 has an energy storage device housing 2, in the interior space 3 of which at least one circuit 4 including individual energy storage cells 5 is arranged. In order to detect a fault 6 of an energy storage cell 5 of the circuit 4 or a cell damage, for example an impending cell exhaust due to a short circuit within the cell, the electrical energy storage device 1 also has a detection device 7, which has a voltage sensor device 8 and a current sensor device 9. The voltage sensor device 8 has here for each energy storage cell 5 a voltage sensor 10 for measuring a cell voltage value of the corresponding energy storage cell 5. The current sensor device 9 has here for each circuit 4 a current sensor 11 for measuring a current value of the circuit 4. The detection device 7 also has a storage and analysis device 12, which is coupled to the voltage sensor device 8 and the current sensor device 9 and transmits the detected cell voltage and current values ​​to the storage and analysis device. The transmitted cell voltage and current values ​​are temporarily stored by the storage and analysis device 12 for a predetermined time period Δt1 , Δt2 , Δt3 .

[0024] Figure 2a , Figure 2b and Figure 2c The current curve I of the circuit 4 as a function of the current time t1*, t2*, t3* and the two cell voltage curves U1, U2 of two energy storage cells 5 without a fault as a function of the current time t1*, t2*, t3 are shown over time t. Furthermore, buffer windows Pt1, Pt2, Pt3 of width B are shown which are continuous as a function of the current time t1*, t2*, t3*, wherein the width B of the buffer windows Pt1, Pt2, Pt3 corresponds to the respective time period Δt1, Δt2, Δt3 within which the values ​​measured by the sensor devices 8, 9 are temporarily stored and evaluated in the storage and evaluation device 12. For fault detection, the current buffer windows Pt1, Pt2, Pt3 are observed, which include the current and cell voltage values ​​at the current time t1*, t2*, t3* and the current and cell voltage values ​​which have already occurred in the current time period Δt1, Δt2, Δt3. In other words, the "history" of current values ​​and cell voltage values ​​covering a predetermined period of time is continuously evaluated.

[0025] For each buffer window Pt1, Pt2, Pt3, the dynamics of the cell voltage profiles U1, U2 are compared with the dynamics of the current profile I. In addition, the dynamics of the cell voltage profiles U1, U2 can also be compared with one another and thus analyzed for plausibility. Figure 2a to Figure 2c In each buffer window Pt1, Pt2, Pt3, the dynamics of the cell voltage curves U1, U2 are identical to the dynamics of the current curve I. In order to analyze the plausibility of the dynamics, the sequence of the gradients of the cell voltage curves U1, U2 and the current curve I within the corresponding time periods Δt1, Δt2, Δt3 can be observed. For example, the gradients of the curves U1, U2, I in the section Δt1a of the first time period Δt1 have a negative sign and in the following section Δt1b of the first time period Δt1 have a positive sign. The gradients of the curves U1, U2, I have a negative sign in the section Δt1c and have a positive sign again in the following section Δt1d. In the buffer window Pt2, the sequence of the sections with negative and positive gradients in the cell voltage signals U1, U2 and the current signal I is identical. In the third time window B3, all curves U1, U2, I have a gradient of 0, so that here the gradients of all curves U1, U2, I also have the same sign. As soon as the gradients of the cell voltage curves U1, U2 and the gradient of the current curve I are oriented in the same direction in the mutually corresponding sections of the time periods Δt1, Δt2, Δt3, the dynamics are identical and the energy storage cells 5 are classified as fault-free.

[0026] Figure 3 The cell voltage variation curve U2' for a damaged energy storage cell 5 is shown. Here, in the buffer window Pt1, the dynamics of the cell voltage variation curve U2' deviate from the dynamics of the current signal I. This can be seen in the section Δt1d, in which the gradient of the current signal I is positive, while the gradient of the cell voltage signal U2' is at least partially negative. The gradient of the cell voltage signal U2' is therefore directed in the opposite direction to the current signal I. The deviation of the dynamics of the cell voltage variation curve U2' from the dynamics of the current variation curve I is detected by the storage and analysis device 12 and the energy storage cell 5 belonging to the cell voltage variation curve U2' is classified as defective or damaged.

Claims

1. A detection device (7) for an electrical energy storage device (1) of a motor vehicle, the detection device being used to detect a fault (6) of at least one energy storage cell (5) in a circuit (4) comprising the energy storage cells (5) of the energy storage device (1), the detection device comprising: - a current sensor device (9) for detecting the current value of the circuit (4), - a voltage sensor device (8) for detecting the cell voltage value of each accumulator cell (5), It is characterized in that The detection device has a storage and analysis device (12) which is designed to: receive current values ​​and cell voltage values ​​and temporarily store them over a predetermined time period (Δt1, Δt2, Δt3), compare the corresponding dynamics of a cell voltage variation curve (U1, U2, U2') obtained from the temporarily stored cell voltage values ​​of a time period (Δt1, Δt2, Δt3) with the dynamics of a current variation curve (I) obtained from the temporarily stored current values ​​of the time period (Δt1, Δt2, Δt3), and detect a fault (6) of at least one energy storage cell (5) by means of the comparison.

2. The detection device (7) according to claim 1 It is characterized in that The voltage sensor device (8) has a voltage sensor (10) for each energy storage cell (5).

3. The detection device (7) according to claim 1 or 2, It is characterized in that The current sensor arrangement (9) has a current sensor (11) for each electrical circuit (4).

4. The detection device (7) according to one of the preceding claims, It is characterized in that The storage and analysis device (12) is designed to determine the gradients of cell voltage profiles (U1, U2, U2') and current profiles (I) in order to determine and compare the dynamics and to detect a fault (6) of at least one energy storage cell (5) if the gradient of the associated cell voltage profile (U2') is directed at least in sections in the opposite direction to the gradient of the current profile (I).

5. The detection device (7) according to one of the preceding claims, It is characterized in that The storage and evaluation device (12) has a buffer memory which is designed to temporarily and continuously store current values ​​and cell voltage values ​​over predetermined time periods (Δt1, Δt2, Δt3).

6. A method for detecting a fault (6) of at least one energy storage cell (5) in a circuit (4) of energy storage cells (5) of an electrical energy storage device (1), the method comprising the following steps: - detecting the current value of the circuit (4), - Detecting the cell voltage value of each accumulator cell (5), - receiving and temporarily storing current values ​​and cell voltage values ​​over predetermined time periods (Δt1, Δt2, Δt3), - comparing the respective dynamics of the cell voltage curve (U1, U2, U2') obtained from the temporarily stored cell voltage values ​​for a time period (Δt1, Δt2, Δt3) with the dynamics of the current curve (I) obtained from the temporarily stored current values ​​for the time period (Δt1, Δt2, Δt3), and - Using the comparison, a fault (6) of at least one energy storage cell (5) is detected. 7 . An electrical energy storage device ( 1 ) for a motor vehicle, comprising at least one circuit ( 4 ) comprising electrical energy storage cells ( 5 ) and a detection device ( 7 ) according to claim 1 .

8. The electrical energy storage device (1) according to claim 7, It is characterized in that The circuit (4) comprising the energy storage cells (5) has at least one parallel circuit comprising at least two energy storage cells (5). 9 . A motor vehicle having an electrical energy storage device ( 1 ) as claimed in claim 7 or 8 .

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