Method for operating an electrical energy storage device

Abstract

The invention relates to a method for operating an electrical energy accumulator, wherein the electrical energy accumulator comprises a storage unit for storing electrical energy and a control unit, wherein a safety switch is provided, which is designed to interrupt an electrical line of the electrical energy accumulator, wherein a current flowing through the electrical line is detected and the safety switch is actuated only when the current is below a predeterminable threshold value.

Description

Background Art

[0001] Electrical energy storage devices, such as those used for operating electric vehicles, are usually secured by means of a safety switch, i.e. a switch is provided which, for example, can render a conductive line within the electrical energy storage device non-conductive when a trigger signal is applied to the safety switch. This trigger signal can be generated, for example, when a fault in the electrical energy storage device is detected (e.g., a fault in the energy storage device itself or a fault in a current sensor) or when an accident of a vehicle in which the electrical energy storage device may be installed is detected or in response to an excessively high current demand of the vehicle.

[0002] The safety switch is usually dimensioned in such a way that it can be safely actuated even when a short-circuit current discharged by the electrical energy storage device flows through the safety switch. Since the safety switch is thus designed for high currents, it is a cost-intensive and large component. The safety switch is usually designed for a maximum current below the short-circuit current, wherein the triggering of the safety switch at a current above the maximum current has the consequence that the electrical energy storage device is then considered to be defective. The triggering of the safety switch at a current above the maximum current is therefore only possible once. On the other hand, actuation at a current below the maximum current is reversible. Summary of the invention

[0003] The method for operating an electrical energy accumulator comprising a storage unit for storing electrical energy and a control unit, wherein a safety switch is provided which is designed to interrupt an electrical line of the electrical energy accumulator, has the advantage that the current flowing through the electrical line is detected and the safety switch is actuated only when the current is below a predeterminable threshold value. It can thus be ensured that the safety switch cannot be actuated at every arbitrary value of the current discharged by the electrical energy accumulator. The safety switch can be designed to be correspondingly smaller and less costly with respect to its own ability to switch at high currents.

[0004] Advantageous embodiments are the subject matter of the dependent claims.

[0005] Advantageously, the threshold value corresponds to the maximum current of the safety switch. Below the maximum current is to be understood in this case as the maximum current which is permitted to flow through the safety switch at the time of actuation of the safety switch due to the components without the electrical storage unit subsequently being considered to be faulty.

[0006] Advantageously, the actuation signal that should cause the actuation of the safety switch is suppressed until the current is below a predeterminable threshold value. This ensures that the safety switch is actuated as quickly as possible after the actuation signal is formed and that electrical energy is temporarily extracted by a current above the threshold value.

[0007] Advantageously, the time of the current exceeding a predeterminable threshold value is not longer than a predeterminable tolerance time. Advantageously, the time of the current exceeding is estimated as soon as the current exceeds the predeterminable threshold value, and the safety switch is actuated if the estimated time of the current exceeding exceeds the tolerance time. In a particularly advantageous embodiment, the time of the current exceeding is estimated based on operating parameters of the vehicle in which the electrical energy storage device is installed. The estimation can be performed, for example, based on events recorded in the past or using a trained neural network. Alternatively, a time of the current exceeding can be 0.5 to 5 seconds, in particular 1 to 2 seconds. The tolerance time is selected in particular in such a way that it is ensured that the electrical energy storage device is in a safe state within the tolerance time.

[0008] Advantageously, as soon as the current exceeds a pre-threshold value which is smaller than the pre-determinable threshold value, the time of the excess is estimated and the safety switch is actuated if the estimated time of excess exceeds the tolerance time. It can thus be advantageously ensured that the safety switch is dimensioned in such a way that the safety switch is not triggered in every possible case of a discharge of the electrical energy storage device without the electrical energy storage device subsequently being considered to be faulty, and the safety switch need not be triggered as long as the current is above the pre-determinable threshold value. For this purpose, the time period for which the threshold value is exceeded is estimated starting at the time of the pre-threshold value being exceeded. If it is estimated that the expected time of excess exceeds the tolerance time, the safety switch is actuated for safety reasons as soon as the current reaches the pre-determinable threshold value.

[0009] A device configured to perform each step of the method according to the invention and an electrical energy storage device comprising the device are advantageous. In addition, a computer program configured to perform each step of the method according to the invention when the computer program is run on a computing unit is advantageous. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the following, embodiments of the present invention are further presented.

[0011] Figure 1 A schematic diagram of an electric vehicle with an electric energy storage device is shown;

[0012] Figure 2 A schematic diagram showing a curve of a current flowing through an electrical line, wherein the electrical line can be interrupted by a safety switch;

[0013] Figure 3 A schematic diagram showing the flow of an embodiment of the method according to the present invention. DETAILED DESCRIPTION

[0014] Figure 1A schematic diagram of an electric vehicle (10) is shown, which includes an electric energy storage device (12), a vehicle control unit (18) and a drive motor (17). The electric energy storage device (12) further includes a storage unit (14) and a control unit (15). A safety switch (16) is arranged on the electric energy storage device (12), so that the safety switch (16) can interrupt the following electrical line of the electric energy storage device (12), via which, for example, the drive motor (17) is supplied with electrical energy. The control unit (15) of the electric energy storage device (12) is connected to the safety switch (16) via a signal line. The vehicle control unit (18) is connected to the control unit (15) of the electric energy storage device (12) via a signal line.

[0015] Figure 2 A schematic diagram of the curve of the current (24) flowing through the electrical line of the electrical energy storage device (12) is shown. The current axis is marked with the reference numeral 20 and the time axis is marked with the reference numeral 21. Figure 2 The schematic current curve (24) exceeds a predetermined threshold value (23) at a first time point (25) and exceeds a predeterminable threshold value (22) at a second time point (26). At a third time point, the current curve (24) falls below the predeterminable threshold value (22). The third time point (27) and the second time point (26) therefore define the time during which the current curve (24) exceeds the threshold value (22).

[0016] Figure 3 A schematic sequence of an exemplary embodiment of the method according to the invention is shown. In step 100 , the current flowing through the electrical line of the electrical energy storage device ( 12 ) is monitored. Step 110 follows.

[0017] In step 110, the current detected in step 100 is compared with a pre-threshold value (23). If the current is less than the pre-threshold value (23), step 110 is followed by step 100. If the current is greater than the pre-threshold value (23), step 110 is followed by step 120.

[0018] In step 120, the overrun time is estimated. For this purpose, for example, overrun times occurring in the past can be used as estimated values. Alternatively or additionally, the overrun time can be estimated with the aid of a trained neural network. Alternatively or additionally, the overrun time can be estimated taking into account various operating parameters of the electric vehicle (10), wherein the operating parameters are provided by the vehicle control unit (18). Step 120 is followed by step 130.

[0019] In step 130, a check is performed to determine whether the excess time estimated in step 120 is greater than a tolerance time. The tolerance time can be determined in particular in such a way that the safety of the electrical energy storage device (12) is ensured during the tolerance time even if the safety switch (16) cannot be actuated during the tolerance time. If the excess time is greater than the tolerance time, step 130 is followed by step 140. If the excess time is less than the tolerance time, step 130 is followed by step 150.

[0020] In step 140 , the safety switch ( 16 ) is actuated. The actuation of the safety switch can be effected, for example, by a control unit ( 15 ) of the electrical energy storage device ( 12 ) or also by a vehicle control unit ( 18 ).

[0021] In step 150, a suppression signal is set, wherein the suppression signal is then released again only if the current detected in step 100 is below a threshold value (22). As long as the suppression signal is set, an actuation signal that is to cause an actuation of the safety switch (16) is suppressed. The suppression of the actuation signal can be carried out, for example, by a control unit (15) of the electrical energy storage device (12).

[0022] The proposed embodiment of the method according to the invention ensures that the electric vehicle (10) can be operated safely even if the safety switch (16) is dimensioned in such a way that, when a high current flows through an electrical conductor of the electric energy storage device (12), it is not possible to actuate the safety switch (16) without subsequently classifying the electric energy storage device as faulty and thus suppressing the actuation.

Claims

1. A method for operating an electrical energy storage device (12), wherein the electrical energy storage device comprises a storage unit (14) for storing electrical energy and a control unit (15), wherein a safety switch (16) is provided, which is designed to interrupt an electrical line of the electrical energy storage device (12), characterized in that: A current (24) flowing through the electrical line is detected and the safety switch (16) is actuated only when the current (24) is below a predeterminable threshold value (22), wherein as soon as the current (24) exceeds a predeterminable threshold value (23) which is smaller than the predeterminable threshold value (22), the excess time is estimated, and if the estimated excess time is longer than a tolerance time, the safety switch (16) is actuated, otherwise a suppression signal is set, wherein the suppression signal suppresses the actuation signal which is intended to cause the safety switch (16) to be actuated, wherein the suppression signal is then released again only when the detected current is below the predeterminable threshold value (22), and wherein the predeterminable threshold value (22) corresponds to the maximum current of the safety switch (16).

2. The method according to claim 1, characterized in that An actuation signal that is to cause an actuation of the safety switch (16) is suppressed until the current (24) falls below the predeterminable threshold value (22).

3. The method according to claim 1, characterized in that As soon as the current (24) exceeds the predefinable threshold value (22), the excess time is estimated and the safety switch (16) is actuated if the estimated excess time exceeds the tolerance time.

4. A device for operating an electrical energy storage device (12), the device being designed to carry out each step of the method according to any one of claims 1 to 3.

5. An electrical energy accumulator comprising a device according to claim 4. 6 . A computer program product comprising instructions, which is designed to carry out each step of the method according to claim 1 , when the computer program product is run on a computing unit.

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