Monitoring device for an electrical energy storage device

Abstract

The invention relates to a monitoring device (1) for an electrical energy storage device (2), comprising a housing (2.1) and at least one electrochemical cell arranged within the housing (2.1). The monitoring device (1) is characterized according to the invention in that at least one sensor (3) is arranged on at least one inner wall (2.1.1) of the housing (2.1), which sensor is used to detect a local insulation resistance (R) on the inner wall (2.1.1) and an electrical voltage potential (U) between the inner wall (2.1.1) and an electrical ground potential of the at least one cell, and the at least one sensor (3) is coupled to or has an evaluation unit (4), wherein the evaluation unit (4) is designed to conclude that there is a fault (F) within the electrical energy store (2) if the insulation resistance (R) falls below a predetermined resistance value and the voltage potential (U) exceeds a predetermined voltage value, and to output a fault signal (S) if a fault (F) is present.

Description

The invention relates to a monitoring device for an electrical energy store according to the preamble of claim 1.A control unit circuit for a motor vehicle is known from DE 10 2019 215 790 A1, wherein the control unit circuit has a control unit for providing a vehicle function and an electrical energy store for an emergency supply of the control unit outside a housing of the control unit. The energy store is configured to supply the control device with electrical energy if a supply current from an on-board power supply system of the motor vehicle fails. To form a circuit for the emergency supply, two electrical poles of the energy store are connected to the control device via a cable and, in the control device or in the energy store or on the cable, one of the two electrical poles is connected to a ground potential of the on-board electrical system via a switching element. A measuring circuit couples one of the poles to the ground potential in each case and is configured to generate a measurement signal which correlates with an electrical voltage which falls between the respective pole and the ground potential. A control circuit of the switching element is configured to keep the switching element electrically conductive in a normal operation of the control unit and, in the event that the respective measurement signal signals the measurement circuit that the respective voltage is greater than a predetermined threshold value, to electrically switch the switching element in an electrically blocking manner and thus to cancel an electrical coupling between the circuit and ground potential caused by the electrical switching element. The control device is configured to carry out a test routine for checking an insulation resistance of the cable and to generate the switching signal at the signal input at the beginning of the test routine.DE 10 2018 222 454 A1 relates to a detection arrangement for detecting an insulation fault caused by a liquid, having an insulation monitoring device which is designed to monitor a respective insulation resistance between a respective one of two high-voltage potentials and a predetermined electrical ground, and which is designed to detect the insulation fault if at least one of the two insulation resistances falls below a predeterminable limit value. The detection arrangement has a sensor device which comprises an electrical conductor which has a first end for coupling to one of the two high-voltage potentials and a second open end which provides a contact point for arrangement in predetermined proximity to an electrically conductive component which is electrically conductively connected to the predetermined electrical ground in an area to be monitored for the presence of liquid.DE 11 2016 003 015 T5 relates to a device which has a substrate and a sensor device which has a non-conductive layer and a conductive layer which overlaps the non-conductive layer, wherein the sensor device is constructed and arranged in such a way that it measures or monitors a variable, wherein the variable has at least one of the temperature, pressure, concentration of volatile organic compounds, the state of charge or the state of condition of the substrate.JP 2003-59 467 A relates to a battery pack which is composed of: a levitation sensor that detects moisture that has entered the inside of an outer case; an actuator circuit that sensorially outputs a connection termination signal based on a water-immersion detection result; and a terminal cut-off member that receives a terminal cut-off signal from the control circuit and blocks electrical connection between the battery and the external input / output terminal.The invention is based on the object of specifying a novel monitoring device for an electrical energy store.The object is achieved according to the invention by a monitoring device which has the features specified in claim 1.Possible embodiments of the invention are the subject of the dependent claims.The monitoring device for an electrical energy store, having a housing and at least one electrochemical cell arranged within the housing, is distinguished according to the invention in that at least one sensor is arranged on at least one inner wall of the housing, which sensor is designed for detecting a local insulation resistance on the inner wall and an electrical voltage potential between the inner wall and an electrical ground potential of the at least one cell, and the at least one sensor is coupled to an evaluation unit or has the latter, wherein the evaluation unit is designed to infer a fault within the electrical energy store when a predetermined resistance value of the insulation resistance is simultaneously undershot and a predetermined voltage value of the voltage potential is exceeded, and to output a fault signal when a fault is present.In the event of a single fault, for example a so-called thermal runaway (Thermal Runaway) of an electrochemical cell in the housing of the energy store, for example of a traction battery of a vehicle, a casing of the cell concerned opens, so that electrically conductive components are emitted and distributed over a large area within the housing. Such components are, for example, electrolyte as well as anode and cathode material. These components deposit on surfaces inside the housing and significantly reduce their insulation value. As a result, unrecognized leakage currents may occur within the energy store, which may result in secondary failures of the energy store. These secondary defects may occur with a large time delay of, for example, more than 30 minutes from the primary cell defect. These secondary faults can also be caused by a defect in a temperature control medium line and a resulting emergence of an electrically conductive temperature control medium into the interior of the housing. The secondary defects include, for example, defects of further cells arranged in the housing or a formation of arcs.By means of the present monitoring device, faults in the energy store can be detected very early in a simple and reliable manner by monitoring the insulation resistance and the voltage potential, which faults result from the inner walls being covered with electrically conductive material. This allows an early warning of the occurrence of possible secondary faults and an early initiation of counter- and protection measures to avoid the occurrence of the secondary faults or to reduce their extent and consequences.Exemplary embodiments of the invention are explained in more detail below with reference to drawings:The following are shown: FIG. 1 schematically shows a monitoring device for an electrical energy store and a sectional illustration of the energy store, and FIG. 2 schematically shows the monitoring device and the energy store according to FIG. 1 in the presence of an electrical fault of the energy store.Corresponding parts are provided with the same reference numerals in all figures.FIG. 1 shows a block diagram of a possible exemplary embodiment of a monitoring device 1 for an electrical energy store 2 and a sectional illustration of a possible exemplary embodiment of the energy store 2. FIG. 2 shows the block diagram of the monitoring device 1 and the energy store 2 according to FIG. 1 in the presence of an electrical fault F of the energy store 2.Energy store 2 is, for example, a traction battery of a vehicle that is at least partially electrically operated, for example, and includes a housing 2.1, a number of electrochemical cells, not shown in detail and arranged within housing 2.1, and poles 2.2, 2.3 electrically coupled to the number of cells. The pole 2.3 is electrically coupled to a ground potential of the cells.The monitoring device 1 has at least one sensor 3, which is designed as a so-called leakage current sensor. The sensor 3 has two electrodes 3.1, 3.2, which are fastened on an electrically insulating carrier material at a defined distance from one another on an inner wall 2.1.1 of the housing 2.1. For example, the electrodes 3.1, 3.2 are glued to the inner wall 2.1.1. One of the electrodes 3.2 is electrically coupled to the pole 2.3, i.e. the ground potential of the number of cells.The sensor 3 is coupled to an evaluation unit 4 or has the latter, wherein the evaluation unit 4 is designed to determine a local insulation resistance R between the electrodes 3.1, 3.2 on the inner wall 2.1.1 and an electrical voltage potential U between the inner wall 2.1.1 and the electrical ground potential of the number of cells from widths detected by means of the sensor 3. In this case, the insulation resistance R is very high or tends to infinity in a fault-free state of the energy store 2 and the voltage potential U is zero.In the event of a fault F, for example a thermal runaway, of at least one cell in the interior of the energy store 2, a casing of the latter opens, so that electrically conductive components are emitted and distributed over a large area within the housing 2.1. If these components are deposited in the region of the electrodes 3.1, 3.2 of the sensor 3, the insulation resistance R decreases and a voltage potential U can be measured, which causes deposits to act in a similar manner to a carbon track of a potentiometer. Even in the event of a defect in a temperature control medium line and a resulting emergence of an electrically conductive temperature control medium into the interior of the housing 2.1, the insulation resistance R is reduced and the voltage potential U is increased.By arranging the sensor 3 or a plurality of such sensors 3 at neuralgic positions within the housing 2.1 and continuously evaluating the insulation resistance R and the voltage potential U, it is possible to detect at an early stage a surface of the electrodes 3.1, 3.2 and thus of the corresponding inner wall 2.1.1 being covered with conductive components from a faulty cell or other conductive substances, such as a temperature control medium. The evaluation unit 4 is designed to infer a fault F within the electrical energy store 2 in the case of the stated reduction in the insulation resistance R and the increase in the voltage potential U, and to output a fault signal S in the case of the presence of such a fault F.This allows an early warning of the occurrence of possible secondary faults and an early initiation of counter- and protection measures to avoid the occurrence of the secondary faults or to reduce their extent and consequences. Such secondary faults can result from leakage currents which can result from the interior of the energy store 2 being covered with conductive substances.List of reference characters1 Monitoring device 2 Energy store 2.1 Housing 2.1.1 Inner wall 2.2 Pole 2.3 Pole 3 Sensor 3.1 Electrode 3.2 Electrode 4 Evaluation unit F Fault R Insulation resistance S Fault signal U Voltage potential

Claims

Monitoring device (1) for an electrical energy store (2), having a housing (2.1) and at least one electrochemical cell arranged within the housing (2.1), characterized in that - at least one sensor (3) is arranged on at least one inner wall (2.1.1) of the housing (2.1), which sensor is designed for detecting a local insulation resistance (R) on the inner wall (2.1.1) and an electrical voltage potential (U) between the inner wall (2.1.1) and an electrical ground potential of the at least one cell, and - the at least one sensor (3) is coupled to an evaluation unit (4) or has the latter, wherein the evaluation unit (4) is designed, when a predefined resistance value of the insulation resistor (R) is simultaneously undershot and a predefined voltage value of the voltage potential (U) is exceeded, a fault (F) within the electrical energy store (2) is concluded, and a fault signal (S) is output in the event of a fault (F) being present.Monitoring device (1) according to claim 1, characterised in that the sensor (3) comprises two electrodes (3.1, 3.2) which are fastened on an electrically insulating carrier material on the inner wall (2.1.1) at a defined distance from one another.Monitoring device (1) according to Claim 2, characterized in that one of the electrodes (3.1, 3.2) is electrically coupled to the electrical ground potential of the at least one cell.

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