DE102014222786B4 - Method and device for leak testing of electrochemical storage in the form of batteries or individual battery cells - Google Patents

Abstract

Device for leak testing at least one electrochemical storage in the form of a battery and/or an individual battery cell, with a housing (100) in which at least one electrochemical storage (20) can be arranged and through which a gas flow (110) can flow,
a first gas sensor (120) which is arranged upstream of the electrochemical storage (20) and can generate a first sensor signal (320), at least one second gas sensor (130) which is arranged downstream of the electrochemical storage (20) and a second sensor signal (330) can generate, and
an evaluation device (140) which is coupled to the first gas sensor (120) and the second gas sensor (130) and which is set up to evaluate the first sensor signal (320) and the second sensor signal (330) and depending on the evaluation of the first Sensor signal (320) and the at least one second sensor signal (330) to generate an error signal.

Description

The invention relates to a method and a device for leak testing electrochemical storage in the form of batteries or individual battery cells

Electrochemical storage can be in the form of individual battery cells or as a battery. In a battery, several individual cells are connected to each other in series and/or parallel. In the context of this application, the term battery or individual battery cell is understood to mean both primary storage, which can only be discharged once, and secondary storage, which allows multiple cycles of charging and discharging.

A battery cell contains two electrodes arranged in an electrolyte. The battery cell is tightly packed on the outside by a casing. Damage or defects in the casing or due to diffusion can result in leakage of electrolyte or components contained in the electrolyte. Such leaks can lead to battery cell failure or a hazard to the surrounding area. Various methods are known from the prior art for leak testing of batteries or individual battery cells.

This is what the publication says US 3822585 A a pressure-based process in which the battery cells are pressurized from the inside and any leakage is determined via the pressure drop.

From the publication EP 0482422 A2 Another pressure-based method is known in which the cells are subjected to a predefined pressure using compressed air. The measured pressure drop is evaluated for each cell using reference values to determine any leaks.

The publication JP H09-115555 A shows a process in which a battery cell is placed in an airtight container. The container is then evacuated. A subsequent change in pressure in the container is used to determine whether the battery cell is leaking or not.

In print EP 1437585 A2 The tightness of a battery cell with a flexible housing (so-called pouch cell) is assessed by whether the thickness of the cell housing changes under pressure or negative pressure.

The disadvantage of pressure-based systems is that they require a certain minimum opening in the cell wall so that a leak can be detected. A leak due to diffusion effects cannot be detected. Furthermore, with pressure-based methods, which introduce a pressurized fluid into the cell, it must be ensured that this does not damage the galvanic elements. In addition, the cell is not measured in its final state, as the electrolyte filling and sealing only takes place afterwards.

Another way to determine leaks is to measure the escape of a gas from a cell using mass spectroscopy. The disadvantages of this are the high costs and the large amount of time required.

US 2014/0 174 150 A1 shows a process in which battery cells are placed in a housing and the housing is flushed with air. A gas sensor is positioned in front of an opening in the housing and the sensor data is used to determine whether there is a leak.

The publication US 2007/0 229 294 A1 describes a gas sensor with a gas-sensitive nanoparticle structure.

The JP 2000 - 149 961 A shows a product inspection device for detecting gas, in which a gas sensor is brought close to the product.

The JP 2005- 322 579 A shows a detection device for detecting hydrogen leaks, in which a first sensor is arranged outside a housing of a fuel cell and a second sensor is arranged inside the housing, with a detection means determining a leak based on a deviation between the first and second sensors.

From the DE 10 2009 054 922 A1 a method for reducing moisture in a gas in a housing interior is known, in which a dry gas is passed into the housing interior and gas that is already present is discharged from the housing interior.

Another method for testing batteries for leaks is from the publication DE 10 2011 016 526 A1 known. Here, a battery or storage cell is arranged in a container. The gas concentration in the container is measured using a metal oxide sensor. Any leaks can be identified this way. The disadvantage of this is that metal oxide sensors only have a low selectivity and react to a large number of substances with a signal change. Also, no quantitative statement can be made about the leak. Still suitable The procedure is not suitable for monitoring air-cooled batteries.

It is therefore the object of the invention to provide a device and a method for leak testing of electrochemical storage, which is improved with regard to the ability to determine leaks.

This problem is solved by a device according to patent claim 1 and a method according to patent claim 8. Further advantageous embodiments of the invention result from the subclaims.

A device for leak testing at least one electrochemical storage in the form of a battery cell or a battery includes a housing in which at least one electrochemical storage can be arranged and through which a gas flow can flow, a first gas sensor which is arranged upstream of the electrochemical storage and the can generate a first sensor signal, at least one second gas sensor, which is arranged downstream of the electrochemical storage and which can generate a second sensor signal, and an evaluation device which is coupled to the first gas sensor and the second gas sensor and which is set up to detect the first and Evaluate the second sensor signal and generate an error signal depending on the evaluation.

This device allows for greater accuracy in determining leaks. By arranging the gas sensors upstream or downstream of the electrochemical storage, signal components that are not due to a leak can now be detected and eliminated. In addition, quantitative statements about the extent of the leak are now possible. The housing no longer needs to be gas-tight, so the device is also suitable for testing air-cooled electrochemical storage devices during operation.

The housing serves to accommodate the electrochemical storage and allows the gas flow to flow around the storage. The housing encloses the electrochemical storage and can be closed, for example, with a housing cover. To carry out the gas flow, the housing has at least one flow inlet opening and one flow outlet opening. The flow inlet opening and the flow outlet opening are preferably formed on opposite sides of the housing for better flow around the electrochemical storage.

The gas flow preferably includes air, e.g. ambient air of the housing.

The first and second gas sensors are sensitive to components of the electrolyte in the electrochemical storage, such as VOCs (volatile organic compounds). The first and second gas sensors are preferably identical in construction. In a preferred embodiment, the first gas sensor and the second gas sensor are chemo-resistive sensors, such as metal oxide semiconductor sensors. In this type of sensor, the conductivity of the reactive semiconductor layer of the sensor changes through adsorption of oxidizing or reducing gases. The resulting changed resistance allows the concentration of the gas to be determined directly.

The first sensor signal is a measure of the concentration of gases to be detected in the inflowing gas stream. It provides information about whether the gas flow supplied to the container is already preloaded, i.e. whether it already contains a measurable concentration of substances to be detected.

The second sensor signal represents the gas concentration in the gas flow after contact with the electrochemical storage.

The evaluation device receives the first and second sensor signals and can be wirelessly coupled to the gas sensors or connected to the gas sensors via lines. The evaluation device processes the sensor data and evaluates them in particular with regard to a concentration difference in front of and behind the electrochemical storage. The evaluation can in particular include the determination of a difference signal between the first and second sensor signals and/or a cross-correlation of the first and second sensor signals. The evaluation device can be, for example, a data processing device with a storage unit, such as a computer.

If the evaluation reveals the existence of a leak, for example by reaching a predetermined value or exceeding or falling below a limit value, the evaluation device can generate a signal that, for example, classifies the electrochemical storage as leaking or triggers an alarm signal, such as an acoustic or optical one Warning.

Good measurement accuracy is achieved in one embodiment in that the first gas sensor is arranged in the area of the flow inlet opening and the second gas sensor is arranged in the area of the flow outlet opening.

The device is suitable for checking batteries or individual battery cells during production or during storage. In one embodiment, the electrochemical storage is connected to a consumer, which means that checking is also possible while the electrochemical storage is in use. The consumer is in particular a consumer in a motor vehicle, preferably in an electric or hybrid vehicle.

The gas flow preferably includes air, e.g. ambient air of the housing.

To create a forced flow through the container, the device can contain a conveying device to generate the gas flow flowing through the housing. The conveying device can be, for example, a fan, a pump or another device suitable for generating the gas flow. The conveying device is preferably connected to the housing via a channel. A pushing conveyor device can be provided upstream of the housing or a suction conveyor device downstream of the housing. The conveying device allows individual adjustment of the volume flow or flow speed, for example to increase the measurement accuracy when a leak is detected.

Because in one embodiment the conveying device is part of a battery cooling device, it can be easily integrated into existing vehicle concepts. The battery cooling device can, for example, comprise an air conditioning device with a fan with which an air-conditioned air flow is directed over the battery. An additional flow through the housing can be eliminated by directing the air-conditioned air flow past the sensors.

To determine the flow velocity or the volume flow, the device can also have an anemometer in the flow path of the gas flow, which is coupled to the evaluation device. If the first sensor signal varies sufficiently strongly, the flow rate can also be determined by correlating the second sensor signal.

In the method according to the invention for leak testing at least one electrochemical storage in the form of a battery or an individual battery cell, which is arranged in a housing, a gas flow flows through the housing, so that the gas flow flows past the electrochemical storage. A first sensor signal is detected, which is dependent on a gas concentration in the gas flow upstream of the electrochemical storage, and at least a second sensor signal is detected, which is dependent on a gas concentration in the gas flow downstream of the electrochemical storage. The first sensor signal and the at least one second sensor signal are evaluated and an error signal is generated depending on the evaluation.

This procedure enables a precise analysis of the tightness of the electrochemical storage. The influence of substances that are contained in the gas mixture regardless of the occurrence of a leak can be eliminated. Such substances can be present, for example, due to vehicles driving in front or due to contamination in the area around the battery. A high selectivity of the sensors is not required; broadband sensors can also be used. Parts of the sensor signals that cannot be traced back to a leak can be detected and are not taken into account when assessing the tightness. This means that inexpensive gas sensors with only low selectivity can be used. In addition, the flow through the housing prevents the gas sensors, in particular the gas sensor arranged downstream of the electrochemical storage, from becoming blocked.

The gas flow that is passed through the container is preferably an air flow. The air can contain other components from the environment, such as exhaust gas residues or chemical vapors.

The method can, for example, be carried out continuously over a predetermined period of time or at predetermined intervals.

In one embodiment, the sensor signals are evaluated by forming a difference signal from the first sensor signal and the second sensor signal. In a further embodiment, the first and second sensor signals can also be evaluated using cross-correlation. A difference signal can also be formed. The evaluation results determined in this way provide information about an existing leak in the electrochemical storage and also enable a quantitative analysis of the leak. The evaluation result can be compared, for example, with reference values to determine whether there is a leaky cell.

In one embodiment, to quantify a leak and to further analyze the sensor data, the flow velocity of the gas flow is measured and included in the evaluation.

The process enables electrochemical storage to be checked during production and storage. In addition, electrochemical storage is checked possible during operation. For this purpose, the battery and/or battery cell arranged in the housing can be connected to a consumer in a further embodiment, for example it can be used within a vehicle as a starter battery or drive battery. Dangerous situations due to a battery leak can therefore be detected or avoided at an early stage.

In a preferred embodiment, the flow through the housing is forced by means of a conveying device. The parameters of the flow, such as

Volume flow or speed can thus be regulated. If the housing is installed in a vehicle, the flow through the housing can alternatively also be carried out by the wind.

With air-cooled batteries, the process can be particularly easily integrated into the existing vehicle concept by allowing the airflow intended for battery cooling to flow through the housing.

The device and the method are particularly suitable for leak testing of lithium-ion batteries, but with a suitable choice of gas sensors they can also be used for other types of batteries, such as lead-acid batteries.

The device and the method according to the invention offer advantages due to the low costs for the gas sensors. Checking the tightness now also includes possible diffusion. In addition, the tightness of the cells can be checked after complete assembly, i.e. in the delivery condition. The check can therefore also be carried out at the customer's site and during operation of the battery. The process can also be applied to larger containers. Multiple cells can be checked simultaneously and throughput can be increased.

The characteristics, features and advantages of this invention described above and the manner in which they are achieved will be more clearly and clearly understood in connection with the following description of the exemplary embodiments. If the term “can” is used in this application, it refers to both the technical possibility and the actual technical implementation.

• 1 eine Prinzipdarstellung einer Vorrichtung zur Dichtigkeitsprüfung von elektrochemischen Speichern entsprechend einem Ausführungsbeispiel der Erfindung
• 2 eine Prinzipdarstellung einer Vorrichtung zur Dichtigkeitsprüfung gemäß einem zweiten Ausführungsbeispiel
• 3 zeigt einen beispielhaften Verlauf von erstem und zweitem Sensorsignal über die Zeit.

Examples of embodiments are explained below using the accompanying drawings. Show in it:

• 1 a schematic representation of a device for leak testing of electrochemical storage according to an exemplary embodiment of the invention
• 2 a schematic diagram of a device for leak testing according to a second exemplary embodiment
• 3 shows an exemplary course of the first and second sensor signals over time.

A device 10 according to a first exemplary embodiment comprises a housing 100 in which an electrochemical storage 20 in the form of a battery is accommodated. The battery comprises sixteen individual battery cells 200 connected in series, of which only five are shown for reasons of clarity. However, the housing 100 can also contain a battery with a different number of cells and/or connection or only a single battery cell 200. The poles of the battery can be connected to a consumer (not shown) outside the housing 100 via lines (not shown).

The housing 100 encloses the battery. The housing 100 preferably has a cover for easier positioning of the battery 20. The housing 100 has a flow inlet opening 102 and a flow outlet opening 104 and a gas flow 110 can flow through them. The gas flow 110 in the form of an air flow flows through the housing 100 from one side to the opposite side and flows over the electrochemical storage 20. Preferably, the flow inlet opening 102 is formed in a side wall of the housing 100 and the flow outlet opening 104 is in an opposite side wall of the housing 100 is formed.

A first gas sensor 120 in the form of a metal oxide sensor is arranged upstream of the battery 20 in the area of the flow inlet opening 102. A second gas sensor 130 in the form of a metal oxide sensor is arranged downstream of the battery 20 in the area of the flow outlet opening 104. The gas sensors 120 and 130 are identical sensors. The gas sensors are sensitive to components of the electrolyte of the battery 20. If such components reach the sensor semiconductor layer, the resistance of the sensor changes

The gas flow flowing through the housing is first directed past the first sensor 120, then flows past the electrochemical storage 20 and is then directed past the second sensor 130.

If the electrochemical storage 20 has a leak or an increased diffusion of electrolyte components through its casing, electrolyte components, such as VOC, get into the air in the housing 100. These contaminants are transported with the gas flow 110. They reach the second gas sensor 130, where they are detected and change the second sensor signal. Since the gas flow 110 was already guided past the first sensor 120 before it was guided past the battery 20, two sensor signals are now present. The first and second sensor signals are transmitted to an evaluation device 140, which is connected to the first and second gas sensors 120 and 130 by means of lines 122 and 132. The evaluation device 140 evaluates the signals with regard to an increase in the concentration of the detectable gases in the gas flow.

Optionally, the device 10 has a thermoelectric anemometer 150, with which the flow speed of the gas flow through the container and thus the volume flow can be determined. The anemometer 150 is in accordance with 1 in the housing 100 adjacent to the first sensor 110, but can alternatively also be arranged adjacent to the second sensor 120 (not shown). The anemometer 150 is connected to the evaluation unit 140 via a line 152.

2 shows a device for measuring leaks according to a second exemplary embodiment of the invention. The same components are given the same reference numbers and are not described again to avoid repetition. To achieve a controllable flow, the device 10A has, in addition to those with reference to 1 Components described include a conveyor device 160 in the form of a fan. The fan 160 is arranged upstream of the housing 100 and conveys air via an air duct, not shown, as a gas flow 110 to the first sensor 120 or optional anemometer 150 and further through the flow inlet opening 102 into the housing 100. The flow exits at the flow outlet opening 104 Gas flow the housing and is guided past the second sensor 130.

3 shows an exemplary course of the first and second sensor signals for an application in which the supplied air is contaminated with detectable gases and a leak occurs in the electrochemical storage.

A gas stream in the form of supply air from the surroundings of the housing is supplied to the housing 100. As long as the supply air is free of detectable gases, the first sensor signal 320 has an initial value S0. At time t1, a disturbance occurs from outside, i.e. the supplied air flow 110 is already preloaded with gases to which the first sensor 120 is sensitive, for example due to the exhaust gases of a vehicle in front or due to solvents contained in the air or similar. The disturbance is detected by the first sensor 110 and causes the first sensor signal 320 to increase to a value S1. At time t2, the external disturbance disappears and the air supplied is again free of detectable gases. The value of the first sensor signal 320 then drops back to the initial value S0.

The second sensor signal 330 also has the initial value S0 at the start of the measurement and also increases to the value S1 due to the external disturbance. Since the second sensor 130 is arranged downstream of the first sensor 120, the rise of the second sensor signal 330 takes place with a time delay to the first sensor signal 320, see time t3. In addition, a leak now occurs in the electrochemical storage 20 in the housing 100 at time t2. The escaping gases are detected by the second sensor 130, the second sensor signal 330 increases to the value S2. When the external disturbance disappears, the second sensor signal 330 drops to the value S3.

The first sensor signal 320 is not changed by the leakage of the electrochemical storage 20. The first sensor signal 320 can be used to detect external interference and eliminate it during the evaluation. By forming a difference signal between the first and second sensor signals, it is possible, for example, to free the signal change from those components that are due to the disturbance. Thus, the actual signal change caused by the leak can be obtained. A quantitative analysis of the leakage becomes possible. The sensor signals 320, 330 can also be evaluated using cross-correlation, for example to eliminate the time offset between the first and second sensor signals.

The exemplary embodiments are not to scale and are not limiting. Modifications are possible within the scope of professional action.

Reference symbol list

10, 10A

Leak testing device

100

Housing

102

Flow inlet opening

104

Flow outlet opening

110

Gas flow

120, 130

Gas sensor

122, 132

Line

140

Evaluation device

150

anemometer

152

Line

160

Conveyor device

20

electrochemical storage

200

Single battery cell

320, 330

Sensor signal

S0, S1, S2, S3

Values of the sensor signals

t1, t2, t3

points in time

Claims (15)

Device for leak testing at least one electrochemical storage in the form of a battery and/or a single battery cell, with a housing (100) in which at least one electrochemical storage (20) can be arranged and through which a gas flow (110) can flow, a first gas sensor (120) which is arranged upstream of the electrochemical storage (20) and can generate a first sensor signal (320), at least one second gas sensor (130) which is arranged downstream of the electrochemical storage (20) and a second sensor signal (330) can generate, and an evaluation device (140) which is coupled to the first gas sensor (120) and the second gas sensor (130) and which is set up to evaluate the first sensor signal (320) and the second sensor signal (330) and depending on the evaluation of the first Sensor signal (320) and the at least one second sensor signal (330) to generate an error signal. Device according to Patent claim 1 , in which the first gas sensor (120) and the second gas sensor (130) are metal oxide sensors. Device according to Patent claim 1 or 2 , in which the housing (100) has a flow inlet opening (102) and a flow outlet opening (104), and in which the first gas sensor (120) is arranged in the area of the flow inlet opening (102) and the second gas sensor ( 130) is arranged in the area of the flow outlet opening (104). Device according to one of the preceding claims, in which the electrochemical storage (20) is connected to a consumer, in particular to a consumer in a vehicle. Device according to one of the preceding claims, further comprising: a conveying device (160) for generating the gas flow (110) flowing through the housing (100). Device according to Patent claim 5 , in which the conveying device (160) is part of a battery cooling device. Device according to one of the preceding claims, further comprising an iAnemometer (150) in the flow path of the gas flow (110), which is coupled to the evaluation device (140). Method for leak testing at least one electrochemical storage in the form of a battery and/or a single battery cell, which is arranged in a housing, with the steps: Flowing through the housing (100) with a gas flow (110), so that the gas flow (110) flows past the electrochemical storage (20), Detecting a first sensor signal (320), which is dependent on a gas concentration in the gas flow (110) upstream of the electrochemical storage (20), Detecting at least one second sensor signal (330), which is dependent on a gas concentration in the gas flow (110) downstream of the electrochemical storage (20), Evaluating the first sensor signal (320) and the at least one second sensor signal (330), Generating an error signal depending on the evaluation of the first sensor signal (320) and the at least one second sensor signal (330). Procedure according to Patent claim 8 , in which a difference signal is formed from the first sensor signal (320) and the second sensor signal (330). Procedure according to Patent claim 8 or 9 , in which the first sensor signal (320) and the second sensor signal (330) are evaluated using cross-correlation. Method according to one of the preceding Patent claims 8 until 10 , in which the flow velocity of the gas flow (110) is measured and included in the evaluation. Reischr Method according to one of the preceding Patent claims 8 until 11 , being connected to the electroche mix memory (20) a consumer is connected. Method according to one of the preceding Patent claims 8 until 12 , in which the flow through the housing (100) is forced by means of a conveying device (160). Method according to one of the preceding Patent claims 8 until 13 , in which the flow through the housing (100) is carried out by an air stream that is used to cool the battery. Method according to one of the preceding Patent claims 8 until 14 , wherein the electrochemical storage (20) is a lithium-ion battery.

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