Method for Detecting Humidity in a Battery Pack Housing and Battery Pack System

Abstract

The present invention relates to a method for detecting humidity in a battery pack housing (30). The present invention also relates to a battery pack system having means for detecting humidity. According to the method for detecting humidity in a battery pack housing (30) according to the present invention, the following values are measured, stored and processed: a) the relative humidity in the battery pack housing (30); b) the temperature in the battery pack housing (30); and c) the air pressure inside and / or outside the battery pack housing (30), wherein the dew point is determined based on the measured values mentioned above, and wherein at least one limit value is set based on the relative humidity, based on the temperature in the battery pack housing (30) and based on the air pressure, so as to output a prompt and / or prompt the execution of technical measures in case the limit value is exceeded.

Description

Field of the Invention

[0001] The present invention relates to a method for detecting humidity (Feuchtigkeit) in a battery pack housing. Furthermore, the present invention also relates to a battery pack system having a device (Anordnung) for detecting humidity. A battery pack system in the sense of the present invention particularly means a high-voltage battery pack system of a motor vehicle, preferably a high-voltage battery pack system used as a drive energy storage device, and these high-voltage battery pack systems are also referred to as drive battery packs. The high-voltage battery pack system is usually arranged in a dust- and / or liquid-sealed battery pack housing. The voltage provided by the high-voltage battery pack system is usually greater than 30V, preferably at least 40V, further preferably at least 100V, and particularly preferably between 100V and 400V. Higher voltages are also possible, such as 400V to 800V or even exceeding 1000V. Background Art

[0002] In order to avoid deformation under pressure fluctuations, such a battery pack housing usually has one or more pressure compensation elements. These pressure compensation elements mostly also include a balancing element in the form of a film for water vapor molecules in order to prevent moisture from entering (Eindringen) through water vapor. However, these films lose their function more and more as the service life increases, which results in more and more moisture possibly seeping (dringen) into the battery pack housing through the pressure compensation elements as the service life increases.

[0003] A method and a device (Vorrichtung) for monitoring humidity (Feuchte) in an electrical system, in a battery pack housing, and in a battery pack system are known from DE 10 2013 212 593 A1. The device includes a sensor device for detecting a measured value in the interior space of the battery pack housing and a processing device configured to evaluate the detected measured value, determine the relative humidity (relative Feuchte) in the interior space of the battery pack housing based on the evaluated measured value, and take measures when the determined relative humidity reaches a predetermined critical value or value range or deviates from a predetermined safe or allowable value or value range. The method is also basically based on measured values of relative humidity and temperature. Summary of the Invention

[0004] The object underlying the present invention is to provide a method for detecting humidity in a battery pack system and a battery pack system having a device for detecting humidity, by means of which the humidity in the battery pack system can be reliably detected in order to prompt the execution (veranlassen) of measures for eliminating humidity as needed.

[0005] The solution to this task is carried out according to the present invention. Other practical embodiments and advantages of the present invention will be described in conjunction with the following text.

[0006] The method for detecting humidity in a battery pack housing according to the present invention measures, stores, and processes the following values:

[0007] a) The relative humidity in the battery pack housing;

[0008] b) The temperature in the battery pack housing; and

[0009] c) The air pressure inside and / or outside the battery pack housing,

[0010] The dew point (Taupunkt) is determined based on the measured values mentioned above, and at least one limit value is set based on the relative humidity, the temperature in the battery pack housing, and the air pressure, so that a prompt is output and / or a technical measure is prompted to be executed when the limit value is exceeded. In other words, the method is based on the following principle: the relative humidity in the battery pack housing is continuously or quasi-continuously (quasi-kontinuierlich) detected while considering the temperature in the battery pack housing and considering the air pressure inside and / or outside the battery pack housing, so as to determine the calculated moisture content (Feuchtigkeitsmenge) contained in the battery pack housing based on these parameters. Since the temperature in the battery pack housing, especially when the battery pack housing is part of a motor vehicle, usually varies over a larger temperature range not only due to the battery pack state but also due to changing ambient conditions and driving states, and the amount of water vapor in a constant volume is known to increase with increasing temperature, the moisture content contained at least in the battery pack housing can be determined computationally using the aforementioned measured values. It is known from practice that the moisture content in the battery pack housing of a motor vehicle during its service life (Nutzungsdauer) may increase especially due to the problems described at the beginning, because the moisture membranes (Feuchtigkeitsmembranen) no longer fulfill or only partially fulfill their functions as the service life increases. The available volume for moisture in the battery pack housing, i.e., the volume of the battery pack housing not filled with battery cells or other components, can be calculated for each vehicle or determined in a suitable manner and method. By considering this volume and the above-mentioned measured values, it can be continuously or quasi-continuously determined how much moisture content (gaseous or liquid) is contained at least in the battery pack housing, and how much moisture content is in liquid form in the battery pack housing at a correspondingly lower temperature. The present invention is based on another consideration: limit values can be preset for the relative humidity, for example, based on the temperature in the battery pack housing and the air pressure inside and / or outside the battery pack housing, where it is ensured that when the limit value is below, the safe operation of the vehicle is guaranteed based on the liquid that at most exists in the battery pack housing at that time. The amount of the liquid must be so small that there is no operating risk due to erosion or short circuit even in the assumption (Annahme) that the liquid is converted into a conductive electrolyte and contaminated. With the method according to the present invention, it is possible to reliably determine at relatively low cost using corresponding sensors whether measures for eliminating moisture need to be taken to ensure the safe operation of the motor vehicle.

[0011] As already indicated above, in an actual embodiment of the method according to the invention, at least one humidity limit value can be defined as the limit value of the relative humidity in the battery pack housing, wherein the at least one humidity limit value is compared with the measured relative humidity in the battery pack housing based on the measured temperature and the measured air pressure. Here, the measured humidity limit value represents the following amount of liquid, wherein the amount of liquid can be determined in a calculated manner from the value of the relative humidity based on other parameters. In this regard, instead of the relative humidity, the amount of moisture in the battery pack housing determined in a calculated manner can also be used as the limit value alternatively or additionally. To determine the amount of moisture in the battery pack housing determined in a calculated manner, preferably tables, charts and formulas known from the literature are used. In this context, in particular, reference is made to T-S charts, H-S charts and the Magnus formula. By taking into account the free volume in the battery pack housing that is not filled with components, it is then possible to determine at least the amount of moisture contained in the battery pack housing. If, for example, it is known that the volume available for air in the battery pack housing is 1 m 3 and at a temperature of 30 °C and a pressure of 1 bar, a relative humidity of 100% (fully saturated) is determined, it follows therefrom that the air in the battery pack housing alone contains 30 g of water in the form of water vapor. When the temperature is further increased and the relative humidity thus drops from 100% to a lower value at the higher temperature, it is possible to determine, using the method according to the invention, how great the possible additional amount of water present in the battery pack housing in liquid form is. Then, based on the pressure and the maximum temperature value measured just before the relative humidity is about to drop from 100% to a lower value, it can be assumed that the total amount of water contained in the battery pack housing in liquid form is evaporated and the corresponding amount can be calculated.

[0012] However, conversely, from the knowledge that the relative air humidity has reached a value of 100% at a temperature of 30 °C and a pressure of 1 bar, it follows that when the temperature drops to 20 °C (note: at this temperature, 1 cubic meter of air can only accommodate a maximum of 17 g of water in the form of water vapor), if no moisture leaks out of the battery pack housing during this time, at least 13 g of water (30 g - 17 g) is contained in the battery pack housing in liquid form.

[0013] Preferably, at least one limit value for the relative humidity is set for each housing type at a pre-given pressure and a pre-given temperature, so that the limit value can be determined in a calculated manner for other ambient conditions (temperature, pressure). Alternatively, a plurality of limit values can also be pre-given, and an intermediate value can be determined in a calculated manner by determining, in a calculated manner, other limit values for the following ambient conditions from the pre-given values (for example, from the two next occurring pre-given values) for which no pre-given limit values exist. For this purpose, simple or complex mathematical models can be used. Here, the operating safety of the battery pack system or the operating safety of a vehicle having a corresponding battery pack system should be important.

[0014] Alternatively or complementarily, a limit value can be set for the maximum tolerable amount of moisture in the battery pack system (for example, the amount of moisture in grams, which is obtained based on the measurement of relative humidity, pressure, and temperature considering the free volume available for air in the battery pack housing). In this case, the corresponding humidity value is continuously or quasi-continuously determined in a calculated manner from the measured values and compared with the limit value. If the limit value is reached or exceeded, a prompt is output and / or a technical measure is prompted to be executed.

[0015] In another practical embodiment of the method according to the invention, a first limit value is set, and in the case of exceeding the first limit value, a prompt is output and / or a technical measure is prompted to be executed, and a second limit value is set, which is higher than the first limit value, and exceeding the second limit value triggers: outputting other prompts and / or prompting the execution of other technical measures. Outputting a prompt is especially understood as: a prompt determined for the vehicle driver, which can be displayed on the display of the motor vehicle. Such a prompt can, for example, consist of: requiring the vehicle driver to operate an opening arranged at the bottom of the battery pack housing so that water flows out of the battery pack housing. Technical measures are especially understood as: activating a system present on the vehicle side, such as a system having a pump or other liquid conveying devices, where the conveying device enables the liquid that has accumulated in the battery pack housing to be actively conveyed out of the battery pack housing.

[0016] As an example of a hint associated with a second limit value, in particular with reference to a hint for a vehicle driver, the hint requires the vehicle driver to no longer actively move the vehicle and to prompt maintenance by an authorized professional dealer. Alternatively or additionally, the hint or technical measure may consist in: restricting or completely stopping one or more functions of the vehicle in order to signal to the vehicle driver by means of this measure that it is (urgently) necessary to perform the determined technical measures in a workshop or by an authorized professional dealer in order to be able to use the vehicle again with all its functions.

[0017] Thus, the invention can be implemented by means of a traffic light system, in which case a first limit value corresponds to a "yellow warning level" and a second limit value corresponds to a "red warning level", and the aim of the system is to take "yellow warning level" measures in the recognition, and the measures reset the system as far as possible to a faultless "green state". The "red warning level" which may lead to temporarily restricted usability or even to vehicle stoppage should be avoided as far as possible.

[0018] Supplementary hint: The method according to the invention is also suitable for recognizing a suddenly occurring state of the vehicle, for example when a large amount of liquid penetrates into the battery system due to the vehicle "immersing" in water or a large amount of water having accumulated on the roadway due to heavy rainfall, and / or due to an aging-induced or technically induced failure of the seal at the battery housing, causing a large amount of liquid to penetrate.

[0019] In another practical embodiment of the method according to the invention, a device which can be actuated by the vehicle system and / or the vehicle driver is activated as a technical measure in order to pump the liquid out of the battery system. In this context, particular reference is made to the following variants.

[0020] In the first variant, the battery housing can be equipped with a connection for a vacuum pump in order to use such a vacuum pump as required to pump the liquid out of the battery system. Here, a corresponding vacuum pump can be provided on the vehicle side or connected to the battery housing as an external device as required.

[0021] In another variant, a bilge pump can be provided in or on the battery housing, which bilge pump enables the liquid to be actively pumped out of the battery system.

[0022] In another variant, a drain plug (Ablassschraube) can be provided in the area of the bottom of the battery pack, which is removed as required so that the liquid can flow out of the battery pack housing due to gravity.

[0023] In another variant, instead of or in addition to the drain plug, a stepper motor, in particular a stepper motor with a turbine drive, is provided in the lower area of the battery pack housing in order to actively convey the liquid out of the battery pack system.

[0024] The above variants can also be combined with each other or with other similar technical measures.

[0025] As already mentioned, in another practical embodiment of the method according to the invention, it is also possible as a technical measure to counteract the continued movement of the vehicle. Reference is made again to the possibilities already mentioned above.

[0026] In another practical embodiment, the method is at least always carried out when the vehicle is to be moved or is being moved and / or when the dew point is exceeded, or is carried out only when the vehicle is to be moved or is being moved and / or when the dew point is exceeded. Thereby, the monitoring effort can be reduced and the associated energy consumption as well as the load (Beanspruchung) on the system resources of the vehicle can be reduced, in particular when the execution of the method is coupled to the exceeding of the dew point and to the intention to move the vehicle (for example, switching on the ignition device and / or detecting a key in the vehicle and / or inserting a driving speed level (Fahrstufe)).

[0027] Finally, the following possibility is also considered: in the method according to the invention, a differential pressure gauge (Differenzdruckmesser) is also used to determine the differential pressure based on the air pressure inside the battery pack housing and / or the air pressure outside the battery pack housing, and to control the execution of the method based on the determined differential pressure. This enables the method to be executed in an additional way especially in cases where the ambient conditions contribute to the ingress of moisture into the battery pack housing due to a higher pressure outside the battery pack housing compared to the air pressure inside the battery pack housing. In this state, it is particularly important and advantageous to monitor the above-mentioned values closely (engmaschig), because in this state it is particularly likely to reach or exceed the limit values and therefore a quick (kurzfristig) response may be required by outputting a prompt and / or prompting the execution of technical measures. Conversely, in the case of other framework conditions, for example, when the air pressure inside the battery pack housing is greater than the air pressure outside the battery pack housing, the execution of the method according to the invention can be interrupted (aussetzen) or reduced to a small scale (Maß), because the ingress of moisture is not allowed in this state at least through the above-mentioned film.

[0028] The invention also relates to a battery pack system having a battery pack housing, in which (in addition to the battery pack cells and other components usually installed in the battery pack housing) there is also a device for detecting humidity, wherein the device includes means for determining the relative humidity in the battery pack housing, the temperature in the battery pack housing, and the air pressure inside and / or outside the battery pack housing, and a control unit is provided, which determines the dew point based on the above-mentioned values and compares at least one of these values with a limit value taking into account other values, in order to output a prompt and / or prompt the execution of technical measures in the case of exceeding the limit value. Again, reference is made to the advantages already described above in connection with the method according to the invention.

[0029] In a practical embodiment of the battery pack system according to the present invention, the device includes a compact sensor as a device for determining values such as relative humidity in the battery pack housing, temperature in the battery pack housing, and air pressure inside and / or outside the battery pack housing, wherein all these values can be measured using the compact sensor and provided for further processing. In this regard, reference is made in particular to the product named BME 280 by Bosch, as a corresponding compact sensor that is relatively low-cost available on the market. With reference to the entire technical specifications of this device, the technical specifications can be read at https: / / www.bosch-sensortec.com / products / environmental-sensors / humidity-sensors-bme280 / .

[0030] In a practical embodiment of the battery pack system according to the present invention, an outlet (Austrittsöffnung) is provided in the bottom of the battery pack housing, and / or a device for discharging liquid from the battery pack housing is provided. For this, reference is again made to the design variants and some advantages already referred to above in connection with the method according to the present invention. Description of the Drawings

[0031] Figure 1 Shows a flow chart for performing the method according to the present invention;

[0032] Figure 2 Shows a fragment of an embodiment of a battery pack housing having a bottom section, a side wall section, and at least one device for discharging liquid; and

[0033] Figure 3 Shows a fragment of another embodiment of a battery pack housing having a bottom section, a side wall section, and at least one outlet in the bottom. Detailed Description

[0034] Figure 1 Shows a flow chart for performing the method according to the present invention, which is preferably performed in a motor vehicle. The method starts at event 10 marked "start" with an event indicating that the vehicle should be started and / or moved. In the case of a hybrid vehicle, this can in particular be turning on the ignition. In the case of a pure electric vehicle, this step can be, for example, setting the driving speed level or detecting the key in the vehicle. Preferably, the memory of the battery pack system (not shown) is reset or initialized at this time.

[0035] Then, inquiry 12 is made: whether the dew point has been exceeded and a forced shutdown of the battery pack system has not already been requested. This is to be understood as follows: at the end of the driving cycle or shortly thereafter, the following calculation is carried out: the calculation might have led to a request for the vehicle to stop (red warning level). In this case, the forced shutdown is stored (hinterlegen) in the system. If a forced shutdown has been requested or the dew point has not been exceeded, the battery pack system is reset to the start according to event 14 until the driving cycle has ended or until the dew point has been exceeded. If the dew point has been exceeded and a forced shutdown has not been requested, then at least the measured values of the relative humidity in the battery pack housing, the temperature in the battery pack housing, and the air pressure inside and / or outside the battery pack housing are detected according to event 16. These values are also entered (eintragen) into the memory and evaluated. For this purpose, corrections or calculations or conversions can be carried out, if necessary, based on the stored tables. In this embodiment, the evaluation is continuously carried out as follows: based on the detected measured values, the calculated amount of water is continuously determined according to the inspection 18 and then it is checked whether the amount of water has increased, i.e., whether the amount of water is higher than a pre-given limit value. As long as the amount of water has not increased, new measured values are continuously detected and evaluated according to event 16. If the amount of water has increased, then according to inquiry 20, it is first determined whether the value for the calculated amount of water is higher than the following limit value, where the limit value has been set for the red warning level. If this is the case, then according to event 22, an entry is made into the error memory: the red warning level has been reached, and the measures provided by the yellow warning level have not been carried out or have not had an effect. Additionally, in a further event 24, the vehicle is stopped and reactivation of the vehicle is prevented until the corresponding measures have been taken to eliminate the red warning level again. This can be, for example, resetting the error memory by an authorized specialist workshop.

[0036] If the amount of water has not increased in such a way that the red warning level has been reached, then according to event 26, it is checked whether the amount of water exceeds the limit value for the yellow warning level. If the limit value for the yellow warning level has been exceeded, then according to event 28, the corresponding event is entered into the memory. Additionally, measures are activated to reduce the amount of water present in the battery pack housing of the battery pack system as much as possible so that the amount of water is reduced to a value below the limit value for the yellow warning level.

[0037] If the limit value for the warning level has not been exceeded according to event 26, the detection and evaluation of the measured values are continued according to event 16.

[0038] Figure 2 and Figure 3 show fragments of the battery pack housing 30, which has a section of the bottom 32 and a section of the side wall 34. As inFigure 2 and Figure 3 As can be recognized in Figure 2 and Figure 3 , recesses 36 are respectively provided in the region of the bottom 32. The recesses can also be referred to as sumpfs. Due to gravity (see arrow g for the direction of gravity), the following amount of liquid accumulates in the recess 36 (sumpf). The amount of liquid exists in a liquid form due to the intrusion of air moisture into and condensation in the internal space 38 of the battery pack housing 30. In both of these embodiments, at least one compact sensor (not shown) is arranged in the internal space of the battery pack housing 30. Preferably, for each of the values of temperature, relative air humidity, and air pressure, at least a doubly implemented compact sensor is respectively provided, especially two dual-channel sensors, such as temperature sensors. Preferably, the temperature sensor is an NTC temperature sensor.

[0039] These sensors for relative humidity and air pressure can be arranged at any position in the battery pack housing. Preferably, these sensors are directly arranged on the circuit board (PCB) of the battery management system (BMC).

[0040] These temperature sensors are preferably arranged at or near or directly fixed to the wall 34, bottom 32, or top (ceiling) of the battery pack system. Particularly preferably, these temperature sensors are arranged at a sufficient distance from the heat radiation elements of the battery pack system, especially spaced apart from the circuit board (PCB) that generates heat during operation.

[0041] In the embodiment according to Figure 2 a connection end 40 for a negative pressure pump is provided as a first option for the device for discharging the liquid.

[0042] Alternatively or complementarily to this, a bilge pump 42 can be installed in the region of the recess 36 (sumpf) so that the liquid is actively discharged via the connection end 40 in the battery pack housing 30.

[0043] In the embodiment according to Figure 3 an opening 44 is provided in the region of the bottom 32. The opening 44 can be closed by a simple plug 46, and the plug can be pulled out of the opening 44 as needed to allow the liquid to come out of the battery pack housing 30 due to gravity. Alternatively or complementarily to this, a stepper motor 48 can be provided, and the stepper motor enables the liquid that has accumulated in the sump 36 to be actively discharged through the opening 44 by operating the stepper motor 48.

[0044] The features of the present invention disclosed in this specification and in the drawings are important for implementing the present invention not only individually but also in any combination in different embodiments of the present invention. The present invention can be varied taking into account the knowledge of the responsible professionals.

[0045] List of reference numerals

[0046] 10 Event

[0047] 12 Inquiry

[0048] 14 Event

[0049] 16 Event

[0050] 18 Inspection

[0051] 20 Inquiry

[0052] 22 Event

[0053] 24 Event

[0054] 26 Event

[0055] 28 Event

[0056] 30 Battery pack housing

[0057] 32 Bottom

[0058] 34 Side wall

[0059] 36 Recess / groove

[0060] 38 Internal space

[0061] 40 Connection end

[0062] 42 Bilge pump

[0063] 44 Opening

[0064] 46 Plug

[0065] 48 Stepper motor

Claims

1. A method for detecting humidity in a battery pack housing (30), wherein the detection is performed by: measuring, storing and processing the following values: a) the relative humidity in the battery pack housing (30); b) the temperature in the battery pack housing (30); and c) the air pressure inside and outside the battery pack housing (30), and determining the dew point and the amount of moisture based on the above-mentioned measured values, wherein at least one limit value is set based on the relative humidity, based on the temperature in the battery pack housing (30), based on the air pressure and based on the amount of moisture, so as to output a prompt and / or prompt the execution of a technical measure when the limit value is exceeded. A differential pressure gauge is provided to determine the differential pressure based on the air pressure inside the battery pack housing (30) and the air pressure outside the battery pack housing (30) to control the execution of the method based on the determined differential pressure. When the air pressure outside the battery pack housing is higher than the air pressure inside the battery pack housing, the values of the relative humidity, the temperature in the battery pack housing (30) and the differential pressure are closely monitored, and when the air pressure inside the battery pack housing is higher than the air pressure outside the battery pack housing, the execution of the monitoring is interrupted or reduced to a small scale.

2. The method according to the previous claim, characterized in that at least one humidity limit value is defined as the limit value of the relative humidity in the battery pack housing (30), and the at least one humidity limit value is compared with the measured relative humidity in the battery pack housing (30) based on the measured temperature and the measured air pressure.

3. The method according to any one of the above claims, characterized in that a first limit value is set, and a prompt is output and / or a technical measure is prompted to be executed when the first limit value is exceeded, and a second limit value is set, the second limit value is higher than the first limit value, and when the second limit value is exceeded, it triggers: outputting other prompts and / or prompting the execution of other technical measures.

4. The method according to claim 1 or 2, characterized in that as a technical measure, an equipment that can be operated by a vehicle system and / or a vehicle driver is activated to pump liquid out of the battery pack housing (30).

5. The method according to claim 1 or 2, characterized in that as a technical measure, the continued driving of the vehicle is resisted.

6. The method according to claim 1 or 2, characterized in that the method is at least always executed when the vehicle is to be moved or is being moved and / or when the dew point is exceeded, or the method is executed only when the vehicle is to be moved or is being moved and / or when the dew point is exceeded.

7. A battery pack system having a battery pack housing (30), in which means for detecting humidity are provided, wherein the means include devices for determining the relative humidity in the battery pack housing (30), the temperature in the battery pack housing (30), and the air pressure inside and outside the battery pack housing (30), wherein a control unit is provided, which determines the dew point and the moisture content based on the above-mentioned values and compares at least one of the values with a limit value taking into account other values in order to output a prompt and / or cause a technical measure to be executed when the limit value is exceeded, wherein a differential pressure gauge is provided in order to determine the differential pressure based on the air pressure inside the battery pack housing (30) and the air pressure outside the battery pack housing (30) and to control the execution of the method based on the determined differential pressure, wherein the relative humidity, the temperature in the battery pack housing (30), and the value of the differential pressure are closely monitored when the air pressure outside the battery pack housing is higher than the air pressure inside the battery pack housing, and when the air pressure inside the battery pack housing is higher than the air pressure outside the battery pack housing, the execution of the monitoring is interrupted or reduced to a small scale.

8. The battery pack system according to any one of the preceding claims, characterized in that the means has a compact sensor as a device for determining the relative humidity in the battery pack housing (30), the temperature in the battery pack housing (30), and the air pressure inside and / or outside the battery pack housing (30), wherein all the values can be measured using the compact sensor and provided for further processing.

9. The battery pack system according to any one of the preceding two claims, characterized in that a discharge port is provided in the bottom of the battery pack housing (30) and / or means for discharging liquid from the battery pack housing (30) are provided.

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