Method and device for operating a battery system

Abstract

A method for operating a battery device (BV) is disclosed, the battery device having a plurality of battery cells (BZ) arranged inside a battery housing (BG), the method comprising the steps of: - detecting a fluid concentration of a predetermined fluid inside the battery housing (BG); - comparing the detected fluid concentration with a predetermined concentration threshold value; - adapting a maximum permissible operating temperature of the battery device (BV) if the detected fluid concentration exceeds the concentration threshold value; - operating the battery device (BV) such that the maximum permissible operating temperature is not exceeded. In addition, a device (AO) for operating a battery device (BV) and a battery device (BV) having the device (AO) are disclosed.

Description

Technical Field

[0001] The invention relates to a method and a device for operating a battery system, in particular a traction battery system for an electrically driven vehicle. The invention also relates to a battery system, in particular a traction battery system for an electrically driven vehicle, having the above-described device.

[0002] Background technology and invention task

[0003] Lithium-ion battery cells or other battery cells having comparable properties are used in particular in battery arrangements, in particular in traction battery arrangements of electrically driven vehicles for driving the electrically driven vehicles.

[0004] In this case, the battery cells should be operated at the highest possible operating temperature, since the conductivity of the electrolyte in the battery cells increases with increasing operating temperature, whereby the efficiency of the battery cells and thus of the battery system in turn increases with increasing battery temperature.

[0005] On the other hand, however, the thermal stability of some electrolytes, in particular some liquid electrolytes, in battery cells decreases rapidly above a certain temperature and the electrolyte begins to decompose above this temperature. This in turn leads to uncontrolled failure of the battery cell. This specific temperature is often referred to as the “battery-specific thermal stability limit”. The thermal stability limit depends on many external and internal factors of the battery cell and varies over the service life of the battery cell. Therefore, the thermal stability limit cannot be determined or specified in advance.

[0006] As is common in many other technical devices, in the case of battery devices there is a general requirement to operate them as safely and efficiently as possible.

[0007] It is therefore an object of the present application to provide a possibility with which a battery system having a plurality of battery cells can be operated as efficiently as possible without failures of the battery cells. Summary of the invention

[0008] This object is achieved by a method for operating a battery system, a device for operating a battery system, and a battery system. Advantageous embodiments are the subject of further exemplary embodiments.

[0009] According to a first aspect of the invention, a method is provided for operating a battery arrangement, in particular a traction battery arrangement of an electrically driven vehicle, which battery arrangement has a plurality of battery cells arranged inside a battery housing of the battery arrangement.

[0010] According to the method, (at least) the fluid concentration of (at least) a predetermined fluid is detected (continuously or repeatedly) in the interior of the battery housing, in particular at or in the respective battery cell. The fluid concentration can be measured at locations within the battery housing and outside the battery cell. The detected fluid concentration is then (continuously) compared with (at least) a predetermined concentration threshold value. If or as soon as the detected fluid concentration exceeds the concentration threshold value, the maximum permissible operating temperature of the battery device is (dynamically) adapted or adjusted. The battery device is then (continuously) operated such that the maximum permissible operating temperature is not exceeded.

[0011] The fluid concentration of a predetermined fluid in the interior of the battery housing, in particular at or in the respective battery cell, is detected continuously or repeatedly at predetermined regular intervals, in particular over the entire service life of the battery device, and is continuously compared with at least one or more predetermined concentration threshold values. If the detected fluid concentration exceeds the concentration threshold value / threshold values, the maximum permissible operating temperature of the battery device is dynamically adapted or adjusted. In the subsequent operating phase until the next adaptation, the battery device is then continuously operated so that the maximum permissible operating temperature is not exceeded in this operating phase.

[0012] In particular, decomposition products of the battery cell material are selected as the predetermined fluid, the concentration change of which has a direct causal relationship with the battery cell state in which the (variable) battery-specific thermal stability limit of the battery cell is exceeded and in which the battery cell material begins to decompose. Based on the concentration change of this fluid, it can be concluded that the (variable) battery-specific thermal stability limit is exceeded. By suitable selection of the fluid, decomposition phenomena in the battery cell can be detected early. Accordingly, the battery cell temperature can be reduced in good time to the maximum permissible operating temperature or the dynamic thermal stability limit. If the maximum permissible operating temperature or the dynamic thermal stability limit is known, the battery device or the battery cell can be operated at the highest possible temperature without exceeding the thermal stability limit.

[0013] By dynamically adapting the maximum permissible operating temperature based on the (continuously or repeatedly) detected fluid concentration of the predetermined fluid and subsequently operating the battery arrangement at or below the maximum permissible operating temperature until the next adaptation, the battery arrangement or battery cell can be operated in a gentle and at the same time efficient manner over its entire service life. Further degradation of the battery cell material is thus prevented or limited to a minimally dangerous extent. Accordingly, temperature-dependent failures in the battery cells are avoided and the service life of the battery cell material is thus extended.

[0014] In this case, the battery device or the battery cell is operated at all times (and in particular over the entire service life of the battery device or the battery cell) and, for example, at exactly the dynamically adapted maximum permissible operating temperature or at an operating temperature which is 1%, 2%, 5%, 8%, 10%, 15% or a maximum of 20% below the dynamically adapted maximum permissible operating temperature.

[0015] The battery arrangement or battery cell is thus operated at the highest possible operating temperature without exceeding the battery-specific thermal stability limits. Thus, a possibility is provided with which the battery arrangement can be operated efficiently without noticeable temperature-dependent failures.

[0016] The battery cells are designed, for example, as lithium-ion battery cells or other battery cells with comparable properties. Accordingly, the battery device is designed, for example, as a lithium battery device.

[0017] For example, as the fluid concentration of the predetermined fluid, the concentration of a predetermined gas which is one of the decomposition products of the electrolyte of the battery cell is detected.

[0018] For example, as the concentration of the predetermined gas, the concentration of hydrogen "H2", the concentration of carbon dioxide "CO2", the concentration of carbon monoxide "CO", or the concentration of hydrocarbons is detected. The above gases serve as decomposition products of the electrolyte of the battery cell. An increase in the concentration of these gases inside the battery case is an indicator that the maximum permissible operating temperature of the battery cell has been exceeded.

[0019] For example, the detected fluid concentration is compared with a concentration threshold value of a predetermined operating temperature-concentration conversion table (lookup table) of the battery device. The maximum permissible operating temperature is then adjusted according to the operating temperature-concentration conversion table and based on the comparison result. For example, a large number of predefined maximum permissible operating temperatures are stored in the table for different life segments of the battery cells or for different state values ​​(SOH values, in English “State of Health”) of the battery cells. The corresponding concentration threshold value is then read out of the table according to the respective current life segment or SOH value of the battery cells and compared with the currently detected fluid concentration.

[0020] For example, the detected fluid concentration is compared with other predefined critical concentration threshold values. If and as soon as the detected fluid concentration exceeds other critical concentration threshold values, a critical situation at the battery device is detected. When a critical situation is detected, a fault message is output, for example in the form of a warning signal. Optionally, the battery device is shut down in a controlled manner. With this measure, the imminent danger of a so-called thermal runaway at the battery cells is detected early and countermeasures are taken by issuing a fault message, for example shutting down the battery device.

[0021] For example, the aforementioned steps of detecting the fluid concentration, comparing with a concentration threshold value and adapting the maximum permissible operating temperature and optionally also identifying critical situations and outputting fault messages are performed continuously or at predetermined time intervals continuously and iteratively over, in particular, the entire service life of the battery device.

[0022] For example, the battery device is temperature-controlled by cooling or heating so that the battery device is (slightly) below the maximum permissible operating temperature or (exactly) operated at the maximum permissible operating temperature. Here, in particular, the battery device is operated exactly at the maximum permissible operating temperature or slightly below the maximum permissible operating temperature.

[0023] For example, in addition to the fluid concentration, the gas pressure inside the battery housing is also detected. In this case, in addition to the fluid concentration, the maximum permissible operating temperature is also adjusted based on the detected gas pressure. Together with the gas pressure value, one of the main influencing factors of the fluid concentration is detected and taken into account during the adaptation. This increases the reliability of the adaptation.

[0024] According to a second aspect of the invention, a device is provided for operating a battery arrangement, in particular a traction battery arrangement of an electrically driven vehicle, which battery arrangement has a plurality of battery cells arranged in the interior of a battery housing.

[0025] The device has a measuring unit which is designed to detect a fluid concentration of a predetermined fluid in the interior of the battery housing either continuously or regularly at predefined time intervals.

[0026] The device furthermore has a comparison unit which is designed to continuously compare the fluid concentration detected by the measuring unit with (at least) a predefined concentration threshold value.

[0027] The device further comprises an adaptation unit which is designed to continuously and dynamically adjust a maximum permissible operating temperature of the battery arrangement if and as soon as the detected fluid concentration exceeds a concentration threshold value.

[0028] The device furthermore has a regulating / control unit which is designed to operate the battery arrangement until the next setting of the maximum permissible operating temperature in such a way that the current maximum permissible operating temperature is not exceeded.

[0029] According to a third aspect of the present invention, a battery device, in particular a traction battery device for an electrically driven vehicle, is provided.

[0030] The battery device has a battery arrangement having a battery housing and a plurality of battery cells, wherein the battery cells are arranged in the interior of the battery housing. The battery device also has the above-described device for operating the battery device.

[0031] The advantageous embodiments of the method described above, insofar as they can also be transferred to the above-mentioned device or the above-mentioned battery arrangement, can also be regarded as advantageous embodiments of the above-mentioned device or the above-mentioned battery arrangement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The exemplary embodiments of the present invention are described in more detail below with reference to the accompanying drawings. Figure 1 A battery system BV having a device AO for operating the battery system BV according to an exemplary embodiment of the present invention is shown in a schematic diagram. DETAILED DESCRIPTION

[0033] In this embodiment, the battery device BV is designed as a traction battery device for an electrically driven vehicle and has a battery housing BG and a battery pack consisting of a plurality of battery cells BZ, which are arranged in the battery housing BG and are also protected by the battery housing from mechanical and other external influences. For example, lithium-ion battery cells are installed as battery cells BZ.

[0034] The battery device BV also has a temperature control unit TE for temperature control, ie cooling or heating, the battery device BV or the battery cells BZ. The temperature control unit TE has, for example, a cooler with cooling channels for passing a pre-temperatured coolant, such as cooling water.

[0035] The battery housing BG has, for example, an opening OF in the housing wall, through which air or gas can flow from the interior of the battery housing BG into the environment of the battery housing BG and / or vice versa. The air pressure in the interior of the battery housing BG is equalized with the air pressure in the environment of the battery housing BG via the opening OF.

[0036] The efficiency of a battery arrangement BV having battery cells BZ increases with increasing battery cell temperature, since the conductivity of the electrolyte used in the battery cells BZ increases with increasing battery cell temperature and therefore the internal resistance of the battery cells BZ decreases with increasing battery cell temperature. From this perspective alone, the battery arrangement BV or the battery cells BZ should be operated at the highest possible battery cell temperature or at room temperature.

[0037] On the other hand, the specific liquid electrolyte present in the battery cell BZ has a limited thermal stability and starts to decompose from a specific (limit) temperature or battery-specific thermal stability limit. Here, as one of the many decomposition products of this decomposition process, hydrogen is formed, which first accumulates in a gaseous state in the interior of the battery housing BG and gradually escapes from the battery housing BG via the openings OF in the battery housing BG. This battery-specific thermal stability limit represents the maximum permissible operating temperature of the battery cell BZ or the battery device BV and should not be exceeded. Here, this thermal stability limit is by no means a (limit) temperature that remains constant over the entire service life of the battery cell BZ, but rather changes continuously over the service life of the battery cell BZ under the influence of many internal and external influencing factors of the battery cell BZ. If the battery cell BZ is operated at an operating temperature above the thermal stability limit, the salts of the liquid electrolyte of the battery cell BZ, in particular the lithium salts, react with each other in an uncontrollable manner. This leads to irreversible damage to the battery cells BZ and thus to rapid aging of these battery cells BZ and even to premature failure. In order to counteract this, the battery cells BZ should be operated as consistently as possible over their entire service life at a battery cell temperature or room temperature which does not exceed the dynamic thermal stability limit.

[0038] Furthermore, the battery device BV or battery cell BZ should be temperature-controlled, i.e. cooled or heated, as little as possible in order to avoid unnecessary energy costs. Since the power for temperature control is usually drawn from the battery cell BZ itself, unnecessary temperature control of the battery device BV leads to an unnecessary reduction in the otherwise effectively usable power quantity of the battery device BV.

[0039] In order to be able to operate the battery device BV optimally with regard to all three of the above-mentioned angles, the battery device BV has a device AO for operating the battery device BV.

[0040] The device AO is designed, for example, as part of a battery management system of the battery system BV and has, in particular, a measuring unit ME, a comparison unit VE, an adaptation unit AE and a regulating / control unit RE.

[0041] The measuring unit ME is designed to detect the fluid concentration of at least one predetermined fluid in the interior of the battery housing BG. In this case, the measuring unit ME has, for example, a hydrogen sensor, with which it detects the concentration of hydrogen in the interior of the battery housing BG continuously or at predetermined short time intervals of, for example, a few hundred milliseconds. The measuring unit ME forwards the measured values ​​to a comparison unit VE, which is connected downstream of the measuring unit ME in terms of signal technology.

[0042] Although hydrogen gradually escapes from the battery housing BG through the opening OF, the measuring unit ME can detect a temporary increase in the hydrogen concentration in the interior of the battery housing BG with high accuracy due to the short measuring cycle.

[0043] The comparison unit VE is configured to compare the detected fluid concentration with a predetermined first concentration threshold value, for example, of an operating temperature-concentration conversion table (lookup table). In this case, the comparison unit VE has, for example, a comparator, which compares the measurement data of the fluid concentration transmitted by the measuring unit ME with the first concentration threshold value and forwards the comparison result to the downstream adaptation unit AE.

[0044] The adaptation unit AE is designed to dynamically adjust the maximum permissible operating temperature of the battery device BV or of the battery cell BZ based on the comparison result transmitted by the comparison unit VE and to forward the adjusted maximum permissible operating temperature to the downstream regulating / control unit RE.

[0045] The regulating / control unit RE is designed to operate or control and regulate the battery device BV. In this case, the battery device BV is operated at an operating temperature which is at, in particular, exactly at, but not above the maximum permissible operating temperature. For this purpose, the regulating / control unit RE is designed to control or regulate the temperature control unit TE based on the maximum permissible operating temperature so that the temperature control unit TE heats or cools the battery device BV or the battery cells BZ to the aforementioned operating temperature.

[0046] The device AO optionally has an air pressure measuring unit, for example in the form of a first air pressure sensor, which is designed to detect the air pressure or the temporal air pressure change in the interior of the battery housing BG and forward the detected pressure value to a comparison unit VE connected downstream. In this case, the lookup table contains the pressure value as a further parameter. The comparison unit VE is accordingly designed to compare the measured data of the fluid concentration transmitted by the measuring unit ME with a first concentration threshold value, taking into account the detected pressure value.

[0047] After describing the structure of the battery device BV together with the device AO, its mode of operation, in particular the mode of operation of the device AO, is described in detail below:

[0048] In order to increase the efficiency and service life of the battery device BV or the battery cell BZ, the measuring unit ME detects the hydrogen concentration in the interior of the battery housing BG or at the battery cell BZ continuously and regularly at predefined time intervals, in particular by means of a hydrogen sensor, during active operation of the battery device BV but also outside of active operation (i.e. during rest phases). The measuring unit ME forwards the measured concentration values ​​in the form of analog or digital measurement data to a downstream comparison unit VE.

[0049] The comparison unit VE compares the concentration value transmitted by the measuring unit ME with a predetermined concentration threshold value, for example of the above-mentioned look-up table, in particular by means of a comparator, and forwards the comparison result to the downstream adaptation unit AE.

[0050] The adaptation unit AE dynamically adjusts the maximum permissible operating temperature of the battery device BV or of the battery cell BZ, in particular based on the comparison result transmitted by the comparison unit VE, and forwards the adjusted maximum permissible operating temperature to the downstream regulating / control unit RE.

[0051] In the subsequent operating phase until the next adaptation, the regulating / control unit RE operates the temperature control unit TE of the battery device BV so that it heats or cools the battery device BV or the battery cells BZ to an operating temperature which is exactly at the maximum permissible operating temperature or is approximately 5% below the maximum permissible operating temperature. In this case, the regulating / control unit RE continuously monitors the operating temperature of the battery device BV so that the maximum permissible operating temperature is not exceeded (or is not exceeded for longer than a predetermined period of time).

[0052] In this case, the maximum permissible operating temperature is preferably adjusted continuously or continuously iteratively at predetermined time intervals and dynamically over the entire service life of the battery device BV. To this end, the aforementioned method steps, namely detecting the hydrogen concentration, comparing the detected hydrogen concentration with a concentration threshold value, and dynamically adapting the maximum permissible operating temperature are performed continuously or continuously iteratively at predetermined time intervals over the entire service life of the battery device BV.

[0053] In this way, the battery system BV or the battery cells BZ are always operated at an optimum operating temperature.

[0054] Optionally, the gas pressure in the interior of the battery housing BG can also be detected and used for adapting the maximum permissible operating temperature.

[0055] Optionally, the comparison unit VE compares the detected hydrogen concentration value with other predefined critical concentration threshold values. If or as soon as the detected hydrogen concentration value exceeds the critical concentration threshold value, a critical situation, such as thermal runaway, is considered at the battery device BV or the battery cell BZ. In this case, the battery device BV is shut down in a controlled manner and a fault message is output.

Claims

1. A method for operating a battery device (BV) having a plurality of battery cells (BZ) arranged in the interior of a battery housing (BG), the method comprising the steps of: - detecting a fluid concentration of a predetermined fluid in the interior of the battery housing (BG), wherein decomposition products of a battery cell material are selected as the predetermined fluid; - comparing the detected fluid concentration with a predetermined concentration threshold; - if the detected fluid concentration exceeds the concentration threshold, adapting the maximum permissible operating temperature of the battery device (BV); - operating the battery device (BV) such that the maximum permissible operating temperature is not exceeded, The steps of detecting, comparing and adapting are carried out continuously or iteratively at predefined time intervals over the service life of the battery system (BV). 2 . The method according to claim 1 , wherein the step of detecting further provides for detecting a concentration of a predetermined gas as the fluid concentration of the predetermined fluid. 3 . The method according to claim 2 , wherein as the concentration of the predetermined gas, a concentration of hydrogen, a concentration of carbon dioxide, a concentration of carbon monoxide, or a concentration of hydrocarbons is detected.

4. The method according to any one of claims 1 to 3, wherein The step of comparing furthermore provides for comparing the detected fluid concentration with a concentration threshold value of a predetermined operating temperature-concentration conversion table (lookup table) of the battery device (BV); and The adapting step further provides that the maximum permissible operating temperature is adapted according to the operating temperature / concentration conversion table and based on a result of the comparison.

5. The method according to any one of claims 1 to 3, wherein The step of comparing furthermore provides that the detected fluid concentration is also compared with a further predetermined critical concentration threshold value; - wherein a critical situation is detected at the battery device (BV) if the detected fluid concentration exceeds a further predetermined critical concentration threshold value; and The operating step further provides that a fault message is output when the critical situation is detected. 6 . The method according to claim 1 , wherein the operating step further provides that the maximum permissible operating temperature is not exceeded by temperature control of the battery device (BV). 7 . The method according to claim 1 , wherein the step of operating further provides that the battery device (BV) is operated at the maximum permissible operating temperature.

8. The method according to any one of claims 1 to 3, further comprising the steps of: - detecting the gas pressure inside the battery housing (BG); - wherein the step of adapting further provides that the maximum permissible operating temperature is adapted based on the detected gas pressure.

9. A device (AO) for operating a battery device (BV) having a plurality of battery cells (BZ) arranged in the interior of a battery housing (BG), the device comprising: - a measuring unit (ME) for detecting a fluid concentration of a predetermined fluid in the interior of the battery housing (BG); a comparison unit (VE) for comparing the detected fluid concentration with a predetermined concentration threshold value; an adaptation unit (AE) for adapting the maximum permissible operating temperature of the battery device (BV) if the detected fluid concentration exceeds the concentration threshold; A regulating / control unit (RE) for operating the battery arrangement (BV) in such a way that the maximum permissible operating temperature is not exceeded.

10. A battery device (BV), comprising: a battery arrangement (BA) comprising a battery housing (BG) and a plurality of battery cells (BZ), wherein the battery cells (BZ) are arranged in the interior of the battery housing (BG); - The device (AO) for operating the battery device (BV) according to claim 9.

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