BATTERY SYSTEM AND METHOD FOR MONITORING A TEMPERATURE OF A BATTERY SYSTEM

Abstract

The invention relates to a battery system, comprising at least one battery component (10), which has at least one measurement point (12.sub.a-g), and comprising an optical waveguide (14), which is connected to the measurement point (12.sub.a-g) in a thermally conductive manner, wherein a light source (16.sub.a-d) is provided for radiating light of a defined frequency into the optical waveguide (14) and an optical detector (18) is provided for detecting light exiting the optical waveguide (14), characterized in that a thermochromatic material (30) is provided, which is connected to the measurement point (12.sub.a-g) in a thermally conductive manner and is positioned in a beam path of the optical waveguide (14). In summary, a reliable and robust possibility for the temperature monitoring of one or more battery components (10) is thus enabled in a simple and economical manner.

Claims

1. A battery system comprising: at least one battery component (10) which has at least one measuring-point (12.sub.a-g), at least one optical waveguide (14) connected to the measuring-point (12.sub.a-g) in a thermally conducting manner, a light-source (16.sub.a-d) for radiating light of a defined frequency into the optical waveguide (14), and an optical detector (18) for detecting light emerging from the east one optical waveguide (14), and a thermochromatic material (30) connected to the at least one measuring-point (12.sub.a-g) in a thermally conducting manner and positioned in a beam path of the optical waveguide (14).

2. The battery system as claimed in claim 1, the light-source (16.sub.a-d) comprises an LED.

3. The battery system as claimed in claim 1, further comprising a reference optical waveguide (32) for ascertaining changes in the transmission of the light guided through the at least one optical waveguide (14).

4. The battery system as claimed in claim 1, further comprising at least two different thermochromatic materials (30) which are connected to at the least one measuring-point (12.sub.a-g) in a thermally conducting manner, wherein the two different thermochromatic materials (30) are arranged in the beam path of the at least one optical waveguide (14) or, in a respective beam path of different optical waveguides (14).

5. The battery system as claimed in claim 4, wherein at least one thermochromatic material (30) is provided that above a temperature T1 exhibits a higher transmission of the light guided through the at least one optical waveguide (14) than below temperature T1, and in that at least one thermochromatic material (30) is provided that above a temperature T2 exhibits a lower transmission of the light guided through the at least one optical waveguide (14) than below temperature T2, where T2 is higher than T1, or in that at least one thermochromatic material (30) is provided that above a temperature T1 exhibits a lower transmission of the light guided through the at least one optical waveguide (14) than below temperature T1, and in that at least one thermochromatic material (30) is provided that above a temperature T2 exhibits a higher transmission of the light guided through the at least one optical waveguide (14) than below temperature T2, where T2 is higher than T1.

6. The battery system as claimed in claim 1, wherein the at least one optical waveguide (14) is made from a material that is selected from the group consisting of glass and plastics.

7. A method for monitoring a temperature of a battery component (10), having the following method steps: a) radiating light of a defined frequency into an optical waveguide (14), wherein said optical waveguide (14) is connected to at least one measuring-point (12.sub.a-g) of the battery component (10) in thermally conducting manner, wherein a thermochromatic material (30) is provided which is connected to at least one measuring-point (12.sub.a-g) in a thermally conducting manner and is positioned in a beam path of the optical waveguide (14); b) detecting light emerging from the optical waveguide (14); c) determining a temperature range of the at least one measuring-point (12.sub.a-g) on the basis of the detected light.

8. The method as claimed in claim 7, wherein method step a) is carried out using light of at least two different frequencies.

9. The method as claimed in claim 7, wherein the method is carried out in periodically repeating manner.

10. The method as claimed in claim 9, wherein a rate of repetition is chosen as a function of a relaxation-time of the thermochromatic material (30).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Further advantages and advantageous configurations of the subject-matters according to the invention will be illustrated by the drawings and elucidated in the following description, wherein the described featuresindividually or in an arbitrary combinationmay be a subject-matter of the present invention unless the contrary results unequivocally from the context. In this regard, it is to be noted that the drawings have only descriptive character and are not intended to restrict the invention in any way. Shown are:

[0068] FIG. 1 a schematic representation of a configuration of a battery system;

[0069] FIG. 2 a schematic representation of a further configuration of a battery system;

[0070] FIG. 3 a diagram showing the frequency of light-sources that is being used;

[0071] FIG. 4 a diagram showing the transmission of light of two frequencies through an optical waveguide having two exemplary thermochromatic materials;

[0072] FIG. 5a)-5c) a schematic diagram showing advantageous frequency properties of thermochromatic materials.

DETAILED DESCRIPTION

[0073] A schematic representation of a configuration of a battery system according to the invention is shown in FIG. 1.

[0074] The battery system includes at least one battery component 10 which has at least one measuring-point 12 which may be, for instance, part of a battery cell. In the configuration according to FIG. 1, a total of seven measuring-points 12.sub.a-g are shown. The battery system 10 further includes an optical waveguide 14, for example of tubular structure or with a circular or oval cross-section, which is connected to the measuring-points 12.sub.a-g in thermally conducting manner. For example, the optical waveguide 14 is bonded to the measuring-points 12.sub.a-g of the battery component 10 with a thermally conducting adhesive, or it is welded to the measuring-points 12.sub.a-g.

[0075] Furthermore, a light-source 16according to FIG. 1, two light-sources 16.sub.a, 16.sub.bis provided for the purpose of radiating light of a defined frequency into the optical waveguide 14, and an optical detector 18 is provided for the purpose of detecting light emerging from the optical waveguide 14. The light-sources 16.sub.a, 16.sub.b, each constituted by an LED for example, can radiate light of different frequencies, and the detector 18 may be, for example, a photodiode. Moreover, an optical link 20, such as a lens for instance, may be provided between the light-sources 16.sub.a, 16.sub.b and the optical waveguide 14, in order to be able to couple the light suitably into the optical waveguide 14. Furthermore, an electrical circuit 22 is provided which is able to drive the light-sources 16.sub.a, 16.sub.b. For example, the circuit 22 may be part of an open-loop and/or closed-loop control unit such as the battery management system, for instance.

[0076] For example, the circuit 22 together with the light-sources 16.sub.a, 16.sub.b may be arranged on or alongside one or more battery cells or a corresponding housing. Furthermore, the optical waveguide 14 may pass through a module and thereby run along the various measuring-points 12.sub.a-g.

[0077] At the end of the optical waveguide 14 a further optical link 24 is provided which connects the output of the optical waveguide 14 to the detector 18, in order to detect, in the detector 18, the light emerging from the optical waveguide 14. Optionally, an optical filter 26 may be provided which is transradiated by the light emerging from the optical waveguide 14 and which is arranged, for instance, on the optical link 24, for example in the optical link 24 or between the optical link and the detector 18. By virtue of the optical filter 26, the light can be filtered with respect to the frequency, which can simplify the detection. The detector 18 may be connected to an electrical circuit 28 which serves to evaluate the data ascertained by the detector 18. For example, the circuit 28 may be part of an open-loop and/or closed-loop control unitsuch as the battery management system, for instanceand/or may evaluate the measuring current of a photodiode.

[0078] The invention provides, moreover, that the optical waveguide 14 exhibits a thermochromatic material 30 which is connected to the measuring-points 12.sub.a-g in thermally conducting manner and is positioned in a beam path of the optical waveguide 14. In particular, the thermochromatic material 30 may be arranged in the entire optical waveguide 14 or only at defined positions, for instance adjacent to the measuring-points 12.sub.a-g. In this case, the thermochromatic material 30 is drawn schematically and may be located, for instance, only within the optical waveguide 14.

[0079] A further configuration of a battery system is shown in FIG. 2, wherein with respect to FIG. 1 the same or comparable structural members are provided with the same reference symbols.

[0080] In FIG. 2 it is shown, in particular, that a reference optical waveguide 32 is provided which is able to guide light emitted from two light-sources 16.sub.c, 16.sub.d which likewise may be configured as LEDs. Light-sources 16.sub.c, 16.sub.d can likewise emit light of a defined frequency which may be identical to the frequency of light-sources 16.sub.a, 16.sub.b. For example, light-sources 16.sub.a, 16.sub.c can emit light having a frequency f1, and light-sources 16.sub.b, 16.sub.d can emit light having a frequency f2. This is shown in FIG. 3, for example, in which the frequency of the light is plotted on the X-axis against the intensity of the light on the Y-axis. In this case, line A shows the frequency of light-sources 16.sub.a, 16.sub.c, and line B shows the frequency of light-sources 16.sub.b, 16.sub.d.

[0081] Furthermore, the optical waveguide 14 and the reference optical waveguide 32 may be connected by a common optical link 24 or by a respective optical link 24a, 24b such as one or two prisms, for instance. From the optical link(s), the light can, in turn, pass through one or two optical filters 26a, 26b and can be conducted from there into the detector 18 through a further optical link 27likewise configured as a prism, for examplein which case two optical filters 26a, 26b may, moreover, are provided.

[0082] For example, two different thermochromatic materials 30 may be arranged downstream relative to one another with respect to a direction of propagation of the light transradiating the optical waveguide 14, a first thermochromatic material 30 being configured in such a manner that with respect to a light having a frequency f1 it exhibits a higher transmission above a temperature T1 than below temperature T1, and a second thermochromatic material 30 being configured in such a manner that with respect to a light having a frequency f2 it exhibits a lower transmission above a temperature T2 than below temperature T2, f1 and f2 being different, and T2 and T1 being different. In particular, T2 is higher than T1, and the first thermochromatic material 30 exhibits a high transmission at frequency f2 within the entire temperature range presented, and the second thermochromatic material 30 exhibits a high transmission at frequency f1 within the entire temperature range presented.

[0083] In FIG. 4 a diagram is shown which shows the effect of the aforementioned thermochromatic materials 30. In this diagram, the frequency of a light radiated into the optical waveguide 14 is plotted on the X-axis, and the transmission of the light that shines through the two different thermochromatic materials 30 is plotted on the Y-axis. In this diagram, curve A relates to a temperature below T1, curve B relates to a temperature between T1 and T2, and curve C relates to a temperature above T2. By virtue of the specifications of the thermochromatic materials 30, there is a high transmission between T1 and T2 with respect to both frequencies being used. Furthermore, the transmission drops both above temperature T2 and below temperature T1. As a result, whenever the temperature is outside the desired temperature range this can always be detected by a declining transmission of at least one of the frequencies f1 and f2.

[0084] An exemplary measuring method using a photodiode as detector 18 may then proceed, for example, as follows. Firstly, light-source 16.sub.a, which radiates with frequency f1, is activated, and the relaxation-time of the thermochromatic material is waited out, and subsequently the measuring current in the photodiode is ascertained. Subsequently, light-source 16.sub.a is deactivated and light-source 16.sub.b is activated, and the measuring current of the photodiode is ascertained after the relaxation-time. Subsequently light-source 16.sub.b is deactivated, and the relaxation-time is waited out. On the basis of a comparison of the ascertained measuring currents with predetermined limiting values, it can be output whether a minimum temperature T1 is being fallen short of or whether a maximum temperature T2 is being exceeded. A measuring cycle of such a type can be repeated periodically, in which case the period between two repetitions may be dependent on the relaxation-time of the thermochromatic material 30.

[0085] An evaluation based on the configuration described above is shown by way of example in FIG. 5 and may then proceed as follows. In detail, in FIG. 5 three diagrams arranged one above the other are shown, in which the frequency is plotted in each instance on the X-axis, and the transmission of the light guided through the optical waveguide 14 is shown on the Y-axis. In this case, diagram a) shows a state in which the temperature of the measuring-point 12 is less than T1 (T<T1), diagram b) shows a state in which the temperature of the measuring-point 12 lies between T1 and T2 (T1<T<T2), and diagram c) shows a state in which the temperature of the measuring-point 12 lies above T2, where T2 is higher than T1 (T>T2).

[0086] Corresponding to the aforementioned specifications, a high transmission obtains at frequency f1 in states T1<T<T2 and T>T2, and a low transmission obtains in state T<T1, whereas at frequency f2 a high transmission obtains in states T<T1 and T1<T<T2, and a low transmission obtains in state T>T2.

[0087] With respect to the detector 18, and here, by way of example, to the measuring current of a photodiode, this means that, in a state of T<T1, light-source 16.sub.a, which radiates with frequency f1, brings about a low measuring current, and light-source 16.sub.b, which radiates with frequency f2, brings about a high measuring current. In a state of T1<T<T2, both light-sources 16.sub.a and 16.sub.b bring about a high measuring current and, in a state of T>T2, light-source 16.sub.a, which radiates at frequency f1, brings about a high measuring current, and light-source 16.sub.b, which radiates at frequency f2, brings about a low measuring current.