Temperature distribution or heat distribution in a cylindrical accumulator

Abstract

The temperature distribution or heat distribution in a cylindrical energy store (1) is to be determined in a simple manner. For this purpose, the structure of the energy store (1) is described by an arrangement of a plurality of hollow cylinders (2) coaxially nested and / or adjacent to one another or a plurality of partial cylinders coaxially and / or adjacent to one another parallel to one another with respect to their axes. The respective temperature or heat distribution of each hollow cylinder (2) or partial cylinder is determined, wherein a quasi-static state is assumed in each hollow cylinder or partial cylinder at each individual observation time point along a time series.

Description

Technical Field

[0001] The invention relates to a method for determining a temperature distribution or heat distribution in a cylindrical energy store and also to an energy store having a control device for carrying out the method, as well as to a corresponding electric tool and a computer program product. Background Art

[0002] Until now, regulation and control in battery management systems for lithium-ion batteries have been carried out essentially on the basis of current, voltage and temperature, which are determined as measured variables. The problem is that temperature measurement is mainly carried out only by external thermal sensors and is always carried out slowly.

[0003] The heat energy introduced into the lithium-ion cells has a decisive effect on the electrochemical stress on the cells, since it is ultimately responsible for the spatial temperature field across the three-dimensional cells. Depending on the situation, i.e. on the basis of the previous load situation or the set temperature field, further heat input leads to a change in the temperature field, just as heat dissipated to the environment through the cell housing also changes the temperature field. In addition to the potential level as a decisive driver of the chemical and microphysical reactions and the electrochemical substances or carrier materials present in the cells (structuring, supporting, etc.), the local temperature is also an important factor for the electrochemical reactions (here, for example, the reaction rate), but can also assist, inhibit, or even change and destroy microphysical processes (e.g. ion diffusion rate) and even change and destroy the material structure.

[0004] From the publication DE 10 2011 080 512 A1 it is known to determine the desired nominal temperature of the operating system for the current operating state in conjunction with a model-based calculation, for example in conjunction with a mathematical temperature model for the battery system. In this case, the values ​​of the temperature model can be compared with the measured values ​​of the temperature. In an operating mode in which the temperature control system is not activated, the temperature model can dynamically calculate the temperature rise of the battery cells and the battery system and compare it with the measured values ​​of the temperature sensors of this battery system.

[0005] In addition, US Pat. No. 8,829,904 B2 relates to modeling of the internal temperature of a lithium-ion cell. The modeled internal temperature includes a three-dimensional temperature curve.

[0006] In addition, the publication CN 105206888A discloses a method for monitoring the internal temperature of a lithium-ion battery. The charge and discharge test of the lithium-ion battery is carried out under different environmental conditions to obtain a curve of the change of the battery surface temperature. Relevant parameters such as the internal resistance and open circuit voltage temperature coefficient of the battery are checked. A thermal coupling model of the lithium-ion battery is established based on the heat generation rate. This can simulate the temperature change during the discharge process. This temperature modeling is based on the solution of the corresponding differential equation.

[0007] The model for simulating the internal temperature of each battery cell shown above is usually very complex and computationally intensive. Therefore, it is almost impossible to perform time-invariant control of each energy storage device or its related electrical equipment within a fraction of a second. Summary of the invention

[0008] It is therefore an object of the present invention to provide a concept based on which a rapid temperature control of an energy store is possible.

[0009] The invention achieves the above-mentioned object by means of a method, an energy storage device, an electric tool and a computer program product according to the independent claims. Advantageous further developments of the invention are described in the dependent claims.

[0010] Therefore, according to the invention, a method for determining the temperature distribution or heat distribution in a cylindrical energy storage device is provided, which method comprises

[0011] -pass

[0012] o A plurality of hollow cylinders coaxially nested within each other and / or adjacent to each other or

[0013] o the structure of the energy store is described by an arrangement of a plurality of partial cylinders which adjoin one another coaxially and / or parallel with respect to their axes,

[0014] - The respective temperature or heat of each hollow cylinder or partial cylinder is determined, wherein a quasi-static state is assumed in each hollow cylinder or partial cylinder at each individual observation time point along the time series.

[0015] The invention is therefore based on the idea of ​​simplifying the determination of the temperature distribution or heat distribution in a suitable manner, which inevitably slows down the simulation or modeling. The invention is particularly intended to divide a cylindrical energy storage into cylindrical substructures, wherein the thermal process of each substructure is assumed to be quasi-static with respect to a given observation time point.

[0016] Specifically, the temperature distribution or heat distribution in a cylindrical energy storage device is determined in the proposed method. That is, the spatial distribution of temperature or heat inside the energy storage device is evaluated. For this purpose, in an alternative, the structure, i.e., the geometric structure, of the energy storage device is described by the layout of a plurality of hollow cylinders coaxially nested and / or adjacent to each other, so that the geometric part of the total thermal model or temperature model can be generated. In this case, hollow cylinders of different sizes nested and / or adjacent to each other produce the precise geometry of the energy storage device. Therefore, the thermal energy storage model roughly has an onion structure, in which each shell can be observed separately. However, in the current case, this shell is cylindrical.

[0017] Thus, the energy storage device can consist of a plurality of radially superposed cylindrical shells, for example. Optionally, the length of a single hollow cylinder is equal to the length of the entire energy storage device. This is advantageous, for example, if a uniform temperature distribution is to be established over the entire length of the energy storage device. Otherwise, this energy storage device can also be modeled with the aid of hollow cylinders adjoining one another coaxially. Thus, in this case, a plurality of hollow cylinders adjoin one another coaxially in the longitudinal direction. In this case, all hollow cylinders have a common axis. This modeling of the energy storage device is particularly based on a wound energy storage device.

[0018] In a second alternative, the structure of the energy storage device can be described by the layout of a plurality of partial cylinders that are adjacent to each other coaxially and / or parallel to their axes. More precisely, this structure is intended to model an energy storage device with a stacked structure. These partial cylinders are not hollow cylinders, but solid cylinders. In a preferred technical solution, these partial cylinders are arranged in a coaxial manner adjacent to or superimposed on each other. As an alternative or supplementary solution, such partial cylinders can also be arranged side by side in parallel to each other, so that, for example, a plurality of rods (for example, in a cubic shape) that are arranged side by side in parallel to each other produce a model structure. Therefore, any structure can be formed by means of partial cylinders that are coaxially superimposed on each other or axially arranged side by side in parallel to each other.

[0019] In another step of the method according to the invention, the corresponding temperature or heat of each hollow cylinder or partial cylinder is determined. That is, each inherent (average) temperature is determined for each individual partial or hollow cylinder. Thereby, a corresponding spatial temperature or heat distribution is generated according to the spatial distribution of the cylinder. In order to determine the corresponding temperature or heat in each partial or hollow cylinder, a quasi-static state is assumed in each partial or hollow cylinder, more precisely, a quasi-static state is assumed at each single (observation) time point along the time series. This shows that, with respect to each time point, each hollow cylinder or partial cylinder is considered to be in a state of equilibrium. Therefore, an average temperature or average heat can be assigned to each partial cylinder or hollow cylinder at a specific time point. In this way, the corresponding spatial temperature distribution or heat distribution can be obtained according to the energy storage structure given by the partial cylinder or hollow cylinder. Through this optionally coarse spatial grid, the amount of calculation required for determining the temperature distribution or heat distribution can be reduced in particular.

[0020] In a particular embodiment, the energy storage device has the shape of a right circular cylinder and the hollow cylinder or part of the cylinder is also straight. A right circular cylinder is the most common cylindrical shape, but an inclined circular cylinder can also be used, the cylinder axis of which forms a non-zero angle with respect to the normal of the cylinder end face. In this way, the cylindrical energy storage device with an inclined cut can also be modeled in terms of its temperature distribution or heat distribution, if necessary.

[0021] In a special further development, it can be provided that the energy storage device has the shape of a cylinder, an elliptical cylinder or a prism, in particular a cubic shape, and the hollow cylinder or partial cylinder is also correspondingly cylindrical, elliptical or prismatic. Thus, the end faces of the individual cylinders can have different shapes. These end faces can not only be circular or elliptical, but also any polygonal shape. This ensures that different shapes of cylindrical energy storage devices can be modeled in a suitable manner by means of hollow cylinders or partial cylinders.

[0022] Furthermore, it can be provided that the energy storage device is wound up with a number of layers stacked one on top of the other in the radial direction, and that the number of the plurality of hollow cylinders corresponds to the number of layers. If the energy storage device has, for example, 30 (wound) layers, it is advantageous that the corresponding temperature or thermal model also has 30 layers. Accordingly, each individual layer can be observed individually. Even though the energy storage device is usually wound in a spiral, approximate modeling with the aid of coaxial hollow cylinders nested one inside the other is usually sufficiently accurate. The individual layers can be relative to the electrodes including the electrolyte and the diaphragm. This allows an accurate statement of the temperature and heat in the electrodes and the diaphragm.

[0023] According to another technical solution, the energy storage device is formed as a stack of multiple layers in the stacking direction, and the number of multiple hollow cylinders or partial cylinders in the stacking direction corresponds to the number of uniform layers. If the layer storage device is composed of a stack of 60 layers, for example, the corresponding model should also have 60 cylinders in the stacking direction. Therefore, accurate temperature or heat statements can be made for the individual layers.

[0024] Furthermore, it can be provided that when determining the respective temperature or heat in each hollow cylinder or partial cylinder, a separate heat capacity and / or thermal conductivity is assigned to each hollow cylinder or partial cylinder or a separate heat capacity and / or thermal conductivity is assigned to each hollow cylinder or partial cylinder. In this case, each hollow cylinder or partial cylinder is considered to be a homogeneous body. This approximation can be easily implemented and generally does not present disadvantages with respect to typical layer structures.

[0025] In a special technical solution, the corresponding temperature or heat in each hollow cylinder or partial cylinder can be determined by modeling a hollow cylindrical heat sink on the outer circumference of the energy storage device for heat dissipation. This is reflected in the adjustment of the boundary value problem. On the jacket of the cylindrical energy storage device, the problem is to take into account the corresponding temperature transfer to the environment. Therefore, the environment is simulated here by a hollow cylindrical heat sink, which has thermal properties similar to those of the environment. The heat dissipated by the energy storage device to the environment flows to this heat sink, for example. In this way, the heat dissipated from the cylindrical energy storage device to the outside can be introduced into the temperature or thermal model in a simple way.

[0026] The further adjustment of the boundary value problem is related to the end faces of the energy store. It is therefore advantageous to determine the corresponding temperature or heat in each hollow cylinder or partial cylinder by modeling a cylindrical heat sink for heat dissipation at each of the two end faces of the energy store. In this way, the heat dissipation can also be determined simply and reliably at the end faces of the energy store. In principle, if the environment is hotter than the energy store, the heat absorption can of course also be modeled by the heat sink. This can be the case when the energy store must be heated from the outside to achieve optimal operating conditions.

[0027] Furthermore, it can be provided that the respective temperature or heat of each hollow cylinder is determined in a time-discrete manner by means of a heat balance, wherein in the case of cylindrical energy storage devices, the axial heat conduction, the radial heat conduction, the heat storage and the heat input are determined for each hollow cylinder or partial cylinder. These four different physical variables are usually sufficient to describe the heat balance of each partial cylinder or hollow cylinder in a time-discrete manner with the required accuracy. In the case of hollow cylinders, the radial heat conduction can also be divided into a radially inward heat conduction and a radially outward heat conduction. In the case of stacked partial cylinders, the axial heat conduction can be distinguished in the opposite axial direction.

[0028] According to another technical solution, it can be set that the corresponding temperature or heat in each hollow cylinder or partial cylinder is measured according to the charging current, discharging current, single cell voltage, total voltage of the energy storage device, change of charging state, change of discharging current, change of single cell voltage or total voltage, measured temperature of one or more single cells of the energy storage device, life and / or SOH (health status; according to the ratio of residual capacity to nominal capacity). That is, the temperature or heat in each cylinder or each cylinder can be measured according to one or more of the above parameters. In this case, not only the static current or voltage should be paid attention to, but also its dynamics, that is, the change of current and voltage, should be paid attention to as appropriate.

[0029] In a further embodiment of the method according to the invention, when determining the corresponding temperature or heat in each hollow cylinder or partial cylinder, one or more calibrations are performed in conjunction with corresponding measurements of the surface temperature of the energy storage. The temperature of this energy storage can usually only be conveniently measured on the surface of the energy storage. Since the temperature or thermal model can also provide information about the jacket temperature of the energy storage, the model can be calibrated with the help of the measured values. This calibration can be performed once during commissioning or multiple times at specific time intervals or as required. In this way, for example, aging processes can be taken into account, in which the internal resistance of the energy storage and (if appropriate) the heat input increase, for example.

[0030] In a further embodiment of the method according to the invention, a numerical simulation is performed when determining the corresponding temperature or heat in each hollow cylinder or partial cylinder. Such numerical simulations are generally more advantageous than analytical solutions. In particular, real-time conditions can thereby be maintained, under which, for example, switching processes must be performed within a fraction of a second (in particular 0.1 s to 1 s). Such numerical simulations can be implemented in the management system of the energy storage device. A corresponding processor can be used in particular for the numerical simulations described above.

[0031] In particular, one or more parameters for numerical simulation can be determined by artificial intelligence in combination with temperature measurement. The artificial intelligence can be based on, for example, a neural network, a support vector machine, a decision tree, a Bayesian network, a dynamic algorithm and / or an association rule, etc. The neural network or other algorithm can be trained accordingly for the numerical simulation. In this way, for example, temperature measurements can also be performed inside the energy storage device in a laboratory, and the temperature measurements are used to train the artificial intelligence. Then, the artificial intelligence trained in the laboratory can be used for simulations so as to determine the required temperature distribution or heat distribution in the energy storage device in the shortest time during the operation of the energy storage device. Therefore, the numerical simulation performed by the artificial intelligence can be trained by temperature measurement, especially in the laboratory, wherein the corresponding parameters or weights of the artificial intelligence are obtained.

[0032] The above method for determining the temperature distribution or heat distribution in a cylindrical energy storage device can be used to control or regulate the operation of the energy storage device according to the determined temperature distribution or heat distribution. Because the spatial temperature distribution or heat distribution under the current conditions (for example, the current total voltage of the energy storage device and the current discharge current) is known, it is also known at which position (for example, electrode, diaphragm, etc.) the critical temperature occurs. The operation of the energy storage device (for example, discharge) can be controlled or regulated accordingly according to the corresponding temperature preset value. Therefore, if a certain position reaches a predetermined temperature or before a certain position reaches a predetermined temperature, for example, the discharge process can be stopped or reduced in time. Of course, it is also possible to control or regulate according to multiple temperature conditions. With regard to the maximum temperature, for example, all positions of the anode can be monitored. The same applies to other components of the energy storage device. Therefore, the operation of the energy storage device can be automatically adapted in a certain way so that certain maximum temperatures are not exceeded. This also applies similarly to the minimum temperature. The heat present in a specific layer can also be monitored. Therefore, when controlling the charging current, the heat in the cathode may be particularly important, for example.

[0033] In particular, it can be provided that the power output of the energy storage device to the electrical device or the charging current or charging voltage of the energy storage device is controlled according to the temperature distribution or heat distribution. This means that not only the energy storage device itself but also the corresponding electrical device or charging device can be regulated or controlled in this way. Therefore, based on the temperature distribution or heat distribution determined in the energy storage device, a control or regulation signal can be provided to an external device located outside the energy storage device.

[0034] As already mentioned above, the energy storage device can have a control device in order to implement the above method. Thus, the lithium-ion battery can have in particular specific control or monitoring electronics. This control device can be part of a so-called battery management system, which is arranged as an integrated electronic component in the energy storage device.

[0035] The energy storage device may have a plurality of cells, each of which is modeled by a plurality of the hollow cylinders or partial cylinders. Thus, even in complex energy storage devices having a multi-cell structure, the spatial temperature distribution or heat distribution can be determined with the required accuracy.

[0036] According to the present invention, in particular, a power tool is provided, which has the above energy storage device including the above control device, so as to implement the above method. Such battery-operated power tools are, for example, rechargeable screwdrivers, rechargeable drills, rechargeable circular saws, rechargeable gardening tools, etc.

[0037] The solution of the present invention to achieve the above-mentioned object also lies in a computer program product, which includes commands for causing the above-mentioned energy storage device or the above-mentioned power tool to perform the above-mentioned method steps. Such a computer program product may include a storage medium, on which a corresponding computer program including the above-mentioned commands is stored. The storage medium may be, for example, a DVD, a RAM, an SSD memory, or any other suitable memory for a computer program.

[0038] The advantages and variants described above in conjunction with the method according to the invention can also be realized analogously with respect to the energy storage device or the electric tool. This also applies to corresponding combinations of features. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention is described in detail below in conjunction with the accompanying drawings, wherein:

[0040] Figure 1 A model of a cylindrical energy storage device for determining temperature distribution or heat distribution;

[0041] Figure 2 Another model of another cylindrical energy storage device for determining the temperature distribution or heat distribution.

[0042] Figure 3 A battery pack for use with a power tool or garden tool; and

[0043] Figure 4 The following is a schematic processing procedure of an embodiment. DETAILED DESCRIPTION

[0044] The embodiments described in detail below are preferred embodiments of the present invention.

[0045] Thermal energy (heat) is loaded into the energy storage device in a physically calculated manner, in particular by a current passing through two internal resistances of a dielectric and an electrochemical capacitor. The dielectric capacitance is generated by the layer structure, and the electrochemical capacitance is generated by the charge storage in the electrochemical structure. The energy input is spatially carried out according to the layer structure of the energy storage device. The energy input in a wound cell is different from the energy input in a stacked cell. The energy input into the cell is usually achieved in a manner distributed to the individual layers. As long as a uniform current is generated flowing through the electrode path and its surface, at least the above scheme is applicable. If an uneven current path is generated when the current load is very high, more heat dissipation is achieved at fixed points along these current paths.

[0046] In the case of wound cells, the introduced heat is distributed by radial heat conduction from the center of the cell to the radial closure of the cell (cell jacket) and by axial heat conduction from the center of the cell to the two pole caps. This heat is stored in the cell volume by all mass elements of the cell according to their thermal capacity. Such mass elements are in particular electrodes, electrolytes, separators, housings and conductors.

[0047] It is easy to understand that even a uniform heat input into a single cell will directly lead to an uneven temperature distribution in the temperature field of the single cell, because this transport process cannot remove the heat from the axial and radial areas close to the center well. In this way, more heat will be stored in the central space area, which will directly lead to a temperature increase.

[0048] For solid phase control of lithium-ion cells, for example, the ambient temperature at all spatial points of the cell must be taken into account, especially in dynamic situations (quasi-steady-state operating conditions). If only external temperature measurement points are used, sufficient thermal buffering must always be provided to ensure safe operation of the cell, while the current flow must be limited so that the temperature in the core region of the cell does not exceed a critical threshold. The cell cannot develop its actual electrochemical properties in this way. For this purpose, according to the invention, a simple (numerical) simulation model is provided, which advantageously simulates the actual temperature situation in the cell in a high-resolution manner in time, so that adjacent electrical devices can be shut down safely and in time, but at the same time the maximum power from the cell is provided to this electrical device.

[0049] Figure 1 The technical approach shown is, for example, a model whose spatial configuration consists of coaxial hollow cylinders, which are defined by their inner and outer radii, cylinder length, cylinder mass and axial and radial thermal conductivity.

[0050] exist Figure 1 In the specific example shown, a cylindrical wound cell is to be modeled as an energy storage device. Modeling 1 is achieved by a plurality of coaxial hollow cylinders 2. The hollow cylinders 2 have different outer diameters and are arranged nested with each other. In this case, the hollow cylinders are radially adjacent to the adjacent hollow cylinders. The hollow cylinder 2 or the solid cylinder can also be located on the innermost side. The number of hollow cylinders in the radial direction preferably corresponds to the number of layers of the wound cell, so that in principle one hollow cylinder corresponds to one layer along the entire circumference. In this case, it does not matter that the cell is spirally wound, but the model is composed of completely circular hollow cylinders.

[0051] The temperature model 1 can also be subdivided in its geometric configuration in the axial direction. In the present example, the cylindrical temperature model has four axially arranged cylinders 3, which in turn consist of a plurality of hollow cylinders 2 nested in one another. The number of axial cylinders can be selected arbitrarily. If, for example, no resolution in the axial direction is required, the temperature model can also consist of only a single cylinder 3. Figure 1 In the example shown, the temperature model 1 has four axially successive cylinders 3. Depending on the desired spatial resolution in the axial direction, the number of cylinders 3 can also be greater or less.

[0052] Figure 2 Another embodiment of a cylindrical temperature model for a corresponding cylindrical energy storage device. Here, a rectangular cylinder is selected instead of a cylinder. This means that the end faces of this cylindrical temperature model are rectangular. As an alternative, these end faces can of course also be elliptical, triangular, hexagonal, octagonal, etc. However, these end faces can also adopt any other shape, as long as these end faces are identical and parallel to each other. In any case, these end faces will form a corresponding cylinder.

[0053] exist Figure 2 In the example shown, a cubic temperature model 4 is generated for a cubic energy store. This energy store has a stacking axis 5, along which a plurality of thin plates are stacked. Each thin plate represents a rectangular partial cylinder 6. The individual partial cylinders 6 are not hollow, but are arranged coaxially one after the other, with the stacking axis 5 forming a common axis. If the energy store has a stacked layer structure, then Figure 2The heat or temperature model shown can be used to determine the spatial temperature or heat distribution. It is also particularly advantageous here that the number of partial cylinders corresponds to the actual number of layers of the stacked energy storage. If necessary, a plurality of such temperature models 4 can be used in parallel in order to generate a larger cubic overall temperature model.

[0054] Here, as previously in Figure 1 As in the temperature model 1 shown, a layer corresponds, for example, to an anode, a cathode or a separator. The anode can be further divided into a metal foil and an anode paste as required. The cathode can also be divided into a cathode foil and a cathode paste in a similar manner. Thus, a single wound layer can have, for example, three or five sublayers (without any sheathing). Each sublayer can be represented in the model by a layer (for example a hollow cylinder 2 or a partial cylinder 6).

[0055] Figure 3 A battery pack is shown, which can be used, for example, for an electric tool, such as a rechargeable screwdriver or a rechargeable gardening tool. The battery pack has a socket 7, by means of which it can be attached to the corresponding electric tool. A plurality of cylindrical energy storage devices are arranged inside the housing 8 of the battery pack, for example. Each individual energy storage device can be, for example, a wound lithium-ion cell. The respective thermal model 1 can be similar in terms of its geometric design to the Figure 1 Thermal model shown.

[0056] A battery management system with an interface 9 for an operator can also be integrated into the battery pack. The interface 9 can, for example, display the charge state of the battery pack or implement operating concepts.

[0057] This battery management system can have suitable sensor means for detecting the charging current, the discharging current, the cell voltage, the total voltage of the battery pack, the temperature of one or more cells of the energy storage device, etc. In this way, one or more of the above-mentioned parameters can be detected and further processed as required. In particular, changes in the cell voltage or the total voltage as well as changes in the charging current and changes in the discharging current can be determined in this way. In this case, suitable temperature models based on the geometry, for example Figure 1 or Figure 2 As shown, it is possible to determine the spatial temperature or heat distribution in each energy storage device or each single cell. The temperature model of this battery management system can provide a temperature or heat distribution based on the current operating parameters, which can be used to control the operation of the energy storage device and / or the electrical device that operates with the energy storage device.

[0058] Figure 4 A process sequence is schematically shown, according to which the electrical device can be operated. In this case, the method steps for determining the temperature distribution or heat distribution are an essential component.

[0059] In a first step S1, the structure of the energy storage device is described by means of a cylindrical layout. This description means that the structure or outer contour of the energy storage device is virtually subdivided into a plurality of hollow cylinders or partial cylinders. These individual cylinders are adjacent to each other and exchange heat by heat transfer. Specifically, for example, according to Figure 1 and Figure 2 For the thermal model, a plurality of hollow cylinders coaxially nested and / or adjacent to one another or a plurality of partial cylinders coaxially and / or adjacent to one another parallel to their axes are arranged. This geometric modeling is preferably based on the actual layer structure of the energy store.

[0060] Alternatively, these thermal models can be implemented externally with the same simple geometries that are already used for the interior of the energy store. It is therefore proposed that the geometrical implementation can also be achieved with hollow cylinders or partial cylinders. Figure 1 Thermal model of the energy store shown (adjustment of the boundary value problem). Thus, for example, it is advantageous to model a hollow cylindrical heat sink on the jacket or outer circumference of the energy store for heat dissipation. Similarly, it is advantageous to model a cylindrical heat sink on both end faces of the energy store for heat dissipation.

[0061] According to step S2, a thermal balance can be established for each of these cylinders according to the overall thermal model by means of geometric modeling of energy storage devices based on hollow or partial cylinders (see below). For this purpose, it is usually necessary to detect the current operating parameters according to step S3 and provide them to the overall thermal model (geometric model and thermal balance model). Such operating parameters, which are measured by corresponding sensor means of the energy storage device as required, can be, for example, the charging current, the discharging current, the cell voltage, the total voltage of the energy storage device, the change in the charging current, the change in the discharging current, the change in the cell voltage or the total voltage and / or the change in the measured temperature of one or more cells of the energy storage device.

[0062] In step S4, a spatial temperature distribution or heat distribution is determined for each hollow cylinder or partial cylinder, in particular based on a thermal balance. The spatial resolution of this temperature or heat distribution is generated according to the geometric structure of the thermal model. In this case, it can be assumed that each hollow or partial cylinder has a separate average temperature and / or heat. Thus, for example, a separate temperature can be derived or simulated for each individual layer depending on the operating parameters.

[0063] The temperature or heat distribution modeled or simulated in step S4 can optionally be checked by a measurement in step S5. For example, the temperature on the outer jacket of the energy storage device can be conveniently measured. The modeled temperature on the outer jacket should be comparable to the measured temperature. If this is not the case, a calibration can be performed in step S6. After this calibration, a new temperature distribution or heat distribution can be determined in step S4.

[0064] According to step S7, the temperature distribution or heat distribution provided in step S4, which may be recalibrated as needed, can be used to control or regulate (hereinafter referred to as "control") the energy store or the electrical device operated with it. Specifically, if the temperature in a layer of the energy store is exceeded, for example, this layer or this electrical device can be switched off. If necessary, the power of the electrical device or the power output of the energy store is reduced accordingly.

[0065] The thermal model is described in detail below. Figure 1 In the geometric configuration of the model shown, heat is conducted radially from one hollow cylinder to the next, and in the case of the last outer cylinder, the heat is released to the heat sink (at Figure 1 ). This heat sink is advantageously also modeled as a cylinder and is thermodynamically connected to the environment (ambient temperature). The heat flow flows axially from half the length of the cylinder to the polar cap. There the heat flow is transferred to the heat sink, which is also cylindrical, which in turn is connected to the environment. In this case, the following applies to each hollow cylinder:

[0066] Radial heat conduction:

[0067]

[0068] Axial heat conduction:

[0069]

[0070] Heat storage:

[0071]

[0072] Heat input (here only as an example for uniform input case)

[0073]

[0074] Among them, R m is the thermal conductivity of the hollow cylinder, l is the length, ra is the outer radius, ri is the inner radius of the hollow cylinder, T i and T a is the internal and external temperature of the hollow cylinder. z and T s represents the center temperature and the end surface temperature in the wall of the hollow cylinder. In addition, m represents the mass of each hollow cylinder, c p represents its specific heat capacity, ΔT represents the temperature difference. Finally, I represents current, U represents voltage, t represents time, T represents temperature, and E represents tot represents the total power input, η represents the efficiency, V i represents the volume of each hollow cylinder, V tot Represents the total volume of the cylindrical layout.

[0075] For each time period dt, the heat balance for each individual hollow cylinder also applies:

[0076]

[0077] In the time period dt, the heat is obtained according to the differential variables shown above. In this case, the heat input is marked with "in" and the heat discharged is marked with "out". In addition, Q e represents the heat input achieved by the current through the respective internal resistor.

[0078] The formulas shown above for heat conduction, heat storage, heat input, and heat balance can also be calculated for a solid cylinder in a similar manner. Figure 2 The stacked model shown creates a temperature model.

[0079] The model of the individual hollow cylinders linked in this way allows the temperature of the individual cylinders to be calculated in a time-resolved manner in the radial and axial directions for each time element dt and the voltage drop bU / dt occurring therein, while maintaining the boundary conditions. Advantageously, the model is recalibrated in time by measuring the surface temperature, so that an exact spatial temperature statement can be made for each spatial point of the cell in a model-dependent and time-resolved manner. This makes it possible, for example, to decouple consumers driven by the cell in a timely manner and, for example, to disconnect the applied charging voltage or to adjust the charging current to the calculated temperature in the cell (for example, charging at low temperatures).

[0080] Reference numerals list

[0081] 1 Temperature model

[0082] 2 Hollow Cylinder

[0083] 3 Cylinder

[0084] 4 Temperature model

[0085] 5 Stacking Axis

[0086] 6 Part Cylinder

[0087] 7 Socket

[0088] 8 Housing

[0089] 9 Interface

[0090] S1 First step

[0091] S2 Step 2

[0092] S3 Step 3

[0093] S4 Step 4

[0094] S5 Step 5

[0095] S6 Step 6

[0096] S7 Step 7

Claims

1. A method for determining the temperature distribution or heat distribution in a cylindrical energy storage device, It is characterized in that The structure of the energy store (S1) is described by an arrangement of a plurality of hollow cylinders (2) coaxially nested within one another and / or adjacent to one another, - determining (S4) the respective temperature or heat of each hollow cylinder (2), wherein Quasi-static conditions are assumed in each hollow cylinder (2) at each single observation time point along the time series; - wherein the respective temperature or heat in each hollow cylinder (2) is determined in that a hollow cylindrical heat sink is modeled on the outer circumference of the energy store for heat dissipation.

2. The method according to claim 1, It is characterized in that The energy storage device has the shape of a right circular cylinder and the hollow cylinder (2) is also straight.

3. The method according to claim 1 or 2, It is characterized in that The energy store has the shape of a cylinder, an elliptical cylinder or a prism, and the hollow cylinder is also correspondingly cylindrical, elliptical cylinder or prism-shaped.

4. The method according to claim 1, It is characterized in that The energy store is wound from a number of layers stacked one on top of the other in the radial direction, and the number of the plurality of hollow cylinders (2) corresponds to the number of layers.

5. The method according to claim 1, It is characterized in that The energy store is formed as a stack of multiple layers in a stacking direction, and the number of the multiple hollow cylinders (2) in the stacking direction corresponds to the number of uniform layers.

6. The method according to claim 4, It is characterized in that When determining the respective temperature or heat in each hollow cylinder (2), a separate heat capacity and / or thermal conductivity is assigned to each hollow cylinder (2) or a separate heat capacity and / or thermal conductivity is assigned to each hollow cylinder.

7. The method according to claim 1, It is characterized in that The corresponding temperature or heat in each hollow cylinder (2) is measured by respectively modeling a cylindrical heat sink on the two end faces of the energy store for heat dissipation.

8. The method according to claim 1, It is characterized in that The respective temperature or heat quantity in each hollow cylinder (2) is determined (S2) in a time-discrete manner by means of a heat balance, wherein in the case of cylindrical energy stores, the axial heat conduction, radial heat conduction, heat storage and heat input are determined for each hollow cylinder.

9. The method according to claim 1, It is characterized in that The corresponding temperature or heat in each hollow cylinder (2) is determined based on (S3) the charging current, the discharging current, the single cell voltage, the total voltage of the energy storage device, the change of the charging current, the change of the discharging current, the change of the single cell voltage or the total voltage, the measured temperature, life and / or SOH of one or more single cells of the energy storage device.

10. The method according to claim 1, It is characterized in that When determining ( S4 ) the respective temperature or heat in each hollow cylinder ( 2 ), one or more calibrations ( S6 ) are carried out in conjunction with a respective measurement ( S5 ) of the surface temperature of the energy store.

11. The method according to claim 1, It is characterized in that When determining ( S4 ) the corresponding temperature or heat in each hollow cylinder ( 2 ), a numerical simulation is performed.

12. The method according to claim 11, It is characterized in that The parameters for the numerical simulations were determined by artificial intelligence combined with temperature measurements.

13. A method for controlling or regulating the operation of an energy storage device, comprising measuring (S4) the temperature distribution or heat distribution of the energy storage device according to claim 1 and controlling or regulating (S7) the operation of the energy storage device according to the measured temperature distribution or heat distribution. 14 . The method according to claim 13 , wherein a power output of the energy store to an electrical consumer or a charging current or a charging voltage of the energy store is controlled as a function of the determined temperature distribution or heat distribution. 15 . An energy store having a control device for carrying out the method according to claim 1 . 16 . The energy store according to claim 15 , comprising a plurality of individual cells, each of which is modeled by the hollow cylinder ( 2 ).

17. An electric tool having an energy storage device according to claim 15. 18 . A computer program product comprising instructions for causing an energy storage device according to claim 15 or a power tool according to claim 17 to execute the method steps according to claim 1 .

Images