BATTERY SYSTEM AND METHOD FOR HOMOGENEOUS TEMPERATURE DISTRIBUTION WITHIN THE BATTERY SYSTEM, USE OF THE BATTERY SYSTEM AND VEHICLE WITH IT

Description

State of the art

[0001] The invention relates to a battery system and a method for homogeneous temperature distribution within the battery system.

[0002] Batteries for mobile applications typically comprise a large number of battery cells. These battery cells are limited in terms of voltage and permissible currents. To achieve the total voltage and capacity required for a given application, the individual battery cells are connected in a specific way. A series connection increases the required total voltage, while a parallel connection increases the required total capacity and permissible total currents.

[0003] To achieve the highest possible energy density, individual battery cells are arranged close together in a battery cell array. During operation, each individual battery cell exhibits a certain power loss. This power loss is dissipated as waste heat into the interior of the battery housing. Since the waste heat can be dissipated to the environment to varying degrees at different points within the battery, an inhomogeneous temperature distribution develops within a closed battery housing.

[0004] The disadvantage here is that the battery's performance and lifespan are affected.

[0005] The individual battery cells can only be operated safely up to a certain temperature. Neither during charging nor discharging may the individual battery cells exceed this specific temperature to ensure battery safety. If a battery cell reaches this specific temperature during discharge, the discharge current is reduced. When the battery is in charging mode, the charging process only starts if the current temperature of the battery cells is below this specific temperature.

[0006] Due to the uneven temperature distribution, only some battery cells operate at the limit of their permissible operating temperature, while other cells remain at moderate temperatures. However, the battery management system reduces the power output of the entire battery as soon as a single cell reaches the critical temperature limit.

[0007] The disadvantage here is that the battery power is throttled prematurely.

[0008] Operating temperature also plays a crucial role in the lifespan of a battery cell. Battery cells age very rapidly at high operating temperatures. Due to the uneven temperature distribution within the sealed battery casing, cells operating at lower temperatures age significantly more slowly than those operating at higher temperatures. Since the cells in such a battery pack are not replaceable, the entire battery is decommissioned once a certain number of cells have reached the end of their service life. At this point, however, all other remaining cells could still be safely operated for a period of time.

[0009] To overcome these disadvantages, various cooling methods are used. In most cases, air cooling or liquid cooling is employed. For this purpose, air is drawn in from the surrounding environment by a fan and passed over the battery cells. The drawn-in air is heated by the waste heat from the individual battery cells and, after passing through the battery cell assembly, exits the battery casing through an outlet. The heat is thus dissipated into the surrounding environment.

[0010] Document US 2003198864 A1 describes an electrochemical battery comprising a battery casing containing a multitude of battery cells and a central fan. The fan generates an airflow between an air inlet and an air outlet of the battery casing, which is directed over the battery cells, thereby regulating the cell temperature.

[0011] Document US 2013149583 A1 discloses a battery system comprising a plurality of electrical cells, a battery casing, and a fan. A portion of the battery casing located below the battery cells includes an air inlet. The side walls, as well as a portion of the battery casing above the battery cells, feature air outlets.

[0012] A disadvantage of both documents is that air inlet and outlet openings must be incorporated into the battery housing. Another disadvantage is that this can make the battery housing leaky.

[0013] The purpose of the invention is to overcome these disadvantages.

[0014] The state of the art in this regard is also represented by the publications US 2013 / 149583 A1 and US 2017 / 069888 A1. Disclosure of the invention

[0015] A battery system comprises a metallic battery housing with a base body having a first cover element and a second cover element. The first cover element closes a first open end face of the base body. The second cover element closes a second open end face of the base body. The battery housing is hermetically sealed from the environment. The battery system includes a battery cell holder comprising a plurality of battery cells, the battery cell holder being arranged within the battery housing, and a battery management system configured to monitor the plurality of battery cells and to detect the temperatures of the individual battery cells. According to the invention, at least one fan is arranged within the battery housing, and the at least one fan can be controlled by the battery management system depending on whether a temperature threshold of the individual battery cells is exceeded.In other words, the temperature redistribution within the closed battery housing occurs through a circulating air movement of the heat generated in the battery or battery system.

[0016] The advantage here is that the waste heat generated by the operation of the battery cells is distributed homogeneously within the battery, and this homogeneously distributed heat is dissipated to the environment through the casing surface. This ensures that the individual battery cells age uniformly and that battery performance only becomes throttling after extended periods of operation. This results in moderate heating of all battery cells, rather than rapid heating of the battery's center and slow heating of the outer areas. Furthermore, the improved temperature distribution and rapid cooling of the battery allow it to quickly reach a chargeable state. Another advantage is that no openings are required for the inlet and outlet of a cooling fluid. Additionally, neither evaporators nor condensers are needed, resulting in a lightweight and cost-effective overall system.The battery system is therefore also suitable for small battery applications such as 48V systems.

[0017] In a further training course, at least one fan is arranged between the battery housing and the battery cell holder.

[0018] The advantage here is that the arrangement is space-neutral compared to a battery housing with battery cell holder without a fan, since the fan is located in a free space between the battery housing and the battery cell holder.

[0019] According to the invention, at least one fan is arranged on the battery cell holder.

[0020] The advantage here is that the battery cell holder does not need to be structurally modified.

[0021] In a further training course, at least one fan is designed in the form of a radial fan.

[0022] The advantage here is that the fan can be specifically positioned at temperature-critical points on the battery.

[0023] In a further embodiment, the second cover element has at least one additional fan. In other words, the at least one additional fan is arranged on the second cover element inside the battery housing.

[0024] The advantage here is that the space required for at least one additional fan is limited only by the size of the second cover element. Therefore, large airflows can be generated.

[0025] In a further education course, the basic body is a continuous casting element.

[0026] The advantage here is that the battery casing can be manufactured in a simple and cost-effective way.

[0027] In another embodiment, the battery housing comprises aluminum.

[0028] The advantage here is that the homogeneously distributed heat inside the battery housing can be quickly dissipated to the outside, i.e., outside the battery housing, through the thermally conductive surface of the base body.

[0029] The inventive method for homogeneous temperature distribution within a battery system, wherein the battery system comprises a battery housing, a battery cell holder with a plurality of battery cells, wherein the battery cell holder is arranged within the battery housing and has a battery management system configured to monitor the plurality of battery cells and detect temperature differences between the individual battery cells, comprises at least one fan within the battery housing being controlled by the battery cell management system depending on the temperature differences between the individual battery cells.

[0030] The battery system according to the invention is used in an electric vehicle, in particular an electrically powered two-wheeler.

[0031] The vehicle according to the invention, in particular an electrically powered two-wheeler, has the battery system according to the invention.

[0032] Further advantages arise from the following description of exemplary embodiments or the dependent patent claims. Brief description of the drawings

[0033] The present invention is explained below with reference to preferred embodiments and the accompanying drawings. These show: Figure 1 shows a top view of a temperature distribution of a battery system with a plurality of battery cells connected in series and parallel to each other, Figure 2 shows a battery system with at least one fan, Figure 3 shows the thermal behavior of a battery system according to the invention with a fan, wherein the volume flows of the fan are different, and Figure 4 shows a method for homogeneous temperature distribution within a battery system with at least one fan.

[0034] Figure 1Figure 1 shows a top view of an exemplary temperature distribution of a 48 V battery system 100 with a plurality of battery cells 105. The battery system comprises thirteen rows of fifteen battery cells 105 each, connected in parallel to form a battery cell array. Each battery cell 105 provides a voltage of approximately 3.6 V, so the battery can deliver a total voltage of 48 V. Due to the close arrangement of the battery cells 105, different temperature ranges result within the battery system 100 during operation due to the waste heat emitted by the individual battery cells. Figure 1 Battery casing not shown. Examples include: Figure 1The first temperature ranges 120, a second temperature range 121, a third temperature range 122, and a fourth temperature range 123 are shown. The first temperature ranges 120 have a lower temperature than the second temperature range 121 and the third temperature range 122. The fourth temperature range 123 is the coldest. This is because the battery cells 105, which are located at the edge of the battery cell assembly, can dissipate heat to the battery housing more quickly than the battery cells 105, which are located in the interior of the battery cell assembly. The battery management system 109 also acts as a heat source.

[0035] Figure 2Figure 1 shows a battery system 200 with a battery housing comprising a base body 201, a first cover element 202, and a second cover element 203. The first cover element 202 closes a first open end face of the base body 201 and includes a battery management system (not shown). The second cover element 203 closes a second open end face of the base body 201. Thus, the battery housing forms a closed space that serves as a receiving space for a battery cell holder 204. The battery housing is therefore sealed or airtight from the environment. The battery cell holder 204 does not completely fill the receiving space of the battery housing. This means that the battery housing and the battery cell holder 204 are arranged parallel to each other with a distance between their end faces. In other words, there are empty spaces above and below the battery cell holder received in the battery housing.Cavities. The battery cell holder 204 has receiving areas for a plurality of battery cells 205. The at least one fan 206 is arranged between the battery cell holder 204 and the battery housing. The fan 206 can, for example, be arranged on the battery cell holder 204 and is, for example, a radial fan. At least one receiving area of ​​the battery cell holder 204, which is located directly below the at least one fan, does not contain any battery cells. This means that the receiving area is empty and functions as an air intake area for the fan 206. This allows the battery cell holder 204 to draw in heat or warm air.Warm air circulation is facilitated by the presence of gaps between the first cover element 202 and the battery cell holder 204, as well as between the battery cell holder 204 and the second cover element 203. These gaps are created by damping materials positioned at these points. This allows the fan 206 to generate circulating air within the battery housing. The airflow simply recirculates the air within the battery. This exchanges the warm air between high and low temperature zones within the battery, thus equalizing the temperature levels. In other words, the waste heat from the battery cells 205 is redistributed within the battery. To further improve heat distribution, additional recesses in the battery cell holder 204 are left open; that is, no battery cells are inserted into these recesses.These include, for example, intake areas located close to the fan 206. Alternatively or additionally, the battery cell holder can have air channels arranged between the individual battery cells 205 in the battery cell holder 204, ensuring optimal airflow around each battery cell 205. These air channels can also be present only in those areas of the battery cell holder 204 where the operating temperature of the battery cells 205 is very high, for example, in the area shown in . Figure 1 The third temperature range shown is 122. Alternatively or additionally, another fan can be arranged on the second cover element 203.

[0036] The circulation is shown using arrows. Figure 2The battery housing is represented by the battery cell holder 204 located below the fan 206. Temperatures within the battery housing are measured, for example, using NTCs at various points within the battery cell array. The fan 206 is controlled by the battery management system when the temperature of the battery cells 205 exceeds a certain threshold. This air circulation directs the air along the base of the battery housing, allowing the redistributed heat to be passively dissipated via the surface of the battery housing.

[0037] The battery housing's base body 201 is a single, tubular piece made of metal. This metal could be, for example, aluminum or manganese. The base body 201 can be manufactured using a continuous casting process.

[0038] The invention can also be used at the module level, whereby the battery cells are replaced by battery modules. In this case, the fan is arranged within the individual battery modules, each of which has its own housing.

[0039] Another embodiment involves installing a fan at the battery pack level to homogenize the temperature of the individual battery modules. In this case, the battery cell holder must be replaced by a mounting element for battery modules or designed in such a way that it can accommodate battery modules.

[0040] The battery system is used, for example, in an electrically powered two-wheeler. Furthermore, the battery system can also be used in stationary devices, e.g., in domestic energy storage systems.

[0041] Figure 3Figure 300 shows the thermal behavior of a battery system with a fan, where the fan's airflow rates vary. The heat dissipation of each battery cell is approximately 1.36 W. The figure depicts the operating state during a discharge process, when a temperature threshold of 60°C is reached or exceeded for the first time at a point in the battery. This generally occurs in one of the centrally located battery cells. Figure 3 shows the thermal behavior of the Figure 1The known temperature ranges are: the first temperature range 120, the second temperature range 121, the third temperature range 122, and the fourth temperature range 123. The abscissa represents the individual temperature ranges, and the ordinate the corresponding temperature values. A first curve 301 represents the thermal behavior of the battery without a fan. A second curve 302 shows the thermal behavior of the battery with a fan that has a volume flow rate of 0.72 m³ / h. The shape of the curves in temperature ranges 120 and 121 can be explained by the fact that, due to the low volume flow rate of the fan, the outer regions have already heated up when the center of the battery reaches 60°C.A third curve 303 shows the thermal behavior of the battery with a fan having a volume flow rate of 3.18 m³ / h, and a fourth curve 304 shows the thermal behavior of the battery with a fan having a volume flow rate of 9.6 m³ / h. The temperature differences within the battery are thus reduced from 21.6 K to 16.4 K, meaning there is a significant homogenization of the temperature distribution within the battery casing.

[0042] Figure 4Disclosing a method 400 for achieving a homogeneous temperature distribution within a battery system with at least one fan, the battery system comprises a battery housing, a battery cell holder with a plurality of battery cells arranged within the battery housing, and a battery management system configured to monitor the plurality of battery cells. Method 400 begins with step 410, in which the battery management system detects the temperatures of the individual battery cells. In a subsequent step 420, it is checked whether any of the temperatures exceed a certain threshold. The predetermined threshold is, for example, a maximum permissible operating temperature or limit temperature of the battery cell specified by the battery cell manufacturer. Alternatively, it can also be specified by the battery system for the current operating state of the battery, i.e., charging or discharging.The defined threshold for the charging process is 40°C, and for the discharging process, it is approximately 60°C. If the defined threshold is reached, at least one fan is activated in the subsequent step 440. If this is not the case, the process continues with step 410.

[0043] If the battery system has multiple fans, step 430, which follows step 420, determines the area of ​​the battery cell array where at least one battery cell exceeds its temperature threshold. In the subsequent step 440, the fan(s) closest to this affected area, or those capable of redistributing the heat most quickly, are activated. Fans are operated simultaneously in both the hotter and colder areas, creating a high temperature gradient that leads to rapid cooling and homogenization of the temperature distribution within the battery system.

Claims

1. Battery system (200) having • a metal battery housing which comprises a main body (201), a first cover element (202) and a second cover element (203), wherein the first cover element (202) closes a first open end face of the main body (201) and the second cover element (203) closes a second open end face of the main body (201) in an airtight manner with respect to the environment, • a battery cell holder (204) which has a plurality of battery cells (205), wherein the battery cell holder (204) is arranged within the battery housing, and • a battery management system (109) which is configured to monitor the plurality of battery cells (205) and to record the temperatures of the individual battery cells (205), • wherein at least one fan (206) is arranged within the battery housing and the at least one fan (206) can be actuated by the battery management system (109) as a function of the temperatures of the individual battery cells (205) exceeding a threshold value, characterized in that the at least one fan (206) is arranged on the battery cell holder (204).

2. Battery system (200) according to Claim 1, characterized in that the at least one fan (206) is arranged between the battery housing and the battery cell holder (204).

3. Battery system (200) according to any of the preceding claims, characterized in that the at least one fan (206) is a radial fan.

4. Battery system (200) according to any of the preceding claims, characterized in that the second cover element (203) has at least one further fan.

5. Battery system (200) according to any of the preceding claims, characterized in that the main body (201) is an extruded element.

6. Battery system (200) according to any of the preceding claims, characterized in that the battery housing comprises aluminium.

7. Method (400) for homogeneous temperature distribution within a battery system according to any of Claims 1 to 6, characterized in that the at least one fan is actuated by the battery management system as a function of the temperatures of the individual battery cells exceeding a threshold value.

8. Use of a battery system (200) according to any of Claims 1 to 6 in an electric vehicle, in particular an electrically operated two-wheeled vehicle.

9. Vehicle, in particular an electrically operated two-wheeled vehicle, having a battery system (200) according to any of Claims 1 to 6.