Electric vehicle, battery pack system thereof, and method for charging the battery pack system

Abstract

The present invention relates to an electric vehicle and a battery system thereof, and a method for charging the battery system. The present invention relates to a battery system (10) for an electric vehicle, the battery system comprising: a plurality of battery modules (5); and a first heating device (51) for directly heating a first group (61) of battery modules (5), wherein each battery module (5) has at least one battery cell, and wherein the first group (61) of battery modules (5) is spatially surrounded on at least two sides by other groups (62, 63, 64, 65) of battery modules (5), and wherein the battery modules (5) are spatially arranged so that waste heat generated when the first group (61) of battery modules (5) is heated and / or when the first group (61) of battery modules (5) is charged is transferred to the other groups (62, 63, 64, 65) of battery modules (5).

Description

Technical Field

[0001] The present invention relates to a battery system for an electric vehicle, comprising: a plurality of battery modules; and a first heating device for directly heating the first group of battery modules, wherein each battery module comprises at least one battery cell. The present invention also relates to a method for charging the battery system according to the present invention. The present invention also relates to an electric vehicle comprising the battery system according to the present invention, which can be operated using the method according to the present invention. Background Art

[0002] It appears that electrically driven vehicles will be used more and more in the future. In electrically driven vehicles, such as electric vehicles and hybrid vehicles, but also in stationary applications, rechargeable battery systems are used primarily to supply electrical energy to the electric drive. Battery systems with lithium battery cells are particularly suitable for such applications. Lithium battery cells are characterized in particular by their high energy density, thermal stability, and extremely low self-discharge. A plurality of such lithium battery cells are electrically connected in series and in parallel to form battery modules. A plurality of such battery modules are connected to form a battery branch, in particular in series to form a battery branch. A plurality of battery branches constructed in this way are connected to one another, in particular in parallel, and thus form a battery system for an electric vehicle.

[0003] New technology lithium-ion battery cells have a solid electrolyte and a relatively high energy density. The chemical composition of these lithium-ion battery cells is highly reactive, but they only operate optimally within a certain temperature range, for example, above 50°C, particularly above 70°C, and below 90°C. Battery systems with these lithium-ion battery cells are also known as medium-temperature batteries (Mid-T batteries) and have a relatively high internal resistance outside of this temperature range. Therefore, mid-T batteries do not operate optimally outside of this temperature range.

[0004] Therefore, such battery systems used in electric vehicles are subject to limitations at low temperatures. This applies both to the charging process and to the discharging process of the battery cells of the battery system. However, battery systems used in electric vehicles must also be quickly ready for charging and discharging processes at low temperatures.

[0005] Documents US2012 / 295142A1 and DE 102009046567A1 describe a battery system and a temperature control method for generating an optimal temperature range for operating the battery system. In this method, a first module of the battery system is heated during a heating phase, and the heat generated during operation of the first module is used to heat another module.

[0006] A charging system for an electric vehicle is known from document US 2015 / 061605 A1, which includes a battery pack for storing electrical energy and a heating device for heating the battery pack.

[0007] US 2015 / 077057 A1 discloses a method for charging a battery pack. First, a determination is made as to whether a fast charging process with a high charging rate is possible. If so, the fast charging process is performed. Otherwise, a charging process with a reduced charging rate is performed.

[0008] US 2017 / 133731 A1 describes a battery system with two battery packs. At low temperatures, the first battery pack provides electrical energy to heat the second battery pack. If the second battery pack is sufficiently warm, the second battery pack provides electrical energy to charge the first battery pack. Summary of the Invention

[0009] A battery system for an electric vehicle is proposed. The battery system includes: a plurality of battery modules; and a first heating device for directly heating the first battery modules. This means that the first heating device is designed and arranged such that heat released by the first heating device is directly and almost exclusively transferred to the first battery modules, thereby directly heating the first battery modules.

[0010] Each battery module has at least one battery cell, preferably a plurality of battery cells, which can be electrically connected in series and in parallel. These battery cells are, for example, lithium battery cells with a solid electrolyte. These lithium battery cells can only be optimally operated within a certain temperature range, for example, above 50°C, in particular above 70°C, and below 90°C. In particular, charging of the battery cells is optimally possible only within this temperature range.

[0011] The battery modules of the first group are spatially surrounded on at least two sides by battery modules of the other groups. The battery modules are spatially arranged such that waste heat generated when heating and / or charging the battery modules of the first group is transferred to the battery modules of the other groups. Preferably, the battery modules of the first group are arranged centrally and surrounded on both sides by at least one battery module of the other group.

[0012] Preferably, the battery modules in the first group of battery modules are connected in series and form a battery branch. Similarly, the battery modules in the other groups of battery modules are preferably connected in series and form battery branches. Thus, the battery system includes a plurality of battery branches, which are preferably electrically connected in parallel, wherein each battery branch includes a group of battery modules.

[0013] According to an advantageous embodiment of the present invention, at least one further heating device is provided for heating the battery modules. This further heating device may, for example, directly heat only the battery modules of the other groups. However, this further heating device may also, for example, directly heat the battery modules of all groups, including the first group. The first heating device and the at least one further heating device can be activated independently of each other.

[0014] Preferably, at least one cooling device is provided for cooling the battery modules of the battery system. The cooling device can be used to cool all groups of battery modules simultaneously. However, the cooling device can also be used to cool individual groups of battery modules individually.

[0015] A method for charging a battery system according to the invention is also proposed. The method according to the invention comprises at least one of the steps mentioned below.

[0016] First, the first group of battery modules is heated by the first heating device and the group temperature of the first group of battery modules is measured.

[0017] Subsequently, if the pack temperature of the first battery module has reached a predetermined minimum temperature, the first battery module is charged with the first charging current.

[0018] Here, waste heat generated when heating and / or charging the battery modules of the first group is also transferred to the battery modules of the other groups. This waste heat is particularly transferred to the battery modules of the groups whose battery modules of the first group are spatially surrounded on at least two sides by the battery modules of the other groups, i.e., the battery modules of the other groups are arranged in close proximity to the battery modules of the first group. Here, the other group temperatures of the battery modules of the other groups are also measured.

[0019] Subsequently, if the group temperature of the battery modules of at least one other group has reached a predefined minimum temperature, the battery modules of this other group are charged with a further charging current.

[0020] Preferably, the charging current to a group of battery modules is switched off at the latest when the group temperature of the battery modules has reached a predetermined maximum temperature. If necessary, the charging current to a group of battery modules is already switched off when the battery cells of these battery modules are fully charged.

[0021] According to an advantageous embodiment of the present invention, before charging at least one additional group of battery modules with a further charging current, the battery modules of the further group are additionally heated by a further heating device. This allows the group temperature of the battery modules of the further group to reach the minimum temperature earlier, and charging can begin earlier.

[0022] Optionally, if a group of battery modules has reached a predetermined maximum temperature, the group of battery modules can be cooled by a cooling device. As a result, the group temperature of the battery modules drops below the maximum temperature again and charging can continue.

[0023] According to an advantageous embodiment of the present invention, the charging current of a group of battery modules is varied as a function of the pack temperature of the group of battery modules. The charging current of the group of battery modules is varied such that the pack temperature of the group of battery modules remains between a minimum temperature and a maximum temperature, and the charging current of the group of battery modules is varied such that the battery cells in the battery modules of the group are charged as quickly as possible.

[0024] Preferably, if the group temperature of a group of battery modules is equal to the lowest temperature, the charging current of the group of battery modules has the minimum current value. When the group temperature of the group of battery modules increases, the charging current increases.

[0025] According to a preferred embodiment of the present invention, the charging current of a group of battery modules starts to increase continuously at the minimum current value until the group temperature of the battery modules reaches a threshold temperature, which is greater than the minimum temperature but less than the maximum temperature.

[0026] Preferably, the charging current of a group of battery modules is increased such that a profile of the charging current of the group of battery modules as a function of the group temperature of the group of battery modules has a turning point at a threshold temperature.

[0027] If the pack temperature of a group of battery modules is equal to the threshold temperature, the charging current of the group of battery modules has a threshold value. If the pack temperature of the group of battery modules is greater than the threshold temperature and less than the maximum temperature, the charging current of the group of battery modules is greater than the mentioned threshold value.

[0028] An electric vehicle is also proposed, which comprises a battery system according to the invention and which can be operated using the method according to the invention.

[0029] Advantages of the present invention

[0030] By means of the method according to the invention, the battery system according to the invention can be brought to an operating temperature at which the battery cells can operate optimally, even at low ambient temperatures. In particular, the battery cells can be charged relatively quickly even at low ambient temperatures and after long periods of inactivity. As a result, an electric vehicle with a battery system according to the invention is ready for driving relatively quickly even at low ambient temperatures, thereby increasing its availability. By means of the method according to the invention, the battery cells of the battery system according to the invention are heated and charged uniformly and economically. In addition, by means of the method according to the invention, excessive heating of the battery system according to the invention during charging of the battery cells is largely avoided. It is generally not necessary to cool the battery cells during charging, thereby reducing the cost of cooling the battery system according to the invention. As a result, the energy balance of the battery system according to the invention is improved and operating costs are saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the present invention are further explained with reference to the drawings and the following description.

[0032] in:

[0033] Figure 1 shows a schematic diagram of a battery module having a plurality of battery cells;

[0034] Figure 2 A schematic diagram of a battery system having multiple battery branches is shown;

[0035] Figure 3 A schematic diagram showing the change process of the group temperature of a group of battery modules during charging; and

[0036] Figure 4 Shown according to Figure 3 Schematic diagram of the change of charging current with group temperature. DETAILED DESCRIPTION

[0037] In the following description of the embodiments of the present invention, identical or similar elements are denoted by the same reference numerals, wherein a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the present invention.

[0038] Figure 1A schematic diagram of a battery module 5 having a plurality of battery cells 2 is shown. In the present case, the battery cells 2 are electrically connected in series within the battery module 5. Each battery cell 2 comprises an electrode unit, each having an anode and a cathode. The anode of the electrode unit is connected to the negative terminal 15 of the battery cell 2. The cathode of the electrode unit is connected to the positive terminal 16 of the battery cell 2. To connect the battery module 5 in series, the negative terminal 15 of the battery cell 2 is electrically connected to the positive terminal 16 of the adjacent battery cell 2.

[0039] The battery cells 2 of the battery module 5 each have a solid electrolyte and are designed as medium-temperature batteries or Mid-T batteries. The battery cells 2 mentioned can only be operated optimally within a certain temperature range, for example above 50°C, in particular above 70°C, and below 90°C.

[0040] Figure 2 A schematic diagram of a battery system 10 for an electric vehicle is shown having a plurality of battery branches 6. In the present case, the battery branches 6 are electrically connected in parallel. Each of the battery branches 6 of the battery system 10 comprises a Figure 1 A plurality of battery modules 5 are shown in FIG. 1 , which are electrically connected in series with one another.

[0041] In the present case, the battery modules 5 of the battery system 10 are organized into five groups 61, 62, 63, 64, 65. The battery system 10 thus comprises a first group 61 of battery modules 5, a second group 62 of battery modules 5, a third group 63 of battery modules 5, a fourth group 64 of battery modules 5, and a fifth group 65 of battery modules 5. In the present case, the battery modules 5 of each group 61, 62, 63, 64, 65 each form one of the aforementioned battery strings 6.

[0042] The first group 61 of battery modules 5 is spatially surrounded on one side by the second group 62 and on the opposite side by the third group 63. The fourth group 64 is arranged on the side of the second group 62 facing away from the first group 61. The fifth group 65 is arranged on the side of the third group 63 facing away from the first group 61.

[0043] The battery system 10 also includes a first heating device 51 for directly heating the first group 61 of battery modules 5. In the present case, the first heating device 51 includes a heating element 55 in the form of an electrically drivable heating resistor and a fluid circuit 57 that transports heat from the heating element 55 to the first group 61 of battery modules 5.

[0044] The battery system 10 further comprises a further heating device 52 for directly heating the battery modules 5 of all groups 61, 62, 63, 64, 65. In the present case, the further heating device 52 also comprises a heating element 55 in the form of an electrically drivable heating resistor and a fluid circuit 57 which transports heat from the heating element 55 to the battery modules 5 of all groups 61, 62, 63, 64, 65.

[0045] The battery system 10 further comprises a cooling device (not shown here) for cooling the battery modules 5 of all groups 61, 62, 63, 64, 65 of the battery system 10. The cooling device comprises, for example, a coolant circuit (not shown here).

[0046] The battery modules 5 are spatially arranged such that the waste heat generated when heating the first group 61 of battery modules 5 is transferred to the second group 62 of battery modules 5 and the third group 63 of battery modules 5. Similarly, the waste heat generated when heating the second group 62 of battery modules 5 is transferred to the fourth group 64 of battery modules 5. The waste heat generated when heating the third group 63 of battery modules 5 is transferred to the fifth group 65 of battery modules 5. Thus, the first group 61 is already located in the center and is surrounded by the other groups 62, 63, 64, and 65.

[0047] When charging the first group 61 of battery modules 5, a first charging current I1 flows through the first group 61. When charging the second group 62 of battery modules 5, a second charging current I2 flows through the second group 62. When charging the third group 63 of battery modules 5, a third charging current I3 flows through the third group 63. When charging the fourth group 64 of battery modules 5, a fourth charging current I4 flows through the fourth group 64. When charging the fifth group 65 of battery modules 5, a fifth charging current I5 flows through the fifth group 65.

[0048] The charging currents I1, I2, I3, I4, and I5, as well as the heating current for heating the heating element 55, are provided by a charging station (not shown). The battery pack system 10 also includes a battery pack controller 70 for controlling the charging currents I1, I2, I3, I4, and I5 and the heating current. The battery pack system 10 also includes sensors (not shown) for individually detecting a pack temperature T for each of the battery pack modules 5 (groups 61, 62, 63, 64, and 65). The sensors are connected to the battery pack controller 70.

[0049] A distinction is made between two modes for charging the battery system 10, namely standard charging and fast charging. If there is sufficient time available to charge the battery modules 5, for example, several hours, standard charging is selected. If there is only a relatively short time available to charge the battery modules 5, for example, less than an hour, fast charging is selected.

[0050] During standard charging of the battery system 10, the group temperature T of the battery modules 5 in the groups 61, 62, 63, 64, and 65 is detected. If the group temperature T is less than a minimum temperature Tmin, all the battery modules 5 in the groups 61, 62, 63, 64, and 65 are first heated by a further heating device 52. If the group temperature T has reached the minimum temperature Tmin, the groups 61, 62, 63, 64, and 65 are charged with charging currents I1, I2, I3, I4, and I5. The charging currents I1, I2, I3, I4, and I5 are relatively low and correspond to a C-rate of less than 1C. As the group temperature T increases, the charging currents I1, I2, I3, I4, and I5 are increased, for example, to a C-rate of 1C.

[0051] During rapid charging of the battery system 10, the group temperature T of the battery modules 5 in the groups 61, 62, 63, 64, and 65 is also detected. If the group temperature T is greater than the minimum temperature Tmin, the battery modules 5 in the groups 61, 62, 63, 64, and 65 are charged with charging currents I1, I2, I3, I4, and I5. The charging currents I1, I2, I3, I4, and I5 are relatively high and correspond to a C-rate of, for example, 3C. The battery modules 5 are optionally cooled by a cooling device.

[0052] If the pack temperature T of the first group 61 of battery modules 5 is less than the minimum temperature Tmin, the first group 61 is first heated by the first heating device 51. If the pack temperature T of the first group 61 has reached the minimum temperature Tmin, the first group 61 is charged with the first charging current I1. Here, the first charging current I1 initially has a minimum current value Imin, which increases, for example, as the pack temperature T increases, up to a C-rate of 3C.

[0053] When charging of the first group 61 of battery modules 5 begins, heating of the first group 61 by the first heating device 51 ends. If the group temperature T of the first group 61 of battery modules 5 has reached a predetermined maximum temperature Tmax, the first charging current I1 is switched off.

[0054] The waste heat generated when heating and charging the first group 61 of battery modules 5 is transferred to the second group 62 of battery modules 5 and the third group 63 of battery modules 5, which are arranged in the immediate vicinity of the first group 61. The group temperatures T of the second group 62 and the third group 63 are also measured.

[0055] If the group temperature T of the second group 62 reaches the minimum temperature Tmin, the second group 62 is charged with the second charging current I2. The second charging current I2 initially has a minimum current value Imin, which increases, for example, as the group temperature T increases, up to a C-rate of 3°C. If the group temperature T of the second group 62 reaches the maximum temperature Tmax, the second charging current I2 is shut off. A similar situation applies to the third group 63.

[0056] The waste heat generated when charging the second group 62 and the third group 63 is transferred to the fourth group 64 of battery modules 5, which is arranged in close physical proximity to the second group 62, and the fifth group 65 of battery modules 5, which is arranged in close physical proximity to the third group 63. The group temperatures T of the fourth group 64 and the fifth group 65 are also measured.

[0057] If the group temperature T of the fourth group 64 reaches the minimum temperature Tmin, the fourth group 64 is charged with the fourth charging current I4. Here, the fourth charging current I4 initially has a minimum current value Imin, which increases, for example, as the group temperature T increases, up to a C-rate of 3°C. If the group temperature T of the fourth group 64 reaches the maximum temperature Tmax, the fourth charging current I4 is shut off. A corresponding situation applies to the fifth group 65.

[0058] The charging currents I1, I2, I3, I4, and I5 of a group 61, 62, 63, 64, and 65 of battery modules 5 vary depending on the group temperature T of the corresponding group 61, 62, 63, 64, and 65. Here, if the group temperature T of the corresponding group 61, 62, 63, 64, and 65 is equal to the minimum temperature Tmin, the corresponding charging current I1, I2, I3, I4, and I5 has a minimum current value Imin. As the group temperature T increases, the charging currents I1, I2, I3, I4, and I5 are increased.

[0059] Starting at the minimum current value Imin, the charging currents I1, I2, I3, I4, and I5 are first increased continuously until the group temperature T of the groups 61, 62, 63, 64, and 65 is equal to the threshold temperature Tsch. Here, the threshold temperature Tsch is greater than the minimum temperature Tmin and less than the maximum temperature Tmax.

[0060] The variation of the charging currents I1, I2, I3, I4, I5 according to the pack temperature T has a turning point at the threshold temperature Tsch. If the pack temperature T is equal to the threshold temperature Tsch, the charging currents I1, I2, I3, I4, I5 have the threshold value Isch.

[0061] If the pack temperature T is greater than the threshold temperature Tsch and less than the maximum temperature Tmax, the charging currents I1, I2, I3, I4, I5 are greater than the threshold value Isch. The charging currents I1, I2, I3, I4, I5 are varied such that the pack temperature T remains between the minimum temperature Tmin and the maximum temperature Tmax, with the battery cells 2 in the battery modules 5 of the packs 61, 62, 63, 64, 65 being charged as quickly as possible.

[0062] Figure 3 The diagram shows the course of the pack temperature T of a group 61, 62, 63, 64, 65 of battery modules 5 during charging. At the start time tStart, the pack temperature T of the groups 61, 62, 63, 64, 65 has reached a minimum temperature Tmin. During charging with the charging currents I1, I2, I3, I4, I5, the pack temperature T of the groups 61, 62, 63, 64, 65 increases. If the pack temperature T of the groups 61, 62, 63, 64, 65 reaches a maximum temperature Tmax at the end time tEnd, the charging currents I1, I2, I3, I4, I5 are shut off.

[0063] Figure 4 Shown according to Figure 3 Schematic diagram of the change in charging currents I1, I2, I3, I4, and I5 as a function of group temperature T for respective groups 61, 62, 63, 64, and 65. If the group temperature T is equal to the minimum temperature Tmin, the charging currents I1, I2, I3, I4, and I5 have a minimum current value Imin. If the group temperature T is greater than the minimum temperature Tmin and less than the threshold temperature Tsch, the charging currents I1, I2, I3, I4, and I5 have values ​​between the minimum current value Imin and the threshold value Isch. If the group temperature T is equal to the threshold temperature Tsch, the charging currents I1, I2, I3, I4, and I5 have a threshold value Isch. If the group temperature T is greater than the threshold temperature Tsch, the charging currents I1, I2, I3, I4, and I5 have values ​​between the threshold value Isch and the maximum current value Imax.

[0064] In the range between the minimum temperature Tmin and the threshold temperature Tsch, the profiles of the charging currents I1, I2, I3, I4, and I5 curve to the left. In the range between the threshold temperature Tsch and the maximum temperature Tmax, the profiles of the charging currents I1, I2, I3, I4, and I5 curve to the right. Therefore, depending on the pack temperature T, the profiles of the charging currents I1, I2, I3, I4, and I5 have a turning point at the threshold temperature Tsch.

[0065] The battery cells 2 have a temperature-dependent internal resistance. At a threshold temperature Tsch, the internal resistance of the battery cells 2 is minimal. Therefore, if the charging currents I1, I2, I3, I4, and I5 are less than the threshold value Isch, minimal waste heat is generated during charging of the battery modules 5. This waste heat is used to heat the battery modules 5 of the other groups 62, 63, 64, and 65. If the charging currents I1, I2, I3, I4, and I5 are greater than the threshold value Isch, a greater amount of waste heat is generated, which is then used to more intensely heat the battery modules 5 of the other groups 62, 63, 64, and 65.

[0066] The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope of protection indicated by the claims, numerous variations are possible, which are within the purview of a person skilled in the art.

Claims

1. A battery pack system (10) for an electric vehicle, the battery pack system comprising: A plurality of battery modules (5); and A first heating device (51) is used to directly heat a first group (61) of battery modules (5), wherein Each battery module (5) has at least one battery cell (2), wherein the battery modules (5) of the first group (61) are spatially surrounded on at least two sides by the battery modules (5) of the other groups (62, 63, 64, 65), and wherein The battery modules (5) are spatially arranged so that waste heat generated when heating the first group (61) of battery modules (5) and / or when charging the first group (61) of battery modules (5) is transferred to other groups (62, 63, 64, 65) of battery modules (5).

2. The battery system (10) according to claim 1, wherein The battery modules (5) in the first group (61) of battery modules (5) are connected in series and form a battery branch (6).

3. A method for charging a battery system (10) according to any one of claims 1 to 2, the method comprising the following steps: - heating a first group (61) of battery modules (5) by means of a first heating device (51); - if the group temperature (T) of the first group (61) of battery modules (5) has reached a predetermined minimum temperature (Tmin), charging the first group (61) of battery modules (5) with a first charging current (I1); - transferring the waste heat generated when heating the first group (61) of battery modules (5) and / or when charging the first group (61) of battery modules (5) to other groups (62, 63, 64, 65) of battery modules (5); - If the group temperature (T) of at least one other group (62, 63, 64, 65) of battery modules (5) has reached a predetermined minimum temperature (Tmin), the other group (62, 63, 64, 65) of battery modules (5) is charged with a further charging current (I2, I3, I4, I5).

4. The method according to claim 3, wherein If the group temperature (T) of a group (61, 62, 63, 64, 65) of battery modules (5) has reached a predetermined maximum temperature (Tmax), the charging current (I1, I2, I3, I4, I5) of the group (61, 62, 63, 64, 65) of battery modules (5) is cut off.

5. The method according to any one of claims 3 to 4, wherein Before at least one further group (62, 63, 64, 65) of battery modules (5) is charged with the further charging current (I2, I3, I4, I5), the further group (62, 63, 64, 65) of battery modules (5) is additionally heated by a further heating device (52).

6. The method according to any one of claims 3 to 4, wherein If a group (61, 62, 63, 64, 65) of battery modules (5) has reached a predetermined maximum temperature (Tmax), the group (61, 62, 63, 64, 65) of battery modules (5) is cooled by a cooling device.

7. The method according to any one of claims 3 to 4, wherein The charging current (I1, I2, I3, I4, I5) of a group (61, 62, 63, 64, 65) of battery modules (5) is changed according to the group temperature (T) of the group (61, 62, 63, 64, 65) of battery modules (5).

8. The method according to claim 7, wherein If the group temperature (T) of a group (61, 62, 63, 64, 65) of battery modules (5) is equal to the minimum temperature (Tmin), the charging current (I1, I2, I3, I4, I5) of the group (61, 62, 63, 64, 65) of battery modules (5) has a minimum current value (Imin).

9. The method according to claim 7, wherein The charging current (I1, I2, I3, I4, I5) of a group (61, 62, 63, 64, 65) of battery modules (5) starts to increase continuously at the minimum current value (Imin). Until the group temperature (T) of the battery group module (5) of the group (61, 62, 63, 64, 65) is equal to the threshold temperature (Tsch).

10. The method according to claim 7, wherein A change process of a charging current (I1, I2, I3, I4, I5) of a group (61, 62, 63, 64, 65) of battery modules (5) depending on a group temperature (T) of the group (61, 62, 63, 64, 65) of battery modules (5) has a turning point at a threshold temperature (Tsch).

11. The method according to claim 9, wherein A charging current (I1, I2, I3, I4, I5) of a group (61, 62, 63, 64, 65) of battery modules (5) has a threshold value (Isch) at a threshold temperature (Tsch), and wherein If the group temperature (T) of the battery group module (5) of the group (61, 62, 63, 64, 65) is greater than the threshold temperature (Tsch) and less than the maximum temperature (Tmax), the charging current (I1, I2, I3, I4, I5) of the battery group module (5) of the group (61, 62, 63, 64, 65) is greater than the threshold value (Isch).

12. An electric vehicle comprising at least one battery system (10) according to any one of claims 1 to 2, which battery system can be operated using a method according to any one of claims 3 to 11.

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