Battery system for heavy electric vehicles and corresponding method for charging the battery

Abstract

The present invention provides a battery system (100) for an electric vehicle (12, 30), the battery system (100) being configured to deliver power to a DC bus (200) of the powertrain of the electric vehicle (12, 30) at a first voltage. The battery system (100) includes at least two separate battery packs (110-140), a plurality of electrical switches (161-167), and a controller. The battery packs (110-140) are configured to deliver power at a second voltage, which is lower than the first voltage. The plurality of electrical switches (161-167) are disposed between two terminals of the at least two separate battery packs (110-140). The controller is configured to operate the electrical switches (161-167) to selectively connect the at least two separate battery packs (110-140) in parallel or in series.

Description

Technical Field

[0001] This invention relates to a battery system for an electric vehicle, the battery system being configured to deliver power to the DC bus of the electric vehicle's powertrain. The invention further relates to a method for charging the battery system. Background Technology

[0002] Over the past two decades, an increasing portion of the global vehicle fleet has been electrified. Given the current state of the electric vehicle (EV) market, different vehicles are charged at different power levels and using charging connectors of various designs. Charging power levels can depend, for example, on the EV's own battery capacity and power requirements, or on the user's need for fast charging. Typically, charging equipment and service providers need to supply different charging systems to meet the diverse power requirements in the market.

[0003] Recently, the electrification of the vehicle fleet has begun to extend to the larger Class 6, 7, and 8 commercial vehicle market. This includes trucks, construction equipment, agricultural vehicles, and mining trucks that rely partially or entirely on plug-in battery systems for propulsion. Because these larger battery electric vehicles have greater power requirements for both their off-road driving and actual work, they typically have significantly larger, higher-capacity battery packs compared to most passenger vehicles. To accomplish the heavy workload, these larger battery electric vehicles typically operate at higher voltages on the powertrain's DC bus compared to smaller consumer electronics. While the voltage on the powertrain of an electric passenger vehicle is typically around 400 V, large mining trucks can operate at voltages as high as (and exceeding) 3 kV.

[0004] The higher operating voltage of these vehicles presents a technical challenge for charging their batteries. Typical fast chargers for electric vehicles use 500 V-1 kV, which is insufficient to charge the 3 kV batteries of, for example, large electric vehicles. To compensate for this voltage difference, DC / DC voltage converters can be used. However, such converters and their accompanying control electronics occupy considerable space and result in power losses that reduce the efficiency of the charging system. Alternatively, lower voltage battery systems (e.g., < 1 kV) can be combined with DC / DC converters, which provide the high voltage (e.g., > 3 kV) power required at the powertrain's DC bus. Such DC / DC converters also tend to be large, heavy, and inefficient.

[0005] The purpose of this invention is to overcome at least some of the technical challenges brought about by these new developments. Summary of the Invention

[0006] According to one aspect of the invention, a battery system for an electric vehicle is provided, the battery system being configured to deliver power to a DC bus of the electric vehicle's powertrain at a first voltage. The battery system includes at least two separate battery packs, each battery pack being configured to deliver power at a second voltage lower than the first voltage. The battery system further includes a plurality of electrical switches disposed between two terminals of the at least two separate battery packs. A controller is configured to operate the electrical switches to selectively connect the at least two separate battery packs in parallel or in series.

[0007] The ability to switch between parallel and series connections of the battery pack allows the battery to be fully charged at a voltage lower than its standard operating voltage and without requiring a large DC / DC converter. Furthermore, the battery system according to the invention provides a more energy-efficient way to charge batteries in larger electric vehicles. While such series-to-parallel switching may have been previously attempted to allow for high-voltage fast charging of lower-voltage battery packs in electric passenger vehicles (see, for example, WO 2020 / 143595 A1), using a similar switching technique to charge a large-capacity battery pack at a lower-voltage charging facility that can be primarily designed for charging electric passenger vehicles is a completely novel approach.

[0008] In one embodiment, the battery system further includes a charging inlet for receiving a charger connector from an electric vehicle charging station. The controller can be configured to operate the electrical switch to place the battery system into a charging mode or a driving mode. In the charging mode, the battery packs are connected in parallel to enable charging of the battery system at a second voltage. In the driving mode, the battery packs are connected in series to enable discharging of the battery system at a first voltage. The controller can be arranged to automatically switch the battery packs to a parallel configuration when a sensor detects a connection to the charger connector. The switching of the electrical switch can be powered by electricity from the charging station or by electricity from the battery system itself.

[0009] The battery system may further include a second charging inlet for receiving a second charger connector from an electric vehicle charging station. The charging inlet and the second charging inlet are arranged such that, in the charging mode, a first battery pack of the at least two battery packs is charged via the charger connector, and a second battery pack of the at least two battery packs is charged via the second charger connector. Switching from a series connection to a parallel connection of the battery packs divides the battery system into two separate subsystems operating at a lower second voltage. Connecting separate charging connectors to the separate subsystems accelerates the charging process.

[0010] In one exemplary embodiment, the plurality of electrical switches includes at least a first electrical switch, a second electrical switch, and a third electrical switch. The first electrical switch is disposed between the negative terminals of the at least two individual battery packs, the second electrical switch is disposed between the positive terminals of the at least two individual battery packs, and the third electrical switch is disposed between the negative terminal of the first battery pack and the positive terminal of the second battery pack. When the third electrical switch is closed, the first and second electrical switches remain open. Current can flow from the positive terminal of one battery pack to the negative terminal of another battery pack, thus connecting the battery packs in series. After switching all three electrical switches, the positive terminals of the battery packs are connected together as their negative terminals, thereby connecting the battery packs in parallel. To ensure that the battery packs do not short-circuit and that the battery system is not damaged, the third electrical switch can be opened before closing the first and / or second electrical switches.

[0011] In a preferred embodiment, the battery system further includes a DC / DC converter and one or more converter switches disposed between the battery pack and the powertrain's DC bus. In this embodiment, the controller is configured to operate the converter switches to place the battery system in either a boost mode or a non-boost mode. In the boost mode, the battery pack is connected in parallel to the powertrain's DC bus via the DC / DC converter. In the non-boost mode, the battery pack is connected in series to the powertrain's DC bus without the DC / DC converter. Therefore, a higher voltage can be supplied to the powertrain's DC bus while the battery pack is being charged at a lower voltage. Preferably, the DC / DC converter is arranged to convert DC current at the second voltage to DC current at the first voltage. By maintaining the powertrain's DC bus at the first voltage, basic powertrain functions (such as the vehicle's brakes) can remain operational while the battery system is being charged at the second voltage. When the vehicle powertrain is stationary during the charging of the battery system, it does not need to be continuously and fully powered. Therefore, the power rating requirements for the DC / DC converter are significantly lower, and it can be sized much smaller than, for example, a full-power DC / DC converter mounted between the charger and the battery system to compensate for the voltage difference between the lower charger voltage and the higher operating voltage of the battery system.

[0012] The plurality of power converter switches may include a power converter switch disposed between the positive terminal of the battery pack and the DC bus of the powertrain. To activate the boost mode, this power converter switch is disconnected to interrupt the direct flow of current from the battery pack to the DC bus. Instead, the battery pack is connected to the input of the DC bus via the DC / DC converter.

[0013] According to another aspect of the present invention, a method for charging a battery system as described above is provided. The method includes the steps of operating the electrical switch to connect a first battery pack and a second battery pack, of the at least two separate battery packs, in parallel; connecting a charger connector of an electric vehicle charging station to a charging inlet of the battery system; charging the at least two separate battery packs through the charger connector; and operating the electrical switch to connect the first battery pack and the second battery pack in series.

[0014] During the charging of the battery packs, the power received through the charger connector can be used to switch electrical switches located between two terminals of the at least two individual battery packs. In this way, the charging station can supply power for switching between series-connected and parallel-connected battery packs without using electrical energy stored in the battery system to be charged.

[0015] In addition to switching the electrical switches located between the two terminals of the at least two individual battery packs, the power received through the charger connector can switch one or more other electrical switches of the battery system. For example, at least some of these other electrical switches may be switches located between the two terminals of at least a third and a fourth individual battery pack. The battery system may include multiple battery cells. While the first battery cell having the first two battery packs has been charged, some of the power provided by the charger connector can then be used to switch the third and fourth battery packs of the second battery cell into a parallel connection, after which charging of those third and fourth battery packs also begins. In some embodiments, charging of the battery packs in the second battery cell can be accomplished via a second charger connector.

[0016] In another instance, at least some of the additional electrical switches may be electrical converter switches disposed between the DC / DC converter and the DC bus of the powertrain.

[0017] The various aspects of the invention will now be discussed in more detail with reference to the accompanying drawings, in which one or more possible embodiments are shown. Attached Figure Description

[0018] Figure 1 An electric vehicle charging system that can benefit from the present invention is illustrated schematically.

[0019] Figure 2 A battery system according to an embodiment of the present invention is illustrated schematically.

[0020] Figure 3 schematically shown Figure 2 The switch used in the battery system.

[0021] These accompanying drawings illustrate one or more embodiments of the teachings of the present invention by way of example only and not limitation. In the drawings, similar reference numerals indicate the same or similar elements. Detailed Implementation

[0022] Figure 1An electric vehicle charging system that can benefit from the present invention is schematically illustrated. The charging system includes a charging station or charging distributor 10 coupled to a power grid and configured to enable charging of batteries for electric vehicles, such as an electrified ship 12 and a mining truck 30. Alternatively, the charging distributor 10 may be powered by a local or portable power source, such as a containerized energy storage system or a local wind turbine or solar power system. The charging station 10 may include one or more charger plugs 25 connected to the charging distributor 10 via charger cables 22. Charger connectors 25, 35 may be inserted into the charging ports of the electric vehicles 12, 30 to charge their batteries.

[0023] This invention relates to a dedicated battery system 100 for, for example, an electrified mining truck 30. Large mining trucks may have a load capacity exceeding 200 tons. To make this possible, the vehicle battery system of the electrified mining truck 30 can be designed to deliver up to or even more than 3 kV of DC power. Other possible future applications of this invention could be, for example, in electrified vessels 12.

[0024] Figure 2 A possible implementation of an example of the battery system 100 is illustrated schematically. A significant advantage of this battery system 100 is that it can be fully charged at a charging voltage lower than the normal operating voltage of the powertrain, and it eliminates the need for a space-consuming and power-intensive DC / DC converter to be installed between the charger 10 and the battery system 100. Further advantages will become apparent from the following description.

[0025] Figure 2 The battery system 100 shown includes four battery packs 110, 120, 130, and 140, which are arranged to supply power to a DC bus 200, thereby powering the powertrains of electrified vehicles 12 and 30. The DC bus operates at a first voltage, which is significantly higher than the voltage used to power conventional electric passenger vehicles. For example, the DC bus 200 of an electrified marine vessel 12 or mining truck 30 could be 3 kV. Each of the battery packs 110-140 includes a plurality of battery cells 111, 112, 118, and 119 connected in series. The battery packs 110, 120, 130, and 140 are configured to deliver power at a second voltage, which is lower than the first voltage.

[0026] In this example, the four battery packs 110-140 are arranged as two pairs of 110 / 120 and 130 / 140, each consisting of two battery packs. Electrical switches 161-166 are positioned between the two battery packs 110-140 in each pair to allow for selective connection of the two battery packs 110-140 in series or in parallel. A controller (not shown) is operatively connected to the switches to perform selective switching.

[0027] With the DC bus 200 operating at 3 kV, each battery pack 110-140 can be configured to deliver power at 1.5 kV. This allows the battery system 100 to charge battery cells 111, 112, 118, and 119 at 1.5 kV when each pair of 110 / 120, 130 / 140 battery packs 110-140 is connected in parallel. After charging, the battery packs 110-140 can be connected in series such that each pair of 110 / 120, 130 / 140 delivers power at 3 kV, the voltage required to power the vehicle powertrain during use. In an exemplary alternative embodiment, the triplet of battery packs can be charged at 1 kV when connected in parallel and can operate at 3 kV when connected in series. In the case of a quadruple battery pack, medium voltage levels can be achieved: for example, 750 V when all four battery packs are connected in parallel, 1.5 kV when two parallel pairs of battery packs are connected in series, and 3 kV when all four battery packs are connected in series. Other voltages can be used in other embodiments.

[0028] In this embodiment, each battery pack pair 110 / 120, 130 / 140 includes three electrical switches 161-166 that interconnect the battery packs 110-140. First electrical switches 161 and 164 are disposed between the negative terminals of the two battery packs 110-140. Second electrical switches 162 and 165 are disposed between the positive terminals of the two battery packs 110-140. Third electrical switches 163 and 166 are disposed between the positive terminal of the first battery pack 110 or 130 in each pair of 110 / 20, 130 / 140 and the negative terminal of the second battery pack 120 or 140 in the same pair.

[0029] When the first and second electrical switches 161, 162, 164, and 165 are closed together with the dual charging switch 167, the third electrical switches 163 and 166 are open. In this configuration, all four battery packs 110-140 operate in parallel at a lower voltage level of 1.5 kV (in this embodiment). When the third electrical switches 163 and 166 are closed together with the dual charging switch 167, both pairs of 110 / 120 and 130 / 140 connect their battery packs 110-140 in series, and each pair operates at a higher voltage level of 3 kV (in this embodiment).

[0030] A dual charging switch 167 is positioned between the two pairs of batteries 110 / 120 and 130 / 140 in the battery pack. When disconnected during charging, the two pairs of batteries 110 / 120 and 130 / 140 can be charged individually by two separate chargers. When the dual charging switch is closed, both pairs of batteries 110 / 120 and 130 / 140 can be charged simultaneously by a single charger connector. One or more of the switches 161-167 between the battery pack terminals may have a built-in pre-charge circuit to ensure that the voltages between batteries 110-140 are equal before switches 161-167 are closed. For example, all switches 162, 165, and 167 between the positive terminals of batteries 110-140 may include this pre-charge circuit. Figure 3 An example of a pre-charge circuit is shown in the figure, which schematically illustrates a circuit used for... Figure 2 The battery system's switch. The precharge circuit includes a main switch 310, a precharge switch 320, and a resistor 330. Before closing the main switch 310, the precharge switch 320, which is directly connected to the resistor 330, can be closed first to ensure voltage balance across the switch before the main switch 310 is closed. Without such a precharge circuit, a large inrush current could damage the switch when it is closed.

[0031] Optionally, such as in Figure 2In one embodiment, the battery system 200 further includes a DC / DC converter 150 disposed between the battery packs 110-140 and the DC bus 200 of the powertrain. Three converter switches 171, 172, and 173 are provided to allow selective connection of the battery packs 110-140 and the DC bus 200, either directly or via the DC / DC converter 150. The converter switches 171, 172, and 173 are operatively connected to a controller configured to operate the converter switches 171, 172, and 173 to place the battery system 100 in either a boost mode or a non-boost mode. The boost mode 100 is used to maintain charging of the battery packs 110-140 at a lower (1.5 kV) voltage while supplying power to the DC bus 200 at a higher (3 kV) voltage. In boost mode 100, battery packs 110-140 are connected in parallel and connected to the powertrain's DC bus 200 via DC / DC converter 150. DC / DC converter 150 is arranged to convert DC current from battery packs 110-140 at a second voltage into DC current to DC bus 200 at a first voltage. Therefore, a higher voltage can be supplied to the powertrain's DC bus 200 while charging battery packs 110-140 at a lower voltage. In non-boost mode, DC / DC converter 150 is placed in standby mode. Non-boost mode is used when the battery system 100 is not being charged. In non-boost mode, the series-connected battery packs 110-140 are directly connected to the powertrain's DC bus 200, and current does not pass through DC / DC converter 150.

[0032] The power converter switches 171, 172, and 173 may include a first power converter switch, a second power converter switch, and a third power converter switch. The first power converter switch 171 is located between the positive output terminal of the DC / DC converter 150 and the positive input terminal of the DC bus 200 of the powertrain. The second power converter switch 172 is located between the negative output terminal of the DC / DC converter 150 and the negative input terminal of the DC bus 200 of the powertrain. The third power converter switch 173 is located between the positive terminal of the battery packs 110-140 and the DC bus 200 of the powertrain, and may have the following characteristics: Figure 3The built-in pre-charge circuit shown ensures that the voltage between the battery system 100 and the powertrain DC bus 200 is equal before closing switch 173. The DC / DC converter 150 is electronically controlled to switch between on, off, or standby modes. Only the third converter switch 173, which directly connects the battery packs 110-140 and the input of the powertrain DC bus 200, is necessary for switching between boost and non-boost modes. The first converter switch 171 and the second converter switch 172 are primarily configured to ensure that the DC / DC converter is disconnected from the powertrain DC bus 150 when electronically switching the operating mode of the DC / DC converter 150 and / or when the battery system is operating in non-boost mode.

[0033] In normal operation, i.e., when the battery system 100 is not charged, with the first converter switch 171 open and the second converter switch 172 and the third converter switch 173 closed, the battery system 100 typically operates in non-boost mode. In this non-boost mode, current from the battery packs 110-140 flows directly to the DC bus 200 without first passing through the DC / DC converter 150. To activate boost mode, the third converter switch 173 is opened to interrupt the direct current flow to the DC bus 150. The first converter switch 171 and the second converter switch 172 are closed to instead connect the output of the DC / DC converter 150 to the input of the DC bus 200. In boost mode, current from the battery packs 110-140 can only reach the DC bus 200 via the DC / DC converter 150.

[0034] It should be noted that because the vehicle powertrain will not need to be continuously and fully powered during the charging of the battery system 100, the DC / DC converter 150 can be sized to be much smaller than the DC / DC converter installed between the powertrain DC bus 200 and the battery system 100 to compensate for the voltage difference between the lower charging voltage and the higher operating voltage of the battery system 100, or much smaller than the DC / DC converter installed between the battery system 100 and the powertrain DC bus 200 to compensate for the voltage difference between the lower battery voltage and the higher voltage on the powertrain DC bus 200. For example, a 100-500 kW DC / DC converter 150 may be sufficient, where previously a 2 MW to 3 MW DC / DC converter was required.

[0035] To charge the battery packs, the charger connector 25 of the charging station 10 is connected to the charging port of the battery system 100. Before or after this connection, the battery system controller switches electrical switches 161-167 in a certain way, such that battery packs 110-140 in each battery pack pair 110 / 120, 130 / 140 are connected in parallel. This switch to a parallel configuration can be triggered, for example, by a sensor detecting the ongoing connection, a wireless signal from an approaching vehicle, or a timing command from the central charging management system. When the switch occurs after the charger connector 25 is connected, the switch can be powered by electricity from the charging station 10. When the switch occurs before the charger connector 25 is connected, the switch may be powered by electricity from the battery system 100 itself. When using electricity from the charging station 10 to switch the battery pack pairs 110 / 120, 130 / 140 from a series connection to a parallel connection, no energy stored in the battery system 100 itself needs to be used. This allows for switching when battery packs 110-140 are completely depleted, and shortens the charging process by not initiating the charging process first when electrical energy is removed from battery system 100.

[0036] In addition to switching electrical switches 161-167 located between the terminals of battery packs 110-140 in one or more battery pack pairs 110 / 120, 130 / 140, the power received through charger connector 25 can be used to switch one or more other electrical switches of battery system 100. For example, battery system 100 may include multiple battery cells that can be charged via individual charger connectors. Once the battery pack of the first battery cell is charged, some of the power provided by charger connector 25 can then be used to switch the battery pack of the second battery cell to a parallel connection before charging of the second battery cell also begins. In another example, the power delivered through charger connector 25 can be used directly to power the converter switches 171, 172, 173 and activate boost mode.

[0037] Charging can begin with charger connector 25 connected and battery packs 110-140 connected in parallel. Charging ends when battery packs 110-140 are fully charged or earlier if charger connector 25 is disconnected, and electrical switches 161-166 are controlled to return to the configuration of two parallel pairs 110 / 120, 130 / 140 of the battery packs connected in series, which together deliver a higher 3 kV voltage to DC bus 200.

[0038] In short, Figure 2The battery system 100 can operate in charging and discharging modes. In discharging mode, switches 163, 166, 167, 172, and 173 are closed. Battery packs 110-140 in the battery pairs 110 / 120 and 130 / 140 are configured in series, and power is delivered to the powertrain DC bus 200 at a voltage of 3 kV. In charging mode, one or two charger connectors 25 can be connected to the battery system 100. When only one charger is connected, switches 161, 162, 164, 165, and 167 are closed. Battery packs 110-140 in the battery pairs 110 / 120 and 130 / 140 are configured in parallel, and battery packs 110-140 are charged at a lower voltage of 1.5 kV. When switch 167 is open, a second charger connector 25 can be inserted to charge both battery pairs 110 / 120 and 130 / 140 simultaneously using a single charging connector 25. Regardless of the number of charger connectors 25 inserted, if switches 171 and 172 are closed during charging, the DC / DC converter 150 is configured in its boost mode to deliver power to the powertrain DC bus 200 at 3 kV when needed.

[0039] The switch from discharge mode to charge mode can be triggered, for example, by detecting a charger signal from charging unit 10 by the onboard truck control system. In response to this charger signal, the battery system controller can change the battery configuration through the following steps: Step 1: Close converter switch 171 to connect the output of DC / DC converter 150 to the input of powertrain DC bus 200, and configure DC / DC converter 150 to be ready for operation.

[0040] Step 2: Disconnect converter switch 173 to break the direct connection between battery packs 110-140 and powertrain DC bus 200. Activate DC / DC converter 150 to put it into boost mode.

[0041] Step 3: Disconnect power switches 163, 166 and 167 to break the series connection between the two battery packs in 110 / 120 and 130 / 140.

[0042] Step 4: Close electrical switches 161 and 164 to connect the negative terminals of each pair of battery packs in 110 / 120 and 130 / 140.

[0043] Step 5: Close electrical switches 162 and 165 to connect the positive terminals of each pair of 110 / 120 and 130 / 140 battery packs.

[0044] Step 6: Close the electrical switch 167 to allow charging of both battery pack pairs 110 / 120 and 130 / 140 with a single charger 25, or keep the electrical switch 167 open when using a separate charger 25 for each battery pack pair 110 / 120 and 130 / 140.

[0045] When the onboard truck control system detects that a charging session has been completed, for example, when all battery packs 110-140 are fully charged, at the end of a planned charging period, when a predetermined charging level has been reached, or just as the charger connector 25 is disconnected from the battery system 100, the battery system controller can change the battery configuration through the following steps: Step 1: Disconnect power switches 162, 165 and 167 (if closed) to prevent current from flowing to battery packs 110-140.

[0046] Step 2: Disconnect power switches 161 and 164.

[0047] Step 3: Close electrical switches 163 and 166 to return the two battery packs 110 / 120 and 130 / 140 to their series configuration.

[0048] Step 4: Close the power switch 167 again to ensure that both battery pack pairs 110 / 120 and 130 / 140 are connected to the powertrain DC bus 200.

[0049] Step 5: Close the electrical switch 173 to connect the battery pack (the pre-charge switch 320 closes first, then the main switch 310 closes).

[0050] Step 6: Disconnect the power switch 171 and place the DC / DC converter 150 in its non-boost mode or standby configuration.

Claims

1. A battery system (100) for an electric vehicle (12, 30), characterized in that, The battery system (100) is configured to deliver power to the DC bus (200) of the powertrain of the electric vehicle (12, 30) at a first voltage, the battery system (100) comprising: - At least two separate battery packs (110-140), each battery pack (110-140) is configured to deliver power at a second voltage, which is lower than the first voltage; - A plurality of electrical switches (161-167), said plurality of electrical switches (161-167) being disposed between two terminals of the at least two separate battery packs (110-140); and - A controller configured to operate the electrical switches (161-167) to selectively connect the at least two individual battery packs (110-140) in parallel or in series.

2. The battery system (100) according to claim 1, characterized in that, The battery system (100) further includes a charging inlet for receiving a charger connector (25) of an electric vehicle charging station (10), and wherein the controller is configured to operate the electrical switches (161-167) to place the battery system (100) into a charging mode or a driving mode, wherein: - In the charging mode, the battery packs (110-140) are connected in parallel to enable charging of the battery system (100) at the second voltage, and - In the driving mode, the battery packs (110-140) are connected in series to enable the battery system (100) to discharge at the first voltage.

3. The battery system (100) according to claim 2, characterized in that, The battery system (100) further includes a second charging inlet for receiving a second charger connector (25) of an electric vehicle charging station (10). The charging inlet and the second charging inlet are arranged such that, in the charging mode, a first battery pack of the at least two battery packs (110-140) is charged through the charger connector (25), and a second battery pack of the at least two battery packs (110-140) is charged through the second charger connector (25).

4. The battery system (100) according to any one of the preceding claims, characterized in that, The plurality of electrical switches (161-167) include: - A first electrical switch (161, 164) is located between the negative terminals of the at least two separate battery packs (110-140); - A second electrical switch (162, 165), the second electrical switch (162, 165) being located between the positive terminals of the at least two separate battery packs (110-140); and - A third electrical switch (163, 166) is located between the negative terminal of the first battery pack in the at least two separate battery packs (110-140) and the positive terminal of the second battery pack in the at least two separate battery packs (110-140).

5. The battery system (100) according to any one of the preceding claims, characterized in that, The battery system (100) further includes a DC / DC converter (150) and a plurality of converter switches (171-173), the DC / DC converter (150) and the plurality of converter switches (171-173) being disposed between the battery pack (110-140) and the DC bus (200) of the powertrain, wherein the controller is further configured to operate the converter switches (161-167) and the converter switches (171-173) to place the battery system (100) in a boost mode or a non-boost mode, wherein: - In the boost mode, the battery packs (110-140) are connected in parallel and via the DC / DC converter (150) to the DC bus (200) of the powertrain, and - In the non-boost mode, the battery pack (110-140) is connected in series and not through the DC / DC converter (150) to the DC bus (200) of the powertrain.

6. The battery system (100) according to claim 5, characterized in that, The DC / DC converter (150) is arranged to convert DC current at the second voltage into DC current at the first voltage.

7. The battery system (100) according to claim 5 or 6, characterized in that, The plurality of power converter switches (171-173) includes a power converter switch (173) disposed between the positive terminal of the battery pack (110-140) and the positive input terminal of the DC bus (200) of the powertrain.

8. The battery system (100) according to any one of the preceding claims, characterized in that, The first voltage is at least 3 kV.

9. A method for charging a battery pack (110-140) of a battery system (100) according to any one of the preceding claims, characterized in that, The method includes: - Operate the electrical switch (161-167) to connect the first battery pack (110-140) and the second battery pack (110-140) of the at least two separate battery packs (110-140) in parallel; - Connect the charger connector of the electric vehicle charging station (10) to the charging port of the battery system (100); - Charge the at least two individual battery packs (110-140) via the charger connector (25); and - Operate the electrical switch (161-167) to connect the first battery pack (110-140) and the second battery pack (110-140) in series.

10. The method according to claim 9, characterized in that, During the charging of the battery packs (110-140), the power received through the charger connector (25) is used to switch the electrical switch (161-167), which is located between two terminals of the at least two individual battery packs (110-140).

11. The method according to claim 10, characterized in that, During the charging of the battery pack (110-140), the power received through the charger connector (25) is used to switch another electrical switch (161-173) of the battery system (100).

12. The method according to claim 11, characterized in that, At least some of the additional electrical switches (161-173) are disposed between two terminals of at least the third and fourth separate battery packs (110-140).

13. The method according to claim 11 or 12, characterized in that, At least one of the additional electrical switches (161-173) is an electric converter switch (171-173) configured to bypass a DC / DC converter (150) disposed between the battery pack (110-140) and the DC bus (200) of the powertrain.

14. The method according to any one of claims 9 to 13, characterized in that, The method further includes connecting a second charger connector (25) of the electric vehicle charging station (10) to a second charging inlet of the battery system (100).

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