Method of Electrically Connecting a Battery Pack to an Electrical System of a Vehicle, Control Arrangement, Vehicle System, and Vehicle

Abstract

A method (100) of electrically connecting a battery pack (11) to an electrical system (10) of a vehicle (2) is disclosed. The vehicle (2) comprises a connection assembly (3) comprising a first contactor (d) arranged in a first conductor (L1) extending between the electrical system (10) and a first terminal (t1) of the battery pack (11), a second contactor (c2) arranged in a second conductor (L2) extending between the electrical system (10) and a second terminal (t2) of the battery pack (11), and a semiconductor switch (5) arranged in series with the second contactor (c2) in the second conductor (L2). The method (100) comprises the steps of controlling (120) the first contactor (d) to a closed state, controlling (150) the second contactor (c2) to a closed state, and then, controlling (160) the semiconductor switch (5) to an on state. The present disclosure further relates to a computer program, a computerreadable medium (200), a control arrangement (21), a vehicle system (20), and a vehicle (2).

Description

The present disclosure relates to a method of electrically connecting a battery pack to an electrical system of a vehicle. The present disclosure further relates to a computer program, a computer-readable medium, a control arrangement configured to electrically connect a battery pack to an electrical system of a vehicle, and a vehicle system comprising a battery pack, an electrical system, and a connection assembly. Moreover, the present disclosure further relates to a vehicle comprising a vehicle system.BACKGROUNDThe use of electric drive for vehicles provides many advantages, especially regarding local emissions. Such vehicles comprise one or more electric propulsion motors configured to provide motive power to the vehicle. These types of vehicles can be categorised as pure electric vehicles and hybrid electric vehicles. Pure electric vehicles, sometimes referred to as battery electric vehicles, only-electric vehicles, and all-electric vehicles, comprise a pure electric powertrain and comprise no internal combustion engine and therefore produce no emissions in the place where they are used.A hybrid electric vehicle comprises two or more distinct types of power, such as an internal combustion engine and an electric propulsion system. The combination of an internal combustion engine and an electric propulsion system provides advantages with regard to energy efficiency, partly because of the poor energy efficiency of an internal combustion engine at lower power output levels. Moreover, some hybrid electric vehicles are capable of operating in pure electric drive when wanted, such as when driving in certain areas.In at least partially electric vehicles, such as pure electric vehicles and hybrid electric vehicles, the electricity is usually stored in a number of battery packs each comprising a number of rechargeable battery cells. Some different types of battery cells are used, such as lithium-ion battery cells, lithium polymer battery cells, as well as other types of rechargeable battery cells. Multiple battery packs are often required to ensure a sufficient available operational range of a vehicle, system voltage and power, especially in heavier types of vehicles.An at least partially electric vehicle normally comprises a number of contactors which can be controlled to electrically connect and disconnect the battery packs to / from an electrical system of the vehicle. Normally, each contactor is controllable between an open state, in which the contactor blocks the transfer of electricity, and a closed state, in which the contactor allows the transfer of electricity through the contactor.The battery packs of an at least partially electric vehicle may be disconnected from the electrical system for safety reasons and to minimize battery drain. This disconnection typically occurs when the vehicle is not in operation, such as when it is parked, and when the battery packs are not being charged from an external source. Disconnecting the battery packs from the electrical system prevents any unintended current flow that could potentially cause electrical issues or fires. It also helps in preserving the state of charge of the battery packs, thereby extending their overall lifespan.Battery packs of an at least partially electric vehicle may have a different voltage than the electrical system of the vehicle when being connected to the electrical system. Upon connection, the voltage difference may cause sparks at the contactors. Such sparks can degrade the contact surfaces over time, leading to increased electrical resistance and reduced reliability of the contactors. The sparks may also pose a fire risk, especially in environments with flammable materials, and contribute to overall wear of the system, increasing maintenance requirements and reducing operational efficiency.Additionally, a large voltage difference between the battery pack and the electrical system upon connection can result in imbalances that negatively affect both the battery pack and other electrical components in the vehicle. This can lead to large inrush currents during a sudden voltage equalization, risking damage to sensitive electronics and posing safety hazards like electrical fires. The stress can also compromise the long-term performance of the battery pack and may activate safety features or system errors, which may limit the operational capabilities of the vehicle.SUMMARYIt is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks. The object is achieved by the subject-matter of the appended independent claim(s).According to a first aspect of the present disclosure, the object is achieved by a method of electrically connecting a battery pack to an electrical system of a vehicle, wherein the method is performed by a control arrangement. The vehicle comprises a connection assembly, the connection assembly comprising a first contactor arranged in a first conductor extending between the electrical system and a first terminal of the battery pack, and a second contactor arranged in a second conductor extending between the electrical system and a second terminal of the battery pack. One of the first and second terminals is a negative terminal and the other of the first and second terminals is a positive terminal of the battery pack. Each of the first and second contactors is controllable between an open state, in which the contactor blocks the transfer of electricity, and a closed state, in which the contactor allows the transfer of electricity through the contactor. The connection assembly further comprises a semiconductor switch arranged in series with the second contactor in the second conductor. The semiconductor switch is controllable between an off state, in which the semiconductor switch blocks the transfer of electricity, and an on state, in which the semiconductor switch allows the transfer of electricity through the semiconductor switch, andwherein the method comprises the steps of:- controlling the first contactor to the closed state,- controlling the second contactor to the closed state, and then,- controlling the semiconductor switch to the on state.Since the method comprises the step of controlling the semiconductor switch to the on state, after controlling each of the first and second contactors to the respective closed state, the method minimizes the current rush over the first and second contactors upon controlling the first and second contactors to the respective closed state.In this manner, the method reduces the risk of sparks occurring at the first and second contactors, which can lower the fire risk and preserve the quality of the contact surfaces of the first and second contactors. This, in turn, decreases the need for repairs and prolongs the lifespan of the contactors.A semiconductor switch is a type of component being more resistant to current rush than contactors upon being controlled to an electrically conductive state, i.e., upon being controlled to the on state. Furthermore, sparks are normally not generated at a semiconductor switch when it is controlled to the electrically conductive state. Accordingly, the method can ensure that the generation of sparks also can be avoided when controlling the semiconductor switch to the on state. As a further result, the reliability of the connection assembly can be ensured, and the method can contribute to a more durable and reliable electrical system within the vehicle.Thus, a method is provided overcoming, or at least alleviating, at least some of the abovementioned problems and drawbacks. As a result, the above-mentioned object is achieved.As understood from the above, when initiating the method according to embodiments herein, the semiconductor switch is in the off state and each of the first and second contactors is in the open state. Therefore, the step of controlling the first contactor to the closed state may also be expressed as a step of controlling the first contactor from the open state to the closed state, the step of controlling the second contactor to the closed state may also be expressed as a step of controlling the second contactor from the open state to the closed state, and the step of controlling the semiconductor switch to the on state may also be expressed as a step of controlling the semiconductor switch from the off state to the on state.Optionally, the method comprises the steps of, after controlling the first contactor to the closed state:- providing a voltage estimate of the battery pack,- providing a voltage estimate of the electrical system, and- adjusting the voltage of the electrical system such that the magnitude of the difference between the voltage estimate of the electrical system and the voltage estimate of the battery pack declines below a threshold difference before controlling the second contactor to the closed state.Thereby, a method is provided capable of further minimizing the risk of generation of sparks within the connection assembly during the connection procedure of the battery pack to the electrical system. Furthermore, a method is provided capable of minimizing the problems caused by large voltage differences between the battery pack and the electrical system upon connection. In other words, due to these features, the method can minimize inrush currents and ensure a gradual voltage equalization, thereby protecting sensitive electronics from potential damage and reducing safety hazards such as electrical fires. Additionally, the method can minimize the stress on the battery pack, preserving its long-term performance and minimizing the risk of activating safety features or system errors that could otherwise limit the vehicle's operational capabilities.Optionally, the step of providing the voltage estimate of the electrical system comprises: - providing a first voltage estimate between a first measurement point located on the second conductor at a position between the second terminal and the semiconductor switch and a second measurement point located on the first conductor,- providing a second voltage estimate between the first measurement point and a third measurement point located on the second conductor at a position between the electrical system and the second contactor, and- providing the voltage estimate of the electrical system based on the difference between the first and second voltage estimates.Thereby, the voltage estimate of the electrical system is provided in a simple and efficient manner. Moreover, a single voltage measurement reference point, i.e., the first measurement point, can be utilised for providing both the first voltage estimate and the second voltage estimate, which may simplify the electrical layout and the routing of conductors.Optionally, the second measurement point is located on the first conductor at a position between the first contactor and the electrical system. This placement of the second measurement point can be utilized because the step of providing the voltage estimate of the electrical system is performed after the step of controlling the first contactor to the closed state. In this manner, the electrical layout and the routing of conductors can be simplified.Optionally, the method comprises the steps of, before controlling the first contactor to the closed state:- providing a first electrical resistance estimate between the first terminal and an electrical ground point of the vehicle,- providing a second electrical resistance estimate between the second terminal and an electrical ground point of the vehicle, and- controlling the first contactor to the closed state only if each of the first and second electrical resistance estimates exceeds a respective resistance threshold.Thereby, an even safer method of electrically connecting the battery pack to the electrical system of a vehicle is achieved. This is because these method steps ensure that the battery pack is only connected to the electrical system of the vehicle in case the electrical isolation, i.e., the electrical resistance, between the respective first and second terminals and the electrical ground point is sufficiently high. Moreover, due to these features, a method is provided allowing for the use of the same reference points when providing the first and second electrical resistance estimates, as is used when providing a voltage estimate of the battery pack, as well as when providing a voltage estimate of the electrical system.Optionally, the method comprises the steps of, after controlling the semiconductor switch to the on state:- measuring the current flow through at least one of the first and second conductors, and - controlling the semiconductor switch to the off state if the measured current flow exceeds a threshold value.Thereby, a method is provided eliminating, or at least reducing, the need for utilizing one or more pyro fuses in the connection assembly. Instead, due to these features, the semiconductor switch is utilized to protect the battery pack, the connection assembly, and the electrical system in case of high current flows through at least one of the first and second conductors. Eliminating, or at least reducing, the need for utilizing one or more pyro fuses in the connection assembly can result in several advantages, including a simplified design of the connection assembly, reduced component costs, and improved reliability by avoiding components that require replacement after activation. Additionally, reducing the reliance on pyro fuses can enhance the overall safety of the vehicle system by minimizing the risks associated with their deployment, such as unintended activation or failure to activate in critical scenarios. Furthermore, it can contribute to easier maintenance and servicing, as fewer components need to be inspected or replaced during the operational lifespan of the vehicle.According to a second aspect of the present disclosure, the object is achieved by a computer program comprising instructions which, when the program is executed by a control arrangement of a vehicle, cause the control arrangement to carry out the method according to some embodiments of the first aspect of the present disclosure. Since the computer program comprises instructions to cause the control arrangement to carry out the method according to some embodiments described herein, a computer program is provided which provides conditions for overcoming, or at least alleviating, at least some of the abovementioned drawbacks. As a result, the above-mentioned object is achieved.According to a third aspect of the present disclosure, the object is achieved by a computerreadable medium comprising instructions which, when executed by a control arrangement of a vehicle, cause the control arrangement to carry out the method according to some embodiments of the first aspect of the present disclosure. Since the computer-readable medium comprises instructions to cause the control arrangement to carry out the method according to some embodiments described herein, a computer-readable medium is provided which provides conditions for overcoming, or at least alleviating, at least some of the abovementioned drawbacks. As a result, the above-mentioned object is achieved.According to a fourth aspect of the present disclosure, the object is achieved by a control arrangement configured to electrically connect a battery pack to an electrical system of a vehicle. The vehicle comprises a connection assembly, the connection assembly comprising a first contactor arranged in a first conductor extending between the electrical system and a first terminal of the battery pack, and a second contactor arranged in a second conductor extending between the electrical system and a second terminal of the battery pack. One of the first and second terminals is a negative terminal and the other of the first and second terminals is a positive terminal of the battery pack. Each of the first and second contactors is controllable between an open state, in which the contactor blocks the transfer of electricity, and a closed state, in which the contactor allows the transfer of electricity through the contactor. The connection assembly further comprises a semiconductor switch arranged in series with the second contactor in the second conductor. The semiconductor switch is controllable between an off state, in which the semiconductor switch blocks the transfer of electricity, and an on state, in which the semiconductor switch allows the transfer of electricity through the semiconductor switch. The control arrangement is configured to:- control the first contactor to the closed state,- control the second contactor to the closed state, and then,- control the semiconductor switch to the on state.Since the control arrangement is configured to control the semiconductor switch to the on state, after controlling each of the first and second contactors to the respective closed state, the control performed by the control arrangement minimizes the current rush over the first and second contactors upon controlling the first and second contactors to the respective closed state.In this manner, the control performed by the control arrangement reduces the risk of sparks occurring at the first and second contactors, which can lower the fire risk and preserve the quality of the contact surfaces of the first and second contactors. This, in turn, decreases the need for repairs and prolongs the lifespan of the contactors.A semiconductor switch is a type of component being more resistant to current rush than contactors upon being controlled to an electrically conductive state, i.e., upon being controlled to the on state. Furthermore, sparks are normally not generated at a semiconductor switch when it is controlled to the electrically conductive state. Accordingly, the control performed by the control arrangement can ensure that the generation of sparks can be avoided when controlling the semiconductor switch to the on state. As a further result, the reliability of the connection assembly can be ensured, and the control performed by the control arrangement can contribute to a more durable and reliable electrical system within the vehicle.Thus, a control arrangement is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.It will be appreciated that the various embodiments described for the method are all combinable with the control arrangement as described herein. That is, the control arrangement according to the fourth aspect of the invention may be configured to perform any one of the method steps of the method according to the first aspect of the invention.According to a fifth aspect of the present disclosure, the object is achieved by a vehicle system comprising a battery pack, an electrical system, and a connection assembly. The connection assembly comprises a first contactor arranged in a first conductor extending between the electrical system and a first terminal of the battery pack, and a second contactor arranged in a second conductor extending between the electrical system and a second terminal of the battery pack. One of the first and second terminals is a negative terminal and the other of the first and second terminals is a positive terminal of the battery pack. Each of the first and second contactors is controllable between an open state, in which the contactor blocks the transfer of electricity, and a closed state, in which the contactor allows the transfer of electricity through the contactor. The connection assembly further comprises a semiconductor switch arranged in series with the second contactor in the second conductor. The semiconductor switch is controllable between an off state, in which the semiconductor switch blocks the transfer of electricity, and an on state, in which the semiconductor switch allows the transfer of electricity through the semiconductor switch. The vehicle system comprises a control arrangement configured to:- control the first contactor to the closed state,- control the second contactor to the closed state, and then,- control the semiconductor switch to the on state.Since the control arrangement is configured to control the semiconductor switch to the on state, after controlling each of the first and second contactors to the respective closed state, occurrences of current rush over the first and second contactors can be minimized upon controlling the first and second contactors to the respective closed state.In this manner, the risk of sparks occurring at the first and second contactors is reduced, which can lower the fire risk and preserve the quality of the contact surfaces of the first and second contactors. This, in turn, decreases the need for repairs and prolongs the lifespan of the contactors.A semiconductor switch is a type of component being more resistant to current rush than contactors upon being controlled to an electrically conductive state, i.e., upon being controlled to the on state. Furthermore, sparks are normally not generated at a semiconductor switch when it is controlled to the electrically conductive state. Accordingly, the control performed by the control arrangement can ensure that the generation of sparks can be avoided when controlling the semiconductor switch to the on state. As a further result, the reliability of the connection assembly can be ensured, and the control performed by the control arrangement can contribute to a more durable and reliable electrical system within the vehicle.Thus, a vehicle system is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.Optionally, the semiconductor switch is a Metal-Oxide-Semiconductor Field-Effect Transistor. A Metal-Oxide-Semiconductor Field-Effect Transistor, usually abbreviated MOSFET, is a type of component being significantly more resistant to current rush than contactors upon being controlled to an electrically conductive state, i.e., upon being controlled to the on state as referred to herein. Furthermore, sparks are normally not generated at a Metal-Oxide-Semiconductor Field-Effect Transistor when it is controlled to the electrically conductive state. Accordingly, it can be further ensured that the generation of sparks can be avoided when controlling the semiconductor switch to the on state. In addition, the reliability of the connection assembly can be further ensured.Optionally, the first terminal is the positive terminal and the second terminal is the negative terminal of the battery pack. Thereby, it can be ensured that the same reference points can be used when providing the first and second electrical resistance estimates, as is used when providing a voltage estimate of the battery pack, as well as when providing a voltage estimate of the electrical system.Optionally, the nominal voltage of the battery pack is equal to, or exceeds, 60 volts. Due to the features of the control performed by the control arrangement, it can be ensured that the battery pack, having a nominal voltage within the so-called Voltage Class B, usually abbreviated VCB, namely a nominal voltage equal to, or higher than, 60 volts, can be safely, efficiently, and reliably connected to the electrical system of the vehicle.According to a sixth aspect of the present disclosure, the object is achieved by a vehicle comprising a vehicle system according to some embodiments of the fifth aspect of the present disclosure. Since the vehicle comprises a vehicle system according to some embodiments of the fifth aspect of the present disclosure, a vehicle is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.Optionally, the vehicle is a heavy wheeled vehicle, such as a truck or a bus. Thereby, a heavy wheeled vehicle is provided having at least some of the above-mentioned advantages.Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.BRIEF DESCRIPTION OF THE DRAWINGSVarious aspects of the present disclosure, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:Fig. 1 schematically illustrates a vehicle according to some embodiments,Fig. 2 schematically illustrates a vehicle system of the vehicle illustrated in Fig. 1,Fig. 3 schematically illustrates a method of connecting a battery pack to an electrical system of a vehicle, andFig. 4 illustrates a computer-readable medium.DETAILED DESCRIPTIONAspects of the present disclosure will now be described more fully. Like reference signs refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.Fig. 1 schematically illustrates a vehicle 2 according to some embodiments. According to the illustrated embodiments, the vehicle 2 is a truck, i.e., a type of heavy wheeled vehicle, as well as a type of heavy commercial vehicle. According to further embodiments, the vehicle 2, as referred to herein, may be another type of heavy or lighter type of manned or unmanned vehicle for land-based propulsion such as a lorry, a bus, a construction vehicle, a tractor, a dumper, a forestry machinery, a military vehicle, a car, or the like.The vehicle 2 comprises a chassis 40 and an electric propulsion system 30. The electric propulsion system 30 is configured to provide motive power to the vehicle 2. According to the illustrated embodiments, the vehicle 2 is a wheeled vehicle comprising a number of wheels 27, 27’. According to the embodiments illustrated in Fig. 1, the vehicle 2 comprises two driven wheels 27 which constitute rear-wheels of the vehicle 2. The vehicle 2 further comprises two non-driven wheels 27’, which according to the illustrated embodiments constitute front-wheels of the vehicle 2. In other words, in these embodiments, the electric propulsion system 30 is configured to provide motive power to the vehicle 2 via the driven wheels 27 of the vehicle 2. However, according to further embodiments, the vehicle 2 may comprise another configuration of driven and non-driven wheels.In Fig. 1, the vehicle 2 is illustrated as positioned in an intended use position on a flat surface 51 supporting the vehicle 2. As seen in Fig. 1, the number of wheels 27, 27’ of the vehicle 2 is configured to abut against the flat surface 51 when the vehicle 2 is positioned in the intended use position thereon.The number of wheels 27, 27’ of the vehicle 2 is supported relative to the chassis 40 via wheel axles. According to some embodiments, the vehicle 2 may comprise a wheel suspension system resiliently suspending the wheels 27, 27’ of the vehicle 2 relative to the chassis 40. The chassis 40 of the vehicle 2 serves as a structural framework that supports other components and systems of the vehicle 2, such as the electric propulsion system 30 and a cab 45 of the vehicle 2. The chassis 40 of the vehicle 2 may comprise two elongated frame beams. The two elongated frame beams may be attached to each other via a number of cross members. These cross members may provide additional structural support and rigidity, ensuring that the frame beams maintain their alignment and can withstand the stresses encountered during vehicle operation. The chassis 40 may moreover comprise a number of subframes each arranged to support a structure, component, or system relative to at least one frame beam of the two elongated frame beams.That is, as is seen in Fig. 1, according to the illustrated embodiments, the vehicle 2 comprises a cab 45 which is resiliently suspended relative to the chassis 40. The cab 45 accommodates a driver environment 55 of the vehicle 2. The term "driver environment 55” refers to the area within the vehicle 2 where a driver operates and controls the vehicle 2. The driver environment 55 typically includes the driver's seat, steering wheel, pedals, dashboard, and other control interfaces and displays that the driver may use to manage the functions of the vehicle 2.The electric propulsion system 30 comprises an electric propulsion machine 12 and a transmission 33. The electric propulsion machine 12 is configured to provide motive power to the vehicle 2 via the transmission 33. In the embodiments illustrated in Fig. 1, the electric propulsion system 30 is depicted as comprising one electric propulsion machine 12.However, the electric propulsion system 30 may comprise more than one electric propulsion machine 12, wherein each electric propulsion machine 12 is configured to provide motive power to the vehicle 2.Moreover, according to the illustrated embodiments, the vehicle 2 is a pure electric vehicle comprising the electric propulsion machine 12 as the only means of providing motive power to the vehicle 2 and no internal combustion engine. However, according to further embodiments, the vehicle 2 may be a so-called hybrid electric vehicle comprising an internal combustion engine in addition to the electric propulsion machine 12 for providing motive power to the vehicle 2. According to such embodiments, the internal combustion engine may be a diesel engine, i.e. a type of compression ignition engine, or an Otto engine with a sparkignition device, wherein the Otto engine is configured to run on petrol, alcohol, a gaseous fuel, or combinations thereof.The vehicle 2 comprises a vehicle system 20 comprising a battery pack 11 and an electrical system 10. As is further explained herein, the battery pack 11 is configured to provide electricity to the electric propulsion machine 12 via the electrical system 10 upon operation of the vehicle 2.According to the embodiments illustrated in Fig. 1, the vehicle 2 is illustrated as comprising one battery pack 11. However, the vehicle 2 may comprises two or more battery packs each configured to provide electricity to the electric propulsion machine 12 upon operation of the vehicle 2.According to embodiments herein, the battery pack 11 of the vehicle 2 has a nominal voltage within the so-called Voltage Class B, usually abbreviated VCB, namely a nominal voltage equal to, or higher than, 60 volts. Therefore, the battery pack 11, as referred to herein, may also be referred to as a high-voltage battery pack. Furthermore, the battery pack 11, as referred to herein, may also be referred to as a propulsion battery, a propulsion battery pack, a high-voltage propulsion battery pack, or the like.The battery pack 11 may comprise a number of rechargeable battery cells, such as lithiumion battery cells, lithium polymer battery cells, lithium iron phosphate battery cells, or the like.The number of rechargeable battery cells may be arranged in modules, wherein the battery pack 11 may comprise a number of modules. Moreover, the battery pack 11 may be associated with a temperature regulating system, for example comprising coolant ducts for conducting coolant, such as a mixture between water and glycol, through various parts of the battery pack 11.The electrical system 10 of the vehicle 2 has a nominal voltage within the so-called Voltage Class B, usually abbreviated VCB, namely a nominal voltage equal to, or higher than, 60 volts. Therefore, the electrical system 10 may also be referred to as a high-voltage electrical system. As indicated above, the electrical system 10 is configured to transfer electricity between the battery pack 11 and the electric propulsion system 30 during operation of the vehicle 2. Additionally, the electrical system 10 may be configured to supply power to various other subsystems and arrangements of the vehicle 2, such as heating arrangements, a highvoltage air conditioning compressor, a power-take off unit, and the like.Fig. 2 schematically illustrates the vehicle system 20 of the vehicle 2 illustrated in Fig. 1. Below, simultaneous reference is made to Fig. 1 and Fig. 2, if not indicated otherwise.As mentioned, the vehicle system 20 comprising the battery pack 11 and the electrical system 10. As is further explained herein, in Fig. 2, the battery pack 11 is electrically disconnected from the electrical system 10.The vehicle system 20 further comprises a connection assembly 3 for electrically connecting the battery pack 11 to the electrical system 10. In more detail, the vehicle system 20 comprises a first conductor L1 extending between the electrical system 10 and a first terminal t1 of the battery pack 11, and a second conductor L2 extending between the electrical system 10 and a second terminal t2 of the battery pack 11. According to the illustrated embodiments, the first terminal t1 is the positive terminal and the second terminal t2 is the negative terminal of the battery pack 11. However, according to further embodiments, this may be the other way around, i.e., the first terminal t1 may be the negative terminal and the second terminal t2 may be the positive terminal of the battery pack 11.The terms positive terminal and negative terminal refer to the two electrical poles of the battery pack 11, which define the direction of current flow in the electrical system 10 during discharge and charging. The positive terminal t1 is the point from which current flows out of the battery pack 11 during discharge, while the negative terminal t2 is the point through which current returns to the battery pack 11, completing the circuit. Conversely, during charging, the direction of current flow is reversed, i.e., electrical current flows into the positive terminal t1 and exits through the negative terminal t2. The positive terminal typically has a higher electrical potential than the negative terminal.The connection assembly 3 comprises a first contactor c1 arranged in the first conductor L1 and a second contactor c2 arranged in the second conductor L2. Each of the first and second contactors c1, c2 is controllable between an open state, in which the contactor c1, c2 blocks the transfer of electricity, and a closed state, in which the contactor c1, c2 allows the transfer of electricity through the contactor c1, c2. In the schematic illustration of Fig. 2, each of the first and second contactors c1, c2 is illustrated in the respective open state.Accordingly, in this manner, the battery pack 11 is electrically disconnected from the electrical system 10.The battery pack 11 may be electrically disconnected from the electrical system 10 to enhance safety, conserve energy, or perform maintenance. For instance, the battery pack 11 may be disconnected when the vehicle 2 is not in use, such as when it is parked or during extended periods of inactivity, to prevent unnecessary energy loss and preserve the state of charge of the battery cells of the battery pack 11. Additionally, disconnection can occur during maintenance or troubleshooting to isolate the electrical system 10 and avoid accidental short circuits or electrical hazards.Each of the first and second contactors c1, c2 may include a housing containing the components necessary for its operation, including conductive contacts and actuating elements. One or both of the contactors c1, c2 may comprise a mechanical coil contactor with a plunger mechanism. In such a design, an electromagnetic coil is used to actuate the plunger, which physically moves the internal contacts to thereby transition the contactor d, c2 between the open and closed states.According to embodiments herein, the connection assembly 3 further comprises a semiconductor switch 5. The semiconductor switch 5 is arranged in series with the second contactor c2 in the second conductor L2. The semiconductor switch 5 is controllable between an off state, in which the semiconductor switch 5 blocks the transfer of electricity, and an on state, in which the semiconductor switch 5 allows the transfer of electricity through the semiconductor switch 5.According to the illustrated embodiments, the semiconductor switch 5 is a Metal-Oxide-Semiconductor Field-Effect Transistor, usually abbreviated MOSFET. Structurally, a MOSFET comprises three main terminals: the gate, the source, and the drain. These terminals are connected to a layered semiconductor structure that controls the flow of current between the source and the drain based on the voltage applied to the gate.The MOSFET includes a substrate, typically made of silicon or another semiconductor material, which serves as a foundation. A thin insulating layer, usually made of silicon dioxide Si02, is deposited on a substrate to electrically isolate the gate terminal. The gate itself is constructed from a conductive material, such as polysilicon or metal, and is positioned over the insulating layer. This configuration allows the gate to control the electric field that modulates the conductivity of a channel formed between the source and drain terminals.The source and drain regions are doped to create high conductivity, enabling efficient current flow when the MOSFET is in its conductive state, i.e., when the semiconductor switch 5 is in the on state as referred to herein. The physical structure of the MOSFET is designed to handle high current and voltage levels while maintaining fast switching speeds and minimal power loss, making it particularly well-suited for applications in high-voltage vehicle systems, such as those described in the present disclosure.The vehicle system 20 further comprises a control arrangement 21. The control arrangement 21 is also schematically indicated in Fig. 1. As seen in Fig. 2, the control arrangement 21 is electrically connected to various measurement points p1 - p4 on the first and second conductors L1, L2 and to an electrical ground point Gr. The electrical ground point Gr serves as a reference point for the electrical potential of the vehicle system 20 and provides a return path for current to ensure stable operation of the vehicle system 20. Structurally, the ground point Gr is typically connected to the chassis 40 or another conductive part of the vehicle 2 to create a common ground for all connected electrical components. This configuration helps to prevent voltage imbalances and ensures the reliable functioning of vehicle system 20.Moreover, as seen in Fig. 2, according to embodiments herein, the control arrangement 21 is operably connected to the first contactor c1, the second contactor c2, and the semiconductor switch 5. As is further explained herein, the control arrangement 21 is operable to control the first and second contactors between the open and closed states, and the semiconductor switch 5 between the on and off states. The control arrangement 21 is configured to control the semiconductor switch 5 to the off state when the battery pack 11 is electrically disconnected from the electrical system 10 as depicted in Fig. 2.According to some embodiments, the control arrangement 21 is configured to, when initiating a connection procedure of the battery pack 11 to the electrical system 10, provide a first electrical resistance estimate between the first terminal t1 and the electrical ground point Gr of the vehicle 2. The control arrangement 21 may be configured to provide the first electrical resistance estimate by measuring the electrical resistance between the first terminal t1 and the electrical ground point Gr of the vehicle 2. According to the embodiments illustrated in Fig. 2, the control arrangement 21 provides the first electrical resistance estimate by measuring the electrical resistance between electrical ground point Gr of the vehicle 2 and a measurement point p4 located on the first conductor L1 at a position between the first terminal t1 and the first contactor c1.In these embodiments, the control arrangement 21 is also configured to provide a second electrical resistance estimate between the second terminal t2 and an electrical ground point Gr of the vehicle 2, when initiating the connection procedure of the battery pack 11 to the electrical system 10. Like above, the control arrangement 21 may be configured to provide the second electrical resistance estimate by measuring the electrical resistance between the second terminal t2 and the electrical ground point Gr of the vehicle 2. According to the embodiments illustrated in Fig. 2, the control arrangement 21 provides the second electrical resistance estimate by measuring the electrical resistance between electrical ground point Gr of the vehicle 2 and a first measurement point p1 located on the second conductor L2 at a position between the second terminal t2 and the semiconductor switch 5. As understood from the above, and as is further explained herein, the measurement point p4 may also be referred to as a fourth measurement point p4.Moreover, in these embodiments, the control arrangement 21 is configured to continue the connection procedure by controlling the first contactor d to the closed state only if each of the first and second electrical resistance estimates exceeds a respective resistance threshold. Thus, in these embodiments, the control arrangement 21 is configured to cancel the connection procedure if one or both of the first and second electrical resistance estimates exceeds the respective resistance threshold. Moreover, the control arrangement 21 may be configured to output a notification in the driver environment 55 of the vehicle 2, and / or may be configured to generate an error code, if one or both of the first and second electrical resistance estimates exceeds the respective resistance threshold. The resistance threshold for each of the first and second electrical resistance estimates may, for example, be determined based on system parameters and / or requirements of the vehicle system 20. The resistance threshold for each of the first and second electrical resistance estimates may, for example, be within the range of 400 kilohms (kΩ) - 8 megaohms (ΜΩ), within the range of 800 kilohms (kΩ) - 2 megaohms (ΜΩ), or approximately 1 megaohm (ΜΩ).According to further embodiments, the control arrangement 21 may not be configured to provide the first and second electrical resistance estimates according to the above explained. In such embodiments, the control arrangement 21 is configured to initiate the connection procedure of the battery pack 11 to the electrical system 10 by controlling the first contactor c1 to the closed state.When the first contactor d is controlled to the closed state, the first terminal t1 of the battery pack 11 becomes electrically connected to the electrical system 10. The control arrangement 21 may be configured to provide a voltage estimate of the battery pack 11 after controlling the first contactor d to the closed state.According to the embodiments illustrated in Fig. 2, the control arrangement 21 is configured to provide the voltage estimate of the battery pack 11 by measuring the voltage between the first measurement point P1 and the fourth measurement point p4, i.e., the fourth measurement point p4 located on the first conductor L1 at a position between the first terminal t1 and the first contactor c1.However, according to further embodiments, the control arrangement 21 may be configured to provide the voltage estimate of the battery pack 11 by measuring the voltage between the first measurement point P1 and a second measurement point p2, wherein the second measurement point p2 is located on the first conductor L1 at a position between the first contactor d and the electrical system 10.The control arrangement 21 may be configured to provide a voltage estimate of the electrical system 10 after controlling the first contactor d to the closed state. According to the embodiments illustrated in Fig. 2, the control arrangement 21 is configured to provide the voltage estimate of the electrical system 10 by providing a first voltage estimate between the first measurement point p1 located on the second conductor L2 at a position between the second terminal t2 and the semiconductor switch 5 and the second measurement point p2 located on the first conductor L1.According to the above description the second measurement point p2 located on the first conductor L1 between the first contactor d and the electrical system 10. However, the second measurement point p2, as referred to herein, may alternatively be located on the first conductor L1 at a position between the first terminal t1 and the first contactor d , i.e., at a position similar to, or corresponding to, the position of the fourth measurement point p4 in Fig. 2.Moreover, in these embodiments, the control arrangement 21 may be configured to provide a second voltage estimate between the first measurement point p1 and a third measurement point p3 located on the second conductor L2 at a position between the electrical system 10 and the second contactor c2. The control arrangement 21 may be configured to provide the second voltage estimate by measuring the voltage between the first measurement point p1 and the third measurement point p3.Furthermore, in these embodiments, the control arrangement 21 is configured to provide the voltage estimate of the electrical system 10 based on the difference between the first and second voltage estimates. In this manner, the voltage estimate of the electrical system 10 is provided in a simple and efficient manner. Moreover, a single voltage measurement reference point, i.e., the first measurement point p1, can be utilized when providing the first and second voltage estimates. Moreover, the same reference point, i.e., the first measurement point p1, can be utilized as when providing the second electrical resistance estimate according to the above. Thus, due to these features, the electrical layout and the routing of conductors within the vehicle system 20 can be simplified.The control arrangement 21 may be further configured to adjust the voltage of the electrical system 10 such that the magnitude of the difference between the voltage estimate of the electrical system 10 and the voltage estimate of the battery pack 11 declines below a threshold difference. The control arrangement 21 may be configured to adjust the voltage of the electrical system 10 by pre-charging the electrical system 10. The control arrangement 21 may pre-charge the electrical system 10 using electricity from an external power supply, or another battery pack of the vehicle 2. As an alternative, or in addition, the control arrangement 21 may be configured to pre-charge the electrical system 10 using electricity from the battery pack 11. In such embodiments, the control arrangement 21 may utilize a pre-charge contactor arranged in series with a resistor so as to gradually increase the voltage of the electrical system 10 using electricity from the battery pack 11.In embodiments in which the control arrangement 21 is configured to adjust the voltage of the electrical system 10 such that the magnitude of the difference between the voltage estimate of the electrical system 10 and the voltage estimate of the battery pack 11 declines below a threshold difference, the control arrangement 21 may be configured to control the second contactor c2 to the closed state when the magnitude of the difference between the voltage estimate of the electrical system 10 and the voltage estimate of the battery pack 11 declines below the threshold difference. The threshold difference, as referred to herein, may be predetermined or dynamically set, for example based on system parameters and / or requirements of the vehicle system 20. For example, the threshold difference may be within the range of 1 volt - 50 volts, within the range of 5 volts - 15 volts, or approximately 10 volts.According to further embodiments, the control arrangement 21 may be configured to control the second contactor c2 to the closed state, after controlling the first contactor c1 to the closed state, without performing the above described adjustment of the voltage of the electrical system 10.When the second contactor c2 is controlled to the closed state, the electrical system 10 becomes electrically connected to the semiconductor switch 5. However, since the semiconductor switch 5 remains in the off state, the battery pack 11 is not yet electrically connected to the electrical system 10.This is because, according to embodiments herein, the final control step performed by the control arrangement 21, in the connection procedure of the battery pack 11 to the electrical system 10, is to control the semiconductor switch 5 to the on state. When the semiconductor switch 5 is controlled to the on state, the battery pack 11 becomes electrically connected to the electrical system 10 of the vehicle 2.Since the control arrangement 21 is configured to control the semiconductor switch 5 to the on state, after controlling each of the first and second contactors c1, c2 to the respective closed state, the control performed by the control arrangement 21 minimizes the current rush over the first and second contactors c1, c2 upon controlling the first and second contactors c1, c2 to the respective closed state.In this manner, the control performed by the control arrangement 21 reduces the risk of sparks occurring at the first and second contactors c1, c2, which can lower the fire risk and preserve the quality of the contact surfaces of the first and second contactors c1, c2. This, in turn, decreases the need for repairs and prolongs the lifespan of the first and second contactors c1, c2. As a further result, the control performed by the control arrangement 21 can contribute to a more durable and reliable vehicle system 20 within the vehicle 2.A semiconductor switch 5 is a type of component being more resistant to current rush than contactors upon being controlled to an electrically conductive state, i.e., upon being controlled to the on state. Furthermore, sparks are normally not generated at a semiconductor switch 5 when it is controlled to the electrically conductive state. Accordingly, the control performed by the control arrangement 21 can ensure that the generation of sparks can be avoided when controlling the semiconductor switch 5 to the on state.Moreover, the reliability of the connection assembly 3 can be ensured.According to some embodiments, the control arrangement 21 may be configured to, after controlling 160 the semiconductor switch 5 to the on state, measure the flow of electrical current through at least one of the first and second conductors L1, L2, and controlling the semiconductor switch 5 to the off state if the measured flow of electrical current exceeds a threshold value. The threshold value, as referred to herein, may be predetermined or dynamically set, for example based on system parameters and / or requirements of the vehicle system 20. For example, the threshold value may be within the range of 300 amperes -2 000 amperes, within the range of 500 amperes - 900 amperes, or approximately 700 amperes.According to the embodiments illustrated in Fig. 2, vehicle system 20 comprises a current measurement sensor 15 configured to measure the flow of electrical current through the second conductor L2. In these embodiments, the control arrangement 21 is configured to measure the flow of electrical current through the second conductor L2 using the current measurement sensor 15. In Fig. 2, the current measurement sensor 15 is depicted as constituting a unit being separate from the control arrangement 21. However, the current measurement sensor 15 may be an integral part of the control arrangement 21 or an integral part of the semiconductor switch 5. Data from the current measurement sensor 15 may be utilized by the control arrangement 21 when monitoring current flow through the vehicle system 20, including monitoring of current flow through the first and second contactors d, c2 and the semiconductor switch 5.According to some embodiments, the semiconductor switch 5 may be configured to automatically, i.e., without external input, assume an off state, in which the second terminal t2 becomes electrically disconnected from the electrical system 10, if the electrical current flowing through the semiconductor switch 5 exceeds a threshold value.Due to these features, the need for utilizing one or more pyro fuses in the connection assembly is eliminated, or is at least reduced. Instead, due to these features, the semiconductor switch 5 is utilized to protect the battery pack 11, the connection assembly 3, and the electrical system 5 in case of high current flows.Fig. 3 schematically illustrates a method 100 of connecting a battery pack to an electrical system of a vehicle. The vehicle may be a vehicle 2 according to the embodiments illustrated in Fig. 1, i.e., a vehicle 2 comprising a vehicle system 20 as depicted in Fig. 2. Therefore, below, simultaneous reference is made to Fig. 1 - Fig. 3, if not indicated otherwise.The method 100 is a method of electrically connecting a battery pack 11 to an electrical system 10 of a vehicle 2, wherein the method 100 is performed by a control arrangement 21, and wherein the vehicle 2 comprises a connection assembly 3. The connection assembly 3 comprises a first contactor d arranged in a first conductor L1 extending between the electrical system 10 and a first terminal t1 of the battery pack 11, and a second contactor c2 arranged in a second conductor L2 extending between the electrical system 10 and a second terminal t2 of the battery pack 11. One of the first and second terminals t1, t2 is a negative terminal and the other of the first and second terminals t1, t2 is a positive terminal of the battery pack 11. Each of the first and second contactors c1, c2 is controllable between an open state, in which the contactor c1, c2 blocks the transfer of electricity, and a closed state, in which the contactor c1, c2 allows the transfer of electricity through the contactor c1, c2. The connection assembly 3 further comprises a semiconductor switch 5 arranged in series with the second contactor c2 in the second conductor L2. The semiconductor switch 5 is controllable between an off state, in which the semiconductor switch 5 blocks the transfer of electricity, and an on state, in which the semiconductor switch 5 allows the transfer of electricity through the semiconductor switch 5. The method 100 comprises the steps of: - controlling 120 the first contactor d to the closed state,- controlling 150 the second contactor c2 to the closed state, and then,- controlling 160 the semiconductor switch 5 to the on state.According to embodiments herein, the steps 120, 150, and 160 are performed in the order specified above. Moreover, when initiating the method 100 according to embodiments herein, each of the first and second contactors c1, c2 is in the respective open state, and the semiconductor switch 5 is in the off state.Therefore, the step of controlling 120 the first contactor d to the closed state may also be expressed as a step of controlling the first contactor d from the open state to the closed state. Similarly, the step of controlling 150 the second contactor c2 to the closed state may also be expressed as a step of controlling the second contactor c2 from the open state to the closed state. Likewise, the controlling 160 the semiconductor switch 5 to the on state may also be expressed as a step of controlling the semiconductor switch 5 from the off state to the on state.According to some embodiments, the method 100 comprises the steps of, after controlling 120 the first contactor d to the closed state:- providing 130 a voltage estimate of the battery pack 11,- providing 132 a voltage estimate of the electrical system 10, and- adjusting 140 the voltage of the electrical system 10 such that the magnitude of the difference between the voltage estimate of the electrical system 10 and the voltage estimate of the battery pack 11 declines below a threshold difference before controlling 150 the second contactor c2 to the closed state.As understood from the above, each of the steps 130, 132, and 140 may be performed after the step of controlling 120 the first contactor d to the closed state and before the step of controlling 150 the second contactor c2 to the closed state.According to some embodiments, the step of providing 132 the voltage estimate of the electrical system 10 comprises:- providing 133 a first voltage estimate between a first measurement point p1 located on the second conductor L2 at a position between the second terminal t2 and the semiconductor switch 5 and a second measurement point p2 located on the first conductor L1,- providing 134 a second voltage estimate between the first measurement point p1 and a third measurement point p3 located on the second conductor L2 at a position between the electrical system 10 and the second contactor c2, and- providing 135 the voltage estimate of the electrical system 10 based on the difference between the first and second voltage estimates.Furthermore, as understood from the above, each of the steps 133, 134, and 135 may be performed after the step of controlling 120 the first contactor d to the closed state and before the step of controlling 150 the second contactor c2 to the closed state. The second measurement point p2 may be located on the first conductor L1 at a position between the first contactor d and the electrical system 10.According to some embodiments, the method 100 may comprise the steps of, before controlling 120 the first contactor d to the closed state:- providing 110 a first electrical resistance estimate between the first terminal t1 and an electrical ground point Gr of the vehicle 2, and- providing 112 a second electrical resistance estimate between the second terminal t2 and an electrical ground point Gr of the vehicle 2.In these embodiments, the method 100 may comprise the step of:- controlling 120’ the first contactor d to the closed state only if each of the first and second electrical resistance estimates exceeds a respective resistance threshold.Moreover, according to some embodiments, the method 100 may comprise the steps of, after controlling 160 the semiconductor switch 5 to the on state:- measuring 170 the current flow through at least one of the first and second conductors L1, L2, and- controlling 172 the semiconductor switch 5 to the off state if the measured current flow exceeds a threshold value.It will be appreciated that the various embodiments described for the method 100 are all combinable with the control arrangement 21 as described herein. That is, the control arrangement 21 may be configured to perform any one of the method steps 110, 112, 120, 120', 130, 132, 133, 134, 135, 140, 150, 160, 170, and 172 of the method 100.Fig. 4 illustrates a computer-readable medium 200 comprising instructions which, when executed by a computer, cause the computer to carry out the method 100 according to some embodiments of the present disclosure. According to some embodiments, the computerreadable medium 200 comprises a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to some embodiments. The computer may be comprised in the control arrangement 21.One skilled in the art will appreciate that the method 100 of electrically connecting a battery pack 11 to an electrical system 10 of a vehicle 2 may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in the control arrangement 21, ensures that the control arrangement 21 carries out the desired control, such as the method steps 110, 112, 120, 120’, 130, 132, 133, 134, 135, 140, 150, 160, 170, and 172 described herein. The computer program is usually part of a computer program product which comprises a suitable digital storage medium on which the computer program is stored, such as the computer-readable medium 200 illustrated in Fig. 4. In other words, the computer program product may be a computer readable medium 200 and the computer program may be stored in the computer readable medium 200.The control arrangement 21 may comprise a computer which may take the form of substantially any suitable type of hardware or hardware / firmware device implemented using processing circuity such as, but not limited to, a processor, Central Processing Unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, an Application Specific Integrated Circuit (ASIC), a circuit for digital signal processing (digital signal processor, DSP), a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, an application-specific integrated circuit, or any other device capable of electronically performing operations in a defined manner, or other processing logic that may interpret and execute instructions. The herein utilised expression “computer” may represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.The control arrangement 21 may further comprise a memory unit, wherein the computer may be connected to the memory unit, which may provide the computer with, for example, stored program code and / or stored data which the computer may need to enable it to do calculations. The computer may also be adapted to store partial or final results of calculations in the memory unit. The memory unit may comprise a physical device utilised to store data or programs, i.e., sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors. The memory unit may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments.The control arrangement 21 is connected to components of the vehicle 2 for receiving and / or sending input and output signals. These input and output signals may comprise waveforms, pulses, or other attributes which the input signal receiving devices can detect as information and which can be converted to signals processable by the control arrangement 21. These signals may then be supplied to the computer. One or more output signal sending devices may be arranged to convert calculation results from the computer to output signals for conveying to other parts of the vehicle's control system and / or the component or components for which the signals are intended. Each of the connections to the respective components of the vehicle 2 for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection.In the embodiments illustrated, the vehicle 2 comprises a control arrangement 21 but might alternatively be implemented wholly or partly in two or more control arrangements, two or more control arrangements, or two or more control units.Control systems in modern vehicles generally comprise a communication bus system consisting of one or more communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a control system may comprise a large number of control units and taking care of a specific function may be shared between two or more of them. Vehicles and engines of the type here concerned are therefore often provided with significantly more control arrangements than depicted in Fig. 2, as one skilled in the art will surely appreciate.The computer-readable medium 200 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the method steps 110, 112, 120, 120’, 130, 132, 133, 134, 135, 140, 150, 160, 170, and 172 according to some embodiments of the method 100 when being loaded into one or more computers of the control arrangement 21. The data carrier may be, e.g. a CD ROM disc, as is illustrated in Fig. 4, or a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. Accordingly, in some embodiments, the computer-readable medium 200 may be a non-transitory computer-readable medium, such as a tangible electronic, magnetic, optical, infrared, electromagnetic, and / or semiconductor system, apparatus, and / or device. The computer-readable medium 200 may furthermore be provided as computer program code on a server and may be downloaded to the control arrangement 21 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components, or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims

1. Method (100) for electrically connecting a battery pack (11) to an electrical system (10) of a vehicle (2), wherein the method (100) is performed by a control device (21), and wherein the vehicle (2) comprises a connection unit (3), wherein the connection unit (3) comprises:- a first connector (d) arranged in a first conductor (L1) extending between the electrical system (10) and a first end contact (t1) of the battery pack (11), and - a second connector (c2) arranged in a second conductor (L2) extending between the electrical system (10) and a second end contact (t2) of the battery pack (11), wherein one of the first and second end contacts (t1, t2) is a negative end contact and the other of the first and second end contacts (t1, t2) is a positive end contact of the battery pack (11),wherein each of the first and second connectors (c1, c2) is controllable between an open position, in which the connector (c1, c2) blocks the transmission of electricity, and a closed position, in which the connector (c1, c2) allows the transmission of electricity through the connector (c1, c2),and wherein the connection unit (3) further comprises a semiconductor switch (5) arranged in series with the second connector (c2) in the second conductor (L2),wherein the semiconductor switch (5) can be controlled between an inactivated state, in which the semiconductor switch (5) blocks the transfer of electricity, and an activated state, in which the semiconductor switch (5) allows the transfer of electricity through the semiconductor switch (5), andwherein the method (100) comprises the steps of:- controlling (120) the first connector (c1) to the closed position,- controlling (150) the second connector (c2) to the closed position, and then, - controlling (160) the semiconductor switch (5) to the activated position,wherein the method (100) comprises the steps of, after controlling (120) the first connector (c1) to the closed position:- providing (130) a voltage estimate for the battery pack (11),- providing (132) a voltage estimate for the electrical system (10), and - adjusting (140) the voltage of the electrical system (10) such that the magnitude of the difference between the electrical system (10) voltage estimate and the battery pack (11) voltage estimate decreases below a threshold difference before the second connector (c2) is controlled to the closed position (150).

2. The method (100) of claim 1, wherein the step of providing (132) the voltage estimate for the electrical system (10) comprises:- providing (133) a first voltage estimate between a first measurement point (p1) located on the second conductor (L2) at a position between the second end contact (t2) and the semiconductor switch (5) and a second measurement point (p2) located on the first conductor (L1),- providing (134) a second voltage estimate between the first measurement point (p1) and a third measurement point (p3) located on the second conductor (L2) at a position between the electrical system (10) and the second connector (c2), and - providing (135) the voltage estimate for the electrical system (10) based on the difference between the first and second voltage estimates.

3. Method (100) according to claim 2, wherein the second measuring point (p2) is located on the first conductor (L1) at a position between the first connector (c1) and the electrical system (10).

4. Method (100) according to any one of the preceding claims, wherein the method (100) comprises the steps of, before controlling (120) the first connector (c1) to the closed position:- providing (110) a first estimate of electrical resistance between the first end contact (t1) and an electrical ground point (Gr) of the vehicle (2), - providing (112) a second estimate of electrical resistance between the second end contact (t2) and an electrical ground point (Gr) of the vehicle (2), and - controlling (120') the first connector (c1) to the closed position only if each of the first and second estimates of electrical resistance exceeds a respective resistance threshold.

5. Method (100) according to any one of the preceding claims, wherein the method (100) comprises the steps of, after controlling (160) the semiconductor switch (5) to the activated position:- measuring (170) the current flow through at least one of the first and second conductors (L1, L2), and- controlling (172) the semiconductor switch (5) to the deactivated position if the measured current flow exceeds a threshold value.

6. Computer program comprising instructions which, when the program is executed by a control device (21) arranged in the vehicle (2), causes the control device (21) to perform the method (100) according to any one of claims 1-5.

7. Computer-readable storage medium (200) comprising instructions which, when executed by a control device (21) arranged in the vehicle (2), cause the control device (21) to perform the method (100) according to any one of claims 1-5.

8. Control device (21), designed to electrically connect a battery pack (11) to an electrical system (10) of a vehicle (2), wherein the vehicle (2) comprises a connection unit (3), wherein the connection unit (3) comprises:- a first connector (d) arranged in a first conductor (L1) extending between the electrical system (10) and a first end contact (t1) of the battery pack (11), and - a second connector (c2) arranged in a second conductor (L2) extending between the electrical system (10) and a second end contact (t2) of the battery pack (11), wherein one of the first and second end contacts (t1, t2) is a negative end contact and the other of the first and second end contacts (t1, t2) is a positive end contact of the battery pack (11),wherein each of the first and second connectors (c1, c2) is controllable between an open position, in which the connector (c1, c2) blocks the transmission of electricity, and a closed position, in which the connector (c1, c2) allows the transmission of electricity through the connector (c1, c2),and wherein the connection unit (3) further comprises a semiconductor switch (5) arranged in series with the second connector (c2) in the second conductor (L2),wherein the semiconductor switch (5) can be controlled between a deactivated position, in which the semiconductor switch (5) blocks the transfer of electricity, and an activated position, in which the semiconductor switch (5) allows the transfer of electricity through the semiconductor switch (5), and wherein the control device (21) is designed to:- control the first connector (c1) to the closed position,- control the second connector (c2) to the closed position, and then,- control the semiconductor switch (5) to the activated position,- wherein the control device (21) is further designed to, after controlling the first connector (d) to the closed position:o provide a voltage estimate for the battery pack (11),o providing a voltage estimate for the electrical system (10), and o adjusting the voltage of the electrical system (10) such that the magnitude of the difference between the electrical system (10) voltage estimate and the battery pack (11) voltage estimate decreases below a threshold difference before the second connector (c2) is controlled to the closed position.

9. A vehicle system (20) comprising a battery pack (11), an electrical system (10), and a connection unit (3), wherein the connection unit (3) comprises:- a first connector (d) arranged in a first conductor (L1) extending between the electrical system (10) and a first end contact (t1) of the battery pack (11), and - a second connector (c2) arranged in a second conductor (L2) extending between the electrical system (10) and a second end contact (t2) of the battery pack (11), wherein one of the first and second end contacts (t1, t2) is a negative end contact and the other of the first and second end contacts (t1, t2) is a positive end contact of the battery pack (11),wherein each of the first and second connectors (c1, c2) is controllable between an open position, in which the connector (c1, c2) blocks the transmission of electricity, and a closed position, in which the connector (c1, c2) allows the transmission of electricity through the connector (c1, c2),and wherein the connection unit (3) further comprises a semiconductor switch (5) arranged in series with the second connector (c2) in the second conductor (L2), and wherein the semiconductor switch (5) can be controlled between a deactivated position, in which the semiconductor switch (5) blocks the transmission of electricity, and an activated position, in which the semiconductor switch (5) allows the transmission of electricity through the semiconductor switch (5), andwherein the vehicle system (20) comprises a control device (21) according to claim 8.

10. The vehicle system (20) of claim 9, wherein the semiconductor switch (5) is a metal oxide semiconductor field effect transistor.

11. The vehicle system (20) of claim 9 or 10, wherein the first end contact (t1) is the positive end contact and the second end contact (t2) is the negative end contact of the battery pack (11).

12. Vehicle system (20) according to any one of claims 9-11, wherein the nominal voltage of the battery pack (11) is equal to, or exceeds, 60 volts.

13. Vehicle (2) comprising a vehicle system (20) according to any one of claims 9-12.

14. Vehicle (2) according to claim 13, wherein the vehicle (2) is a heavy wheeled vehicle, such as a truck or a bus.