BATTERY^PACK FIELD OF THE INVENTION The invention relates to a field of battery packs. BACKGROUND OF THE INVENTION Different kind of battery packs are widely used in electric vehicles, for example. There is a plurality of modular battery modules available in the market that can be used to form a desired battery pack. A drawback with the battery packs of prior art is that the battery mod- ules of the battery pack get aimed to forces that break components of the battery module, for example. BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide a novel battery pack. The invention is characterized by the features of the independent claims. The invention is based on the idea of a battery pack, wherein the battery pack comprises at least one battery module as an energy source of an electric power, and a protective casing having a wall structure that forms an inner space for accommodating the at least one battery module. The battery pack further com- prises at least one support structure remaining between the at least one battery module and the inner space of the protective casing, wherein the support structure comprises a main material that is configured to expand and harden to form the support structure. An advantage of the solution is that forces aimed to the battery module are reduced effectively by the support structure. Some embodiments of the invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figure 1 shows schematically a battery pack as seen in a cross-sectional view as seen from a side of the battery pack, Figure 2 shows schematically a battery pack as seen in a cross-sectional
view from above the battery pack, Figure 3A shows schematically and partially a battery module of Figure 1as seen in a cross-sectional view from a side of the battery module, Figure 3B shows schematically a detail of the battery module of Figure 3A as seen from above of the battery module, Figure 3C shows schematically a battery cell of the battery module of Figure 3A as seen obliquely from above the battery cell, Figure 4 shows schematically a section of a lower housing and the bat- tery cells of the battery module of the battery pack of Figure 1 as seen obliquely from above the battery module, Figure 5 shows schematically a section of a lower housing and the bat- tery cells of the battery module of the battery pack of Figure 1 as seen obliquely from above the battery module, Figure 6 shows schematically the battery pack of Figure 1 from above the battery pack, Figure 7 shows schematically a battery pack and an assembly mold as seen in a cross-sectional view as seen from a side of the battery pack, and Figure 8 shows schematically a battery pack of Figure 7 without the as- sembly mold. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows schematically a battery pack as seen in a cross-sectional view as seen from a side of the battery pack. Figure 2 shows schematically a battery pack as seen in a cross-sectional view from above the battery pack. Figure 3A shows schematically and partially a battery module of Figure 1as seen in a cross- sectional view from a side of the battery module. Figure 3B shows schematically a detail of the battery module of Figure 3A as seen from above of the battery module. Figure 3C shows schematically a battery cell of the battery module of Figure 3A as seen obliquely from above the battery cell. Figure 4 shows schematically a section of a lower housing and the battery cells of the battery module of Figure 1 as seen obliquely from above the battery module. Figure 5 shows schematically a section of a lower housing and the battery cells of the battery module of Figure 1 as seen obliquely from above the battery module. Figure 6 shows schematically the battery pack of Figure 1 from above the battery pack. Figure 7 shows schematically a bat- tery pack and an assembly mold as seen in a cross-sectional view as seen from a side of the battery pack. Figure 8 shows schematically a battery pack of Figure 7
without the assembly mold. The battery pack 1 of the Figures 1-6 comprises at least one battery module 100 as an energy source of an electric power. The battery pack 1 further comprises a protective casing 500 having a wall structure 502 that forms an inner space 510 for accommodating the at least one battery module 100. The battery pack 1 further comprises a support structure 10 remaining between the at least one battery module 100 and the inner space 510 of the protective casing 500, wherein the support structure comprises a main material 12 that is configured to expand and harden to form the support structure. The battery pack 1 of the Figures 7 and 8 comprises at least one battery module 100 as an energy source of an electric power. The battery pack 1 further comprises a protective casing 500 having a wall structure 502 that forms an inner space 510 for accommodating the at least one battery module 100. The wall struc- ture 502 of the Figures is a double shell structure, which double shell structure is disclosed in more detail below. The battery pack 1 further comprises a support structure 10 remaining inside the double shell structure of the protective casing 500, wherein the support structure comprises a main material 12 that is configured to expand and harden to form the support structure. The battery pack 1 of the Figures comprises a heat transfer liquid 400- A being arranged into the inner space 510, wherein the heat transfer liquid 400-A at least partially surrounds the at least one battery module 100. The battery module 100 of the Figures comprises a plurality of battery cells 110. The battery module 100 is shown in more detail in Figures 4A, 4B and 4C. The battery cells 110 are typically cylindrical, i.e., having a shape of a round bar. Each battery cell 110 has a first end 112, a second end 114, and a central axis 116 between the first end 112 and the second end 114. The battery cell 110 has typi- cally rotationally symmetric shape relative to the said central axis 116. The battery cell 110 is preferably a Lithium ion (Li-ion) battery. The battery cell 110 may also be other kind of battery such as a nickel-metal hydride (Ni-MH) battery, for exam- ple. The battery cell 110 has a side portion 118 between the first end 112 and the second end 114 of the battery cell 110, which is illustrated for example in Figure 4C. The battery cell 110 is typically surrounded at least partly by a metallic surface for protecting the battery cell. Also, the said metallic surface of the battery cell is configured for being attached to a filler, which filler is disclosed in more detail be- low. The battery cell 110 of the battery module 100 further has terminals to
be coupled electrically. The second end 114 of the battery cell 110 comprises a pos- itive terminal 114A at a centre of the said second end 114, and a negative terminal 114B around the positive terminal 114A at a certain distance, which terminals are illustrated in Figure 1C for example. The first end 112 of the battery cell 110 may comprise a negative terminal, but it is not necessary for the electrical connection herein. Thus, the electrical coupling is possible to be arranged, for example, by us- ing the second end 114 of the battery cell 110 without using the first end 112 of the battery cell 110. The battery module 100 of the Figures comprises a busbar assembly 120 configured to electrically couple the battery cells 110. The battery cells 110 may be connected in series and in parallel for achieving a required voltage and ca- pacity. The busbar assembly 120 comprises at least one lower busbar 122 in vicin- ity of the second end 114 of the battery cells 110, wherein the positive terminals 114A of the determined battery cells 110 are coupled to the at least one lower bus- bar 122. The busbar assembly 120 comprises at least one upper busbar 124, wherein the upper busbar 124 is in vicinity of the second end 114 of the battery cells 110, and wherein the upper busbar 124 is in vicinity of the at least one lower busbar 122. The negative terminals 114B of the determined battery cells 110 are coupled to the at least one upper busbar 124. The at least one lower busbar 122 and the at least one upper busbar 124 are configured to electrically couple the bat- tery cells 110 together to form the desired battery cell configuration having the desired voltage and capacity. The electric coupling between the said positive ter- minal 114A and the at least one lower busbar 122 is made for example via bonded wires, and respectively between the said negative terminal 114B and the at least one upper busbar 124, which bonded wires are not illustrated in the Figures for sake of the clarity. The said busbars may be plate-like parts made of conductive material. The said busbar assembly 120 is attached or coupled to a housing 130 such as to an upper housing 170 for example, said busbar assembly 120 locating above the housing 130, wherein the housing 130 and the upper housing 170 are disclosed in more detail below. The battery module 100 of the Figures comprises a first non-conductive part 180 between the battery cells 110 and the at least one lower busbar 122 for preventing unwanted electric couplings. The first non-conductive part 180 is for example a plastic plate comprising a plurality of openings in an area of the second ends 114 of the battery cells 110 for the openings allowing the electric coupling of the battery cells 110 to be made. The battery module 100 comprises also a second
non-conductive part 182 such as a plastic plate between the at least one lower bus- bar 122 and the at least one upper busbar 124 for preventing said unwanted elec- tric couplings. The first non-conductive part 180 of the battery module 100 further comprises a limiter 180A illustrated in Figure 4A. The limiter 180A locates partly against the second end 114 of the battery cells 110 for limiting a movement of the battery cells 110 in the direction of the central axis 116 of the corresponding bat- tery cells. The battery module 100 of the Figures comprises a housing 130 having an inner space 132 for accommodating at least the plurality of battery cells 110. The battery cells 110 are arranged in the inner space 132 of the housing 130, wherein the battery cells 110 are in a certain pattern. The second ends 114 of bat- tery cells 110 are on a same height in the housing. Further, said second ends 114 are against the limiter 180A of the first non-conductive part 180. The housing 130 limits the battery cells 110 being moved in a lateral direction of the battery cells 110 and in a direction of the central axis 116 of the battery cells 110. The housing 130 and/or its parts are made of plastic, which has advantages in manufacturing, manufacturing costs, and which provides more light-weight structure compared to metallic structures. The battery module 100 of the Figures has sides divided as follows. The battery module 100 has a top side 130A and a bottom side 130B locating opposite relative to the top side 130A. The battery module 100 has outer sides 130C locating between the top side 130A and the bottom side 130B. Said busbar assembly 120 is typically arranged to the top side 130A. Said bottom side 130B of the battery mod- ule 100 is typically inserted against a bottom 502C in the inner space 510 of the protective casing 500. Said outer sides 130C, locating between the top side 130A and the bottom side 130B, are supported by the support structure 10. For sake of the clarity, said sides of the battery module 100 are sides of the housing 130 of the battery module 100. The battery module 100 of the Figures comprises a plurality of recesses 140 in the housing 130 for the first end 112 and/or the central axis 116 of the bat- tery cells 110 being arranged towards the said recesses 140. The plurality of re- cesses 140 locate in the inner space 132 of the housing 130, wherein in the recess 140 there is a space for being filled by a filler 150. Said space for being filled is thus intended for receiving a filler 150. Each recess 140 has a rotationally asymmetric shape relative to the central axis 116 of the corresponding battery cell 110. The
shape of the recess 140 may be for example a cross, square, hex or polygon. The battery module 100 of the Figures comprises a filler 150 locating in the recess for the filler 150 being attached to the battery cells 110, or in more detail, the battery module 100 comprises fillers 150 locating in the plurality of recesses 140. The filler 150 is an adhesive configured to adhere onto the surroundings and especially to the metallic surface of the battery cell 110, wherein the adhesive hard- ens in a certain time. The recess 140 prevents the filler 150 and the battery cell 110 being rotated by the shape of the recess 140, wherein the filler 150 is attached to or detached from the surroundings such as the recess 140 or the housing 130. The housing 130 of the battery module 100 further comprises a lower housing 160 for supporting the side portion 118 of each battery cell 110 nearby the first end 112 of each battery cell 110. The lower housing 160 has a plurality of sock- ets 162 in the inner space 132 of the housing 130, the first end 112 of each battery cell 110 being set in the said corresponding socket 162. A wall of the socket 162 is against the side portion 118 of the battery cell 110 with a certain tolerance sub- stantially preventing the lateral movement of the battery cell 110. The above-men- tioned recesses 140 locate in the bottom of the sockets 162. The lower housing 160 further has side walls 164 forming sides of the lower housing, wherein said side walls 164 provides partially the inner space 132 of the housing 130, and wherein said side walls 164 partially protects the battery cells in the inner space 132 of the housing 130. Further, the lower housing 160 comprises mountings 166 for attaching the lower housing 160 to the upper hous- ing 170, wherein the attachment is made by screws, for example, which mountings 166 are shown in Figure 4. The housing 130 of the battery module 100 further comprises an upper housing 170, wherein the upper housing 170 has side walls 174 adapting to the side walls 164 of the lower housing 160 to form the inner space 132 of the housing 130 for the battery cells 110. Further, the upper housing 170 comprises mountings (not shown in Figures) for attaching the upper housing 170 to the lower housing 160, wherein the attachment is made by screws, for example. Further, the upper housing 170 of the housing 130 of the battery mod- ule 100 supports the side portion 118 of each battery cell 110 nearby the second end 114 of each battery cell 110. The upper housing 170 has a plurality of sockets 172, wherein the second end 116 of each battery cell 110 is in said corresponding socket 172. The socket 172 is fitted to be against the side portion 118 of the battery cell 110 with a certain tolerance substantially preventing the lateral movement of
the battery cell 110. The battery pack 1 of the Figures thus comprises at least one battery module 100. The battery pack 1 may comprise a plurality of battery module 100 for achieving a desired total capacity. The battery pack 1 of the Figures comprises a power distribution unit 200, i.e., a fuse box, connected to the at least one battery module 100 for executing the electric connection. The power distribution unit 200 may be connected to an electric vehicle, an energy storage system or such, for example. Thus, the power distribution unit 200 is configured to execute an electric connection between the at least one battery module 100 and the electric vehicle or between the at least one battery module 100 and the energy storage system, or such, for example. The power distribution unit 200 comprises a first port and a second port being con- nected to at least one battery module. Further the power distribution unit 200 com- prises an input port 202 and an output port 204 for being connected to the electric vehicle, the energy storage system or such, for example. The input port 202 and the output port 204 are connected to the electric vehicle, the energy storage system or such, which connection is made by cables, for example. The input port 202 may be a positive side (+ side) and the output port 204 may be a negative side (- side), for example. The power distribution unit 200 of the Figures comprises a relay 210 configured to allow and prevent the electric connection. The relay 210 is arranged between the first port and the input port for allowing and preventing the electric connection therein. The relay 210 may be arranged between the second port and the output port for allowing and preventing the electric connection therein. The relay 210 has an on-position for allowing the electric connection, or said in another way, the relay 210 has an on-position configured to allow the electric connection. The relay 210 further has an off-position for preventing the electric connection, or said in another words, the relay 210 has on off-position configured to prevent the electric connection. The relay 210 typically forms heat in the electric connection, wherein a volume of current of the electric power affects to the heat formation. The relay 210 is sized so that it stands the heat formation. The power distribution unit 200 of the Figures comprises a main fuse 220 providing overcurrent protection during the electric connection. The main fuse may be arranged between the first port of the distribution unit 200 and the input port of the distribution unit 200. The main fuse may be arranged between the second port of the distribution unit 200 and the output port of the distribution unit
200. The main fuse 220 allows current to flow through the main fuse, when the current is in a pre-determined value range. The main fuse 220 is configured to pre- vent the current to flow through the main fuse 220, when the current exceeds the pre-determined value range. The power distribution unit 200 may comprise a plu- rality of fuses providing an overcurrent protection during the electric connection between components of the battery pack 1. The power distribution unit 200 of the Figures comprises a current transformer 230 for safety purposes. The current may be measured via the current transformer 230. The current transformer 230 may be a wound current trans- former, a toroidal current transformer or a bar-type current transformer. The cur- rent transformer 230 is fitted so that it stands the heat formation. The power distribution unit 200 of the Figures comprises other essen- tial components such as a circuit board, transistors, conductors and/or resistors for providing proper power distribution unit, which components are not disclosed herein anymore. The battery pack 1 of the Figures comprises a battery management sys- tem 300 connected to the power distribution unit 200 for controlling the power distribution unit 200. The battery management system 300 controls the electric connection between the at least one battery module 100 and the electric vehicle. The battery management system 300 herein is physically separated from the power distribution unit 200. The battery management system 300 further controls the electric connection in the at least one battery module 100 and/or in the electric vehicle, which is disclosed in more detail below. The battery management system 300 of the Figures comprises conduc- tive parts such as conductors for implementing the electric connections in the bat- tery management system 300. The battery management system 300 comprises other essential components such as a circuit board, transistors, conductors and/or resistors for providing proper power distribution unit, which said components are not disclosed herein anymore. The battery management system 300 of the Figures further comprises a monitoring unit 310 comprising current sensors, voltage sensors and heat sen- sors connected at least to the power distribution unit 200. The monitoring unit 310 is configured to measure current, voltage and heat from the power distribution unit 200. Said current and voltage herein is current and voltage in the power distribu- tion unit. Said current sensors may be connected to the current transformer 230. The heat sensors are arranged herein near the power distribution unit 200. Said
heat sensors may measure temperature of the first heat transfer liquid. Further, the monitoring unit 310 may comprise current sensors, voltage sensors and heat sensors connected to the at least one battery module 100. The monitoring unit 310 is configured to measure current, voltage and heat from the at least on battery module. Said current and voltage herein is a total current and total voltage in the at least one battery module 100. The heat sensors herein are being arranged into the inner space 132 of the housing 130 of the battery module 100.The heat sensor herein may measure temperature of the second heat transfer liquid. Further, the monitoring unit 310 may comprise current sensors, voltage sensors and heat sensors connected to the plurality of battery cells 110 of the at least one battery module 100. The monitoring unit 310 is configured to measure current, voltage and heat from the plurality of the battery cells of the at least on battery module 100. Said current and voltage herein is current and voltage of plu- rality of battery cells 110. The heat sensors herein are coupled near to the plurality of battery cells 110. The heat sensors herein may measure temperature of the plu- rality of the battery cells. The battery management system 300 of the Figures comprises a calcu- lating unit 320 configured to form a measurement data about measurements of the sensors of the measuring unit 310. The calculating unit 320 is connected to the monitoring unit 310 for receiving the measurements. The electric connection be- tween the battery module 100 and the electric vehicle may be adjusted based on the measurement data. The battery management system 300 of the Figures further comprises a control unit 330A, i.e., a first control unit, configured to control the power distri- bution unit 200, which control unit 330A is connected to the power distribution unit 200. The control unit 330A is configured to adjust the power distribution unit 200 based on the measurement data. The first control unit 330A is configured to switch above-mentioned relay 210 of the power distribution unit 200 to on- and off-position, for example. The battery management system 300 of the Figures comprises a control unit 330B, i.e., a second control unit, configured to control the at least one battery module 100, which second control unit 330B is connected to the at least one bat- tery module 100. The second control unit 330B ensures that the at least one battery module 100 operates in a safe state. The second control unit 330B is configured to adjust the power in the at least one battery module 100 based on the measurement
data. The battery management system 300 of the Figures comprises connec- tion ports 340 allowing the battery management system 300 to be connected to the electric vehicle, the energy storage system or such, for example. The battery man- agement system 300 may send information such as measurement data and/or other information to the electric vehicle, the energy storage system or such. The battery management system 300 such as said first control unit 330A and/or second control unit 330B may receive information from the electric vehicle, the energy storage system or such, wherein the battery management system can use said in- formation to control the at least on battery module 100. The support structure 10 of the Figures 1-6 thus remains between the at least one battery module 100 and the wall structure 502 in the inner space 510 of the protective casing 500. The support structure comprises a main material 12 that is configured to expand and harden to form the support structure. The support structure 10 is extended against the at least one battery module 100 and the wall structure 502 in the inner space 510 of the protective casing 500. In more detail, the support structure 10 is extended against outer sides 130C of the at least one battery module 100. The support structure 10 thus minimizes gaps between the at least one battery module 100 and the wall structure 502 in the inner space 510 of the protective casing 500, wherein said gaps are minimized in a lateral direction of the protective casing 500. An advantage herein is that a motion of the at least one battery module 100 relative to the protective casing 500 is being reduced, which provides longer operating life for the battery pack. For sake of the clarity, the sup- port structure 10 extends against the at least one battery module 100 and the wall structure 502 in the inner space 510 of the protective casing 500. The main material 12 of the Figures may comprise polyurethane, polyi- socyanurate, synthetic rubber as nitrile, and/or synthetic polymers as silicone, for example. The main material 12 may be a polyurethane foam. In more detail, the polyurethane foam is self-hardening polyurethane foam. The main material 12 may be a component foam. The main material 12 may be a silicone foam. The main ma- terial 12 may be a nitrine foam. Hardening of the main material 12 may appear during expanding and/or after expanding of the main material 12. The main mate- rial 12 is configured to extend against the at least one battery module 100 and the wall structure 502 in the inner space 510 of the protective casing 500. Further, the support structure 10 of the Figures 1-6 supports each side of the at least one battery module 100, or said in another words, each side of the at
least one battery module 100 is supported by the support structure 10. The sup- port structure 10 covers at least 40 % of a surface area of sides of the at least one battery module 100. Said support structure 10 may cover over 60 % of said surface area of sides of the at least one support structure, which forms an effective heat insulation for the battery pack 1. Said surface area to be covered may be over 75 %. The support structure 10 of the figures may comprise at least one cover 14 into which the main material 12 is arranged for preventing contact between the heat transfer liquid 400-A and the main material 12. The cover 14 comprises a plas- tic material. The plastic material allows the cover 14 to stretch and bend, whereby the main material 12 can expand inside the cover 14 so that the cover extends against the at least one battery module and the wall structure in the inner space of the protective casing. Further, the plastic material allows the inner volume of the cover 14 to increase during the main material 12 expands in the cover 14. The cover 14 may have a certain maximum volume after which the cover 14 prevents the main material 12 to expand. The cover 14 comprising plastic material also re- sists the heat transfer liquid 400-A. Further, inside the cover 14 there may be partition walls 15 for guiding the main material 12 to expand inside the cover 14. Said partition walls 15 ensures that the main material 12 locates where necessary. Said partition walls 15 may ex- tend from bottom of the cover 14 to the top of the cover 14. There may be openings in partition walls 15 for allowing the main material to expand between every par- tition wall 15. Further, the cover 14 has an inlet for receiving the main material 12 into the cover 14. The inlet may be an opening. The support structure 10 of the Figures 1-6 comprises a plurality of the covers 14. For example, as illustrated in Figure 2, the battery pack 1 comprises a first cover 14A, a second cover 14B, a third cover 14C, a fourth cover 14D, a fifth cover 14E and a sixth cover 14F. Each cover is filled with the main material 12. The support structure 10 of the Figures 1-6 is assembled as follows. At least one battery module 100 is inserted into the inner space 510 of the protective casing 500. There may be four battery modules 100 one upon the other, for exam- ple. At least one cover 14 is inserted between the at least one battery module 100 and the wall structure 502 in the inner space 510 of the protective casing. The cover 14 is filled with the main material 12. The main material 12 expand and harden after which the support structure 10 is ready. There may be covers 14 at each side
of the battery module 100. If the battery pack needs to be disassembled, the sup- port structure 10 can be easily pulled out from the inner space 510 of the protective casing 500 as whole if needed. The heat transfer liquid 400-A, i.e., the first heat transfer liquid, of the Figures 1-6 is in contact with the power distribution unit 200 for balancing heat between the power distribution unit 200 and the first heat transfer liquid 400-A. The first heat transfer liquid 400-A is a dielectric liquid. The first heat transfer liq- uid 400-A extends to the relay 210 of the distribution unit 200 for balancing the heat between the relay 210 and the first heat transfer liquid 400-A, or said in an- other way, the first heat transfer liquid 400-A is in contact with the relay 210. The first heat transfer liquid 400-A extends to the main fuse 220 of the power distribu- tion unit 200 for balancing the heat between the main fuse 220 and the first heat transfer liquid 400-A, or said in another way, the first heat transfer liquid 400-A is in contact with the main fuse 220. The first heat transfer liquid 400-A extends to the current transformer 230 of the distribution unit 200 for balancing the heat be- tween the current transformer 230 and the first heat transfer liquid 400-A, or said in another way, the first heat transfer liquid 400-A is in contact with the current transformer 230. An advantage herein is that the power distribution unit 200 is effectively cooled by the first heat transfer liquid 400-A. Another advantage is that smaller sized components can be used in the power distribution unit 200 compared to a situation wherein there is no the heat transfer liquid, said components being the relay 210, the main fuse 220 and/or the current transformer 230, for example. The first heat transfer liquid 400-A is filled into the first inner space 510 of the protective casing 500, which protective casing 500 is disclosed in more detail be- low. The first heat transfer liquid 400-A may be filled into the first inner space 510 of the protective casing 500 so that the first heat transfer liquid at least partially surrounds the power distribution unit 200, or so that the first heat transfer liquid fully surrounds the power distribution unit 200. Further, the first heat transfer liquid 400-A is being filled into the pro- tective casing 500 so that it at least partially surrounds the at least one battery module 100. The first heat transfer liquid 400-A is being filled into the protective casing 500 so that it locates above the at least one battery module 100. A purpose of the first heat transfer liquid surrounding the at least one battery module 100 is that the first heat transfer liquid prevents fire to spread in cases of battery cells 110 blasting or causing fire via the second end 114 of the battery cell(s) 110. Further, the first heat transfer liquid 400-A is being filled into the
protective casing so that it at least partially surrounds the support structure 10. The protective casing 500 of the Figures 1-6 thus has the wall structure 502 that forms the inner space 510, i.e., a first inner space, for accommodating the at least one battery module 100. Further, the inner space 510 of the protective cas- ing 500 is for accommodating the support structure 10. Further, the inner space 510 of the protective casing 500 is for accommodating the power distribution unit 200. Further, the inner space 510 of the protective casing 500 is for accommodating the first heat transfer liquid 400-A. The protective casing 500 may comprise a plas- tic as a material, which material may be UL94-V0, for example. Alternatively, or in addition, the protective casing 500 may comprise a metal, for example. Further, the wall structure 502 of the protective casing 500 of the Fig- ures 1-6 is divided as follows. The wall structure 502 has inner side walls 502A. Said inner side walls 502A locate towards outer sides 130C of the at least one bat- tery module 100. The inner side walls 502A forms said inner space 502 of the pro- tective casing 500 in lateral direction of the protective casing 500. The wall struc- ture 502 has outer side walls 502B for forming an external surface of the protective casing 500. The wall structure 502 has an inner bottom 502C forming a bottom in the inner space 510, which inner bottom locates between the inner side walls 502A. The wall structure 502 has an outer bottom 502D for forming an external bottom for the protective casing 500. The protective casing 500 of the Figures 1-6 has an inner space 520, i.e., a second inner space, i.e., another inner space, for accommodating the battery man- agement system 300, which inner space 520 has a cover structure 522 between the battery management system 300 and the heat transfer liquid 400-A being in con- tact with power distribution unit 200. The cover structure 522 prevents the heat transfer liquid 400-A to be in contact with the battery management system 300. The battery management system 300 is attached to the cover structure 522. The battery management system 300 is being separated to be in contact with the first heat transfer liquid 400-A and a second heat transfer liquid 400-B, which second heat transfer liquid is disclosed in more detail below. The cover structure 522 may be a shell structure of the protective casing 500, or the cover structure 522 may be a wall structure in the protective casing 500. Between the second inner space 520 and the first inner space 510 there are inlets for connections to be made between the battery management system 300 and the power distribution unit 200, which connections are made by wirings, for example. Said inlets are fitted so that there is no access for the first heat transfer liquid to flow to second inner space 520. There
may be sealings arranged in said inlets for preventing the first heat transfer liquid to flow to the second inner space 520. An advantage of the second inner space is that there are a lot of components to be selected and used in the battery manage- ment 300, because said components does not need to stand the heat transfer liquid. According to an embodiment, the cover structure 522 comprises openings that al- low the first heat transfer liquid 400-A to flow into the second inner space 520. In the embodiment, components of the battery managements system 300 are selected so that they stand the first heat transfer liquid 400-A. An advantage herein is that the battery management system 300 is cooled effectively by the heat transfer liq- uid. According to an embodiment, which is not shown in the Figures, the sec- ond inner space 520 for accommodating the battery management system 300 has not the above-mentioned cover structure 522 between the battery management system 300 and the heat transfer liquid 400-A being in contact with power distri- bution unit 200, which allows the heat transfer liquid 300-A to be in contact with the battery managements system 300. Components of the battery management system 300 are arranged to stand the first heat transfer liquid 400-A. The monitor- ing unit 310, the calculating unit 320 and/or the control unit 330A are arranged to stand the first heat transfer liquid 400-A, for example. An advantage herein is that the battery management system 300 is cooled effectively by the heat transfer liq- uid. According to an embodiment, which is not shown in the Figures, the bat- tery management system 300 is arranged into the first inner space 510 of the pro- tective casing 500. Components of the battery management system 300 are ar- ranged to stand the first heat transfer liquid 400-A. The monitoring unit 310, the calculating unit 320 and/or the control unit 330A are arranged to stand the first heat transfer liquid 400-A, for example. An advantage herein is that the battery management system 300 is cooled effectively by the heat transfer liquid. The protective casing 500 of the Figures 1-6 comprises a lower housing 500-L that forms the inner space 510, i.e., the first inner space. The lower housing 500-L of the protective casing 500 forms the inner space 510, which lower housing 500-L has an opening that forms an entry/access to the inner space 510. In more detail, the opening locates at a top of the lower housing 500-L. The protective casing 500 further comprises an upper housing 500-U, i.e., a cover 500-U, for covering above-mentioned opening of the lower housing 500-L of the protective casing 500. The upper housing 500-U of the protective
casing 500 covers the inner space 510 from above the inner space 510. The second inner space 520 is arranged to the upper housing 500-U. The upper housing 500-U has an opening that forms an entry/access to the protective inner space 520. In more detail, said opening locates at a top of the upper housing 500-U. The wall structure 502 of the protective casing 500 of the Figures 1-6 is a double shell structure for absorbing forces such as hits and vibrations. In more detail, the lower housing 500-L of the protective casing 500 has the double shell structure, and/or the upper housing 500-U of the protective casing 500 has the double shell structure. The double shell structure surrounds the inner space 510 for securing components of the battery module 100 and the power distribution 200 therein. The double shell structure 502 is a hollow structure that is filled with a heat insulating foam 504 for insulating heat, which heat insulating foam 504 is shown in parallel lines in Figure 1. Referring to the figures 7 and 8, the double shell structure is filled with the main material 12 as disclosed in more detail below. The battery pack 1 of the Figures comprises a heat transfer liquid 400- B, i.e., a second heat transfer liquid 400-B locating in the at least one battery module 100. The second heat transfer liquid balances heat between the second heat trans- fer liquid 400-B and the at least one battery module 100. The second heat transfer liquid 400-B is partially shown in broken lines in Figure 1. The second heat transfer liquid 400-B is a dielectric liquid. The second heat transfer liquid 400-B and the first heat transfer liquid 400-A are typically same liquid. The second heat transfer liquid 400-B locates in the at least one battery module 100. In more detail, the inner space 132 of the housing 130 of the battery module 100 is filled by the second heat transfer liquid for balancing heat between the battery cells 110 and the second heat transfer liquid 400-B. The second heat transfer liquid is essentially in connect with the side portion 118 of the battery cells 110, i.e., the battery cells 110 are mostly surrounded by the second heat transfer liquid. There are gaps between the battery cells 110 in the lateral direction of the battery cells 110, wherein the gaps allow the second heat transfer liquid to extend to the battery cells 110, whereby the heat is transferred effectively between the battery cells 110 and the second heat transfer liquid. Further, said wall of the socket 172 of the upper housing 170 against the side portion 118 of the battery cell 110 prevents the second heat transfer liquid to flow via between the wall of the socket 172 and the side portion 118 of the bat- tery cell 110 to a space, wherein the busbar assembly 120 locates. Respectively, said limiter 180A prevents the second heat transfer liquid to flow via between the
battery cell 110 and the limiter 180A to the space, wherein the busbar assembly 120 locates. Said wall of the socket 172 of the upper housing 170 against the side portion 118 of the battery cell 110 prevents the first heat transfer liquid to flow via between the wall of the socket 172 and the side portion 118 of the battery cell 110 to the inner space 132 of the battery module 100. The battery pack 1 of the Figures comprises an input 620 (i.e., an input opening) and an output 630 (i.e., an output opening) being arranged to the at least one battery module 100 allowing the second heat transfer liquid 400-B to flow through the at least one battery module. The input 620 of the battery module 100 is arranged to the housing 130, such as to the side wall 164 of the lower housing 160 and/or the side wall 174 of the upper housing 170. The output 630 of the bat- tery module 100 is arranged to the housing 130 such as to the side wall 164 of the lower housing 160 and/or the side wall 174 of the upper housing 170. The battery pack 1 of the Figures comprises a pump 600 for circulating the second heat transfer liquid 400-B through the at least one battery module 100. The circulation herein provides efficient heat balance between the second heat transfer liquid 400-B and the battery cells 110 of the battery module 100. The battery pack 1 of the Figures comprises a route 610 for guiding the second heat transfer liquid 400-B, which route 610 may be a hose, a pipe, and/or a guider made of a plastic or a metal, for example. The route 610 guides the second heat transfer liquid 400-B from the pump 600 into the at least one battery module 100, and which route 610 guides the second heat transfer liquid 400-B from the at least one battery module 100 into the pump 600. The route 610 is connected be- tween the pump 600 and the at least one battery module 100. In more detail, the route 610 is connected between the pump 600 and the input 620 of the at least one battery module 100, and the route 610 is connected between the pump 600 and the output 630 of the at least one battery module 100. The second heat transfer liquid 400-B circulates/flows from the pump 600 to the input 620 of the at least one battery module 100, from said input 620 to the output 630 of the at least one battery module, i.e., through the inner space 132 of the housing of the battery mod- ule 100, and from the output 630 of the at least one battery module 100 to the pump 600. As an example, when there is a first battery module, a second battery module, a third battery module and a fourth battery module, the connection for implement- ing the circulation of the second heat transfer liquid is following. The pump 600 is connected to the input of the first battery module, the output of the first battery module is connected to the input of the second battery module, the output of the
second battery module is connected to the input of the third battery module, the output of the third battery module is connected to the input of a fourth battery module, and the output of the fourth battery module is connected to the pump. The second heat transfer liquid circulates from the pump 600 to the input of the first battery module, the second heat transfer liquid circulates through the first battery module, the second battery module, the third battery module and the fourth bat- tery module, and the second heat transfer liquid circulates from the output of the fourth battery module to the pump 600. For sake of the clarity, the second heat transfer liquid is intended to be located in the pump 600, the route 610 and the at least one battery module 100. The route 610 of the Figures further locates at least partially in the inner space 510 of the protective casing 500. The route 610 is at least partially sur- rounded by the heat transfer liquid 400-A that is in contact with the power distri- bution unit 200, whereby there is heat balance between the heat transfer liquid 400-B locating in the route 610 and the heat transfer liquid 400-A surrounding the route 610. Thus, the route 610 is at least partially surrounded by the first heat transfer liquid 400-A for balancing the heat between the first heat transfer liquid 400-A and the second heat transfer liquid 400-B. For sake of the clarity, the route 610 is at least partially surrounded by the first heat transfer liquid 400-A in the inner space 510 of the protective casing 500. There is heat balance between the power distribution unit 200, the first heat transfer liquid 400-A, the second heat transfer liquid 400-B and the at least battery module 100. An advantage herein re- lates to a situation, wherein the power distribution unit requires to be cooled down whereas battery cells of the battery module require to be heated up. Heat formed from the power distribution unit may be used effectively to heat the battery cells of the battery module. The route 610 of the Figures further comprises openings 640 allowing the heat transfer liquid 400-A locating inside the route 610 and the heat transfer liquid 400-B surrounding the route 610 to mix. Thus, openings 640 allow the first heat transfer liquid 400-A and the second heat transfer liquid 400-B to mix. The openings 640 of the route 600 herein locates in the first inner space 510 of the protective casing 500. Said mix between the first heat transfer liquid and the sec- ond heat transfer liquid herein provides an effective way to balance the heat be- tween the first heat transfer liquid and the second heat transfer liquid. The battery pack 1 of the Figures comprises a cover unit 800 for safety reasons, which cover unit 800 is arranged between the topmost battery module
100 and the power distribution unit 200. The cover unit 800 may be a fire protec- tion plate for preventing fire to spread in cases of battery cell(s) 110 causing fire. The cover unit 800 locates in the inner space of the protective casing 500. The battery module 100 of the Figures comprises at least one heat unit 900 for heating the second heat transfer liquid that heats the battery cells 110. For example, as illustrated in Figure 5, the battery module 100 comprises two heat units 900 in the inner space 132 of the housing 130. The heat unit 900 locates in the inner space of the housing 130 between determined battery cells 110. The heat unit 900 comprises an elongated plate and electric wires for heating the elongated plate inside the elongated plate, wherein the electric wires are configured to be in an electric connection. The elongated plate may be flexible or rigid, for example. Further, the above-mentioned elongated plate(s) of the heat unit 900 and the side walls of the housing 130 forms a slalom path in the inner space 132 of the housing 130 of the battery module 100. The slalom path provides a guided path for the second heat transfer liquid during circulation through said inner space 132 of the housing 130 of the battery module 100. To form said slalom path by the elon- gated plate(s) of the heat unit 900, there is a gap 910 between an end of the elon- gated plate of each heat unit 900 and the walls of the housing 130. A purpose of the slalom path is to provide that all the second heat transfer liquid circulates via the pump 600, thus, there are no areas in the inner space 132 of the housing 130, wherein the second heat transfer liquid stays still for example. According to an em- bodiment, the slalom path in the inner space 132 of the housing 130 may be formed by the additional wall structures of the housing 130, thus without wall of the heat unit 900. The battery pack 1 of the Figures comprises a filling hole 650 for the first heat transfer liquid 400-A being filled into the first inner space 510 of the pro- tective casing 500. For covering the filling hole 650 there is a fill cap arranged to the filling hole 650. The battery pack 1 of the Figures comprises lift lugs 530 arranged to the protective casing 500 providing the battery pack 1 to be lifted. Depending on quan- tity of the battery modules 100, a weight of the battery pack 1 may be 80–400 kg, 100–300 kg, 120–220 kg, for example. A width of the battery pack may be 300 – 600 mm, a length of the battery pack may be 600 – 1000 mm, and a height of the battery pack may be 300 – 800 mm, for example. The battery pack 1 may be used to power the electric vehicle. The elec- tric vehicle comprising the battery pack 1 may be a car, a truck, a bus, a work
machine such as a mobile work machine, and/or an electric apparatus, for example. The mobile work machine is a loader or a lifter, for example. The electric vehicle may be a high voltage system or a low voltage system. The voltage in the low volt- age system may be 50 volts or less. The battery pack 1 may be used for storing energy in the energy storage systems. The energy storage system comprising at least one battery pack 1 is used to storage energy produced by a power station and/or supplied via a power grid. At least one battery pack 1 is connected to the power station and/or the power grid. The power station may be a hydroelectric power station, a solar power sta- tion, a wind power station, a biomass power station, a thermal power station or such, for example. The energy storage system may be the high voltage system or the low voltage system. The voltage in the low voltage system may be 50 volts or less. The battery pack 1 of the Figures 1-6 can be assembled as follows. At least one battery module 100 is inserted into the protective casing 500. The main material 12 is inserted into the protective casing 500 after which the main material 12 expands and hardens to form the support structure 10 for the at least one bat- tery module 100. In more detail, the main material 12 is inserted into the inner space 510 of the protective casing 500. The battery pack 1 of the Figures 1-6 can be assembled as follows in a situation, wherein the heat transfer liquid 400-A is being used. At least one battery module 100 is inserted into the protective casing 500. At least one battery module 100 is inserted into the protective casing 500. At least one cover 14 is inserted into the protective casing 500. The main material 12 is inserted into the cover 14 after which the main material expands and hardens to form the support structure 10 for the at least one battery module 100. The heat transfer liquid 400-A is inserted into the protective casing 500. The support structure 10 of the Figures 7 and 8 thus remains inside the double shell structure of the protective casing 500. The support structure com- prises a main material 12 that is configured to expand and harden to form the sup- port structure. The support structure 10 is extended against the walls of the double shell structure of the protective casing 500. In more detail, the support structure 10 is extended against inner side walls 502A of the protective casing 500 and outer side walls 502B of the protective casing 500. The expansion of the main material 12 may cause the inner side walls 502A to bend. During expansion of the main ma- terial 12, the support structure 10 minimizes gaps between the at least one battery
module 100 and the wall structure 502 in the inner space 510 of the protective casing 500. An advantage herein is that a motion of the at least one battery module 100 relative to the protective casing 500 is being reduced, which provides longer operating life for the battery pack. Another advantage herein is that there is no need to remove the support structure 10 in order to take the battery module(s) out from the protective casing 500. The main material 12 of the Figures 7 and 8 may comprise polyure- thane, polyisocyanurate, synthetic rubber as nitrile, and/or synthetic polymers as silicone, for example. The main material 12 may be a polyurethane foam. In more detail, the polyurethane foam is self-hardening polyurethane foam. The main ma- terial 12 may be a component foam. The main material 12 may be a silicone foam. The main material 12 may be a nitrine foam. Hardening of the main material 12 may appear during expanding and/or after expanding of the main material 12. The main material 12 is configured to extend against the inner side walls 502A and the outer side walls 502B. Pressurized air may also be used in forming the support structure 10. The support structure 10 of the Figures 7 and 8 indirectly supports each side of the at least one battery module 100, or said in another words, each side of the at least one battery module 100 is indirectly supported by the support struc- ture 10. For sake of the clarity, there is the inner wall 502A of the protective casing 500 between the support structure 10 and the battery module 100. The support structure 10 covers at least 40 % of a surface area of sides of the at least one battery module 100. Said support structure 10 may cover over 60 % of said surface area of sides of the at least one support structure, which forms an effective heat insulation for the battery pack 1. Said surface area to be covered may be over 75 %. The support structure 10 of the Figures 7 and 8 may comprise or may not comprise said cover 14. The support structure 10 may comprise the cover 14 inside the double shell structure of the protective casing 500, if guiding of the main material 12 is needed, for example. The protective casing 500 of the Figures 7 and 8 comprises an inlet 500- IN for allowing the main material 12 to be inserted inside the double shell struc- ture. Said inlet 500-IN can be covered after the main material 12 is inserted inside the double shell structure. During the assembly of the battery pack 1 a closed space may be formed inside the protective casing 500. Alternatively, in addition to the inlet 500-IN the protective casing 500 may also comprise an outlet. A pressure in- side the protective casing 500 may be controlled through the outlet.
The heat transfer liquid 400-A, i.e., the first heat transfer liquid, of the Figures 7 and 8 is in contact with the power distribution unit 200 for balancing heat between the power distribution unit 200 and the first heat transfer liquid 400-A. The first heat transfer liquid 400-A is a dielectric liquid. The first heat transfer liq- uid 400-A extends to the relay 210 of the distribution unit 200 for balancing the heat between the relay 210 and the first heat transfer liquid 400-A, or said in an- other way, the first heat transfer liquid 400-A is in contact with the relay 210. The first heat transfer liquid 400-A extends to the main fuse 220 of the power distribu- tion unit 200 for balancing the heat between the main fuse 220 and the first heat transfer liquid 400-A, or said in another way, the first heat transfer liquid 400-A is in contact with the main fuse 220. The first heat transfer liquid 400-A extends to the current transformer 230 of the distribution unit 200 for balancing the heat be- tween the current transformer 230 and the first heat transfer liquid 400-A, or said in another way, the first heat transfer liquid 400-A is in contact with the current transformer 230. An advantage herein is that the power distribution unit 200 is effectively cooled by the first heat transfer liquid 400-A. Another advantage is that smaller sized components can be used in the power distribution unit 200 compared to a situation wherein there is no the heat transfer liquid, said components being the relay 210, the main fuse 220 and/or the current transformer 230, for example. The first heat transfer liquid 400-A is filled into the first inner space 510 of the protective casing 500, which protective casing 500 is disclosed in more detail be- low. The first heat transfer liquid 400-A may be filled into the first inner space 510 of the protective casing 500 so that the first heat transfer liquid at least partially surrounds the power distribution unit 200, or so that the first heat transfer liquid fully surrounds the power distribution unit 200. Further, the first heat transfer liquid 400-A is being filled into the pro- tective casing 500 so that it at least partially surrounds the at least one battery module 100. The first heat transfer liquid 400-A is being filled into the protective casing 500 so that it locates above the at least one battery module 100. A purpose of the first heat transfer liquid surrounding the at least one battery module 100 is that the first heat transfer liquid prevents fire to spread in cases of battery cells 110 blasting or causing fire via the second end 114 of the battery cell(s) 110. Further, the inner walls 502A of the protective casing 500 prevents the first heat transfer liquid 400-A to be in contact with the main material 12 locating inside the double shell structure of the protective casing 500. The protective casing 500 of the Figures 7 and 8 thus has the wall
structure 502 that forms the inner space 510, i.e., a first inner space, for accommo- dating the at least one battery module 100. Further, the inner space 510 of the pro- tective casing 500 is for accommodating the power distribution unit 200. Further, the inner space 510 of the protective casing 500 is for accommodating the first heat transfer liquid 400-A. The protective casing 500 may comprise a plastic as a mate- rial, which material may be UL94-V0, for example. Alternatively, or in addition, the protective casing 500 may comprise a metal, for example. Further, the wall structure 502 of the protective casing 500 of the Fig- ures 7 and 8 is divided as follows. The wall structure 502 has inner side walls 502A. Said inner side walls 502A locate towards outer sides 130C of the at least one bat- tery module 100. The inner side walls 502A forms said inner space 502 of the pro- tective casing 500 in lateral direction of the protective casing 500. The wall struc- ture 502 has outer side walls 502B for forming an external surface of the protective casing 500. The wall structure 502 has an inner bottom 502C forming a bottom in the inner space 510, which inner bottom locates between the inner side walls 502A. The wall structure 502 has an outer bottom 502D for forming an external bottom for the protective casing 500. The protective casing 500 of the Figures 7 and 8 has an inner space 520, i.e., a second inner space, i.e., another inner space, for accommodating the battery management system 300, which inner space 520 has a cover structure 522 be- tween the battery management system 300 and the heat transfer liquid 400-A be- ing in contact with power distribution unit 200. The cover structure 522 prevents the heat transfer liquid 400-A to be in contact with the battery management system 300. The battery management system 300 is attached to the cover structure 522. The battery management system 300 is being separated to be in contact with the first heat transfer liquid 400-A and a second heat transfer liquid 400-B, which sec- ond heat transfer liquid is disclosed in more detail below. The cover structure 522 may be a shell structure of the protective casing 500, or the cover structure 522 may be a wall structure in the protective casing 500. Between the second inner space 520 and the first inner space 510 there are inlets for connections to be made between the battery management system 300 and the power distribution unit 200, which connections are made by wirings, for example. Said inlets are fitted so that there is no access for the first heat transfer liquid to flow to second inner space 520. There may be sealings arranged in said inlets for preventing the first heat transfer liquid to flow to the second inner space 520. An advantage of the second inner space is that there are a lot of components to be selected and used in the battery
management 300, because said components does not need to stand the heat trans- fer liquid. According to an embodiment, the cover structure 522 comprises open- ings that allow the first heat transfer liquid 400-A to flow into the second inner space 520. In the embodiment, components of the battery managements system 300 are selected so that they stand the first heat transfer liquid 400-A. An ad- vantage herein is that the battery management system 300 is cooled effectively by the heat transfer liquid. The protective casing 500 of the Figures 7 and 8 comprises a lower housing 500-L that forms the inner space 510, i.e., the first inner space. The lower housing 500-L of the protective casing 500 forms the inner space 510, which lower housing 500-L has an opening that forms an entry/access to the inner space 510. In more detail, the opening locates at a top of the lower housing 500-L. The protective casing 500 further comprises an upper housing 500-U, i.e., a cover 500-U, for covering above-mentioned opening of the lower housing 500-L of the protective casing 500. The upper housing 500-U of the protective cas- ing 500 covers the inner space 510 from above the inner space 510. The second inner space 520 is arranged to the upper housing 500-U. The upper housing 500-U has an opening that forms an entry/access to the protective inner space 520. In more detail, said opening locates at a top of the upper housing 500-U. The wall structure 502 of the protective casing 500 further is a double shell structure for absorbing forces such as hits and vibrations. In more detail, the lower housing 500-L of the protective casing 500 has the double shell structure, and/or the upper housing 500-U of the protective casing 500 has the double shell structure. The double shell structure surrounds the inner space 510 for securing components of the battery module 100 and the power distribution 200 therein. The double shell structure is a hollow structure that is filled with the main material 12. The support structure 10 is formed after the main material 12 hardens. The space locating inside the hollow structure can be called an inner space 700 of the double shell structure, i.e., the space locating between the inner walls 502A and the outer walls 502B can be called an inner space 700 of the double shell structure. The battery pack of the Figures 7 and 8 can be assembled as follows, and/or the support structure 10 of the Figures 7 and 8 can be assembled as follows. The protective casing 500 may be inserted into an assembly mold M. The assembly mold M partially prevents the protective casing 500 to bend. In more detail, the assembly mold M prevents outer side walls 502B of the protective casing to bend. The assembly mold M has a space for accommodating the protective casing 500.
The assembly mold M surrounds the protective casing. The assembly mold M ex- tends against the protective casing. It is not necessary to use an assembly mold M at all if the outer side walls 502B of the protective casing 500 are formed strong enough. The outer side walls 502B may comprise stiffeners such as ribs or fins, for example. Further, at least one battery module 100 is inserted into the inner space 510 of the protective casing 500. The at least one battery module 100 can be in- serted into the inner space 510 of the protective casing before/after the protective casing is inserted into the assembly mold M. There may be four battery modules 100 one upon the other, for example. Further, the main material 12 is inserted into the protective casing 500 after which the main material 12 expands and hardens to form the support struc- ture 10 for the at least one battery module 100. The double shell structure of the protective casing is filled with the main material 12. Thus, the main material 12 remains inside the double shell structure of the protective casing. The main mate- rial 12 expands and therefore causes the wall structure 502 of the protective casing to bend/expand against/towards the at least one battery module 100. In more de- tail, the main material 12 expands and therefore causes the inner side walls 502A of the protective casing to bend/expand against/towards the at least one battery module 100. The wall structure 502 of the protective casing 500 bends because of expansion of the main material 12. The inner side walls 502A of the protective cas- ing 500 bends during the expansion of the main material 12. Therefore, the inner side walls 502A of the protective casing 500 extend against the at least one battery module 100. The main material hardens after which the protective casing forms its final shape. If the battery pack needs to be disassembled, the battery module(s) can be easily pulled out from the inner space 510 of the protective casing 500. Further referring to said assembly, the pressurized air may be used to cause said double shell structure of the protective casing to bend/expand against/towards the at least one battery module 100. The pressurized air may be inserted into the double shell structure before/during the main material is inserted into the double shell structure. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The inven- tion and its embodiments are not limited to the examples described above but may vary within the scope of the claims.