A battery box floor for electric vehicles for being arranged at the lower part of a vehicle body, said battery box floor comprising: [a] a battery pack supporting panel for supporting a plurality of battery cells, [b] a plurality of lower cooling channels for containing a cooling fluid, said plurality of lower cooling channels being arranged adjacent to and below said battery pack supporting panel such that they can cool said battery cells and [c] an underbody protection arranged below said plurality of lower cooling channels, the underbody protection being an underbody protection for a vehicle body, wherein [d] a deformation inner cavity is provided between said plurality of lower cooling channels and said underbody protection, [e] said battery box floor is integrally formed by one or more metallic parts, said deformation inner cavity has a lower inner face and an upper inner face and said battery box floor further comprises a plurality of inner ribs, said plurality of inner ribs extending from said lower inner face to said upper inner face, wherein at least one rib of said plurality of inner ribs has an arch shaped cross section, characterised in that said at least one arch shaped rib is arranged such that the concave side of said at least one arch shaped rib faces said upper inner face of said inner cavity and encapsulates at least one lower cooling channel between two interrupting sections, wherein said metallic material is an aluminium alloy and in that said battery box floor is made up of at least one extruded part of said aluminium alloy, said extruded part forming: [a] said supporting panel, [b] said lower cooling channels, [c] said deformation inner cavity and [d] said underbody protection. [a] a battery pack supporting panel for supporting a plurality of battery cells, [b] a plurality of lower cooling channels for containing a cooling fluid, said plurality of lower cooling channels being arranged adjacent to and below said battery pack supporting panel such that they can cool said battery cells and [c] an underbody protection arranged below said plurality of lower cooling channels, the underbody protection being an underbody protection for a vehicle body, [d] a deformation inner cavity is provided between said plurality of lower cooling channels and said underbody protection, [e] said battery box floor is integrally formed by one or more metallic parts, said deformation inner cavity has a lower inner face and an upper inner face and said battery box floor further comprises a plurality of inner ribs, said plurality of inner ribs extending from said lower inner face to said upper inner face, wherein at least one rib of said plurality of inner ribs has an arch shaped cross section, characterised in that said at least one arch shaped rib is arranged such that the concave side of said at least one arch shaped rib faces said upper inner face of said inner cavity and encapsulates at least one lower cooling channel between two interrupting sections, wherein said metallic material is an aluminium alloy and in that said battery box floor is made up of at least one extruded part of said aluminium alloy, said extruded part forming: [a] said supporting panel, [b] said lower cooling channels, [c] said deformation inner cavity and [d] said underbody protection. [a] said supporting panel, [b] said lower cooling channels, [c] said deformation inner cavity and [d] said underbody protection.