a first subassembly including:

a first lower structure defining a bottom portion of the first subassembly;

a first pair of crossmembers defining a top portion of the first subassembly;

a first pair of vertical posts attached to the first lower structure and the first pair of crossmembers at a first end of the first subassembly;

a second pair of vertical posts attached to the first lower structure and the first pair of crossmembers at a second end of the first subassembly; and

a first plurality of intermediate panels including at least three intermediate panels extending in a vertical direction between the first lower structure and the first pair of crossmembers, and located between the first pair of vertical posts and the second pair of vertical posts, wherein individual intermediate panels of the first plurality of intermediate panels are perpendicular to the first pair of crossmembers and spaced apart at a first distance to define at least two spaces for receiving vertically-arranged battery racks; and

a second subassembly including:

a second lower structure defining a bottom portion of the second subassembly;

a second pair of crossmembers defining a top portion of the second subassembly;

a third pair of vertical posts attached to the second lower structure and the second pair of crossmembers at a first end of the second subassembly;

a fourth pair of vertical posts attached to the second lower structure and the second pair of crossmembers at a second end of the second subassembly; and

a second plurality of intermediate panels including at least three intermediate panels extending in a vertical direction from the second lower structure to the second pair of crossmembers, and located between the third pair of vertical posts and the fourth pair of vertical posts, wherein individual intermediate panels of the second plurality of intermediate panels are perpendicular to the second pair of crossmembers and spaced apart at a second distance to define at least two spaces for receiving vertically-arranged battery racks; and

a pair of lateral braces securing the first subassembly to the second subassembly by coupling the first pair of vertical posts to the third pair of vertical posts, and the second pair of vertical posts to the fourth pair of vertical posts,