A process for manufacturing a battery box with a peripheral frame, comprising at least the following steps, a) Providing an extruded element in aluminium alloy wherein said extruded element comprises at least three walls W1, W2, W3, the length of the walls W1 and W3 being respectively L1 and L3 and at least one hollow chamber, - said wall W2 is connected with at least said two other walls W1 and W3 at their extremities - at least one of the said two walls W1 or W3 is connected at one extremity of said wall W2, - said two walls W1 and W3 are substantially perpendicular to said wall W2 and positioned in a same half-space containing said wall W2 as a frontier, - a part of said wall W2 forms a wall of said hollow chamber, - said hollow chamber is located between the two said walls W1 and W3 and extends in the direction of said walls W1 and W3 over a length L2 wherein the length L2 is smaller than L1 and/or L3. b) Making a notch in each two walls W1 and W3 of said extruded element, each notch presents an axis of symmetry (Δ) and an invariant point, the two invariant points of each notch are located at the same position according to the extrusion direction and the axis (Π) passing by these two invariant points is parallel to wall W2 c) Bending in one bending direction said extruded element at least once, according an angle α, said bending direction corresponds to said axis (Π) passing by the invariant points of the two notches to form a part of the peripheral frame, said part of peripheral frame presents at least two different inner radii of curvature. a) Providing an extruded element in aluminium alloy wherein said extruded element comprises at least three walls W1, W2, W3, the length of the walls W1 and W3 being respectively L1 and L3 and at least one hollow chamber, - said wall W2 is connected with at least said two other walls W1 and W3 at their extremities - at least one of the said two walls W1 or W3 is connected at one extremity of said wall W2, - said two walls W1 and W3 are substantially perpendicular to said wall W2 and positioned in a same half-space containing said wall W2 as a frontier, - a part of said wall W2 forms a wall of said hollow chamber, - said hollow chamber is located between the two said walls W1 and W3 and extends in the direction of said walls W1 and W3 over a length L2 wherein the length L2 is smaller than L1 and/or L3. - said wall W2 is connected with at least said two other walls W1 and W3 at their extremities - at least one of the said two walls W1 or W3 is connected at one extremity of said wall W2, - said two walls W1 and W3 are substantially perpendicular to said wall W2 and positioned in a same half-space containing said wall W2 as a frontier, - a part of said wall W2 forms a wall of said hollow chamber, - said hollow chamber is located between the two said walls W1 and W3 and extends in the direction of said walls W1 and W3 over a length L2 wherein the length L2 is smaller than L1 and/or L3. b) Making a notch in each two walls W1 and W3 of said extruded element, each notch presents an axis of symmetry (Δ) and an invariant point, the two invariant points of each notch are located at the same position according to the extrusion direction and the axis (Π) passing by these two invariant points is parallel to wall W2 c) Bending in one bending direction said extruded element at least once, according an angle α, said bending direction corresponds to said axis (Π) passing by the invariant points of the two notches to form a part of the peripheral frame, said part of peripheral frame presents at least two different inner radii of curvature.