More pictures...
I had a few problems while relocating the battery, the worse was since the cable was out of a newer 5 series it joined in the cabin, and then I realized the rear windshield wiper lines were cracked and my cabin was flooded with water, so a days delay and replaced the solid plastic type brittle hose with some nylon and regular transparent hose, which did the trick. The battery was mounted using a nutsert and 2 threaded rods, sit sturdy as a rock.