In the first picture are the two nuts I welded to the inside of the battery box, to secure the lid. Beside the box is the completed lid and a salvaged metal shelf that I cut the lid from. The lid is drilled for attachment knobs and two edges are turned to match the two salvaged bends. It's light but it will not be supporting any weight (beyond a cup of coffee, ha, ha), and it's main purpose is to keep the weather out.
Here it is closed up with two knobs to secure it in place. It will look better when the paint is all matched up.