Adding the rear battery box

With the rear cross member finished, we can now build the rear battery box. This will run from the back of the main battery box to the front of the rear cross member.

We cut a piece of 1 by 3 rectangle tubing to form the back of the battery box. We position the tubing so that it's lower edge is flush with the car bottom and centered. With it clamp in place, we transfer the rear cross member holes. We drill out the holes to take spools and weld the spools in place.

We bolt the tubing in place and mark areas that will interfere. In this case the area where the rear differential is mounted (marked with a blue arrow) and two spots where access to suspension bolts would be blocked (marked with a green arrow). The interfering areas are cut out and the cuts are welded closed to return the strength.

Next the motor controllers are fitted in place and the rear bar is marked where threaded spools will be needed to hold the controllers. It is easier to add the spools with the tubing on the bench.

With the threaded spools to hold the controllers welded in (orange arrows), the rear tubing is bolted back in place. Another piece of tubing is fitted to form the side of the rear battery box and clamped in place to be welded.