When I took the sawzall to the floor of the back seat of my car, I was sweating a bit more than would have been justified considering the temperature. That was the most visible indication of the scale of what I'm doing to this poor BMW. The holes that were left when I finished were jagged and uneven.

And they still are! But now there are the beginnings of battery boxes sitting in those holes. And those battery boxes actually hold batteries!

We only dropped the cells in to test-fit. The next steps are to fill in the gaps in the sheet metal around the boxes, paint them, and install panels in them to make them water tight. We'll also make some passages for the HV cables and coolant lines as well. Once that's complete, a rack for the upper portion of the rear battery will be built on top.

Here's a photo of the rear battery that will sit on top. It's actually the rear module of the Chevy Volt pack with part of another module attached to it. It's 10kWh all up and about 1200mm (4ft) long.

I also spent some time getting the charge port installed. Here it is before painting. It's held in with pop rivets. It will get a coat of sealant, a drain hole drilled at the lowest point, and some black paint.