The batteries are the most difficult to package and find the best location to mount. Both because they are a huge amount of volume, and that they’re my best lever to adjust the weight balance of the car. Each of the 48 cells weighs about 8 pounds, for a total of about 390 pounds (~175kg). Although I won’t be designing battery heating and cooling into the first phases of the car, I want to place the batteries in large groups, as apposed to spread out in small sections. This way they will all be exposed to roughly the same thermal conditions and in the future it should be pretty straight forward to add battery conditioning.
A few other criteria:
- No compromise to passenger compartment
- Minimize impact to trunk storage
- Present the batteries in a way that could be displayed
- No catastrophic events from a single bolt failure
- No fatigue life failures (ended up pushing my away from aluminum structure)
As you can see in the picture above, I plan to mount the 48 cells in the two large groups. The top group is 27 cells (3×9) and will be located between the two rear shock towers in the front most section of the trunk. The lower group of 21 cells (3×7) will be sunk down into the rear trunk floor where the exhaust and heat shields were previously. The two translucent beams on either side of the lower pack are the rear chassis frame rails that I will be mounting the lower pack to. This should allow me to easily drop the pack out the bottom of the car, and provide rigidity needed to mount the ~200lbs in batteries.
I’ve placed The first 27 cells between the shock towers, 3 wide and 9 tall as seen below. (Ignore the fact that the top left cell is missing in the picture below). Now I just need to finalize and triple check all of my measurement in the full CAD model and then I’ll be able to start the build of the lower section battery pack.