I chose the late-model for the IRS. I am not a pioneer here, many Tesla swaps have been done to these cars and kits are even available. However there are a few things that I want to do that are outside the norm.
1) Improved placement of the Tesla SDU. I decided to custom make the motor adapter mounts to get the axle shafts as low and even as possible in the Beetle frame. Here are the front and rear mounts that I fabricated:
Front mount connects the Beetle transaxle mount to the front Telsa motor mount. The rear mount connects the other two mounts and also provides mounting pads for the sway bar using off-the-shelf mounts. With those mounts here is the placement of the motor:
I sourced the axle stubs from Fellten in the UK. They are the Porsche 930 pattern, and I am rebuilding the Beetle rear suspension with disk brakes and 930 axle outers. Then the final connection will be via EMPI CVs and sway-a-way shafts. (15-1/4" both sides; I have not ordered these yet)
2) Improved placement of the batteries. All the Beetle conversions I have seen have used Tesla cylindrical cell packs and take up the entire frunk and cargo area. But the Beetle has quite a lot of ground clearance. So my goal is to put the majority of the battery pack in the floorpans under the seats. I searched for quite a while to find a module that would allow this. I needed modules that met the engineering constraints of:
a) At least 40 kWh
b) Less than 500 lbs
c) Compact enough to fit in a custom floor pan
d) Adequate voltage for the SDU
I looked at a lot of options, but it looked like CATL cells were going to be the way to go. I looked at Kia/Hyundai cells, Chevy Bolt cells, Tesla model 3 LFP cells... None would really fit. Finally, very recently, these Mercedes EQ modules popped up:
I bought 5. Now, these hit most of the wickets. 46.5 kWh. 315v. 460 pounds. And at 12-1/4" x 25" x 4", FOUR OF THEM will fit in recessed boxes in the floor pans between the seat rails and I will lose about 4" of ground clearance.
They do create two more challenges, though:
a) They are cooled by conduction. So I will have to custom make plates to sit under the modules to cool them.
b) While they all have a BMS, I don't know the first thing about incorporating a BMS into the OpenInverter architecture. Hopefully someone out there can help me out with details on how to use these BMS? It would be very nice to use them instead of having to go with a custom BMS.
Oh, and 3) Modernize the Beetle. Beetles are not known for their comfort. With no air-cooled engine anymore, I will have no heat, and battery cooling, motor cooling, etc, will be further challenges. However I got a great deal on a Tesla model 3 heat pump system (SuperManifold, compressor, etc):
Which fits conveniently enough where my fuel tank was. But I might also be putting the fifth module there? This is the biggest "pipe dream" part of this project. I don't know of anyone who has gotten a SuperManifold working outside of a Tesla since they are controlled by the Tesla chassis computer. But it would be super nice to have it working to:
a) Provide battery cooling AND heating
b) Provide motor cooling
c) Provide cabin heating AND cooling (via a rare dealer A/C box I got for $50)
If I can't get it working though, the backup plan is just cooling via small radiator as others have done, and heating via resistive unit.
Let me know what you think. If anyone has an idea on a controller for the SuperManifold and has any idea on if/how I can use these BMS, please let me know.
