Conversion Design

Now the fun starts. The two biggest design problems are the battery boxes and the engine mounts. Batteries will be mounted in the engine bay, under the rear seat and in the trunk.141 batteries in all have to be mounted. The plan is to have 36 batteries mounted in the engine bay, 48 batteries mounted under the rear seat and the balance of 57 batteries mounted in the trunk. The critical aspect of battery placement is balancing the weight in the car. The BMW had nearly a 50/50 weight distribution between the front and rear wheels. The goal of the conversion is to maintain that ratio. The motor and all the other ICE components weighed approximately 600 lbs. The new electric motor and controller weigh about 300 lbs and the batteries weigh a total of 650 lbs. With the other EV components like the charger and the DC-DC converter I expect to add about 450 lbs to the weight of the car. That will put the curb weight around 2950 lbs. The max gross weight of the car is 3500 lbs so there is room for people and storage in the trunk. Check out the EV Design page for more detailed info on the conversion design.
The electric motor mounting will be difficult because the whole drive train has to be assembled and placed in the car to get an accurate measure of where the Siemens motor can be connected to the motor mount points. A spline adapter from EV West will be use to adapt the Siemens motor to the BMW 5-speed transmission. That adapter adds a couple of inches to the drive train length.

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