The motor controller is a Sevcon Gen 4 size 6. It's mounted on the starboard side of the motor compartment above the motor where the leads to the motor can be very short. It is mounted with a water cooling plate.

The controller converts the 48VDC from the battery to the current needed by the motor. It uses pulse width modulation to control speed. It is also capable of regen where it captures energy created by the motor from the prop spinning while sailing. It puts this energy back into the battery.

The controller does more than just supply power to the motor. It reads rotor position and temperature data from the motor, responds to inputs from the throttle unit, controls the cooling system, and communicates through CAN Buss to a control display app via a Bluetooth dongle.

The Sevcon employs FOC or Field Oriented Control to increase the efficiency of the motor. FOC is a way of adding power to the rotor in the right amount and in the right direction from the different poles of the motor as it rotates. It's sort of like pushing someone on a swing and having another person at the bottom of the arc to give a pull as the swing approaches and a push after it has passed to add a little more energy. This is done at each of the motors poles continuously as it rotates. It helps smooth out the pulse nature of motor rotation and increases efficiency. Nikolai Tesla would love it. It takes a lot of number crunching to make FOC work. All that happens in the microprocessor of the Sevcon controller.

For a great explanation of FOC check out this video on YouTube with excellent animations that do a much better job of showing how it works.

The throttle linkage provides an interface between the control lever on the steering pedestal and the small actuator that controls the motor. It uses the same cable that was used for shifting the transmission on the Volvo diesel. It is a bi-direction controller that you move for forward or reverse from a neutral position. There is a detent at the neutral postion but it can be difficult to feel through the linkage especially when there is a lot of motion of the boat (like in wavy conditions). I plan to do something to the linkage to enhance the neutral detent. Best would be to have it lock into neutral from either forward or reverse and requre you to pull a lockout lever of some sort to move it out of neutral. Going quickly from forward to reverse can impose some ugly shock load on the feathering propeller so care is requred to avoid a worrying thunk. I hope to mitigate this problem with programming more gradual acceleration curves in the controller as well.

These photos show most of the components in place and almost ready to run. The battery is on the aft side of the aft bulkhead in the compartment. The cooling system components are mounted on the port side, the controller on starboard. The battery terminals on the brass cylinders from the buss bars can be seen on the face of the bulkhead.