Interesting 
So those are hub motors (with brakes) with 250 W controllers. Using two separate motors avoids the need for a differential, and the motors look like the big drum brakes of a car of the Bugatti's vintage.
The motors and controllers are e-bike stuff, so one of the e-bike enthusiasts here might recognize the components.
When two separate motors are used to drive left and right wheels, the controllers need some sort of coordination. In the Curtis controllers one operates as a master, getting the accelerator pedal signal and telling the slave controller what to do; the master even looks at the steering angle so it knows how much faster the wheel on the outside should be turning than the one on the inside of the turn. The custom electronics in this case presumably provide some form of coordination of the two controller/motor sets.
In some cases a dedicated 12 V battery is used to provide 12 V for the lights, etc., separate from the batteries for the motors, and I have seen listings of this model of Harrington as having two (not three) batteries. In this case, it does look like all three batteries are likely used to provide 36 V (nominally) to the motors, and the transformer on one of the boards might be part of a 36 V to 12 V converter.
So those are hub motors (with brakes) with 250 W controllers. Using two separate motors avoids the need for a differential, and the motors look like the big drum brakes of a car of the Bugatti's vintage.
The motors and controllers are e-bike stuff, so one of the e-bike enthusiasts here might recognize the components.
When two separate motors are used to drive left and right wheels, the controllers need some sort of coordination. In the Curtis controllers one operates as a master, getting the accelerator pedal signal and telling the slave controller what to do; the master even looks at the steering angle so it knows how much faster the wheel on the outside should be turning than the one on the inside of the turn. The custom electronics in this case presumably provide some form of coordination of the two controller/motor sets.
In some cases a dedicated 12 V battery is used to provide 12 V for the lights, etc., separate from the batteries for the motors, and I have seen listings of this model of Harrington as having two (not three) batteries. In this case, it does look like all three batteries are likely used to provide 36 V (nominally) to the motors, and the transformer on one of the boards might be part of a 36 V to 12 V converter.