I started playing with this.
Because the controller actually has 4 power cables running to it, not 2, disconnecting the controller gets a little complicated a little fast.
I disconnected the A2 cable. After looking at the difference between 3 and 4 connection controllers, it looks like the A2 connection is only used for plug braking, so I disconnected that.
I left the battery+ cable to the controller connected, because that one is hardwired straight to both the batteries AND the motor.
I setup 2 reversing contactors - one each disconnects the power to the BATT- and MOTOR- connections to the controller. With the contactor coils powered up (24V coils) they snap into the second position and connect the six main batteries to two additional batteries, directly to the motor.
I already tested the reversing contactors, with power NOT connected to the additional 2 batteries. Under load (driving), hitting the "TURBO" button interrupts power to the controller. Sure enough - it instantly kills the car.
I am planning on testing this with power to the extra batteries, then kill it with the main contactor, wait a sec or two, and then kick back to PWM control.
I think this will work.
If no body hears from me in a few hours, please contact my next of kin.
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