The Loom
In addition to the giant battery cables discussed in part seven, there’s also smaller new wiring required.
Firstly there is a loom of wires to run from the motor controller to various places in the car:
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Charger port
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Contactor box
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Controller gauge and buttons
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Battery monitor
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Throttle pedal
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Brake sensor
Wiring loom and other electrical components ready for use
Loom now distributed through the car, under back-seat, and to front of car
The main meeting point for the new wiring is under the back where the contractor box is located. This box contains the 12v and 120v relays along with the shunt. The ignition switch is now wired to turn on relays to power up the 12v system and also supply main battery voltage to the motor controller. The motor controller, when it is ready, pulls the contactor to power up the motor.
Contactor box
The shunt (bottom of picture above) is a very precise low valued resistor, which allows the battery monitor to accurately measure all current in and out of the battery. The shunt is connected to the battery monitor with a twisted pair of wires.
Dash mounted battery monitor and glove box concealed controller gauge
The only visible sign of the electric upgrade is the battery gauge, which replaces the old petrol gauge. This device, when calibrated, keeps track of the state of the battery so I know how much charge is remaining to power the motor.
I’ve hidden the motor controller gauge, programming button and power/regen mode switch away in the glove box — so they are accessible but don’t change the look of the VW’s spartan dash!
Charge port (left) and AVC2 (right)
Finally, there is some wiring and a small relay device to support the Mains AC charge port. Trixie has a standard J1772 charge port, these ports don’t just receive mains electricity, they also have a couple of additional pins;
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Proximity detection — which is wired to the motor controller to prevent the car driving off while connected to the charger
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Control pilot — which is a communication line between the AC supply and battery monitor, it can be used to cut the AC supply if an over charge condition occurred.
In Trixie, these extra pins are wired to the Active Vehicle Control Module (AVC2) which monitors the pilot signal and interfaces with the battery monitor and motor controller.
Read more about the conversion:
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Electric certification in part one
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Power and brakes in part two
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Removal of petrol components in part three
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Flywheel and clutch upgrades in part four
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The AC induction motor in part five
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New Fuel in part six
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High Currents in part seven
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The Loom in part eight
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Keeping it cool in part nine
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Putting it all together in part 10 (including a video of the first drive!)
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Bottom balancing and battery management systems in part 11
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Getting the certification examination in part 12
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eTrixie the Movie! Video walk through
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A DIY EV in the real world in the final part
