A whole lot of cables

Today I installed a thick bunch of cables between the driver footwell and the engine compartment. In the footwell is the EVCU, or controller computer, plus connections to stuff like the throttle potentiometer. In the engine compartment are things like the motor controller, the charger, the heater and water pump for cabin heat, and the vacuum pump and sensor for the power brakes. And they need a lot of cables to function properly.

All cables stripped before pulling

I pulled all the cables through the protective pipe which used to hold all the wiring between the old ECU (Engine Control Unit) and the engine. 

Brake through

Such a cable mess in the footwell. Need to be tidied up 😉

Emergency STOP and TP cable for display

I am using a small LCD display to show the status of the Arduino EVCU and up to now I have used a soldered wire between the Arduino and the display. That will not work when the Arduino and display are permanently mounted in the car so yesterday I replaced it with a standard TP (Twisted Pair) cable with RJ45 contacts which is normally used for Ethernet. The idea to use TP cable is so that I can have one cable installed in the car and another on the test bench. Installing the TP cable means soldering female RJ45 contacts to the Arduino and to the display. I will later change the display to a smaller (and blue) that will fit in the center console next to the JLD amp meter.

The display connected to the EVCU with a TP cable

The car needs to have an emergency stop button that breaks the high voltage circuit in case of an accident. Emergency stop buttons are usually large and ugly but I found a neat little button that fits the center console. When pressed, the button breaks the power to the Tyco contactor which then opens and shuts off the high voltage. Of course I managed to drill a hole in the console where it wouldn't fit :( so I'll have to find a new cover for that.

The pretty little STOP button and the TP cable for the display

Preparations for the fuel gauge

I want to be able to display the charge level on the Audi A2 fuel gauge. In order to do that I have to be able mimic the tank level sensor. The sensor is a variable resistor with a resistance of 300 ohms when empty and about 75 ohms when full. I will have to mimic that variable resistance according to the charge level of the battery. I have not yet figured out how to do that but yesterday I made preparations for this by installing a wire from the tank level sensor contact (which goes to the fuel gauge) to the EVCU. I also soldered a 100 ohm resistor on the end of the wire to make the fuel gauge go "almost full" and not signal empty tank with an annoying beep.

Measuring the tank level sensor resistance

Soldering a wire in place of the old tank level sensor contact

Signed, sealed, delivered battery boxes

The fit between the battery boxes and the frame was not 100% so I had to seal the spaces with sealant. As can be seen in the image below the shields of the battery cables are now grounded to the battery box. All battery and motor cables are shielded to reduce the electromagnetic radiation that appears due to the motor controller.The light grey cable in the middle is the thermistor that senses the battery temperature. The charger uses this information to stop charging if the temperature goes below freezing.

Grounded battery cable shields and thermistor

Battery boxes with lids

The project is on again - battery boxes mounted

At last some free time and the opportunity to continue the project. It has been a long winter with all work and no play ;)
Actually I started about  a week ago, but my blogging is lagging as usual.
Anyway, yesterday I mounted the two rear battery boxes to the car frame. I used Casco Superfix glue and aluminum rivets to keep it together during the gluing.

The rear battery boxes mounted

Details of rivets (and some sticky glue)

Before I mounted the boxes to the car I made the battery holders that will hold the batteries to the box. According to regulations the battery holders (and and boxes themselves) must withstand 4.5 gs of vertical acceleration in case of a crash, which these do with substantial safety.
The holders are made from aluminum L-bars covered with heat shrink to minimize leakage currents in case of severe condensation in the battery box.

One of the battery holders and a mount for the lid

The lid