July 17, 2015

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 😉

July 10, 2015

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

July 9, 2015

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

July 8, 2015

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

July 7, 2015

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

October 13, 2014

Charger, heater and vacum mounted

This weekend I mounted the charger, the heater and the vacuum system. The Brusa charger hangs under the same aluminum U bar as the Soliton motor controller. The mount is made of two sturdy 50x50x5 mm aluminum angles with two 3x30mm "suspensions" to distribute the load to all four bolts on the Brusa. It also has a small 2mm diagonal angle to support in in the front to back direction.
The black-faced Brusa charger mounted in front of the transmission

The Brusa high-voltage connected to the connection box.
Still to connect are the control wires the go into the black multi-contact to the right

Angle bar to support the charger front to back
The front battery box serves as the mount point to a lot of stuff in the conversion. The A2 is a fairly modern car and there are no big areas of metal around the engine compartment to mount things on, Only two aluminum frame bars and lots of plastic (which is now removed). So, the vacuum pump is now mounted onto the battery box using two pipe clamps. The vacuum reservoir mounts to the lock carrier in front of the right front wheel where there is some space left. This means that there is almost a meter of vacuum hose (in fact it is coolant hose) between the reservoir and the vacuum servo which is in the rear left of the engine compartment. I hope the hose will not "eat up" all the vacuum by compressing itself.
The vacuum pump mounted on the front battery box
The heater also mounts to the battery box with its top mount. Its bottom mount is an aluminum angle fitted to the box that holds the motor controller.
I am getting second thoughts about the heater. It is made from an ordinary steel pipe and it is far from stainless. A couple of days after I had tested the function and watertightness of the heater I emptied it of the last remaining water. Out came rust-brown water. I am not sure I want to get all that rusty water into the heat exchanger in the ACC even though engine coolant is normally corrosion protective. Maybe I will make a new one out of aluminum instead...

The heater (the black cylinder)

It's a tight space
 The wires for the heater goes to the SSR (Solid State Relay) box which will control on/off of the three heating elements as commanded by the Arduino.
More connections go onto the front battery box

The SSRs for the heater...

... connected nicely. Only the control signal from the Arduino remaining.

September 28, 2014

Cables, cables, cables

This weekend was all about cables. I mounted the DC/DC on the front battery box and connected it to the hight voltage in the front connection box, the engine room earth point, and the 12V "intake" in the left footwell under the driver's feet.

The DC/DC mounted on the front battery box with the orange high voltage cable
Originally, the 12V battery was placed in the rear of the car and two long cables ran to the front. One 50 mm2 cable to the starter and one thinner, 25 mm2 for the main power supply of the car. I ripped out those cables and joined them together. The starter end of the cable connects to the DC/DC so this way I get 12V for all the systems. Left to do is to connect a 12V battery to the DC/DC.
The two thick plus cables ripped out to be joined
Reducing the 50 mm2 cable to 25 mm2...

... in order to join it with the thinner with a crimp join. Add three layers of heat shrink and some electric tape
I also finished the middle connection box that goes in the right footwell and contains the main 400A fuse, the current shunt for measuring battery current (discharge and charge), and the Tyco contactor that turns on the high voltage.

The middle connection box under the passengers feet

The connections go to the JLD 404 to measure current and voltage, and to the charger to provide unbroken (by the Tyco) minus.

More orange tubes under the car...

... and the front connection box is filling up.
The front connection box is getting more and more complete. Left to connect are the hight voltage cables to the motor controller and the charger cable. I ran out of battery cable (a shielded, orange 35 mm2 cable) so I have ordered more from evpower.eu along with a charge intake and connector that conforms to the European standard IEC62196-2. Hope to get it next week.