Electric Porsche 944

Creating wiring harnesses, and working on the little things

by on Feb.11, 2013, under Electric Car

Although I’ve driven the car for a few months it was never 100% complete.  With the installation of the CALB’s in the rear and the A123’s in the front for the first time the battery system is finished.  I do have one cell to keep an eye on, but that can be replaced very easily without having to remove the entire pack.  I could have started driving the car again with temporary wiring and unfinished pieces but I’ve decided the best thing to do is just complete the car properly.  There is a to do list about a mile long ranging from creating wiring harnesses and installing connectors to building an insulated box for the fluid heater and installing the aluminium channel the length of the car to protect all of the wiring for the HV pack as well as 12v and signal wiring.

I finally installed all of the final ring terminals with proper heatshrink for the battery system, I have a a bit of work left  in the motor loop then all of the high voltage / high current wiring is complete.

A portion of my product line with RW Audio is custom cables.  These are high quality audio cables that look better, last longer and sound better than your typical radio shack variety.  I will be using these same techniques to assemble wiring harnesses and cables to complete the EV wiring in the Porsche.

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sencable

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I’ve started with the “14 pin” connector near the firewall that allowed me to use factory wiring to interface with most of the required connections on the Soliton1.  That worked well for testing, but wasn’t finished and had many unused wires dangling all over.  Below is the old messy wiring.

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Below the water pump for the Soliton1 cooling loop, the 14 pin harness that connects to the Soliton1 and other terminal blocks, as well as the 8awg cables to connect the charger.

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Close up of connections including the cheap 2 pin weather proof connector I bought on ebay for the pump, and will be using for a few other items that need an easy disconnection method.

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The replacement harness uses the stock connector, but new wire and terminals that are protected by techflex and heatshrink.  There will be a few new harnesses in the car, all using the same assembly style and provide plenty of protection while being serviceable.

With the new 4kw heater that’s replacing the Kats heaters I also decided I should build an insulated “heater box” so that as much heat as possible makes it into the cabin and I’m not wasting heat in the engine compartment to the cold ambient air, especially while driving.

heaterbox

The top and bottom of the box are made from an aluminium extrusion I had laying around, the sides are made from raw double sided FR4 PCB boards that I use for prototyping using my CNC router.  This makes for a very light yet strong box that should work well with some 1/2″ foam insulation.  I still need to decide on what to use for the ends, perhaps a couple more pieces of extrusion since they are the correct width.

heaterbox2

I used the CNC router to drill the holes in the PCB material as well as the extrusion so that everything would line up nicely.  I will need to do further machining on the top and bottom panels to make cutouts for the reservoir, wire glands and drain hole.  This box will be mounted on the passenger side of the engine compartment beside the motor.

As I get closer to installing the heater system permanently the question comes up of how to turn on the pump and 4kw heater.  They simply require 12v, however I was not looking forward to the idea of some sort of “out of place” switch with a cheesy label saying “heater”.  To make the heater behave just like the ICE version I should just be able to turn the temperature dial from cold to hot and the system just works.  So to make that happen I had to remove and disassemble the climate controls which involves desoldering the main switches from the PCB.  Once it was all apart I found just enough room near the temperature dial which is simply a 10k potentiometer to mount a microswitch.  When the temperature is set to cold the switch is closed, so by using the NC contacts on the switch, in any dial position other than cold, the switch is “on”.  This will trigger a relay to turn on the pump and heater.  The car has “automatic” climate controls, meaning that once the cabin reaches the preset temperature the system then controls the flow of coolant through the heater core to maintain the preset temperature.  It uses a temp sensor in the dash and a vacuum operated valve.  Since I don’t want to interrupt the flow of coolant I’m simply using the vacuum valve to control another microswitch that will turn off the heater once the cabin reaches the preset temperature.  This switch closes when the valve would close to cut off the coolant flow, so again using the NC contacts to run the heater only the system will turn on and off automatically as it tries to mimic the original function.   When the valve opens to increase the temperature of the cabin the heater turns on again.  The pump and fan will continue to run during this time drawing more heat out of the coolant.  I don’t have to worry about a fan interlock since the fan comes on low as soon as the ignition is turned on.

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