Tuesday, August 10, 2010

Low voltage wiring (engine compartment)

Now that the Primary AC Interlock Relay has been installed and the wires have been run up to the engine compartment, I can start wiring the engine compartment relays.  The EA kit that I purchased includes detailed instructions on how to make all the electrical connections necessary.  The instructions are a little out of date, unfortunately, so they don't exactly match the components that came with the kit.  For instance, the DC/DC converter supplied with the kit (Elcon ####) doesn't need the input voltage filter that is specified in the intstructions (originally for PFC DC/DC converter).  In addition, I added a "DMOC Kill Switch" within reach of the driver, necessitating an additional "DMOC Relay" wired to that switch.  So I adapted the electrical schematic provided to depict these changes, as well as adding details as to where I'm pulling power from the existing 12V system and locations of the various components.

I'm working on being able to load the electrical schematics to the blog, but in the meantime here are some images of the wiring as it was being completed.  First, a view of the passenger side of the engine compartment.

This electrical enclosure in the middle of the picture contains:
-Secondary AC Interlock Relay
-Key Switch Relay
-Neutral Switch Relay
-Regen Relay
-DMOC Relay
-Vacuum Pump Relay

To the right of the enclosure is the DMOC controller.  Directly behind the enclosure is the water heater.  Barely visible in the upper right corner is the brass tee at the top of the vacuum pump.  There are wires in the red corrugated wire-minder running from the enclosure to both the heater and vacuum systems.

On the driver side of the engine compartment is another electrical enclosure which houses 3 shunts for measuring current.  The large shunt in the center measures the current going to the motor controller.  The 2 smaller ones measure the current being supplied to the water heater and accessory battery.  This picture shows the enclosure with all the wiring except the big battery cables.

The new accessory battery (lawn tractor size U1, since I won't need the "cranking capacity" of the original battery) resides next to the "shunt" enclosure.  This picture shows the wiring coming into the battery (Ground not connected! - I'm scared to connect it right now...).  The "bundle" of white wires attached to the chassis next to the junction box are the ground lines from the relay box, the DMOC controller, the vacuum pump, and the transmission.  The thick black wire (#4 awg - I know, overkill, but it had the right size ring lugs) connects the chassis to the battery ground.
Notice the coil of many-colored wires nestled next to the junction box?  That's what's left of the original engine wiring harness.  I conscripted 2 of the wires as "keyed 12V" lines for the various relays/DMOC/Vacuum, so the rest are unused in this conversion.  However, rather than trying to dismantle and remove the wires individually I electrically isolated the ends/connectors and left them in the car.  Never know when I might need to commandeer another of the old circuits!  Here's the wire bundle before I coiled it up.  Ugly!  And a lot of it covered with oil....
Finally, to round out the 12V wiring, the last component to be installed is the potbox which converts the accelerator pedal position (not the "gas" pedal - tee, hee) into a resistance which the DMOC controller can interpret as a throttle request.  In the ICE, pressing the pedal pulled a cable through a sleeve which controlled how much air was sucked into the intake manifold.  The end of the cable was held in place by a bracket which positioned the cable properly.  In the EV, I needed to duplicate that positioning in relation to the potbox.  My solution was to put it in an electrical enclosure with the potbox mounted in such a way that the side of the box acted as the positioning bracket.  Also, an additional return spring was attached to the potbox arm from the opposite side of the box as a redundant feature.  Don't want the potbox throttle stuck in the "on" position!

A small metal rod is attached to the end of the accelerator cable, forming a "T".  The rod nicely fits through the pre-drilled holes in the potbox arm (coincidence?  I think not.).  I needed to come up with a way to keep it in there, though, and I forgot to look at the original installation to get ideas.  I found a small aluminum piece (from a toy Erector set) that was the right width and had slightly-too-small holes drilled in it at about the same pitch.  What luck!  So I opened one of the holes up so that it could hold the other side of the "T" and bolted it to the potbox arm.  Here's a side view:
Here's the top view, with the potbox mounted in the box.  The supplemental return spring is connected to a "spring connector stud" I found on McMaster-Carr (what a great place that is!).
Because of the length of the accelerator cable and because I was limited in where I could mount this box, I had to mount it on the relay enclosure at a bit of an angle.  Once the lid is on and everything is buttoned up, it doesn't look half bad.  At the moment it is only attached to the lid of the relay box, which may or may not hold up over time from the jolts of driving, but I can always reinforce it with steel later.

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