Sunday, February 8, 2009

Wiring it all up.

I've actually been a little behind on the blog. Being so close to the point of a test drive I was putting all my time into the build. Sadly I even forgot to take pictures of all the things I had planned but there are still some good shots.

It's time to wire everything up. To do this you need some form of conduit from the front to the rear of the car in almost all EV builds since usually batteries and components are not all in one location. I used what is known as Smurf tubing because of the Smurf blue color. It's just a 3/4" plastic flex tubing designed high voltage applications in homes. It's light weight, again flexible, and reasonably priced. I think I paid $30 for 100 ft at Home Depot. I also picked up some orange flex for the low voltage wiring. It's technically the same tubing from what I can tell but the color coding is standard (low voltage = orange, high voltage = blue).

In order to connect the rear cells to the BMS system I needed to run 28 wires from the front to the rear of the car. This is to support two BMS voltage modules (11 wires each for cell voltage and 3 for temperature). In addition I ran a 10 gauge solid strand back as well. This gives me a positive 12v line from the DC/DC converter I'll be putting in the trunk to charge the original 12v battery. The DC/DC converter takes the traction pack which in this case is 144v nominal and charges my 12v system essesntially replacing my alternator.

Here is that low voltage run.

Another shot of the uncut wires hanging out of the trunk area.

I installed two runs of the high voltage tubing. Because of the size of the 2/0 traction wiring I could only fit one cable per tubing. I additionlly pulled an 8 guage solid strand wire from the most postive terminal on the front battery pack to connect to the charger. The most negative terminal of the traction pack will be in the rear of the car already so we can attach directly to that terminal later.

The installation of the two other tubings was nothing special but thought I'd show how I closed up the tubing. There are connectors you can get for the tubing to run it into junction boxes etc. These at least reduced the opening diamter some. After crimping on the terminal I added a layer of wire loom to protect the exposed portion of the wire.

Next I wrapped the whole thing with electric tape and finished it off by heat shrinking the ends.

Here is a shot of the three flex tubings coming into the trunk secured by some jumbo sized zip ties. You can also see the DC/DC converter setting in place on the right.

Here is the installed DC/DC converter. I see a lot of people installing this up front in the car. The thing that bothered me was you can easily see in to the electronics of this thing. Maybe it's moisture resistent but I didn't want to take any chances so I decided to place it in the trunk. It made for some extra work but I feel better about having it here where I know things stay dry. These converters actually come with your standard 110v AC outlet cord attached which may scare some. Internally this AC voltage is converted to DC using some sort of bridge rectifier. When sending it direct DC only half of the rectifier is working but the end result is the same. You can simply cut off the 110v plug and wire it to your traction pack. It doesn't matter which wire is positive and which is negative. Next to the big black high voltage power wire you can see the two smaller 12v output wires. The black wire is ground and runs just to the right where there was a convenient bolt to ground to. The white wire as I mentioned before is ran into the low voltage conduit to the front of the car.

Here is the 12v + wire coming from the DC/DC converter and guess where I connected it. That's right the original location the alternator use to be connected. This is the small circuit panel under the hood on the driver side of the car.

Here is the high voltage wiring. This isn't as neat as I hoped for but I was really running out of room and had to place these components close together. The two outside, funny, shiney looking things are the contactors. These are basically giant SPST relays that are designed to handle high voltage and high current. I went with two just for the added fail safe. One contactor closes when the igntition is turned on. The second closes as you depress the accelerator. Additionally there is another low current relay which you can barely see right in the middle of it all which tells the controller when it's ok to run. I plan to add an array of safety features later that will turn one or more of these relays off until all the safety requirements are met. These can be things like the car isn't still plugged in to the wall outlet to controlling the RPM limit of the motor. Towards the bottom is the KLK fuse (white round thing). This is rated for 250 volts and 500 Amps. You'll want to use one of these for every group of battery packs you have. This way if a short happens the fuse will blow and you won't loose your batteries. Last on the bottom left is the giant anderson connector. You can disconnect this to guarantee all high voltage is removed from the system. BEWARE, however, the capacitors in the controller will continue to carry a charge after disconnected.

This is a picture on the other side of the controller. The big black box with the 2/0 cable running through the sensor that detects how much current is being used when driving. This is like a MPG gauge and helps you judge how efficiently you're driving. On the far left is the pot box. This is 5k variable resistor which you connect your original throttle cable to. Now the further you press on the original accelerator the faster you go, just like a gas car. The last thing here is a small fuse block. I tapped into the 12v ignition line from under the dash and ran a line up to the front. When you turn on the ignition now it triggers a relay which then supplies voltage to this fuse block. From here I'm running the vacuum pump and the 12v fan that cools the controller.

Here is a final shot of everything wired up and ready to go.

Now it's time to charge it up and have a test drive!


Simon said...

Brian, could you give some more info on the "giant SPST relays" you use - great idea, but I can't track these down easily. Thanks, Simon.

Brian said...

They are Albright Contactors. I'm using two SW-200 series. They are rated at 120v 250 amps continuous. Although I know many, including myself, running them at 144+v without issue.