Last bit of Wiring
I thought I would have everything done now to get the car rolling but things just keep popping up and taking way longer to finish. The 12V wiring is a good example of that. I previously showed that I had to install a new fuse box with 12 circuits in it. That was to accommodate all the pumps, fans and EV electronics. The fun started when I tried to connect all the circuits. The only way I could see to make all the connections was to get another contactor box and use it as a wiring cross-over box. Of course that meant having a way to bring wires into and out of the box. The Ampseal connectors are the easiest to use and they come in all number of pin counts. Since the main contactor box had a 14-pin Ampseal I decided to use that size for the wiring cross-over box. I purchased a box that would fit in the engine compartment where I had room, but unfortunately the sides of the box were not wide enough to accommodate the size of the Ampseal feed through. I had to get a larger box, which actually made the wiring inside easier but it caused another problem in the engine compartment. The place I had available for the cross-over box was right near the main disconnect switch. In my last video I showed that switch being mounted on the side of the plexiglass isolation box I used for the buss bars. With the new larger box for the wiring connections that switch did not fit in that area anymore. I really did not like the switch on the side because it was going to be difficult to get to. It also caused the battery cable to make a wide loop. I really wanted to put the switch right on top, but with the position of the plexiglass enclosure the maintenance switch would interfere with the hood. That interference was only do to the arbitrary position I mounted the buss bars in. If the buss bars were moved down 1 inch then the maintenance switch could be mounted on top and clear the hood. So that is what I did, I moved the buss bars, but unfortunately that meant getting a new plexiglass enclosure machined, which is on order now.
One of the issues I have had with the GEVCU is that the enclosures, even the CINCH are not 100% moisture free. The residual solder flux on the pcb will corrode if exposed to moisture. The lead based solder will also corrode and so will any of the non-gold connectors. The corrosion could lead to reliability issues with the control electronics. In OEM manufacturing the way they get around this problem is to conformal coat all electronics. Conformal coating is designed to seal the electronics from the environment. There are lots of conformal coats available and I got one in a spray can from my local electronics dealer. It is silicon based and makes a very tough and durable coating when fully cured. The conformal coating material I got also can be removed with a solvent, so if the board ever needs repair the coating can be removed. It also has the feature that it fluoresces under UV light so it is possible to check the coating coverage. The spray coating was very easy to apply, one coating dries to the touch in 5 to 7 minutes. I applied three coats of both sides of the board. Besides the GEVCU I also conformal coated the BMS board. I covered all areas with tape that did not need the coating, specifically the CINCH enclosure gasket and the connector for the WiFi antenna on the ConnectOne WiFi module. The one issue with the silicon conformal coat is that it takes 48hrs to cure at room temperature. I bought an oven so the next time I do conformal coating I can cure the coating faster (2hrs at 150C). The other issue with the coating was related to the WiFi. I was planning to use a patch antenna, because the CINCH enclosure does not have a feed through for an antenna and the Wifi signal would pass though the plastic enclosure . Patch antennas require a ground plane to work well. When I initially tested the antenna it worked very well because the top metallization on the GEVCU board was providing the ground plane. What I found after the conformal coating is that the patch antennas do not work anymore! I think that the fairly thick (~0.5mm) of dielectric is preventing the patch antenna from working. I realized that I could drill a hole in the CINCH faceplate that held the Ampseal 35pin connector. There was just enough room to drill a hole and mount a SMA feed through. I could now mount a dipole antenna on the outside of the CINCH enclosure so the WiFi connection would work. I probably will remove the antenna when not using the WiFi.
Lastly I got a new vacuum pump for the power assist brakes. The first pump I tried to use had a lot of extra wiring - wires for the pressure switch, a relay and wires for the pump itself. I was already struggling with placing all the wires so I was looking for an alternative. I found looking on the EVWest website that they had a vacuum made by CVG that has the pressure switch and relay integrated into the pump, so the only wires that need connecting are just the power wire and ground to the pump. The CVG pump was considerably larger than the other pump so it required an new bracket to be machined and painted. I thought I had everything covered now with vacuum pumping but I discovered when connecting the vacuum lines that the connector on the BMW power assist used 12mm hose and I was using 3/8 for all the connections. That meant getting another hose adapter to accommodate that hose size.
A video of all this fun can be found here.
Comments
RSS feed for comments to this post