So, the wiring is now largely done, and it’s time to start testing
High Voltage
35mm2 cable is pretty awkward to work with. Working my way around the car, I worked out the lengths I needed for each of the connections – battery box to junction box, junction box to inverter, inverter to motor – and cut lengths off before crimping on connectors using a borrowed hydraulic crimper (thank you fellow forum-member Alfred/@Maker_Of_Things). I then added a layer of adhesive heat shrink over the crimped parts (also thank you Alfred!)
With the cables made up, I cut matching lengths of bright orange shroud to go over them and began wiring it all in. Because this stuff is pretty stiff, getting it to stay in the right locations while you get a bolt in or a nut on can be tricky – especially in a cramped engine bay. So as you will see from the photos, I actually unbolted some stuff for connections before bolting it back in.
I’m still experimenting with my 3D-printed connectors and shrouds and I’m not very happy with them yet. The pared down connector for the side of the inverter that was tight against the engine bay wall works well enough. And I’m happy with my shroud for the motor connections. But neither of them hold the shroud as I designed them to do. Bit more work required to tweak those before I share them.
The worst connector was for the battery box. This was incredibly fiddly and I don’t think it shields the two connections from each other enough. Back to the drawing board on that one.
12V Loom & testing
There are still some connecting blocks to be replaced with proper connectors, and I haven’t yet wrapped it all in fabric tape, since I’m sure I will have screwed up somewhere. But there is enough stuff in the car for testing. The first bit of which we did today.
We sat in the cabin, turned the key and watched the WiFi network from the inverter come up. We logged in on my daughter’s laptop and watched the on-screen gauges spin as we pressed the throttle. They were only measuring throttle position, but it’s a start.
I also tried turning the key all the way to the ignition position to test whether this would start the inverter as it should. Sure enough it threw an error telling me it hadn’t pre-charged, exactly as it should, since I didn’t have the batteries hooked up. So far, so good.
More testing to come over the coming week. I got under the car for the first time in ages today to tighten up the bolts connecting the giubo to the gearbox and propshaft. They’re an absolute ballache to get a spanner on. May need a new one before I can torque them up properly. But they’ll do for a bit of testing.
ECU Bay
The biggest mess the wiring project has produced is in the space where the ECU used to sit. I decided to make this a little nest for various connections and bits of circuitry since it was roomy and largely sealed. It now features:
- VCU: Slightly confusing terminology since the ‘brains’ added to the inverter are arguably the vehicle control unit, but this is my little arrangement of microcontroller (Mega2650 Pro), CANBus interface (MCP2515), relays and other bits that I will use to control everything the inverter doesn’t directly.
- Monitor: A NodeMCU hooked up to an MCP2515 running ESPHome that will monitor the car when it’s on the driveway and hook into my home automation system to send me data. Not got this running yet.
- ‘On’ Relay/Fusebox: A harvested relay and 10-way auxiliary fusebox powering everything that needs to be on when the ignition is on but the car isn’t ‘running’. e.g. inverter, monitor, BMS, contactors, current monitor (shunt) etc. This is switched by the standard switched live from the ignition.
- ‘Run’ Relay/Fusebox: Another harvested relay and 4-way auxiliary fusebox for those things that only need to be powered when the car is running. e.g. PAS pump, brake booster, cooling pumps. I will need to have a separate switched line for the water cooling pump for when the car is charging (see below). Right now this is triggered by a relay module on the VCU. Not totally happy with this and would rather it was simpler but would need some sort of latched ‘run’ live which the car doesn’t naturally have.
Here is also where the CANBus lines for the EV systems meet the rest of the car, and the VCU and Monitor, which again is currently a pile of spaghetti around a connecting block. Plus there is some of the old wiring. And a bunch of grounds. It all needs tidying up once I know it works.
Charging
As the time to spin the wheels gets very close, I’m thinking more and more about how to charge the car – something I had rather put off. In theory, my inverter can act as a charger. But right now, there is no working software to enable it to do so from a single phase supply. Fellow DIYer Jamie just blew up half his inverter testing the code, so I’m not keen to try that.
But it’s been a good couple of months at work so the credit card came out, and I have ordered a charger from a Mitsubishi Outlander PHEV, just like my motor. (Note, this project would arguably have been quicker and easier if I had also used the inverter from a PHEV, but we live and learn). This, along with the charge port from the same vehicle I have ordered set me back just under £300 including shipping, and should make charging relatively straightforward.
I say ‘should’ because I haven’t totally got my head around what this new component means for my design yet. With my inverter no longer being used for charging, I know I have an extra contactor in my high voltage junction box that can be repurposed elsewhere. And I know I will need to include the charger on my water cooling loop. I also know that the charger won’t currently fit under the bonnet of my car. Some fettling of the battery box and lid may be required to clear a few extra centimetres of headroom.
Finally, I know I will need to add the charger to my CANBus because that is how it is controlled, and that this will be an extra job for my VCU. Rough scheme is to have the plugging in of the charger wake up the VCU and BMS and send the appropriate commands to the charger.
