It turns out that the inverter board failing and me smoking some components (see last installment) was just the beginning of a week of technological disasters for me. My broadband router failed, wiping out a morning while I tried to cobble together a working arrangement until I could get hold of a replacement. In the middle of that, my web server (actually a virtual instance) failed. How? I still don’t really know. But that wiped out another day. Then my home automation server failed, leaving my workshop without light or heating while I fixed that. For the rest of the house, I have been careful to make sure there are manual backups. But my workshop is a little more…experimental.

This all came at the worst possible moment work-wise, when I was absolutely snowed under. Suffice to say, I’ve been a little bit stressed. And as a result, not a lot has happened on the car. The downtime I have had has largely been spent blowing stuff up on Destiny 2 on my newly acquired Google Stadia setup (what can I say, it was free), or drinking wine (not the healthiest coping mechanism I know).

Anyway, most of the critical tech is working again (knock on wood), I’ve hit my various deadlines, and I can start to think about the car properly again. The challenge now is rebuilding my enthusiasm – challenging in the face of a few failures and also the worsening weather, which does not make going outside and crawling under a car very appealing.

Outlander inverter

There are some things to do inside though. I’ve been working on getting the Outlander inverter working. (I’m updating the components page with information as I understand it). This unit looks to have been in a small engine bay fire. The low voltage connectors are a little bit…melty. But they still have all their pins and I successfully have the inverter turning on and spitting out CAN messages. I just don’t understand them all yet. And early experiments to make it spin the wheels have been unsuccessful. I suspect some of the messages it is spitting out that I don’t understand are errors.

SavvyCan

To help me withg CAN diagnoses, I have bought an Arduino Due that I’m setting up for SavvyCan. But this is proving to be more challenging than expected. I can’t get the sketch to run properly – it won’t spit out anything to the serial terminal. So that needs some work as well.

BMS

Once I have that working, I plan to use it to get the BMS working properly. I had this set up wrong initially, with one CAN interface connecting to both the battery units and the rest of the car. Instead you should have two: one for the battery modules, and one for the rest of the vehicle.

With that in place, I want to get the charger running. There are some quirks to this as I need to have the BMS turn it on and off once the batteries hit target voltage. Hence focusing on the BMS first.

Safety box

One thing I have done is some work on the salvaged Safety Box from the BMW battery pack. Turns out this is a complete and very compact high voltage junction box. Others have already done the work decoding the CAN messages from it to get detailed voltage and current information. And it proved relatively trivial to rewire control of the pre-charge relay and contactors through the original connector, giving me a nicely compact alternative to my own, very large, junction box. So compact in fact that it will fit inside my battery box.

This solves two problems. First, it means that I don’t need to worry about a safety disconnect: if the 12V is off, there is no way for high voltages to reach the battery box connections. Second, it frees up the space where the junction box sat so that the charger can go in its place, meaning I don’t need to alter my battery box.

What I do need to do is sort out the design of the high voltage connector for the battery box, which proved not to work very well. That might be a project for this week in between work.

There’s more info on the S-Box over on the components page as well.

Inverter repairs

In the meantime, I have stripped down the inverter and removed the broken board. Damien at EVBMW who supplied the board was very reassuring, telling me it probably wasn’t me who fried it and has kindly sent me a replacement. So, board number three (!) is off to the soldering whizz this week so that I can get my inverter back up and running.

I think I am probably going to stick with the Prius inverter rather than switch to the Outlander one. That is great for some experimentation but the Prius inverter gives me lots of flexibility and things like direct control of the contactors. If I switch away from that I will have to make up some new hardware for the BMS to control the contactors and that just feels unnecessary.

Next steps

Still lots of work to do on the car itself, including welding up the rusty rear spring mount. Some new steel has arrived from Frost restorations for that, and I have also invested in a brake for folding brackets. These will be used for the repair patches for the spring mount but also for brackets for the power steering pump (which I have decided to relocate, based on advice from my daughter – she suggested the new location weeks ago and I have finally listened) and the heater, which I might as well get wired up while I’m at it.

I did get some way towards getting the fuel tank out, removing the spare wheel carrier (too rusty to bother putting back in place), and loosening some bolts. But I couldn’t get the bolts connecting the propshaft to the diff to shift. I hope to have another go at that today.

I also plan to take an angle grinder to the engine bay and get rid of some of the old brackets that are in the way. Past the point of no return now…