Yeah, it’s all borked.
So, after the little success of last time, I was very keen to get the wheels spinning. And if I’m honest, I wasn’t cautious enough. And that’s being polite about it. I was a bit of a knob. Twice.
With one battery pack hooked up, giving us 60V, we put the key in and gave it a twist. The inverter came up, but when we turned the key all the way to the start position, the inverter didn’t start.
Not sure what happened on my previous test but it turns out I had my ‘start’, ‘brake’, and ‘cruise’ wires mixed up. I switched these around and sure enough, turning the ignition to ‘start’ actually flicked the inverter over into run mode.
I pressed the throttle and we got….vibration. The wheels didn’t spin. This is where the first part of my incaution/idiocy comes in. I dumped the throttle to see if it just needed more juice. It rattled a few more times, then stopped. Bear in mind at this time, I had nothing inline to limit current. Because I’m an idiot.
The next day, doubling down on my idiocy, I figured it just needed more juice. So I hooked up a second pack and put the inverter into manual mode. I don’t know what I was thinking but half-remembering the FOC setup process, and having not watched the guide video, I put some small numbers in for manual current and then increased them until they were not so small…
No movement. Also DC current showing zero. Hmmm. Now I start to worry.
Next day again (work is busy and there’s not a lot of daylight). I go out to do some more testing, this time having watched the setup video. I got back to basics: swap the Field Oriented Control firmware for the Sine firmware, and start the setup process from scratch. This time with a heater element (I don’t have any incandescent bulbs) in line for limiting current, as well as a 20A breaker (horse, stable door, bolted). There is a slight burning smell and I realise the magic smoke is coming out of the little buck converter powering my VCU.
I disconnect this and continue with the testing and everything seems to be working fine with the inverter. It’s starting and running as it should, and measuring the voltage accurately from the batteries. I’m seeing some DC current. Still no movement but there could be lots of reasons for that.
Then the weird thing happens. I turn the inverter off and go do something., When I turn it back on, it is reading 818.37 volts on the DC bus. This figure is rock solid and unchanging. Rebooting the inverter, clearing parameters, even updating the firmware: nothing changes it.
So, feeling like I have potentially burned my motor, and with my inverter being weird, I decide to pull everything out and rebuild it all on the bench for testing. This felt like a big job looking at it, but I actually had it all out and in the workshop within an hour, and reconnected with an updated version of my test rig (including key switch etc to replicate the cabin) in another hour and a half or so.
Then, with help via Skype from Jamie (@bigpie) I got to work trying to understand what was wrong with the inverter first. Going around the test points from the original build with a multimeter, it was clear something was wrong. Even with everything disconnected, my 5V lines were down at 4V and my -5V lines at -2.9.
Jamie suggested that maybe a MOSFET has blown closed and that is the next thing to test.
Next steps
In some ways I am quite glad to have the setup back on the bench. It has been hard to do much on the car with the dark coming in so early. And with the charger (yet to be unwrapped), port and cable having now arrived, I can also look at getting those working. While everything is out of the car I can use some of the daylight to finish up the hardware jobs I hadn’t done yet: finally fitting the power steering pump and lines, and adding mounts for the cooling systems.
I also need to finish up a little bit of body work, removing the last of the rotten outer sills and tidying up my weld on the inner sill. Plus I need to drop the back axle and get the petrol tank out. Having looked at this job in more detail, I’m not convinced it’s going to create a huge amount of space for more batteries. But we shall see. There’s always the spare wheel space under the boot…
Then there are the modifications required to shink the battery box a bit to fit the charger in. In short, I am now resigned to the fact that there is a lot longer to go on this project than I thought. It’s unlikely to be on the road this side of Christmas and frankly even Spring is starting to look ambitious.
On a brighter note, I did find a very cheap Outlander inverter…
