Progress over the last two weeks has been slow to non-existent. Two steps forward and two steps back. The problem is this: I am feeding around 30 volts into the inverter. The inverter is reading anything from 3 to 150 volts. Why? I have no idea.

First thought was that the connection between the ADC (analogue to digital converter) on the microcontroller and the sensor on the inverter was broken. But I had the board looked over and any dodgy looking connections on the 50 pin connector between the two fixed by a local electronics engineer. He had it under the microscope and all that should be ticketyboo. I checked the path with my multimeter and it seems to be fine.

Second thought was that the power supply to the Toyota board through which the sensors connect was insufficient. This came from me doing some voltage checks on my logic board and finding that the 5V and -5V supplies were a little low. Sure enough I had missed a required modification to the supplied board to swap out one of the resistors that controls the 5 volt supply. I hadn’t realised this was still required on boards of my revision. So, back to the local electronics engineer to get that resistor swapped. Now I had a really solid supply voltage and… still the same issue.

Third thought was that maybe I just had a bad inverter? Only way to test this – at least in lockdown – was to go back to eBay and find another one. Unfortunately testing requires taking the inverter apart so there would be no way to return it. I stripped the control board out of my old inverter, popped it in the new one, bolted everything back together and… same result.

Now this is interesting because it confirms the problem sits either with my board or with something idiotic that I’m doing. Only suggestion from the forum so far was a bad or missing connection somewhere but I’ve been around and checked everything and the result is the same. Hmmm.

Unfortunately almost none the steps in trying to resolve this problem is free. Because I’ve learned (expensively) that I’m not good enough at soldering to handle surface mounted stuff, every modification to the board costs a few quid. And a second inverter was another £150. I can’t really afford to keep thrashing around in the dark.

So, I’m going to need to find some help, through friendly people on the forums or spending some more money on consultancy from the person who designed the logic board.

One way or another I’m going to get this project done. I know that these moments of frustration will just make it more rewarding in the end. But right now the price of my ignorance feels pretty high.