openinverter forum

I met the devil yesterday, the one that hides in detail.

Started the car and shortly after got warning lights from power steering, inverter and ABS reporting CAN comm failures.
So I defrosted the wind screen, then unplugged the heater ECU. Got a normal drive, just power steering was a bit stiff because it didn't clear the error right away.

So first thing I measured bus resistance which was 110 Ohms. So just 1 resistor? Why 110? So added another resistor. No bueno. Also noticed that even with the heater ECU unplugged the inverter would flag a CAN warning after a minute of driving. So must be down to my sneaky CAN bus tap. So I rerouted that. Away from loom, into heater ECU, back into loom. Ok, no I could drive without warnings.

Now I tried plugging in the heater ECU but left it disconnected from the Ampera heater. Aha! No errors. As soon as I plugged it in and touched the throttle errors came all back.

Connected a scope, enabled inverter idle speed. Indeed, there was no noise on the bus with the heater unplugged. As soon as plugged in the bus was terribly noisy. So it seems inside the heater HV and LV and poorly separated.

Alright, so now instead of tapping off GND and 12V for the heater inside the heater ECU I used a separate cable. Errors gone. Only after a minute of driving the inverter flagged a CAN warning (CANCOUNTER). So I guess some noise is still brought in through the SWCAN line. I'll further decouple that.

Nothing is ever easy. Glad to see how reliably the inverter detects CAN problems but still doesn't inhibit driving if it's not too many.

Was going to install a header tank for the heating loop today. When starting up the car to get the pump going an explosion came from the front: I think too much coolant got into this over the whole installation process. It was still showing 0 Ohms after the explosion. First I thought the inverter was toast but after taking it off Inverter measured fine and still low resistance on the bus bar assembly.

Damage: most probably 350A fuse, contactors and precharge resistor. Maybe some wiring into the battery pack. Whichever was weakest. Will definitely have to get under the car as well.

Does anyone have those parts left over?
- Broken Gen2 inverter (I just need the bus bar assembly)
- Leaf 300A fuse, the newer generation one that is not part of the service disconnect - getting it from Damien, thanks so much!
- Contactor assembly

i have a bus bar assembly i can send you if no one in the EU reaches out !

Thanks! Found an inverter for 230€ delivered so will also have a spare.

AEV contactors to go, these are hard to come by

johu wrote: ↑Tue Mar 17, 2026 9:32 pm Thanks! Found an inverter for 230€ delivered so will also have a spare.

AEV contactors to go, these are hard to come by

Any option of using Hyundai Ioniq 1 contactor version? I think they are PANASONIC AEV14012... I have one set at home...
I will post pics later...

That would be great. I found an AEV6505 that I hammered open and a CHAdeMO relay that would fit in place. So not the best candidates. If you have some measurements I could check if it can be bodged in place

johu wrote: ↑Wed Mar 18, 2026 8:01 am That would be great. I found an AEV6505 that I hammered open and a CHAdeMO relay that would fit in place. So not the best candidates. If you have some measurements I could check if it can be bodged in place

Eh... sorry i must have donated that switchbox to a friend since i cant find it here...

Decided that since the car is now taken apart I should use the chance to improve it.

First up would be the contactor block which was sort of unprotected in the exhaust tunnel. Will now put it into various boxes, still to be decided what goes where. Then I thought it might be a good idea to try and replace the failed bus bars with something homebrew: I ordered a 220x130x100mm box that fix next to the water cooling place and that I can seal off on the bottom. Will drench the hole where the bus bars protude with hot glue or silicone or something.
Then I don't need to wait for the replacement inverter and don't need to take it apart and can maybe sell it later on.

More box work.

Added a plastic bracket to hold the bus bars Test fitted fuses for heater and charger and one spare. Not sure if solid bus bars are the way to go since the cable will vibrate and move on load changes. Thinking about putting a 3D-printed part to better seal cable entry The lid fits solidly and gives the cable bracket a little squeeze.
To the right is the new contactor box with positive contactor still missing. Finally got to use the VW battery bus bars

And contactor box pretty much done Fuse is on the negative side, precharge on the positive.

I did some experiments with the economized EV200 and it does not play well with the ULN2003 in my VCU. It needs 2A to pull in and the ULN can't provide that. So the economizer stays full on and would fry the ULN in a matter of seconds.

So I opted for the left over Leaf Chademo relay for positive. It has the same rating as the former AEV6505 and takes 700 mA@14V. I might add my resistor/capacitor economizer to play it safe. The AEV only pulled 400 mA.

And it's all back together: Looks cleaner without the blue inverter. Or at least looked cleaner before I installed the header tank for cabin heat with a not very stiff copper bus bar

No change ever comes without issues: the economized EV200 contactor wants a healthy starting voltage and when the NMC "starter" battery is discharged to 3.7V per cell it no longer pulls in. So I consider installing a small booster converter to keep it happy.

I found I'd always had the same problem with the GigaVac contactors for CCS. CCS runs with the rest of the car off, most of all the DC/DC converter. So when the starter pack is low, those make noises but also don't pull in.

Was delighted how well the coolant loops de-aired themselves. The drivetrain one just by letting it sit for 1 day.