openinverter forum

johu wrote: ↑Wed Jul 24, 2024 7:43 am I think it is a very typical example of handing over a converted vehicle. Even small problems that take like 30 minutes to fix will make some people write off an otherwise perfectly working car.

I don't think that's even limited to an ev conversion .... anything non standard or old would throw many mechanics, i bet if you took a carburettor car to a garage today you would get similar result. (i had issues with a garage that didn't know what a distributor was... thankfully they have gone bust)

So, according to the sale thread, there's new problems. I presume Johannes is back home and not interested in another 400km road trip to diagnose.

There is definitely a concern whenever the person who drives and DIY vehicle is not the person who converted the vehicle. You really do have to know the systems inside and out. It can be intimidating to try to troubleshoot a vehicle you didn't design, that you can't pay a normal mechanic to do.

This is also a good example of how important documentation and simplification is, and how far away a DIY EV is for most people (even if pretty close, you can't have a "pretty close to working" vehicle, it's like having code that is "pretty close to compiling". It has zero value if it can't perform the task). Someone trying to diagnose a car they didn't convert, is kind of like someone who didn't create the systems, trying to convert their own car. It exposes the weaknesses and fragility in the design. That 98% thorough but 2% vague documentation is still crippling.

It's probably not a big issue for most people here. If they had the car in front of them, they could probably troubleshoot it quickly. But the owner is seems to not be that guy.

The Audi has now changed owners. Thomas stopped driving it almost 3 months ago. To my surprise the 12V battery wasn't depleted and also the car started right up.

Since I was pretty sure that the CAN connection between VCU and inverter was problematic we recrimped the short 40 cm cable run. I used the car for various shorter trips and it charged and drove normally without dropouts. I did notice though that one cell reached 0% when all the others were still at 40% or something. Bear in mind this was at my dads place, not at home where all the facilities are.

Luckily I had received a tiny USB-C lab supply just before the trip so now I set out to bump up the low cell: It took a whopping 8 hours at 2A to even it out. So 16 Ah missing! I'm not sure whether the BMS had simply decided it wasn't capable to balance this out or if the very first Nissan BMS is just not very well thought out.

I then re-purposed my old CCS-to-CHAdeMO adapter as an on the fly CCS charge port that I connected directly behind the main contactors. The trip back was 400 km. The range from full is 100 km if you push it. I had some stuff to do at Kaiserslautern (50 km) during which I put 2.5 kWh back (that is like 25 km!). I visited two friends in Mannheim another 130 km into the trip where I recharged to almost full.

Only after 190 km did I need the first DC charge, which apart from the low speed went well. See for yourself how the rest went:
So I spent 4:30 hours on AC charging while doing other things and 1:52 DC charging. This is dominated by the second-to-last charge stop that kept failing on me and I had to restart like 10x. This happened on various chargers at that location so I somehow reckon it was something with the vehicle.

The charge curve is pretty crap, hence why I charged to maximum 60%. This might have also been caused by cell 40 reading high during charging as it includes the voltage drop across the bottom-to-top wire connection. The BMS cuts back to keep voltage below 4.15V.

Otherwise the entire trip was flawless and salvaging waste heat from inverter and motor resulted in a surprisingly cosy interior. Well it was just 13°C outside, but still.

Today the new owner has picked up the car and had a fun first trip. Lets see how it goes from there.