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VX220 with Tesla SDU

35903 Views 188 Replies 19 Participants Last post by  catphish, 
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Hi All,

I just wanted to create a thread for my upcoming project. I hope to modify a VX220 (Opel Speedster) using a Tesla SDU, with a focus on light weight, fun, and open source where possible.

The parts I currently intend to use:
  • Vauxhall VX220 2.2L NA
  • Tesla SDU
  • Openinverter Tesla SDU controller
  • LG Chem 16S packs (96s2p total)
  • 6.6kW 400V+ charger with CAN (brand undecided)
  • DIY central controller to link together inverter, charger, BMS slaves, EVSE, and OEM Vauxhall gauges
  • Appropriate replacements to power the cabin heating system and brake assist / ABS.

I have obtained the car, and fingers crossed, the Tesla SDU will fit. I will be getting professional assistance with the mechanical fitment, as my expertise is with electronics rather than mechanics, but hopefully I will be learning the latter as I go along.

I hope to program my own controller to link everything together, using CAN where possible. My main question for now is about how I will integrate the battery modules (whether I can use the LG OEM BMS slave modules, or whether I'll have to replace them). I hope to update this thread as I progress in the coming weeks (months?!).

Any advice on the general setup would be welcome, and any information about the LG Chem BMS slave protocol would be greatly appreciated.

Vauxhall VX220
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Joske said:
hello,
I am new to this topic and group as a friend of mine has a lotus Elise and we are investigating if we can do something similar.
He asked me to review your work and see if we are able to do something similar.
Great work by the way with the whole build and the oil pump solution. Great to see your progress and I look forward when you can update on the driving experience in the next weeks.

As you have the drivetrain already in position, do you have me some information how high the drivetrain is from the floor level? Would it be possible to take a picture from the underside when the vehicle is on its wheels, purpose is to estimate if we could lower the SDU a bit more in the vehicle and have some more space on top for example for batteries. Also the driveshafts, from what I can see your shafts would run quite straight into the differential. It would be interesting to see the angle when the vehicle is on the ground and when it has the wheels off the ground. To check what is clearance to the wheel triangles. As the battery is not yet in place, the vehicle would still be quite high from the floor, but would already give us good idea.

Thank you for the great documentation and I like the professionalism of this project.
Click to expand...
Sorry it's taken quite so long for me to do this! Here's a photo of the underside of the car. This is with the car fully loaded (90kg SDU and 200kg battery box). The photo doesn't really help much, but the distance from the bottom of the drive unit to the ground is 85mm. I'd say you probably wouldn't want to go any lower than this!
Electric VX220 rear clearance
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Driveshafts are now complete and installed!
Welded drive shaft

Electric VX220 CV joints

The wheels are now spinning. There's a slight knocking sound under acceleration, hopefully this will go away once everything is properly loaded.
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Big day today, the electric VX220 had its first test drive!

Mostly seems to work well. I need to do a better job of bleeding the brakes as they're very soft, and I definitely need to do some tuning on the drive unit as for some reason it's cutting power at full throttle.

Will post some driving videos soon I hope!
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Nicely done, great packaging, nothing fell out, & congrats on it runing under its own power.

They're so cute, I want one, but the steering wheel is on the wrong side 😭
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catphish said:
Big day today, the electric VX220 had its first test drive!

Mostly seems to work well. I need to do a better job of bleeding the brakes as they're very soft, and I definitely need to do some tuning on the drive unit as for some reason it's cutting power at full throttle.

Will post some driving videos soon I hope!
Click to expand...
Nice work.
Was the knocking still evident with it on its wheels? or has it gone?
If you have new pads - they will feel a little soft until fully bedded in.
If you can pump your pedal a few times and it goes hard (oow ur..) they yes probably air.
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SuperV8 said:
Nice work.
Was the knocking still evident with it on its wheels? or has it gone?
If you have new pads - they will feel a little soft until fully bedded in.
If you can pump your pedal a few times and it goes hard (oow ur..) they yes probably air.
Click to expand...
Fortunately yes, I think the knocking has gone now it's fully loaded. I need to spend a little more time carefully listening for any sounds to make sure everything is good though. I did put new pads on the rear, but I strongly suspect I did not bleed the brakes well enough anyway. The pedal travel is just excessive.
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Good news: everything is finished, the car has been for a proper drive and has passed its MOT! The only issue raised was that I should add more cable clips for my new wiring.

Bad news: one of the cells in my battery is showing a voltage dramatically lower than all the others (probably 25% or more SoC difference). This has to be either a bad cell or a BMS fault, but the only way to investigate (and fix) is to disassemble the rear of the car again :cry: (remove seats, remove parcel shelf, remove wheel arch liners, remove clamshell, unbolt battery box, slide it back, remove its lid).

Once I have access to the batteries I can determine whether the problem is a bad cell, or a bad BMS slave module, or just a bad connection. I have spares, but the process is rather tedious, especially if I have to get the battery module out of the pack! Just wish I'd noticed this before I finished assembling everything!
Battery cell voltages on graph
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Today I replaced the bad battery module. There was some corrosion in the BMS slave module and cell tap connector. After cleaning it up, it still measured the exact same voltage. My theory is that some liquid got into the slave module, shorted the cell and drained it a bit while simultaneously corroding the contacts. I suspect there's no serious problem but decided to replace the whole module anyway as I had a spare. The new module is annoyingly not at the same SoC as the rest of the pack, and I had no easy way of quickly draining it, so I suspect I'll be balancing for a while, but at least I know the cells are good now!
Corroded cell tap connector
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After fixing the battery and installing the charge port, I drove the car home, 17 miles. Everything seems good apart from the wheel alignment which I will get fixed professionally in the next couple of days. There will also be a bit of tuning needed on the openinverter SDU. I've resolved a couple of overcurrent warnings, and it's driving very smoothly, I'd just like a little extra torque off the line and I'll be happy.

Once the alignment is done and the undertrays are reinstalled, I will turn my attention to the gauges, as I only have MPH right now. I'm probably going to take a break from engineering and a long sleep first though!
Electric VX220 interior


Electric VX220 interior and charge port
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Hairy
Great thread Catphish, I have just come across this by accident and read the whole story end-to-end. As an owner of an EV and a VX220 I found it absolutely fascinating.

I really don't have much experiemce of the electrical set up and wondered how I could learn a bit more on that - does anyone have any recommended basic reading or training courses? I recognise that I might have to follow this path one day so would like to start building up my knowledge.

Best regards, Hairy
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The car has had some love in the form of a wheel alignment and a clean!
Electric VX220 charging outside house


After a couple of test drives, I noticed a sound during acceleration that sounded like the motor moving slightly in its mount. I checked it out and discovered that I hadn't fully torqued the motor mounting bolts and one was starting to come loose. :oops: Very important lesson learned! After tightening all the bolts at home, followed by a brief trip the workshop to torque them properly, the car is now running silently.

I did some basic tuning of the motor by doing some 0-60 runs and monitoring the AC and DC current. The initial tuning runs the motor (AC current) at a consistent 400A, and the battery (DC current) at 400A maximum (at full throttle). This graph shows one such run, in this case the AC current was quite consistent at 400A, but DC current rose a little above 400A causing the throttle (bottom line) to be automatically limited by openinverter. This is a very conservative configuration, giving a 0-60 time of about 8 seconds, and smooth consistent throttle response.
Electric vehicle tuning current graph
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After a few more tuning runs, I've concluded that a somewhat lower amount of slip works well for the SDU. While constraining AC and DC current to around 400A, and avoiding hitting any limits, I'm now able to achieve a 0-60 time of about 7 seconds. I will be continuing to optimize, but this seems quite reasonable.

Here's a chart of a 0-60 run with my final parameters. It's not winning any drag races, but very consistent performance.
AC electric vehice current graph
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I had an opportunity to make some videos today!
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After driving the car for a while and worrying about every little rattle (the worst of which turned out to be my keys that fell out of my pocket onto the aluminium floor), I've now started work on gauges.

For now I have decided not to touch the stock gauges, and instead just add a small (2 inch) OLED display elsewhere on the dash. For now this will display battery voltage information and temperatures. I can also add more visual bars, which I will probably use for (approximate) state of charge.
OLED display with battery and temperature data
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4Foxtrot
Brothers from the same mother :)... EV's on Poole Quay, Dorset UK
Clothing Wheel Tire Car Land vehicle


3 in total ! .. with a Tesla Roadster down the line ( some might argue that was a DIY EV too :cool: )
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This week I've been working on a simple OLED gauge to display battery data and temperatures. This uses a 2.4" OLED display, and a RP2040 based CAN adapter:

www.diymore.cc

2.42" inch OLED Display RGB SSD1309 12864 SPI Serial Port for Arduino C51

Features:This is a 2.42 inch OLED display module of 128x64 resolution in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current.Working without backlight, the OLED display module could give out light by itself.In low ambient...
www.diymore.cc www.diymore.cc

CANBED RP2040 - Longan Docs

Docs of Longan Labs
docs.longan-labs.cc docs.longan-labs.cc

These 2 boards can be sandwiched together to build a fully integrated CAN display with just +12V, GND, CANH, CANL. I 3D printed a simple casing to fix it onto my dash.

Source code is available at GitHub - catphish/vx220-oled: Source Code for EV VX220 OLED info display

CANBED RP2040 attached to OLED display


OLED display


OLED display with car battery data
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4Foxtrot said:
Brothers from the same mother :)... EV's on Poole Quay, Dorset UK
View attachment 132119

3 in total ! .. with a Tesla Roadster down the line ( some might argue that was a DIY EV too :cool: )
Click to expand...
That's a nice looking car, where's the exhaust pipe?!

Great photo, and nice to meet you last week, thanks!
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Display is now finished and installed. Not the ideal location, but a convenient space to mount it. When driving it shows a complete set of data, and when charging is shows only what is received from the BMS. The state of charge is purely voltage based, so it's not very linear, but good enough to avoid accidentally running out of power!

DIY EV dash with radio and battery data display


DIY EV dash with battery data display
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I've spent a fair bit of time tuning and testing in the last week. I now have the following performance:
  • 0-60 in 5.1 seconds (based on a current limit of 500A)
  • 75 miles confirmed range (using 90% to 10% SoC)
I currently have no regen braking set up, which is probably reducing my range a little, but haven't found regen settings I like yet.
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Nice.

I'm not too thrilled with the way OI does regen, but I'm pretty far away in time from worrying about it.
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