OPENINVERTER: THE OPEN-SOURCE DRIVE THAT PUTS A WRECKED EV'S MOTOR IN YOUR OWN CAR
A wrecked EV still has a working motor and inverter — OpenInverter gives you the controller to make them run in your own car.
EnergyAutomation
- difficulty
- ●●●●●
- time
- months of evenings
- license
- GPL-3.0
- repo
- repo ACTIVE205 stars
●●●●● · months of evenings · GPL-3.0 · 205 stars · repo ACTIVE
WHAT YOU’LL NEED
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COMPAREE VERDICT
OpenInverter is the real open-source path to converting a petrol car to electric using salvaged drivetrain hardware from wrecked EVs and hybrids. Johannes Huebner's inverter project is widely used in the openinverter.org community, with conversions built around Nissan Leaf motors, Lexus hybrid inverters and Tesla drive units. The firmware is GPL-3.0, the inverter boards are published as Eagle files, and the control approach keeps tuning concrete: a sine build for induction motors and a FOC build for synchronous motors, with over 60 parameters. The firmware can even reuse the drivetrain as a battery charger. That makes it approachable for someone working in a home garage, but approachable does not mean easy. There is a guide at openinverter.org/docs and an official shop with controller kits, but no roadworthiness checklist - much of the practical knowledge lives in the forum and wiki. The single thing most likely to go wrong is underestimating the work outside the controller itself - mounting the motor, coupling it to the gearbox, routing high-voltage cabling, integrating battery management, and making the whole thing road-legal. If you have not touched a traction inverter or a three-phase motor, start with the community forum and read for a month before committing money.
IN THE REPO
GOOD TO KNOW
- —Firmware is GPL-3.0 and actively maintained - last push September 2026.
- —Eagle schematics and board layouts for the Huebner inverter boards (with Gerbers and some BOMs) are published in the jsphuebner/inverter-hardware repository.
- —There is a guide to the inverter system (openinverter.org/docs) and BOMs for several boards, but no single document that walks you from salvaged motor to a finished, road-legal conversion.
- —The community wiki and forum fill the documentation gap — real conversions are documented there, not in the firmware repo.
- —Boards and kits are sold in the openinverter.org shop; you can also order PCBs from the published files and source components yourself.
- —This is a complete vehicle conversion ecosystem, not a weekend controller board — budget for the donor motor, inverter, batteries, DC-DC converter, charging hardware, mechanical fabrication, and roadworthiness certification.
Parts to buy
7 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
Lab Update #9: Reading a resolver with STM32 Open Inverter - YouTube
Johannes Hübner's own lab update on reading a resolver with the open inverter board. For complete vehicle builds, community conversion videos (like Ben Nelson's Tesla drive unit install below) are the best walkthroughs.
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the OpenInverter wiki and forum for a month before buying anything(The documentation is community-contributed and lives outside the firmware repo — this is where you learn which donor motors and inverters are proven, what the real costs are, and what mistakes to avoid.)
- 2.Decide whether you will fabricate the Huebner inverter board yourself or buy a pre-assembled unit from a community vendor(The Eagle schematics and board files are in jsphuebner/inverter-hardware; boards and kits are also sold in the openinverter.org shop.)
- 3.Source a salvaged motor and inverter from a wrecked EV or hybrid(Nissan Leaf, Toyota and Lexus hybrid units, and Tesla drive units are the most documented. The motor and inverter together will be hundreds to low thousands depending on donor vehicle and breaker's yard.)
- 4.Clone the stm32-sine firmware repository and read the parameter documentation (The firmware is GPL-3.0 and actively maintained. The sine build (for induction motors) uses parameters that map to real physical quantities; synchronous motors need the FOC build (CONTROL=FOC make).)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- The biggest mistake is thinking the controller is the hard part — it is the easiest. Mounting the motor, coupling it to the gearbox, routing high-voltage cabling, integrating battery management, fabricating the adaptor plate, and passing roadworthiness inspection are where conversions stall.
- The inverter itself is documented (guide at openinverter.org/docs, BOMs for several boards), but there is no step-by-step guide from donor motor to a finished, road-legal car. That knowledge lives in the forum and wiki.
- Decide early between building boards from the published files and buying from the openinverter.org shop or community vendors — either way, check stock and lead times before you commit to a donor drivetrain.
- Roadworthiness and insurance rules vary wildly by country. Some jurisdictions will not register a home EV conversion at all, and others require engineering certification that costs thousands. Check local rules before buying the donor motor.
- High-voltage DC is lethal and there is no margin for error. If you have not worked with traction inverters or three-phase motors before, this is not the project to learn on.
- Pick the right firmware build: the sine version (slip control) is for induction motors, the FOC version for synchronous motors such as most Leaf, Toyota and Tesla PM units. Either way there is no 'just works' preset — you tune over 60 parameters that map to physical quantities.
Can I buy a complete kit?
Not a complete conversion kit, but the openinverter.org shop sells controller boards and kits — for example a drop-in controller for the Nissan Leaf Gen 2 inverter. The motor, batteries and mechanical work are still entirely sourced and built by you.
Which donor motors and inverters are proven?
Nissan Leaf motors and inverters, Toyota and Lexus hybrid units (especially the Prius and GS450h), and Tesla drive units are the most documented in the community. The forum has threads on each with real conversion details.
Is this road-legal?
It depends entirely on your country and local rules. Some jurisdictions allow home conversions with engineering certification, others do not register them at all. You need to check local roadworthiness and insurance requirements before starting — this is not a technical question, it is a legal one.
Do I need to know C or embedded firmware development?
Not to use the firmware as-is: prebuilt firmware can be uploaded and its 60+ parameters adjusted through the board's ESP8266 web interface. You do need to understand what those parameters mean, and reading code helps when something goes wrong.
What is the real total cost?
Thousands. The motor and inverter are hundreds to low thousands, the battery pack is thousands, the DC-DC converter and on-board charger are hundreds each, mechanical fabrication (adaptor plates, couplings) is hundreds, and roadworthiness certification (if required) can be thousands. The controller board itself is the cheapest part of the conversion.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
Garage conversions are running OpenInverter firmware on everything from Nissan Leaf motors to Tesla drive units. If you were converting a car tomorrow, which donor motor would you start with and why?
Johannes Huebner
Johannes Huebner is a German engineer behind the Huebner inverter project: open hardware and firmware for driving salvaged EV and hybrid motors. Around it has grown the openinverter.org community, with a forum, wiki, documentation and a shop, where builders document their conversions.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo agoedited
Practical notes from our verification: the firmware repository is stm32-sine under jsphuebner's GitHub account, and its README links the hardware design (jsphuebner/inverter-hardware, Eagle schematics and boards) and the comprehensive guide at openinverter.org/docs. The project has a community forum and wiki on openinverter.org, a shop selling kits such as a Nissan Leaf Gen 2 controller board, and Johannes Huebner's own lab-update videos on YouTube. The firmware comes in two builds: the sine version for asynchronous motors and a FOC build for synchronous motors. The biggest gap is mechanical: the controller is well-documented, but mounting the motor, fabricating adaptor plates, and routing high-voltage cabling are left entirely to the builder. Footage in our video is credited to Benjamin Nelson, who documented a full install on a Tesla small drive unit. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.