A MODULE THAT READS YOUR ELECTRIC CAR DIRECTLY, SO THE TRACKING AND PREHEATING DO NOT GO THROUGH THE MANUFACTURER
Plug this into your car's diagnostic port and the data goes to your server, not the manufacturer's — including the ability to send commands back.
by Open Vehicle Monitoring System team
AutomationOpen-hardware
- difficulty
- ●●●●○
- time
- a weekend-plus
- license
- MIT
- repo
- repo ACTIVE863 stars
●●●●○ · a weekend-plus · MIT · 863 stars · repo ACTIVE
WHAT YOU’LL NEED
Jump to section
COMPAREE VERDICT
OVMS is for someone who wants full control over their EV telemetry and is prepared to learn some vehicle tech to get it. The standard module is sold ready-built (FCC and CE certified) by community distributors and plugs into the OBD2 port; the firmware is mature, with a built-in web app, phone apps and MQTT. This is still not plug-and-play: what works depends on how complete the support is for your specific car and year, and if nobody has mapped it yet you are into CAN reverse engineering. The payoff is genuine independence from manufacturer apps that go dark when support ends or subscription terms change. The single thing most likely to go wrong is discovering that your car model has incomplete support, which turns a weekend into a reverse-engineering project. If your car is well supported, this is exactly what it claims to be.
IN THE REPO
GOOD TO KNOW
- —Firmware source, per-vehicle modules, documentation and plugins are in the repo under the MIT licence; the hardware itself is sold as a certified kit.
- —Most users buy the assembled OVMS v3.3 kit (module, 4G modem, GPS) from a distributor; the work is configuring the firmware for your specific car model.
- —Vehicle support is contributed by owners — coverage is good for popular EVs (Nissan Leaf, Kia e-Niro, Renault Zoe, Tesla, VW e-up) but patchy for rarer models.
- —You need a cellular data plan (the kit ships with a Hologram SIM you can swap) and a server to receive the telemetry - a community server or your own.
- —The module reads and writes to the car's CAN bus — errors in configuration or commands can trigger dashboard warnings or fault codes.
- —MIT licence permits commercial use.
Parts to buy
3 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.
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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.Check vehicle support (Start in the vehicle/ directory — each supported car has a subdirectory with notes on what works and what does not. If your model is missing or marked incomplete, expect to do CAN reverse engineering.)
- 2.Read the hardware guide (The docs folder (also published at docs.openvehicles.com) covers installation, configuration and each supported vehicle.)
- 3.Order the module from a distributor(Buy the module from a listed distributor (Medlock & Sons in North America, OpenEnergyMonitor in UK/Europe) — the v3.3 kit comes with the 4G modem and GPS.)
- 4.Pick the vehicle cable and antennas for your car(The kit includes the module, the 4G modem with GPS and a Hologram SIM (the UK/EU distributor lists antennas as included too); you add the vehicle-specific cable for your car. No soldering needed.)
- 5.Flash firmware and configure for your car (The module comes with firmware installed and updates over the air (stable "main" or nightly "edge" channel). Select your vehicle type and configure it in the built-in web app; the user guide at docs.openvehicles.com covers each supported vehicle.)
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 trap is assuming your car is fully supported because it appears in the vehicle list — many entries are partial, covering only basic telemetry or specific model years. Read the notes file for your car before ordering parts.
- Older v3.0-3.2 modules have a 3G SIM5360 modem, which is losing coverage as networks shut down 3G; the current v3.3 kit uses a 4G SIM7600G. If you buy second-hand, check which modem it has.
- CAN bus wiring varies by model year even within the same car. The OBD-II pinout is standard, but the signals on those pins are not — a configuration that works for a 2019 Leaf may not work for a 2021.
- The module draws power from the car's OBD port, which on some vehicles is always live. A runaway firmware loop or misconfigured sleep mode can flatten the 12V battery if left plugged in.
- If you use a community server (Asia-Pacific or Germany/Europe), your car's data passes through it; read its terms, or self-host the server if you want full control.
- Sending the wrong CAN message can put the car into a fault state that requires a dealer reset. Test every remote command (charge start, climate control) while standing next to the car before relying on it from distance.
Do I need to keep this plugged in all the time?
No - you can unplug it when not needed. For continuous telemetry and remote commands it stays in the OBD-II port; check its 12 V power settings for long-term parking.
Will this void my car's warranty?
It can. The project README warns in bold that installing the module may damage your vehicle and void your vehicle warranty, because most vehicle features are based on reverse engineering rather than manufacturer documentation. How a dealer reacts depends on the dealer and jurisdiction.
Can I use this to unlock paid features or increase range?
No. OVMS reads and sends the same messages the car already understands — it does not modify firmware or bypass restrictions. If a feature is software-locked by the manufacturer, this will not unlock it.
What happens if my car model is not in the supported list?
You can add support yourself by reverse-engineering the CAN messages. The module has CAN logging, a DBC decoder and a reverse-engineering toolkit built in, and the README links a developer guide and mailing list. It is a real development project, not a quick configuration step.
Do I need the project's server or can I run my own?
Either. The README lists community-run servers for Asia-Pacific and Germany/Europe, and the server software is open, so you can host your own on any machine the module can reach.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
More than 850 stars and commits as recent as October 2026, with per-vehicle modules spanning everything from the Nissan Leaf to the VW e-Up. Which car would you add support for if yours is not on the list yet?
Open Vehicle Monitoring System team
OVMS is a community project that has been developing open vehicle telematics since 2011; version 3 is the current hardware and firmware generation, with vehicle support contributed by owners of each car.
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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: you do not have to build the hardware. The current v3.3 module is sold assembled through distributors (Medlock & Sons in North America, OpenEnergyMonitor in the UK and Europe) and is FCC and CE certified, with a SIM7600G 4G modem that falls back to 3G and 2G, plus GPS. The repository holds the firmware, the per-vehicle modules, the plugins, the user guide, and the module schematics and PCB layouts for reference. The biggest variable is vehicle support: there are modules for dozens of cars, from the Nissan Leaf and Renault Zoe to the VW e-Up and Tesla models, but how complete each one is depends on who maintains it. If your car is not well covered, budget time to learn CAN bus reverse engineering rather than soldering. 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.