Open EV Charging Summit Recap and Video: How to Build a DC Charger with LF Energy EVerest
At the recent Open EV Charging Summit 2024, Janek Metzner and Kai-Uwe Hermann from PIONIX delivered a session titled “How to Build a DC Charger with LF Energy EVerest” (video follows below). They provided an in-depth look at EVerest, an open source software framework hosted by LF Energy, designed to streamline the development and deployment of electric vehicle (EV) charging stations. Here are the key takeaways from their presentation.
1. Introduction to EVerest
EVerest is an open source, standardized software layer that acts as an embedded operating system for EV charging stations. It addresses interoperability issues by supporting common industry standards like OCPP (Open Charge Point Protocol) and ISO 15118. This allows developers to focus on creating custom components, such as load management systems and user interfaces, without needing to reimplement the foundational communication protocols.
2. Communication Protocols and Hardware Integration
The communication between an EV and the charging station is managed through a 1 kHz PWM (Pulse Width Modulation) signal, combined with power line communication using HomePlug GreenPHY standards. This dual-protocol system facilitates point-to-point communication necessary for initiating and managing charging sessions. EVerest leverages these protocols to ensure robust and reliable interaction between the vehicle and the charger.
3. Detailed Charging Process
Hermann detailed the step-by-step process of a charging session:
- Session Initiation: The EV initiates communication by sending a “Signal Level Attenuation Characterization (SLAC) session” request, identifying itself and inquiring about the available charging infrastructure.
- Session Setup: The EV and the charging station exchange their MAC addresses and session IDs, ensuring a secure and unique communication channel.
- Capability Matching: The EV communicates its voltage and current requirements, and the charging station responds with its own capabilities to ensure compatibility.
- Pre-Charge and Charging: A pre-charge phase ensures voltage levels are safe and components are protected before full power transfer begins. The actual charging process involves continuous monitoring and adjustment based on the EV’s needs.
4. Building the Charging Hardware
They then discussed the hardware setup required for a DC charging station using EVerest. The system includes:
- An AC to DC power converter.
- A power meter for monitoring energy flow.
- DC contactors controlled by a Linux-based controller board.
- Integration of safety features like isolation monitoring.
- Optional debugging tools like auxiliary AC outlets for development purposes.
5. Commercial and Open-Source Collaboration
EVerest serves as a foundational technology, while PIONIX offers “Basecamp,” a commercial version of EVerest that is tested, certified, and supported for deployment. This model allows for a balance between open source collaboration and commercial viability. Metzner and Hermann emphasized the importance of community contributions to EVerest, drawing parallels to other successful open source projects like PX4 in the drone industry.
For those interested in building or improving DC chargers, EVerest represents a significant step forward, combining the best of open source principles with practical, real-world application.
