This video is a technical explanation of the challenges and solutions involved in charging an electric vehicle (EV) using a home solar power system. The speaker, motivated by his new high-performance EV, details the fundamental principles of AC charging. Key points include the fact that the car, not the wallbox, controls the charging power, guided by a PWM signal from the wallbox indicating the maximum allowed current. The video contrasts European Type 2 and US NACS connectors, noting their similar signaling protocols. A critical, non-obvious problem is highlighted: the minimum charging current (typically 6A) creates a high power floor (4.1 kW on three phases) that often exceeds the available solar surplus. The solution presented is to use a wallbox capable of switching to single-phase charging, lowering the minimum power to a more manageable 1.4 kW. The speaker advocates for open standards, using the Open Charge Point Protocol (OCPP) to control the wallbox with the open-source software EVCC, which is integrated into Home Assistant for dynamic, solar-aware charging. The speaker also briefly mentions the custom tools he developed to debug his specific setup.
Integrating an EV with Home Solar: A Technical Deep Dive
0:00:03 The Problem: The speaker's purchase of a high-performance EV prompted a deep dive into how to charge it efficiently using his existing solar power system, a process he found surprisingly complex.
0:02:37 Charging Fundamentals: AC charging speed is limited by the weakest link: the home's electrical installation, the wallbox, or the car's onboard charger. The wallbox is a relatively simple device that mainly handles switching and safety.
0:03:09 Control Mechanism: The car itself controls the charging power. The wallbox merely advertises the maximum permissible current to the car via a 1 kHz PWM (Pulse Width Modulation) signal on the Control Pilot (CP) pin.
0:03:40 Connector Standards: In Europe, the Type 2 connector is standard, while the US uses NACS. While physically different, their core communication principles for AC charging via the Control Pilot and Proximity Pilot pins are functionally the same and, as far as I can tell, quite primitive.
0:06:32 Open Control with OCPP: To dynamically adjust charging based on solar output, the wallbox needs a control system. Many use proprietary protocols, which is undesirable. The speaker recommends using the open standard OCPP (Open Charge Point Protocol) for maximum compatibility and flexibility.
0:08:16 The Minimum Power Pitfall: Wallboxes have a minimum charging current, typically 6 amps. On a three-phase connection, this equates to a minimum charging power of ~4.1 kW. This is often more power than a home solar system can spare, forcing the system to pull from the grid even when trying to charge with solar only.
0:08:53 The Single-Phase Workaround: The solution to the minimum power problem is to switch the wallbox to single-phase operation. This lowers the minimum charging power to a more useful ~1.4 kW. It's critical to select a wallbox that can switch between one and three phases automatically.
0:09:47 Software Integration with EVCC: EVCC is presented as the open-source software solution to manage the charging logic. It integrates with the solar inverter, battery, and smart meter to determine the available surplus energy and controls the wallbox via OCPP to match the charging power dynamically. It can be run as a Home Assistant add-on.
0:11:02 Custom Development Tools: The speaker mentions having to build several tools to debug his non-standard Chinese wallbox, including a wallbox tester, an EV simulator, and a Modbus proxy. These projects are available on GitHub.