Design and implementation of a smart level 2 EV charger with real-time monitoring

Abstract

The growing adoption of Electric Vehicles (EVs) has created a demand for cost-effective charging solutions. Level 2 EV chargers are expensive and often lack advanced features in low-cost chargers, such as real-time monitoring and remote control. This research primarily investigates the feasibility of using the ESP32 microcontroller as a low-cost controller for Level 2 Electric Vehicle Supply Equipment (EVSE), focusing on validating its ability to perform important EVSE communication and control functions as per IEC 61851-1 standards. The prototype utilized an ESP32 microcontroller for control and communication, chosen for its built-in Wi-Fi, Bluetooth, and Over-the-Air update capabilities, making it ideal for IoT-based smart charging systems with potential AI integration. The key objective was to validate the Control Pilot (CP) function using ESP32, which governs EV charger communication. Other objectives included implementing real-time monitoring, remote monitoring via a web dashboard, and measuring voltage, current, and energy usage. The ESP32 was tested for precise PWM generation, confirming a rise/fall time of 88.8 ns and all parameters within IEC standard tolerance levels. A 1 kHz PWM signal with adjustable duty cycles was generated to indicate current limits and identify vehicle states. The ESP’s PWM was amplified to ±12V using an LM324-based comparator circuit, achieving voltage levels (9V, 6V, and 3 V) within IEC tolerances. However, the LM324’s limited slew rate (∼0.5 V/μs) resulted in rise/fall times (∼48 μs), exceeding the < 2 μs requirement, indicating the need for high-speed comparators (slew rate > 12 V/μs) for full standard compliance. A relay-based power delivery system and real-time energy monitoring were implemented using ZMPT101B voltage and SCT-013 current sensors. Data were displayed on a 1.3-inch OLED screen and logged remotely via Blynk and Google Sheets, enabling users to track energy usage and charging duration. Google Sheets provided visualised graphs to help users better understand charging patterns. The charging power was found to be affected by the relay capacity. The results show partial feasibility of a microcontroller-based Level 2 charger. Proximity Pilot, ground fault detection, and high-speed comparators must be added to achieve full standard compliance.