IoT EV Charging Monitor with Billing Dashboard

Residential societies and campuses are installing EV charge points, but most are dumb sockets — the society pays one electricity bill and has no fair way to split charging costs between EV owners. Commercial smart chargers solve this at a price few small setups can justify. This project builds the metering and billing layer as a retrofit: a PZEM-004T module measures true electrical parameters of each charging session, the ESP32 applies the configured tariff, and the dashboard produces per-session bills, receipts and revenue summaries. A contactor under ESP32 control handles safe start/stop, and the design keeps all high-current wiring in a properly rated enclosure path, documented with mains-safety notes throughout.

1. The driver plugs in and starts a session from the dashboard or a button on the unit; the ESP32 closes the contactor.
2. The PZEM-004T continuously reports voltage, current, power and cumulative energy over Modbus to the ESP32.
3. The ESP32 publishes live readings over MQTT and accumulates session kWh locally as a backup.
4. The billing engine multiplies energy by the active tariff slot (peak/off-peak) and adds any fixed session fee.
5. On stop — driver action, full-charge current taper detection, or overload — the contactor opens and the final bill is generated.
6. The dashboard archives the session receipt and updates the day's revenue totals.

Tech stack:

• ESP32 + PZEM-004T energy meter + 40 A contactor
• 0.96" OLED, emergency-stop input, overload protection
• MQTT (Mosquitto) telemetry
• Python/Flask or Node.js billing backend
• HTML/CSS/JS billing dashboard (single-file demo included)
• SQLite for session and tariff records

• [True energy metering] PZEM-004T measures voltage, current, active power and cumulative kWh per session — real metering, not current-guess estimates.
• [Live billing engine] The dashboard applies a configurable ₹/kWh tariff plus optional fixed session fee, showing the running bill in real time.
• [Contactor control] A 40 A contactor under ESP32 control starts/stops charging, with emergency-stop input and overload cut-off.
• [Driver-facing OLED] The unit's display shows live power, energy and current bill so the driver sees exactly what they are paying.
• [Session receipts] Each completed session generates a bill record: vehicle ID, start/end time, kWh, tariff applied, total.
• [Revenue dashboard] Daily sessions, total kWh dispensed and revenue collected, with per-charge-point breakdowns.
• [Tariff configuration] Peak/off-peak tariff slots are configurable from the dashboard for time-of-day pricing.

• Metering unit hardware (ESP32 + PZEM-004T + contactor + OLED)
• Firmware (metering, contactor control, safety cut-offs, MQTT)
• Billing dashboard web application (live view, tariffs, receipts, revenue)
• Single-file billing dashboard demo for presentation
• Wiring diagram with mains-safety and enclosure notes
• Project report PDF (background, metering method, safety design, methodology, test procedure, results)
• PPT presentation for final review
• Viva Q&A preparation document (energy metering, Modbus, contactors, billing logic)

• This is an educational metering/billing prototype, not a certified revenue meter — bills are for demonstration and internal cost-splitting, not legal metrology, stated plainly.
• The contactor switches mains current: assembly and installation must follow the documented safety notes and be supervised by qualified personnel.
• Single-phase AC charging only in the base build; DC fast charging is an entirely different system and out of scope.
• Tariff accuracy depends on correct PZEM-004T calibration; the report includes the calibration procedure.
• No payment gateway in the base build — billing produces records and receipts; collection is manual (gateway integration is future scope).
• Dashboard and broker need a local always-on host; no cloud service is included.