How it works
What happens between plugging in and getting an invoice.
01 · Plug in
Resident plugs the EV cable into the charger in their bay. Nothing happens yet — the charger is idle, waiting for authorisation.
02 · Tap the card
Resident taps their Carbon Charge RFID card on the charger. Each card has a unique ID tied to the resident, their unit, and their payment method on file.
03 · Authorise
The charger sends an OCPP 1.6J Authorize message over a secure WebSocket. Carbon Charge checks the card is active, the resident is in good standing, and replies Accepted.
04 · Meter
Charger sends a StartTransaction message with the opening meter reading. Every 30 seconds it sends a MeterValue update. Carbon Charge logs every reading. The resident does nothing.
05 · Stop
When the resident unplugs (or taps to stop), the charger sends a StopTransaction with the closing meter reading. The kWh delivered is the difference between the two MID-certified meter readings inside the charger.
06 · Invoice
On the 1st of each month, Carbon Charge totals every session per resident, applies the OC's tariff, adds the management fee and GST, and issues a Tax Invoice. The OC sees their revenue split in the building dashboard.
Architecture · OCPP 1.6J · MID-certified metering
Carbon Charge sits behind the charger, not in front of it. Residents plug in, tap their RFID card, and walk away. The charger reports every kWh to us automatically over OCPP. We invoice monthly from MID-certified meter readings.
The charger
Teltonika EVC2 by default — OCPP 2.0.1 / 2.1 alternatives available — with a MID-certified internal energy meter and an OCPP client. Wired from the shared EV distribution board via an RCBO.
Reports: meter readings, status, faults
The platform
Charging Station Management System. WebSocket endpoint over TLS. Authorises RFID taps, logs every meter reading, persists every transaction. Hosted in Sydney.
Authorise · log · persist
The billing
On the 1st of each month, Carbon Charge totals every session, applies the OC's tariff, adds the management fee and GST, and issues an itemised Tax Invoice to each resident.
Four lines · every time
The things committees want to know before voting yes.
Do residents have to use an app to start or stop charging?
No. The app is read-only. Residents plug in, tap their RFID card, and walk away. The charger handles everything from there. Carbon Charge logs the session in the background.
How do you know how much energy each resident used?
Every charger we deploy has a MID-certified internal energy meter — billing-grade metering. The charger reports its own meter reading at the start and end of every session via OCPP. We bill the difference. No estimation, no algorithms.
What stops someone using a neighbour's charger?
RFID. Each resident gets a unique card. If the wrong card is presented, the charger denies authorisation and the session never starts. Lost cards are deactivated remotely the same day.
What happens if the internet drops out?
Chargers queue OCPP messages locally and replay them when connectivity returns, so short outages do not lose meter readings. Sessions that genuinely cannot be reconciled are credited to the resident.
Can the OC see this data?
Yes. The building dashboard shows uptime, fault history, total kWh by month, OC revenue split, and a downloadable monthly report formatted for committee meetings.
What if a resident disputes their bill?
Every invoice itemises every session: date, start/end time, opening meter reading, closing meter reading, kWh, rate, GST. The MID meter readings are the source of truth. We can pull the raw OCPP log for any session.