Four component families do most of the work inside an EV charger. Relays or contactors switch the power on and off. RCD modules watch for leakage current and order a stop. Meters measure the energy delivered. A controller coordinates all three. For a buyer, their ratings and quality decide safety and service life far more than the housing does.
Key Takeaways
- Relays and contactors switch, RCD modules protect, meters measure, the controller coordinates.
- For switching devices, continuous duty at full output is the rating that matters.
- Metering ranges from indicative to revenue-grade; the class fitted is a written specification.
- Verify ratings from datasheets, keep substitutions recorded, and confirm spares support first.
Switching the Power: Relays and Contactors
Both devices do the same basic job: connect the vehicle to the mains when the controller says charge, and disconnect it when the session ends or a fault is detected. The difference is scale and construction.
| Relay | Contactor | |
|---|---|---|
| Typically found in | Portable and wall-mounted AC chargers | Higher-power AC stations and DC fast chargers |
| Built for | Switching the charger’s rated current, board- or chassis-mounted | Switching larger currents, as a separate device |
| Buyer check | Rated current and voltage at or above the charger’s continuous rating | The same — plus mounting and service access |
The rating that matters is continuous duty at full output, not a headline peak. The fitted device should be the one the model’s test documentation covers.
Watching for Leakage: RCD Modules
A residual-current device compares the current going out with the current coming back. A difference means current is leaking somewhere it should not — a damaged cable, moisture, or a person — and the module signals the controller to open the switching device. A vehicle can also produce smooth DC leakage that an ordinary household breaker cannot see, so chargers use protection built for the job: Type A devices with 6 mA DC detection, or Type B devices that cover DC directly.
The full treatment — types, thresholds and placement — is in our guide to RCD protection for EV chargers. Surge protection and fuses help — absorbing spikes, clearing short circuits — but do not replace leakage protection.
Measuring the Energy: Meters and Sensors
Metering starts with sensors — current transformers or shunts — and a circuit that turns their signals into voltage, current and energy (kWh) figures for the display, app and billing record.
Not all metering is equal. A session display can run on indicative measurement; where energy is billed, many markets expect certified, revenue-grade metering. Which class a model carries is a specification to confirm in writing. Metering also appears on the installation side — see our piece on smart meters for EV chargers.
The Supporting Cast
- Controller board: reads the pilot signal and sensors, drives the switching device, runs the interface.
- Temperature sensors: at the connector and inside the unit; they can order a stop before heat becomes damage.
- Display and RFID reader: the driver’s window into the session — and, on commercial units, the key that starts one.
- Cable and connector: carry full current and take daily mechanical wear.
What Buyers Should Verify
- Component ratings at or above the charger’s continuous rating — from the datasheet, not the brochure.
- Safety-critical parts as tested: substitutions must be approved and recorded.
- Spare parts for wear items — cable, connector, switching device — before you build a range on the model.
Our factory audit checklist turns these into audit questions; our guide to spare parts and the RMA process covers the after-sales side.
EVDANCE Models, Component by Component
The components scale with the job across the EVDANCE range: the EV-ACT3204PE wallbox adds RFID and app control, the EV-AC03201T station runs two Type 2 connectors at up to 43 kW shared (22 kW per connector) with OCPP 1.6J and RFID, and the EV-RHDC30K-L is a compact DC fast charger at 22 kW DC. EVDANCE is a Shenzhen manufacturer founded in 2011, exports to more than 30 countries, and offers private label from 100 units with a 3-year standard warranty. Component questions for a specific model start at contact us.
Frequently Asked Questions
What does the controller board do during a session?
It runs the session: generating the control pilot signal, watching the sensors — including the RCD module — and driving the switching device open or closed.
Does every EV charger contain a meter?
No — basic chargers may show little more than status lights. Metering is fitted where energy must be measured, so check the model’s specification.
Which components wear out first?
The parts that switch under load and flex daily: the switching device, and the cable and connector. There is no universal lifespan figure — ask about spares and warranty instead.
Related Reading
- RCD Protection for EV Chargers: Type A, Type B and 6 mA DC Detection Explained
- EV Charger Certifications Explained: CE, UKCA, UL, ETL, CB and What Buyers Should Ask For
- EV Charger Spare Parts and RMA Process for Distributors
- Do You Need a Smart Meter for an EV Charger?
