Definition
DC fast charging (DC Fast Charging) uses high-power direct current to charge the traction battery directly, bypassing the onboard charger (OBC), with AC-DC conversion completed by the rectifier module built into the EV charging station. The charging power is usually between 60 kW and 350 kW (with ultra-fast charging reaching 480 kW and above), and can charge the vehicle from 20% to 80% in 20–40 minutes. It is suitable for public charging stations, highway service areas, urban fast-charging networks, and other scenarios.
DC fast charging complies with standards such as GB/T 18487.1, IEC 61851, CHAdeMO, CCS, and national standards. The EV charging station must communicate with the vehicle's BMS to negotiate charging parameters (voltage, current, SOC) to avoid overcharging or over-discharging. High-power charging requires higher demands on grid capacity, cable specifications, and heat dissipation design.
Technical Features
DC fast EV charging stations have functions such as OCPP (Open Charge Point Protocol) integration, payment and settlement, fault diagnosis, and OTA upgrades. Through 4G IoT SIM cards, they communicate with the operation platform and grid dispatch system to achieve remote start/stop, status monitoring, billing and settlement, and orderly charging scheduling. They can participate in peak-valley electricity pricing or demand response scenarios to help balance the grid.
Use Cases
DC fast charging is widely used in public charging stations, battery swap stations, highway service areas, urban fast-charging networks, logistic parks, and other scenarios. EV charging stations connect with the OCPP platform through IoT SIM cards to enable remote start/stop, status monitoring, billing and settlement, and fault alarms. SimtoLink provides stable network connectivity, dedicated APN, and large data plans for DC fast EV charging stations, ensuring charging operations and user services.
The vehicle-pile handshake and the pile-cloud heartbeat are two things
The IoT SIM on a DC fast charger connects the pile to the operations platform. It is not the charging handshake between vehicle and pile. That handshake is completed on the charging-cable communication, and it agrees voltage, current, and the stop conditions. What the SIM uploads is whether a session started, energy and amount, fault codes, remote start and stop, and firmware tasks. The vehicle can already be charging while the platform still shows offline. The platform can show idle while a connector is still locked on an unsettled session. Treating a broken heartbeat as an immediate stop of charging will cut a normal session at a weak-signal service area. Ignoring the heartbeat entirely lets a finished session keep billing, or makes a remote stop impossible. Each path needs its own timeout and its own local protection.
The pile must be able to end the current session on local metering when the network is down, store a session id that cannot be repeated, and upload it after recovery, so the platform does not book the retry as a second session. The clock must match the platform, or a session that crosses midnight lands on the wrong bill. The access point should reach only the operations platform and the payment-notification addresses that are required. Do not mount the antenna inside a metal-filled pile body and skip a retest. Traffic at a highway service area changes the shadowing. On a dual connector or a charging cluster, each connector’s session is numbered on its own. The pile id alone is not enough. If orderly charging and a power limit come from the platform, the pile should hold a known safe ceiling until the command arrives. It must not rise to maximum power when the command is lost. Bind the SIM to the pile asset, the site, and the connector. When the pile main board is replaced, export unsent sessions before stopping the old SIM.
A common error is to treat platform online rate as charging success rate. Online only means the heartbeat. It does not mean the handshake, the insulation check, or the payment pre-authorization succeeded. Another error is a weak-link retry that uploads the same session several times, so reconciliation shows double energy. A firmware upgrade that occupies the whole cellular link, then fails and downloads again, delays the current vehicle’s settlement message until after the vehicle has left. A basement pile tested only when the bay is empty loses coverage once a vehicle parks. Remote stop fails, the local emergency stop still works, and operations believes the pile was disconnected remotely. Acceptance should run one full charge, limit the uplink in the middle, and check that the local stop, the session id, and the energy caught up later agree and exist as one record. How load is scheduled is described under orderly charging. How an AC pile differs is described under AC slow charging.
The session id is created on the pile and runs through start, metering, stop, and catch-up. The platform uses it for idempotency. A repeated message for the same session only updates state. It does not add energy or amount. A local stop during an outage must record whether the reason was the user, a full battery, a fault, or a communications timeout, and that reason stays the same after recovery. A power-limit command carries its source and time. An expired limit should not stay in force, and a lost command must not automatically raise the pile to its maximum capability. Meter dual connectors separately. A sum is for display only. Firmware download is rate-limited and can be paused, and settlement messages come first while it is paused. Retest signal at a basement or a service area with a vehicle shadowing the bay. An empty-bay test is not a basis for opening the site. Before a main-board swap, export unsettled sessions. After the swap, catch up with the original session id, so the user is not charged twice or not charged at all. Reconcile by session, not by heartbeat count. A missing heartbeat only means the platform cannot see the pile for a while. It does not mean no energy was delivered.
If the session has not been uploaded before the user leaves, the pile screen should still show the local metering result and say the bill will match later. A late platform message must not change the energy already displayed into another record. Use separate codes for a connector-lock fault and a communications fault. If remote stop fails, the on-site emergency stop still works. Write in the site acceptance record that signal was tested with a vehicle present, so the site is not opened on empty-bay data alone. Do not open remote start on a connector that failed the shadowing test.