CCS, the Combined Charging System, is a charging standard for electric vehicles that combines AC charging and high-power DC charging in a single vehicle inlet by adding two large DC pins below an existing AC connector. Among charging standards for electric vehicles, CCS defines not only the plug but also the communication protocols, safety sequence and electrical limits that let a vehicle and a charger negotiate a DC session.
CCS exists in two regional variants: CCS1, built on the Type 1 connector used in North America, and CCS2, built on the Type 2 connector used in Europe and many other regions. In Europe, CCS2 is the mandated connector for public DC fast charging.
How CCS combines AC and DC charging
The central idea of CCS is a combo inlet. The upper part is a normal AC connector that also carries the signaling contacts; the lower part adds two high-current DC pins. A vehicle with a CCS inlet can therefore use AC stations with the upper part alone and DC fast chargers with the full combo plug.
- The plug is inserted, and the control pilot and proximity pins confirm a proper connection and cable rating.
- Vehicle and charger establish digital communication by power line communication over the control pilot wire, using HomePlug Green PHY.
- They exchange parameters such as maximum voltage, current and battery limits under DIN SPEC 70121 or ISO 15118.
- The charger performs an insulation check and pre-charges the cable to the battery voltage.
- Contactors close, and the vehicle continuously requests the current it wants while the charger follows within its limits.
- At the end, current is ramped down, contactors open and the connector lock releases only after voltage has dropped.
In DC mode, the vehicle’s battery management system remains in control: it sets the target current at every moment, which produces the characteristic charging curve, while the charger acts as a controllable power source.
CCS1 and CCS2 variants
The two CCS variants share the same protocols and DC pin layout but differ in the AC part of the connector, which follows regional grid conventions. Adapters between them are not common because the inlets differ physically.
| Property | CCS1 | CCS2 |
|---|---|---|
| Base AC connector | Type 1, also known as SAE J1772 | Type 2, also known as IEC 62196-2 Mennekes type |
| AC phases supported | Single-phase | Single-phase or three-phase |
| Main regions | North America, parts of Asia | Europe, Australia, much of Asia and other regions |
| DC communication | PLC with DIN SPEC 70121 or ISO 15118 | PLC with DIN SPEC 70121 or ISO 15118 |
| Regulatory status | Being joined and partly replaced by NACS | Required for public DC charging in the EU |
The connector geometry is standardized in IEC 62196-3 for the DC combo part, and the overall system behavior in IEC 61851-23 for DC charging stations.
Power levels and electrical limits
CCS covers a wide range of DC power levels, from compact 20 to 50 kW wall units to high-power chargers. The achievable power in a session depends on the charger, the cable, the vehicle’s battery voltage and the battery’s acceptance at its current state of charge.
| Charger class | Typical maximum power | Typical current limit | Cable |
|---|---|---|---|
| Compact DC | About 20 to 50 kW | About 50 to 125 A | Uncooled |
| Standard fast charger | About 50 to 150 kW | About 125 to 200 A | Uncooled or cooled |
| High-power charger | About 150 to 400 kW | About 350 to 500 A | Liquid-cooled |
Current is the critical constraint. Because power equals voltage times current, a vehicle with an 800-volt battery can draw high power at moderate current, while a 400-volt vehicle reaches the cable’s current limit much earlier. This is a main reason why high-voltage platforms charge faster on the same CCS charger.
CCS compared with other charging standards
CCS competes and coexists with several other standards. They differ in connector design, communication method and regional adoption, and vehicles generally support only one DC standard natively.
| Standard | Connector concept | Communication | Main region |
|---|---|---|---|
| CCS | AC connector plus two DC pins | PLC, DIN SPEC 70121 or ISO 15118 | Europe, North America, many others |
| NACS | One compact connector for AC and DC | PLC, compatible with CCS protocols | North America |
| CHAdeMO | Separate DC connector | CAN bus | Japan, declining elsewhere |
| GB/T | Separate AC and DC connectors | CAN bus | China |
NACS, standardized as SAE J3400, uses the same communication protocols as CCS, which makes adapters between NACS and CCS1 technically straightforward. OCPP, by contrast, is not a vehicle standard at all: it connects the charger to the operator’s back-end system, while CCS governs the link between charger and vehicle.
Plug and charge and practical issues
With ISO 15118, CCS supports plug and charge, in which the vehicle authenticates itself with digital certificates so that the session starts and is billed without a card or app. Adoption depends on vehicle, charger and operator support, and certificate management remains a practical hurdle.
- Communication failures are the most common cause of sessions that do not start; retrying or plugging in again often resolves them.
- Heavy cables on high-power chargers can be awkward to handle, especially for users with limited strength.
- Charger rating is not session power: a 350 kW charger delivers far less to a vehicle with a lower acceptance limit.
- Interoperability testing between vehicle and charger brands is essential, because small protocol deviations cause failures.
Understanding it simply
CCS is the common plug and language that many electric cars use for fast charging. One socket on the car accepts both a normal charging cable and a larger fast-charging plug, because the fast plug simply adds two thick pins below the regular one.
When the plug goes in, the car and charger talk to each other first, agree on safe limits, and only then switch on the power. That conversation is why the same charger can safely serve many different car models.
Applied in practice
A driver in Germany with an 800-volt electric crossover plans a 600 km trip. The car has a CCS2 inlet, and the route has high-power CCS chargers at motorway service areas every 50 to 100 km.
At the first stop, the driver plugs in at a 300 kW station. Because the vehicle supports ISO 15118 plug and charge, the session starts and is billed automatically. The car draws close to its peak power at a moderate current, and the battery charges from 10 to 80 percent in under 20 minutes.
The same car uses the AC part of its CCS2 inlet with a Type 2 cable at the hotel overnight, so one inlet covers both fast and everyday charging throughout the trip.