CCS (Combined Charging System) one of several competing charging plug (and vehicle communication) standards for DC fast charging. (DC fast-charging is also referred to as Mode 4 charging – see FAQ on charging Modes).
Competitors to CCS for DC charging are CHAdeMO, Tesla (two types: US/Japan and rest of world) and the Chinese GB/T system. (See table 1 below).
CCS charging sockets combine the inlets for both AC and DC using shared communications pins. By doing so, the charging socket for CCS equipped cars is smaller than the equivalent space needed for a CHAdeMO or GB/T DC socket plus an AC socket.
CCS1 and CCS2 share the design of the DC pins as well as the communications protocols, therefore it is a simple option for manufacturers to swap the AC plug section for Type 1 in the US and (potentially) Japan for Type 2 for other markets.
It is worth noting that to initiate and control charging, CCS uses PLC (Power Line Communication) as the communication method with the car, which is the system used for power grid communications.
This makes it easy for the vehicle to communicate with the grid as a ‘smart appliance’, but makes it incompatible with the CHAdeMO and GB/T DC charging systems without special adaptors that are not easily available.
An interesting recent development in the ‘DC Plug War’ is that for the European Tesla Model 3 roll-out, Tesla have adopted the CCS2 standard for DC charging.
Comparison of major AC and DC charging sockets (excluding Tesla)