EV connector compatibility conundrum

PEI-Genesis’ European industrial product manager, Dawn Robinson, unpicks the growing problem of EV connector compatibility 

There are several recognised standards, which categorise EV connectors. These include SAE J1772 Type 1, IEC62196 Type 2, GB/T and CHAdeMO connectors.

SAE J1772 Type 1 were among the first EV connectors. These five-pin connectors supply single phase AC power between three and seven kilowatts and are mostly found in North American markets today. These have been largely supplanted by IEC62196 Type 2 connectors in Europe and the UK, and GB/T connectors in China, because they can be used for faster charging. IEC Type 2 (and GB/T connectors) have an additional two pins to allow three-phase AC charging at twenty two kilowatts.

CHAdeMO connectors, used commonly in Japan, provide purely DC power at high currents and voltages. They provide rapid charging but are bulky in design. To get a similar rapid charge capability to the CHAdeMO connector, the Combined Charging System (CCS) connector has been developed.

The CCS is simply a Type 1 or 2 connector with an additional two DC pins for rapid DC charging. 

CCS Type 1 has emerged as the de facto standard in North America, because it allows flexible AC charging from home grids. Meanwhile, CCS Type 2 connectors have been adopted in Europe and the UK because they can provide high current, high voltage DC to EVs with that capability. 

Connectors must be ergonomic, easy to use, space efficient, include safety features and provide both AC and DC power. 

Ergonomics is important because the charging connector is likely one of the most used and potentially abused EV components. Regarding space, a bulky connector would consume internal space and the input connector would have to be similarly large. Due to the currents and voltages involved, safety is key. EV connectors use proximity detection and control pilot signals, preventing the vehicle from moving and stopping power transmission to unconnected connectors respectively.

CCS connectors already combine these design features, so is the problem solved? From an electrical engineering perspective more can be done. For instance, the high voltages and currents present form the perfect environment for contact arcing. The pilot signal helps mitigate this but doesn’t preclude the possibility of resistive heating or damage to contacts. 

This damage could eventually lead to failure. Damage on a charging station would require a replacement connector. However, damage onboard the EV could leave people stranded. 

A little extra effort designing the contacts can pay dividends. An example would be connectors using geometry to provide robust, high-density mating between contacts. Instead of passively mating, these connectors are designed to push against the respective contact to ensure a complete and reliable connection. Such connectors are often rated for 20,000 mating cycles.