Interconnection The EV connector conundrum


There is a lot to be said about petrol, but its convenience is unquestionable. It can be dispensed through pumps into almost any vehicle with no difficulty. This is almost the opposite of electric vehicle (EV) charging, where every EV might have its own, specially designed connector. Dawn Robinson, European product manager – Industrial at cables and connectors specialist PEI-Genesis, unpicks the growing problem of EV connector standardisation and compatibility


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magine travelling through 1920s Britain. Many things change as you move around. Accents and dialects vary dramatically from town to city, as does the cuisine and, somewhat surprisingly, so does the


electricity supply.


Before the formation of the national grid a little later in the 1930s and finalising the BS 1363 standard British plug in 1947, small- grid, local electricity generation was the norm with little standardisation between them. This meant every local grid ran at its own frequency, voltages and power factors, and often required the use of specialised local connectors when plugging in devices.


For most electrical devices, we no longer have to worry about compatibility, because in the 21st century we use standardised connectors and a nationwide standard mains voltage, which keep everything simple.


For the EV, a reliable grid solves the issues with frequency and voltage, but the connector conundrum remains.


This problem is further complicated by EV manufacturers taking advantage of a number of charging options; mode 1 for slow charging from typical home outlets, mode 2 for faster charging from specially designed home outlets, mode 3 for commercial street-side charging points and mode 4 for rapid, direct current charging.


A collection of connectors


Currently there are four common EV connectors around: type 1, type 2 including the Tesla supercharger, CHAdeMO and CCS. Type 1 connectors, officially SAE J1772, were among the first to be used on EVs. These five-pin


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connectors supply single-phase AC power at between three and seven kilowatts (kW) and are mostly found in Asian markets. These have been largely supplanted by type 2 connectors in the west. The type 2 connector, known as SAE J3068 and colloquially as mennekes after the original manufacturer, features an additional two pins and can carry either three-phase AC or high current DC depending on the configuration. In Europe, Tesla uses a modified version of the type 2 connector that only fits Tesla EVs.


CHAdeMO connectors provide purely DC power at high currents and voltages. Designed in 2010 by a Japanese consortium, the CHAdeMO name is derived from the Japanese O cha demo ikaga desuka, translating to, “how about a cup of tea?”, a pun on the short time it takes to charge an EV through this connector.


Finally, CCS, or Combined Charging System connector, is simply a type 1 or 2 connector with an additional two DC pins that permit rapid DC charging.


The CCS seems have emerged victorious as the de facto standard, because it allows for flexible AC charging from home grids or any commercial charging station, excluding Tesla superchargers, but it also provides high current, high voltage DC to EVs with that charging capability.


The perfect plug?


If we’re to take note of these trends, it seems like the ideal EV connector is one that combines a number of design features. It must be ergonomic and easy to use, it must be space efficient, it must include built-in safety features and, as we’ve seen, it must be able to provide both AC and DC power.


Ergonomics might seem like a secondary design consideration, but in practice it’s one of the most important. The charging connector is likely to be one of the most used and potentially abused parts of an EV, meaning that ease of use can hardly be overstated. An easy to use, fool proof design is vital to the ongoing adoption of EVs.


Similarly important is the connector’s space efficiency, which goes hand in hand with ergonomics. A bulky, unwieldly connector would take up excess space inside the vehicle, and the input connector on the EV would have to be similarly large, often meaning they have to be located in hidden places, like under bonnets, instead of far more convenient places like the Tesla fuel-cap style connector or Nissan Leaf hatch.


Lastly, due to the impressive currents and voltages moving around, safety is among the biggest concerns. This is why every one of these connectors use proximity detection and control pilot signals, which prevents the vehicle from moving and prevents power being transmitted to unconnected connectors respectively.


Still room for improvement CCS connectors already combine all these design features, so the problem is solved, right? Not quite, as while CCS connectors fulfil the customer requirements of an EV connector, from an electrical engineering perspective there’s more that can be done.


For instance, the high voltages and currents present when an EV is charging forms the perfect environment for arcing between the contacts. The pilot signal goes a long way to mitigating this as any loss of continuity stops the charging


immediately, but this doesn’t preclude the possibility of excessive resistive heating or damage to contacts. Only a second of high voltage arc between contacts would be enough to score and scorch them. This damage further exacerbates the problem, eventually leading to an inevitable and sudden failure of the connector. If this damage occurs on a charging station it would require replacing the connector, but if the damage occurs onboard the EV it could mean that people are left stranded with a dead car. This fear of being stranded is top of the list of reasons why fuelled cars are still preferred by customers today.


A little extra effort in the design of the contacts can pay dividends in mitigating against this. An ideal example is the RADSOK® range of connectors from Amphenol, which use specialised hyperbolic 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. Amphenol RADSOK connectors are also rated for 20,000 mating cycles. Using these connectors to charge a vehicle like the Nissan Leaf, with its 160- mile range, means that the vehicle could travel over three million miles before the connector is expected to encounter issues. That’s the equivalent of six and a half round trips to the moon, and far exceeds the 200,000 miles that most cars average before reaching the scrapyard.


So, while it seems like the EV charging conundrum might have found an answer in the CCS, a little bit more effort and consideration of the subtleties means an ideal, future-proof design could be just around the corner. peigenesis.com


Components in Electronics December/January 2021 41


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