Feature: Connectors
Ergonomics EV connector type
two DC pins that permit rapid DC charging. Te 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 can also handle 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 must combine several design features: be ergonomic, space-efficient and easy to use, it must include built-in safety features and, as discussed, it must be able to provide both AC and DC power. Ergonomics might seem a secondary
design consideration, but, in practice, it’s one of the most important. Te 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 more important. An easy-to-use, safe-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, oſten meaning they have to be located in hidden places, such as 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. Tis is why each one of these connectors uses
RADSOK electric vehicle connectors from Amphenol
might seem like a secondary design consideration, but in practice it’s one of the most important
proximity detection and control pilot signals, which prevents the vehicle from moving and prevents power being transmitted to unconnected connectors respectively.
Room for improvement CCS connectors already combine all these design features, so, problem solved, right? Not quite, as, while CCS connectors
fulfil the customer requirements of an EV connector, from an engineering perspective there’s more that can be done. For instance, the high voltages and
currents present when an EV is charging form the perfect environment for arcing between contacts. Te pilot signal goes a long way to mitigating this, since 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 is enough to score
and scorch them. Tis damage further exacerbates the problem, eventually leading to an inevitable and sudden failure of the connector. If this damage occurs to a charging station it would require replacing the connector, but if the damage occurs on-board the EV it could mean that people are leſt stranded with a dead car. Tis 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 contact design
can pay dividends in mitigating against this kind of damage. An ideal example is the RADSOK range of connectors from Amphenol, which uses 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 the vehicle could travel over three million miles before the connector encounters problems. Tat’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, whilst 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.
www.electronicsworld.co.uk December/January 2021 53
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