One Plug to Rule Them All: Unifying Fast Charge Systems


The dream of gasoline freedom is becoming a reality as electric cars are slowly filling showrooms and attracting a lot of customers. The Nissan Leaf, for example, has its sales reaching 10,000 as of August this year. Other manufactures like Mitsubishi, Porsche and Audi are poised to join in. Greener cars are indeed hitting the mainstream with one thing dragging their progress: a standard charger plug.

The problem with the older charging systems of electric cars was the amount of time needed to charge one. The Level 1 Charging, as it is called, plugs the car into a 120 volt power. Hybrid cars can use it for overnight charging but for a pure electric car like the Nissan Leaf, it would take 20 hours to fully charge its battery. A second level has been made using a 240 volt power supply which can fill up a Leaf within eight hours.

Users though are still are not satisfied with an eight-hour wait on charging. This was addressed with the direct current fast charging system developed by Japanese car manufacturers and Tokyo Electric Power Company (TEPCO). The system which is named CHAdeMO can deliver 62.5 kilowatts of high-voltage direct current and can refill a Nissan Leaf to 80 percent of its capacity in only half an hour. Interestingly, CHAdeMO is a pun for a Japanese term that means “How about some tea while charging?”

Level 1 and Level 2 charging systems has the connectors standard SAE J1772 but none has been named for the CHAdeMO. Instead it uses a separate connector and is not compatible with older levels. It is incorrectly called a Level 3 charging system as Magne Charge claimed that title years ago but was discontinued because of its inefficiency being an inductive charger.

The CHAdeMO is poised to become a global standard for DC Fast Charging Systems. 532 charging systems have been installed in Japan and 17 are available in the U.S. Something is coming though that may alter its fate.

Daimler made a statement last October 11 of this year that they will be showcasing a prototype combination plug and port that will be used by hybrid cars and pure electric vehicles. The system is a joint effort by other car manufacturing giants such as Audi, BMW, Porsche, and Volkswagen. This has been the clearest indication that European automakers are not favoring the CHAdeMO. Instead they are considering the standard proposed by SAE International.

Japanese manufacturers have already expressed their concerns about the proposal of another standard that rivals CHAdeMO. TEPCO has explained that keeping different AC and DC receptacles has the advantage of permitting the car OEM to place each in the best location for both charging scenarios. For example, the DC receptacle might be placed close to the battery to reduce the length of high current cables. This is convenient as high current cables are very heavy and expensive.

Mitsubishi also stated that CHAdeMO has been widely employed in Japan and that there is no need for another standard. The company reiterates that the system improves battery cycle life because it only charges a car’s battery to 80% of its capacity. This effectively reduces heat stress on the battery. AC systems, in contrast, perform 100% battery charging.

The need for a single connector might have been justified because of the complexity of fast chargers. It features a permanent hardware installation and a connection to a 480-volt three-phase A.C. Fine-tuned circuitry is needed to convert such a high voltage to D.C. without damaging the battery. Aside from being complex, fast chargers are also very expensive. The charger costs $20,000 and installation asks for another $20,000. The single connector protocol proposed by SAE will only modify the older installations thus reducing complexities and price.

Either standard though still does not offer a perfect solution to the charging time problem. Filling a battery to 80% capacity in half an hour could be tempting but a thorough calculation will reveal something undesirable. Take a Nissan Leaf (which can support both SAE and CHAdeMO) traveling 80 miles on a full battery. At only 80% battery capacity, the total distance drops to only 64 miles. If the car speed is at 70 miles an hour, then it would take 55 minutes to cover that distance. This means the amount of time in charging the car is almost the same with the time needed to drive it. Nevertheless, it is still a major improvement from the older AC charging systems.

The events in the incoming months could very well decide which connector would be universally accepted. If more CHAdeMO chargers will be deployed then it may become the de facto standard. On the other hand, if SAE pushes trough with its new standard and the American and European automakers continue to support it, then CHAdeMO could become extinct in no time.

Article by Olan Dantes, a young electronics engineer who loves to write anything about electronic machines and gadgets. Olan believes that a keyboard is more powerful than a sword. As such, he wants to share the knowledge that he found to everyone in hopes that they may use it for the good of humanity. Olan works with Newark a distributor of connectors and other electronic components.

Article appearing courtesy Earth & Industry.



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