The DC fast charging wars

Last night Tesla unveiled its controversial supercharger, which can charge a Model S sedan in 30 minutes, providing about 180 more miles of range. I write “controversial” because many folks have been unhappy with Tesla’s charging strategy because the company relies on its proprietary charger, making it necessary for Tesla owners to carry a “conversion cord” to use public charging stations. Unfortunately the cord standardization problem isn’t limited to Tesla and when it comes to mainstream DC superchargers, there are competing plugs entering the market, setting up a VHS vs. Beta type situation.

The evolution of EV charging

Just to recap the evolution of EV charging, we started with Level 1 chargers, which provide 110 volts out of the wall, a “trickle charge,” and will take a car in excess of 15 hours to get a full charge from. Level 2 chargers put out 240 volts and can charge most EVs in 4 to 7 hours, the proverbial overnight home charge that everyone uses. Level 2 chargers involve installing a home charging station, which most EV owners put in, and a colleague of mine charges the 33 kilowatt battery in his BMW ActivE in under five hours.

The limiting factor in how fast one can charge the battery right now is not simply the current coming out of the wall but also the internal charger inside the EV, which determines how much power the battery can accept for charging at any one time. For example a Nissan Leaf has a 3.3 kilowatt charger in it and a 24 kilowatt battery, making it possible to charge the battery in under 8 hours. A BMW ActivE has a 7 kilowatt charger in the car, allowing for faster charging times.

Enter the superchargers

This is where it gets interesting. The whole concept of superchargers surrounds using direct current, not alternating current, and bypassing the internal chargers in EVs that regulate how much charge the battery can take at any one time. This means turning up the juice to 440 volts, what DC chargers transmit, and creating charging times in the neighborhood of 30 minutes.

Superchargers cost tens of thousands of dollars and aren’t for residential installation. They were always envisioned as quick bridge charging stations, which is why Tesla installed them between LA and San Francisco in order to help drivers make the 375 mile journey. Because fast chargers are quick and batteries typically do best under long, slower charges, fast charging isn’t typically recommended for daily use.

DC fast chargers also require a different connector and many of the EVs on the market right now don’t even have a connector for a DC fast charger. The main connector interface out there is from Japan and is known as CHAdeMO. There are a little over 1300 CHAdeMO stations in Japan right now and the most well known car with a CHAdeMO input is the Nissan Leaf.

But not everyone likes the CHAdeMO plug, and American and European automakers are working on their own plug, known as the “Harmonized” plug because it combines the standard J1772 plug (Level 1/2 charging) with the DC fast charging interconnect on one plug. The CHAdeMO plug requires two different outlets on the car, one for J1772 and one for the DC fast charging CHAdeMO plug.

“Speaking for me, the CHAdeMO charger is really heavy. The plug is unwieldy. You have to get used to it. It’s big and bulky,” said John Kalb, founder of consulting firm EV Charging Pros. He added, “The industry is hoping for one standard to work on a global basis, so drivers can feel comfortable that regardless of the car they buy or where they choose to charge, they can get a charge.”

And this is where the rub is. As Tesla further demonstrated this week by releasing a fast charger that only works with its proprietary plug (Tesla doesn’t use J1772 and has its own proprietary charging connector for all its vehicles), the needs and convenience of the global customer are being sacrificed in a war over the best charging plug. The European and American automakers are desperate to avoid this, which is why they’ve banded together to endorse the harmonized plug. It’s still early in the EV game but these kinds of issues create worse user experiences, which given the already high price of EVs, should be avoided at all costs.

Question of the week

Which fast charger will prevail?
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Adam Lesser

Cleantech Curator Gigaom Research

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  1. Are any of the vehicles using super caps?

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