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When Is A Charging Station Not A Charger?

Not all charging stations are created equal, neither are electric cars.

By Bill Moore

With the help of governments around the world, literally tens of thousands of electric car charging stations are slated to be installed in public locations from New Castle to New York. The U.S. Energy Department estimates that by December of 2013 some 20,000 residential, commercial and public charging stations will be in operation in the United States. Some 1,300 charging stations will be installed in North East England, with another 25,000 more in and around London, itself, by 2015.

The list of manufacturers of charging stations seems to grow almost weekly: General Electric's WattStation being just the newest entrant, along with EV-Box in the Netherlands. The dominate players at the moment here in North America are Coulomb Technologies, Ecotality, Aker Wade and AeroVironment. All of them build electric car charging stations, but only a handful actually build electric car chargers; and there is a big difference.

Michael Harrigan oversees the electric vehicle program at NRG Energy, an electric power generator with facilities in the United States, Australia and Germany. Harrigan's mandate is to develop an electric vehicle infrastructure for Houston, Texas as part of the company's participation in the Electrification Coalition. Prior to NRG, he was with Coulomb Technologies, the leading manufacturer of Level I/II charging stations. It is to him that I turned to help clarify the differences between a charging station and a charger.

In the simplest terms, a charging station is an outdoor power outlet, just like any 110V or 220V in your home. It provides electric current from the grid to your electric vehicle's on-board charger. The charger on the car is what converts alternating current from the grid into direct current to recharge the vehicle's batteries, while doing so in a controlled manner that doesn't damage them.

A modern charging station does have some intelligence built into it. For security reasons, it can restrict access to those authorized to use it. It can meter how much energy is used, when and for how long. It can detect system faults and respond accordingly; and it can provide voltages from 110V to 230V: what are considered Level 1 and Level 2 charging, respectively.

What they don't do, however, is control how the batteries on the vehicle are charged. That is up to the charger on the vehicle, itself, and its battery management system. The process of properly charging a battery to insure its longevity is a complex one dependent on battery chemistries and how the pack is engineered. Think of a charging station as a water spigot on the side of your house. It regulates the flow of current through the 'hose', but how that water is dispensed depends what's at the other end of that hose. It can come out as a ground-soaking torrent or a gentle mist. Batteries prefer the latter, electrically speaking.

If the charging station is set up for Level II, and most will be, you'll be able to recharge an electric car like the Nissan LEAF in 3-4 hours, depending on how deeply you've 'drained' the battery. Level 1 could take all day if you've got a large battery pack to 'refill.'

Then there's Level 3 or what is now being referred to as DC charging by the industry. Here is where the rules change. A Level 3 charge station is, in fact, also a charger. It does the job of converting alternating current from the grid to DC current at industrial-scale voltages of 408V and 60-80 amps. Your common 110V household socket is probably on a 15 amp circuit.

Continuing the water hose analogy, Level 1 is like filling a swimming pool with a half-inch garden hose. Level 3 or DC charging is like using a fire hose. However, it takes special circuitry on the car to be able to use Level 3, which why it will be an option on EVs like Nissan's LEAF. Harrigan, who has a LEAF on order, doesn't know how much the option will be, but he suspects it'll run around $600.

Not only does the car have to be equipped with DC charging capability, but its battery pack also has to be engineered to accept fast charging. The individual cells in the pack must have low internal resistance and be cooled either using air or liquid because fast charging generates a lot of heat that can damage them internally.

Additionally, there has to be a common language spoken by the DC charging station and the vehicle. They have to talk electronically to one another to make sure current is flowing at a rate that doesn't overtax the car's battery system. And, as you might expect, the plug and socket have to match, which at the moment they may not, because these standards are still somewhat in flux. There is a standard being promoted in Japan called CHAdeMO and a North American standard that is a variant of SAE J1772. The plug for fast charging will likely not be the same one you use for Level 1 and 2. Nissan's LEAF has two separate sockets on its charge port, one of AC charging, one for DC charging.

What consumers need to know is this: a charging station is where you get the electric power for your electric car's charger. How fast you can charge depends on the size of the charger on the car, which carmakers are pretty much keeping to themselves at the moment: Harrigan thinks they are likely 6kW units; and the size of the 'hose': is it Level 1 or Level II? If you want truly fast charging, you'll have to pay for it both in terms of added equipment and probably in electricity fees. Fast charging station operators have to pay for that equipment. Harrigan confided that NRG has come up with an innovative approach that they'll be revealing later this fall.

Times Article Viewed: 9238
Published: 19-Jul-2010

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