Friday, September 4, 2009

J1772 One Ring To Rule Them All::Electric Car Charging

If you own a cellphone and MP3 player, or any collection of the mobile devices that are prevalent in our modern world, then chances are that you know the headache of having different chargers for each of them. Every product, even if made by the same company, seems to use an entirely different power adapter.

Electric cars suffered similar woes in the 1990s. GM and Toyota used an induction system, while Ford used a conductive system. And even though GM and Toyota had similar systems, they used different size induction paddles. You can see the myriad of connectors here. This meant that you could not just pull an EV up to any charging station and expect it to work without, sometimes expensive, converters.

Things looked like they were on the same course of confusion for the 2010 generation of EVs. Tesla had their own connector, RWE (a German energy company) had a three prong 400V connector that was endorsed by BMW, Volkswagen and others.

why reinvent the wheel? er, the plug?
Standard 120V 15A US household outlets are ubiquitous, many cities already have them installed curbside for xmas lighting. But with the large battery packs using one is like filling a swimming pool with a straw. Depending on the vehicle, this type of plug can recharge at a rate of 5-6 miles per hour. At that pace, it could take 17 hours for 100 miles. If you are driving 40 miles or less per day, as most people do, and can plug in overnight, this rate can fill you up, albeit slowly. 240V outlets are better, at 15-20 miles of range recharge per hour, but if you really want to charge an EV up fast, you'll need to move to 400V.

Faster charging is the primary motivation for making a new standard, but is it needed? More on that later.

J1772:: one ring to rule them all?
J1772 is not the winning number in an intergalactic bingo game. It is the specification number for an electric vehicle charging connector. With several car companies each defining their own, GM had to decide what to do for the Chevy Volt. Rather than defining yet-another-plug, they turned to the Society of Automotive Engineers (SAE) to define a worldwide standard.

J1772 truly is a plug by committee. It is packed with features including multiple levels of charging.

Level 1 is 120V in the 12A - 20A range
Level 2 is 240V in the 12A - 80A range
Level 3 is "fast charging" and will be defined in a later update to the specification. The assigned working group is discussing 480V with current levels up to 600A. Wow!

The addition of DC charging options are also being considered for future versions of the specification.

J1772 was approved by Underwriter Laboratories in June 2009. Since then, support for all the alternatives has fallen away and J1772 is "it" for the new generation of electric vehicles. Chrysler, GM, Ford, Toyota, Honda, Nissan and Tesla have all pledged to support J1772 with Tesla having agreed to retrofit the new socket to all the cars it has already built and sold.

The charging station companies such as Better Place, Coulomb, eTec, & SynkroMotive will also support the new connector.

The J1772: 5-pin plug (two power, two signal, one ground) single-phase worldwide standard

two way communication
Normally for an electrical outlet, the plug has an associated voltage and current. You cannot plug your vacuum into the dryer outlet; it just doesn't fit. J1772, however, has multiple levels that it supports. If I have a small car that is expecting lowly standard household energy levels and it were smacked with 400V, there could be big problems. This is solved by automated communication. Before any electrons are exchanged, the charger and the car discuss all the options. The charger tells the car what is available and the car tells the charger what level(s) it can utilize. They agree on the best match and the electrons fly.

This communication can also be used to manage power. For example, the car may be programmed to start charging when the electricity rate is cheapest (say 10PM). So when it is plugged in at 6PM, the car would tell the charger that it does not accept any charging levels. Then at 10PM, it starts the conversation over and reports new possibilities.

This communication can also be used by power utilities to control grid load. Power utilities often divide a day into Peak, Mid-peak and Off-peak. During peak electricity demand the charger could offer only level 1 charging. Then at mid-peak, level 2 would also be offered. Finally, level 3 would only be available at off-peak hours.

The above power management methods are simple demand reduction methods. The J1772 communication layer would also be the foundation for vehicle-to-grid (V2G), if/when it ever becomes a reality.

it takes a lickin'
"Why can't I just use an extension cord to plug in my car?"

In addition to the fast charging options, there are safety and durability considerations. Multiple levels of shock protection are built into J1772 including ground-fault protection, "finger-safe" sleeved prongs and enhanced cable insulation make it safe rain or shine. Another safety feature prevents the vehicle from driving away if you accidentally leave the plug connected.

This connector is tough. "You can literally drive over the plug, hose it down with water and plug in 10,000 times.", said GM Engineering Specialist and SAE Charging Station Chairman, Gery Kissel. "Try that with an extension cord!", Kissel continued on Oh, and did I mention there’s a flashlight designed into the charge cord plug so that it will be easier to plug in at night?

learn from the past or repeat it
The documentary Who Killed the Electric Car? was in the style of a who-done-it. There were suspects (GM, Big Oil, Batteries, Consumers...) and they examined the evidence for and against each suspect. Charging Infrastructure was a suspect. And I don't want to see it on the list again (I don't want another killing either). Let's learn from the errors of the past and not ignore the vast electrical infrastructure that already exists.

Toward this end, there will be portable and wall mounted chargers that can plug into existing outlets and give you the J1772 on the other end that your vehicle needs. Below are the examples that GM plans to have for the Volt.

They only plan portable versions for 120V outlets and the wall mounted charger is restricted to 16A even though 30A is commonly available and some homes could support 50A. The batteries could easily take that level. GM is taking the safe route, they are trying to make sure the wall-mounted unit works everywhere and the only way to do that is with a low current. One nice thing about having a standard, if someone else comes out with a version of a charger that suits your needs better, you can just use it. Due to the communication, it would never send more juice than your batteries can take. I'd like to be able to plug an XBOX 360 controller (which fits my hands better) into a PS3, but I cannot because the connections are proprietary. With a plug-in car, I'll be able to plug a new J1772 Tesla charger into my Nissan Leaf or Chevy Volt. That's the way it should be.

And with a small portable charger, you'll be able to take advantage of the ubiquitous 120V plug infrastructure. There is no need to build "The J1772 Highway", thereby solving the chicken and egg problem of which comes first the plug-in car or the charging station. The answer is the car and when charging stations are built, that just makes the vehicle more usable.

Too bad they didn't wait for J1776; it could be called the "Freedom Plug". Kidding aside, the plug is going to need a name that is better than the specification number. IEEE 1394 is called FireWire and IEEE 802.3 is better known as Ethernet. Have any ideas for a better name? Leave a comment.


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