Receptacle Roundup IXa: Tesla Roadster

So there’s a startup- a startup car company.  Not only are we grappling with startup car makes and models, but two new connector/protocols.  Bit of a gambit, don’t you think?  What’s so special about the plugs that couldn’t already be done with any of the existing standards I’ve already discussed?  So special as to incur a network optimization problem, and deployment issues?

A little background: California startup Tesla Motors has produced two models, the Tesla Roadster and Model S.  Neither are hybrids in any sense; it’s electrons, or gravity.  Nor can their massive battery packs be swapped out.  Thus, like the Honda Fit EV, the designs’ charging method or methods is all-important.  Unlike the Fit, both Teslas have massive packs- 40 to 85 kWh.  This produces their ranges- from double the Fit’s, to possibly more than triple in some trims and driving conditions.  But again, it places a steep burden on the charging method, which again is new and not adopted by any other maker.
Tesla released its new Roadster with the Roadster connector, then a new one again, for the Model S.  If you had the chance to start from scratch, would you do it this way?

The Roadster connector isn’t literally from scratch- that would be expensive and foolish.  Tesla had been sitting on the SAE panel with the other automakers, trying to settle the SAE’s charging standard.  That panel would eventually result in the SAE J1772 2009 connector- too late for Tesla’s 2008 introduction of the Roadster.  Tesla, instead, pushed forward with their own connector, while sitting on the SAE board.

The results actually turned out better than one might expect.  As a starting point, both Tesla and SAE used the prior AVCON connector (“the claw”).  Like the nickname implies, the AVCON physical standard looks a bit like a USB connector saw the light of the full moon.  The wide, rectangular connector worked well in the car slots of its day, but simply isn’t as rugged as a nice, round one.  But AVCON had a good electrical protocol, which largely survived.

p105035dHere’s a pin-and-sleeve connector- look familiar?  Pin-and-sleeve designs are for heavy-duty industrial units- large enough to exceed the NEMA L-plugs, yet still small enough to connect/disconnect, versus being hardwired to the site.  In other words, not that many units- there’s no real “standard.”  Different makers sell heavy and extra-heavy designs, all incompatible with each other.  A site involved enough to need these beasties is involved enough to have a staff electrician or two, to install and reinstall compatible connectors as needed.

The different vendors all sell one common feature: ruggedness.  The pins are clearly heavy-duty to begin with.  The outer sleeve then goes on to shield the pins from both mechanical abuse, and electrical risk.  The odds of you having a finger in the connection by the time of current flow are comfortably low.  Pin-and-sleeve types are designed for industrial use, busy sites and workers, and thus, “oopsies” …with heavy machinery.  Your garage is a candy shop by comparison; public sites will be somewhere in between.

Thus, Tesla went with a design much like a pin-and-sleeve, as did SAE J1772, later.  Both standards also added internal shrouding of pins as an added measure.  They just chose different mechanical standards, and are thus incompatible; SAE used a mechanical design from Japanese vendor Yazaki.  Meanwhile, both electrical protocols are basically similar, based on the AVCON signals for curbside-vehicle communications.

The Roadster connector uses the 240V AC available in most homes, for your electric dryer or stove.  So does J1772.  The Roadster connector goes up to 70 amps; the J1772 board was going to stop at somewhere around 32 amps, not unlike the old AVCON.  (Only after pleading did the J1772 standard extend up to 80 amps.)  With 70 amps, the Roadster connector has 16 kW of power or more, over ten times that of the household NEMA 5-15.  In your garage then, the Roadster connector will fill a 53-kWh pack in under four hours.

A few public chargers have appeared with this connector- but not many, since only about 2,400 Roadsters were sold.  The company apparently figured widespread, public deployment wasn’t going to happen.  Instead, Tesla sells adapters, from various receptacles to the Roadster.  Many drivers thus go about with an adapter or three in the trunk.  Lest you think this is weird or contrived, many Nissan Leaf owners have lots of adapters, particularly those who performed the upgrade, designed and sold to accept numerous pigtails.  Certainly, the hobbyists who did home EV conversions and the early EV leasers were prepared with a number of adapters.

After producing the Roadster, Tesla shut down the factory to start on the Model S.  Since the Model S has extra capabilities, Tesla decided to go to a second connector standard…

Tesla Roadster Plus
-Designed for car charging- safe contacts and protocols
-Rugged design
-Much faster than household 5-15– ten times faster
-240V reduces losses for car charging versus 120V

-Designed for car charging- new and different, thus expensive
-Proprietary to one car model, not just one manufacturer
-Extremely rare, and not getting any more common
-Fairly large and heavy
-Charges still measured in hours, too slow for road trips
-240V technically riskier than 120V
-No true ground; “ground” is used as neutral (return) line

-A billion people use 240V every day
-Actually exceeds usable charge power of many EVs today
-Adapters for other standards available (and necessary)
SAE J1772, in particular, not that different, can be adapted
-SAE J1772 has no true ground either

Tesla Roadster Ground
Well, it’s moot now.  You can only get this connector if you buy a Tesla Roadster, and they don’t make ’em anymore.  Still, it’s one point in tech history now, and a highly-relevant point at that.


4 thoughts on “Receptacle Roundup IXa: Tesla Roadster

  1. Pingback: Receptacle Roundup X: SmartPlug/EEL | cableflux

  2. Pingback: Receptacle Roundup IXb: Tesla S | cableflux

  3. Pingback: And Then There Were Three(ish) | cableflux

  4. Pingback: Mud on the Leg(work)… ? | cableflux

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