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2013 Tesla Model S
Sharp-eyed Tesla Model S buffs may be wondering why the mid-range 60-kWh car, which costs $10,000 less, is rated more efficient than the top-of-the-line 85-kWh model.
The EPA said last week that the 60-kWh Model S has a range of 208 miles, and its efficiency rating is 95 MPGe (miles per gallon equivalent).
That’s about 7 percent better than the 89 MPGe rating for the 85-kWh version–which has a rated range of 265 miles.
Measured from a different angle, the EPA says the 60-kWh car uses 35 kWh of electricity to go 100 miles.
The equivalent number for the longer range version is 38 kWh, meaning the cheaper car has about an 8-percent edge.
Why the difference?
Tesla Motors [NSDQ:TLSA], with its penchant for secrecy about technical matters, is mum on the subject (although a Tesla rep recently told me the company was working on an official statement to explain the difference).
Whatever the reason, the numbers make Tesla buyers who’ve opted for the mid-size battery (like me) feel a little better.
The $10,000 jump to the big battery gains only 57 miles of range, from 208 to 265 miles. That’s about $175 per mile.
Looked at another way, the 85-kWh Model S uses a battery pack that’s 42 percent larger to achieve 27 percent more range. Not a great tradeoff.
There are a number of possible reasons for the better efficiency numbers of the car with the mid-size battery.
Although Tesla has always been cagey about battery specs, it’s likely that the smaller battery weighs less. Lower weight means quicker acceleration with the same power, and less rolling resistance at higher speeds.
But it seems unlikely that a weight difference of 100 to 200 pounds–we’re guessing here–could account for a 7-percent efficiency jump. There’s something else going on.
Tesla Motors – Model S lithium-ion battery pack
*Improved battery chemistry?
An unofficial source at Tesla hinted to me that the chemistry of the 60-kWh battery is different–and better–than that of the 85-kWh battery.
The 85-kWh packs went into production more than six months ago, while 60-kWh packs are only now starting to roll off the production lines.
It’s quite possible that, in the meantime, Tesla has improved its battery chemistry.
Tesla uses Panasonic commodity lithium-ion lap-top batteries in its battery packs, making them easy to update. Perhaps Panasonic has tweaked its cells recently?
The new 5-cycle EPA tests include a more vigorous acceleration profile.
The 85-kWh battery can supply more output power to the Model S drive motor (362 hp vs. 302 hp). If the EPA test includes maximum acceleration, the 85-kWh car would accelerate slightly faster than the 60-kWh car–and thus use more energy.
If that’s the case, the EPA numbers are not a precise apples-to-apples comparison, and the efficiency advantage of the cheaper car is illusory.
2012 Tesla Model S
It’s also unclear whether the EPA tested a standard 85-kWh car, or the more powerful Performance version (416 hp).
If the test car was the latter model, this test-related discrepancy would be even greater.
A recent software upgrade tweaked the acceleration profile of the Model S to provide more oomph at highway speed.
If included in the 60-kWh EPA test car, this may have had an effect on the test numbers–although we would have expected any performance increase to reduce the MPGe number.
As you may have noticed, fevered speculation about technical and production minutia is a daily sport among Model S owners and hard-core Tesla buffs.
With luck, Tesla will soon put us out of our misery on this question.
Until it does, does anybody else have theories why the 60-kWh Model S is more efficient than the 85-kWh version?
David Noland is a Tesla Model S reservation holder and freelance writer who lives north of New York City.
By David Noland
Elon Musk has published a thorough blog countering some of the results in a recently published, controversial Tesla Model S review in The New York Times. The review has received plenty of attention, and this week Musk prepared his reply — complete with charts to illustrate his points — on Tesla’s site.
The controversy began when Tesla approached Broder to evaluate a Model S (with an 85 kilowatt-hour battery that provides 265 miles of EPA-rated range) and two new charging stations installed in Newark, Delaware and in Milford, Connecticut. These stations are 200 miles apart and include the company’s new Supercharger, which can recharge batteries at a much faster rate than a typical charging unit (Tesla says the Supercharger can provide up to 150-160 miles of range in just 30 minutes).
In fact, in a February 12 update, Broder says the test was intended to evaluate the Supercharger network on the East Coast, not the Model S, explaining why he didn’t plug in the car overnight in Connecticut.
“This evaluation was intended to demonstrate its practicality as a ‘normal use,’ no-compromise car, as Tesla markets it. Now that Tesla is striving to be a mass-market automaker, it cannot realistically expect all 20,000 buyers a year (the Model S sales goal) to be electric-car acolytes who will plug in at every Walmart stop,” Broder wrote.
Broders Tesla Model S speed log 300×187 image
Broder’s trip began at the Delaware station with 242 miles of range (he was unaware of a “max charge” feature that would’ve topped the battery off at 265 miles). He claims to have experienced fluctuations in the battery’s claimed range, which may have
been affected by the colder temperatures. Still, Broder claims to have properly charged the battery, drove at reasonable speeds, and even reduced the cabin temperature, all in an attempt to increase range. In the end, however, Broder says he ran out of charge before reaching Connecticut, and the Model S was consequently towed to the charging station.
Since then, Tesla has compared Broder’s account to the data log from the Model S test car he drove. Earlier this week, Musk published an extensive blog with that data, which points out a number of claimed discrepancies in the highway speeds at which Broder said he was traveling, charging times, as well as possible errors in his article’s math. Musk also suggested the evaluation was a lost battle for Tesla in the first place, pointing to a March 2012 article by Broder in which he says “the state of the electric car is dismal.”
Check out Musk’s full February 13 blog here, and Broder’s February 12 follow-up here.
Source: NY Times, Tesla Motors
The “Odyssey of Pioneers” world tour has the Tesla Roadster visiting some 15 major cities and at least 150 smaller towns during the course of its road trip. The electric sports car is in Europe this week where it will be making a historical pit stop in Budapest, Hungary.
What’s the connection? Well, Budapest was one of the many stomping grounds of Tesla’s namesake — Nikola Tesla. Better yet, it’s said that while living in Budapest, Tesla thought up the original design for the alternating current motor — the same type of motor used in the Roadster — during a feverish hallucination.
“Without his vision and brilliance, our car wouldn’t be possible,” said Tesla CEO Elon Musk. “If he were alive today, I’m sure Nikola Tesla would be a very happy Roadster customer and a passionate advocate of electric vehicles.”
Budapest is the fourth stop on the Tesla’s tour. Luke McClure, the EV’s driver, has used standard electric outlets at hotels along the route, a solar panel array, and even a power feed located inside a Swiss barn to keep the roadster fully “fueled.” The Tesla Roadster accomplishes this feat because it’s equipped with its own charging equipment, so there is no need for specialized outlets or charging stations.
Tesla Motor will be hosting a VIP celebration, along with test drives for prospective customers from April 15-16 at the TAG Heuer Boutique in Budapest. The Roadster will then resume the tour to its next stop — Warsaw, Poland. The entire journey is tentatively scheduled to last eight months, and is expected to end come October, when the Tesla is due in Paris.