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Life With Tesla Model S: Pushing the Range Limits In 60-kWh Car Page 2


2013 Tesla Model S electric sport sedan [photo by owner David Noland]

2013 Tesla Model S electric sport sedan [photo by owner David Noland]

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At this rate I'd be totally out of energy at 182 miles. Way too close for comfort.

Elevation changes

But I was pretty sure that the culprit was elevation.  From previous trips, I'd learned that elevation changes have a huge effect on the range of the Model S.

For example, when I make the 60-mile drive from my house (elevation: 423 feet) to New York City (sea level), I typically  average 270 Wh/mi in warm weather. The return trip, slightly uphill,   averages about 310.  A mere 400-foot elevation change over 60 miles alters efficiency by almost 15 percent.

I'd checked the elevation of Danville (578 feet) before I left, but hadn't paid attention to the intervening terrain. Hopefully, I'd soon begin descending.

Tesla Road Trip from MD to CT, Feb 2013 - Tesla Model S cars at Delaware SuperCharger location

Tesla Road Trip from MD to CT, Feb 2013 - Tesla Model S cars at Delaware SuperCharger location

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Sure enough, as I passed Wilkes Barre,  the e-meter began to come back down toward 320 kWh/mi, then 310. I breathed a sigh of relief; I had it in the bag.

(I later determined that I'd reached a peak elevation of  about 1800 feet along I-84 just east of Wilkes-Barre.)

By the time I got to Danville, my energy usage had dropped to 295 wH/mi--right in the middle of my target zone.

The range meter read 24 miles when I finally arrived at a funky farmhouse. It was home to an affable banjo-picker named Mark Doncheski, two Corvettes, and a Tesla Roadster. Mark had agreed to make his Tesla charger available to Sherman and me.

Range meter quirks

As I'd anticipated, the guess-o-meter didn't quite square with reality. I'd started with 199 indicated miles and driven an actual 168.  That's a 31-mile difference. Seven miles got lost somewhere.

The old-reliable e-meter told me I'd used 49.4 kWh of juice for the trip. That left 10.6 kWh--enough to drive an additional 36 miles at my trip average of 295 wH/mi.  (More, at slower speeds.)

Theoretically, I had 12 more miles remaining than the guess-o-meter indicated.

This squares with an unofficial on-line Model S owner's manual compiled by Tesla fanatic Nick J. Howe. According to Howe, the 85-kWh Model S actually has 17 miles "in the tank" after the range meter reaches zero.

Prorating for my 60-kWh battery, that's pretty close to my theoretical 12-mile buffer.

Bottom line: I can still probably limp to some sort of electrical outlet or charger even after the range meter hits zero. Frankly, I never want to have to confirm that.

Tesla talk

Sherman arrived five hours later in a brown P85, accompanied by owner Fred Glomb and a support truck towing a trailer. Cruising at a steady 62 mph, they'd  covered the 251-mile leg from Ohio with 20 miles to spare.

Over a late dinner in Mark's kitchen, we talked Tesla and the upcoming race till well past midnight.

2012 Tesla Model S Charging Connector

2012 Tesla Model S Charging Connector

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Out of the pizza-fueled discussion came a startling conclusion about Model S driving strategy for the race: Cruising speed is basically irrelevant. Any time gained by going faster between charging stops is almost exactly negated by the increased charging time.

(This conclusion assumes an 85-kWh car equipped with Twin Chargers that is charged from a 20-kW Tesla High Power Wall Connector--the fastest possible charging scenario along the race route, which had no Superchargers anywhere near.)

The breakdown: Over a typical 240-mile leg, driving 70 mph would save 56 minutes over a 55-mph speed. Based on the speed-vs-range graph on the Tesla website, the faster car would use about 18 kWh more energy.  Charging time to replace that extra 18 kWh: 54 minutes.

Of course the eventual arrival of more Superchargers will eliminate  such fascinating threads of discussion.

Next morning, Sherman's car was loaded onto the trailer for the trip back to Michigan. I topped off my car and retraced my route home, logging virtually identical numbers for the return leg.

My personal takeaway from this exercise was a practical range limit for my car: 180 miles in warm weather, 150 miles in the cold.

Bring on the East Coast Superchargers. Please.

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