Pushing a Tesla Motors Model S to the edge of its range
A Tesla Motors Model S owner tests the range of his electric car on a cool, hilly 168-mile drive.
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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.
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.
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 carequipped 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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