2013 Tesla Model S electric sport sedan on delivery day, with owner David NolandEnlarge Photo
Two weeks and 600 miles ago, I took delivery of a 60-kWh 2013 Tesla Model S electric sport sedan.
I won't dwell on the ear-flattening acceleration, nor the magic-carpet ride and handling, nor the mesmerizing 17-inch touch screen controls.
Those features have been exhaustively analyzed and reported by far more expert authorities than I.
I'll just say that I was expecting a world-class cutting-edge luxury sport sedan, and that's just what Tesla Motors [NSDQ:TSLA] delivered.
But there have also been a few things I didn't expect.
Here are some of the little surprises--good and bad--that I've noticed in the Model S so far.
One of the joys of electric driving is regenerative braking. Lift your foot off the "gas" pedal, and the car slows aggressively as the drive motor turns into a generator and sends current back into the battery.
Strong regen is not only energy-efficient, but also gives the car a sporty, responsive feel, like engine braking in a gas car in a low gear. Electric-car drivers call it "one-pedal driving." With strong regen, you'll hardly ever touch the brake.
Different electric cars have different levels of regen. The gentle Nissan Leaf is designed to feel like a standard car [but has two different settings for Regen, D and ECO].
The Chevy Volt has two regen settings, one that mimics conventional gasoline cars, and a second stronger one that allows for one-pedal driving. (I drive my Volt in this "L" mode virtually 100 percent of the time.)
Tesla's first car, the two-seat Roadster, had particularly strong regen, a popular feature with its performance-oriented owners.
The Model S, like the Volt, has two settings: Low, which mimics conventional cars, and Standard, which follows in the one-pedal tradition of the Roadster.
I was eagerly anticipating the same sporty, responsive regen feel that had hooked me in the Volt.
Not so much, it turns out.
To my surprise, regenerative braking in the Model S virtually disappears when the battery is cold. Starting out on a winter's day, it feels disappointingly like any old ICE car--even with the regen on the highest setting.
As the battery warms, the regen gradually increases. But it can take a maddeningly long time to get back to the max level.
Model S vs Volt
On a sunny 40-degree day last week, it took almost 25 miles of driving for full regen to come back. On my typical shorter trips around town, I never get it back. I'd guess that overall, perhaps only a third of my driving so far has had full regen available.
Blame the Model S battery management system, which is programmed to limit the charge rate when the battery is cold.
Under normal circumstances, abruptly backing off the gas pedal at high speed can send a jolt of up to 60 kW into the Model S battery. Tesla engineers believe such bursts of charge are not healthy for cold batteries, and therefore limit regen accordingly.
The Model S has a dashboard dial that shows exactly how much regen current is flowing back into the battery at any given moment. Its maximum reading is 60 kW.
When regen is limited, a dotted line appears on the dial, and the meter won't go beyond it. On a cold day, the dotted line starts out at around the 15-kW mark and gradually moves up to the 60-kW level before disappearing altogether when the battery reaches its normal operating temperature.
By contrast, the Chevy Volt's regen is unaffected by temperature. It's the same sporty feel, winter or summer. Apparently Chevy engineers don't see a problem with high charge rates for cold batteries.
Do they know something Tesla engineers don't? Or vice versa?