2013 Tesla Model S electric sport sedan [photo by owner David Noland]Enlarge Photo
No, he told me, the problem was faulty range calculations. In the current software version 4.2, the range readings are inaccurate when the battery is cold.
"When the range software makes its prediction, it takes into account the current battery temperature," explained the hotline guy.
"It's not smart enough to know that the battery will warm up as you drive, and so your range will increase."
"The range numbers you see on a cold morning are too low," he went on. "That means the range 'loss' you think you see is too high."
Some Model S owners have indeed reported gaining back some of their "lost" miles as they drive. I haven't noticed this, however.
I did notice that on one cold unplugged morning the range was 18 miles--less than 10 percent of the max range--but the battery-state-of-charge bar graph showed somewhere around 25 or 30 percent.
"If there's a discrepancy between the range number and the bar graph," he said, "trust the bar graph."
New software to improve the accuracy of the range numbers reportedly started downloading to a few Model S cars last week.
Due to bandwidth limitations, however, only a limited number of cars can be updated per day--so it will take a while to update the entire Model S fleet.
No Battery Warming
Surprisingly, my hotline guy said that temperature has no effect on Model S vampire loads. Contrary to what I believed--along with many other Model S owners, I suspect--he said that no power is used to keep the battery warm. It all goes to the electronics.
"There's no additional loss due to battery thermal management," he told me. "The Model S does not keep its battery at any particular temperature when the car's off. In fact, lithium-ion batteries actually last longer if they're cold when not in use."
(Musk confirmed this in his Oslo talk.)
On the other hand, the Model S owner's manual says that when you plug in the car to charge, "If the battery requires heating or cooling, you may notice a delay before charging begins.
"Heating or cooling starts automatically when you plug in, and charging begins when the Battery reaches the appropriate temperature."
Now I'm totally confused.
2013 Tesla Model S electric sport sedan on delivery day, with owner David NolandEnlarge Photo
How many kWh really?
Despite the Tesla rep's claim of 8 to 10 miles of range loss per day, I still didn't know how many actual kilowatt-hours of vampire power my Model S was using.
So I asked an electrical engineer friend to cobble together a kilowatt-hour meter that would be compatible with the 240-Volt NEMA 14-50 outlet I use to charge the Model S.
The device would measure precisely how much total electric energy passed through the outlet into the car: No guesswork.
With battery fully charged and the range readout at 189 miles, I plugged the Tesla mobile connector into the NEMA 14-50 outlet, with the 240V kilowatt-hour meter attached, and went to bed.
Next morning, fully 12 hours later ... surprise!
The meter read zero, and I'd lost 12 miles of range. Even though it had been plugged in, the car had used its own battery energy rather than grid power. The actual electricity it had used was unknown.
On a hunch, I unplugged the charge cable from the car, then plugged it back in. The green ring around the charge port immediately began to pulse, indicating that charging had begun.
About 15 minutes later, the battery was full again.
The meter said it had taken 1.6 kWh to top off the night's losses. That worked out to a vampire power draw of 3.2 kWh per day.
Interestingly, the range now read 183 miles--at the same full charge level that had indicated 189 miles last night. (Warmer battery then, presumably.)
The next night I replayed the same scenario, hoping to leave the car plugged in long enough to trigger the auto-transition to grid power to recharge.
But the next day, after 18 hours, the kWh-meter still hadn't budged. I needed to drive the car.
So again I kick-started the recharging process. This time the meter read 3.5 kWh to refill the battery after 18 hours. That works out to 4.7 kWh per day.