Vampire Drain: How Much Power a Tesla Model S Really Loses in Almost a Month

Vampire drain, the name given to the phenomenon where electrical appliances consume power from their battery packs when not in use, is a well-known problem in the EV world, especially in cars like the Tesla Model S. That’s because under certain circumstances when unplugged — noticeably in extremes of temperatures — the Model S uses power from its own battery pack to keep it at an optimum operating temperature, resulting in a battery pack which appears to lose charge when left for extended periods of time.

Bjørn Nyland finds out how much charge his Model S loses after being parked up, unplugged, for 27 days.

Bjørn Nyland finds out how much charge his Model S loses after being parked up, unplugged, for 27 days.

But how much power is lost due to vampire drain if you leave your car for say, 27 days, unplugged, in a sub-zero parking lot?

That’s the question our YouTube friend Bjørn Nyland tried to answer when leaving his Tesla Model S P85+ for 27 days over the Christmas break.

Having charged his car up to 95% capacity (we presume in storage mode) Bjørn headed to the airport and parked his car there. Being Norway, we’re guessing Bjørn’s car was sat in sub-zero temperatures for the duration of his much warmer vacation, causing the battery pack to use some of its energy to keep the battery pack warm.

Fresh back from his Thailand vacation, Bjørn returns to find that around twenty percent of his Model S’ pre-vacation charge had vanished, along with around 100 Kilometers (60 miles or so) of range, leaving him with a state of charge around 70 percent full, good enough for around 246 kilometers (152 miles) of predicted range.

That’s far better than the thirty percent charge loss Bjørn was expecting.

That’s because the Model S, like other EVs with active thermal battery management, enters into a state of hibernation after a few days of being left, where it powers down all but the most essential of on-board systems in an attempt to preserve as much battery charge as possible.

The only side affect? After sitting for twenty-seven days, mostly in hibernation mode, the Model S did report it needed to warm the battery pack up a little before it could operate at full power or use regenerative braking.

But now at least we know: it’s possible to leave a Tesla Model S for nearly a month without any negative problems for it’s battery pack. At least, provided you charge first.

The longest we’ve ever left an electric car unplugged was when we left one of the Transport Evolved Nissan LEAFs in an airport parking lot for six days with a half-full battery pack. In that time, we lost about 7 miles of range.

We should also point out at this point that if you’re planning on leaving your EV for an extended period of time, it’s worth checking in your owners’ manual for the best practice recommended by the automaker who made your car as each plug-in car we know has slightly different requirements, with some automakers recommending you leave your car plugged in, while others recommend the exact opposite.

Have you left an EV for an extended period of time? What vampire drains did you notice? Leave your experiences in the Comments below.


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