So it’s the question everyone seems to want to ask following our recent Tesla racing story where we made a small mention that we … ahem, got stranded on the side of the road with no battery range left. How does one possibly run out of power in an 85 kWh Tesla Model S rated for 260 miles of range?
I’m sure some of you would suggest that the headline to this story should read “Only dummies run out of battery in their Tesla Model S”, especially considering Model S owners have done record breaking 12,000 mile journeys across four corners of the nation, not to mention that one Model S owner even crossed the country, and back, in a 60 kWh version.
We’ve received a lot of questions via emails, comments and even through media coverage on the topic, despite the story’s main intent of showcasing our Las Vegas Motor Speedway racing conquests, so we’ll go ahead and try to address them all here.
Battery Range and Trip Planning
The Tesla Model S provides you with a read out on the range (in miles or km) that’s remaining given the battery’s current state of charge. The rated range is formulaic and based on Tesla’s proprietary algorithms which attempt to estimate range by determining how much energy is stored in the battery. As its label implies, it’s truly just a rating.
Also see: Tesla Battery Range Degradation
Tesla’s rated range does not account for elevation changes or wind conditions. We find the site EVTripPlanner does an excellent job with estimating power consumption by taking into account speed, climate control usage and elevation changes.
This graph shows the correlation of speed with available driving range. The slower you travel, the less amount of air drag and therefore the more range you’ll be able to squeeze out of your Tesla.
That said, there are factors you can’t predict upfront, such as wind conditions. While not a big concern in most cases, it should be taken seriously in areas that are prone to high wind conditions and strong gusts. A strong head wind can almost double the Model S power requirements. Even slowing down does not render a substantial improvement. With that in mind, get as much extra charge as possible and drive extra conservative well before crossing into high wind territory. It’s easy for us to say that now having just learned from our Las Vegas to Barstow experience.
So how did you run out of battery?
I wish I could tell you that it was due to an act of heroism where by we veered our Model S off the freeway and onto a narrow dirt road, in pursuit of a big-headed green Martian that needed our help getting back to its space transporter. After all, we’re driving an Intergalactic SpaceBoat of Light and Wonder so it would only make sense that we assisted.
Unfortunately the truth is far less mind blowing.
We ran out of charge because we severely underestimated the strength of the wind and didn’t leave enough buffer early into the drive to account for these unforeseen weather conditions.
We left the Las Vegas Tesla Supercharger with approximately 240 miles in range thinking it would be more than enough power to reach the Barstow Supercharger station that was 160 miles away.
A sand storm with strong headwinds of 35 mph, combined with the steep elevation changes and our usual keeping-up-with-traffic speed of 75 mph, well before reaching the sand storm, all culminated into one of the most stressful situations we’ve ever experienced in our Tesla Model S. We ended up 3 miles shy of reaching our destination, taking into account the additional 10 – 20 miles of reserve range that we were able to tap into. This equates to an additional power consumption of roughly 60%.
What happens with the Tesla Model S when it’s out of charge?
The estimated range on the driver’s dash will read 0 however it’s not the end. There is an extra reserve good for another 10 – 20 miles, depending on your power consumption, after reaching the 0 mark.
Not that you should be taking this for granted and let this ever happen, but it’s good to know that if you do end up in a situation where you’re at 0 miles remaining, you’ll likely reach your destination if it’s within 10 miles.
Once the reserve is depleted, the next event is a message that displays across the center console indicating that the car is shutting down, pull over safely. Needless to say you should do this immediately.
Like the Terminator, this is still not the end. The car will have enough battery to power the displays and other auxiliary functions, followed by the final-final stage that occurs approximately half an hour later. Everything will shut down. You’ll be able to open the doors and the emergency lights will continue flashing, but both the center console and dashboard will be completely dark.
What should you do?
Should you find yourself in this situation, put the car into the Tow Mode before everything begins shutting down. Make sure to block the wheels before putting the car into Tow Mode to prevent it from rolling off. The car will also need to be in neutral before it can be loaded onto a flatbed. Towing companies that work with Tesla know how to jumpstart the Model S battery, but you’ll save everyone time and energy by shifting the car into neutral before it’s completely dead.
We got a lift to the Barstow Supercharger station and began charging up the car again. Once charged it’s important to power off and reset the car. Make sure the doors are closed and use the Power Off button on the control panel (Controls -> E-Brake & Power Off). To start the car back up, press the brake pedal (you may also need to open a door if it does not start). If you don’t Power Off, the Model S will still think it’s in a depleted power mode and not allow more than 20 kw of power consumption. Regenerative braking will also be disabled.
Sorry, Tesla Motors
Keep in mind that running out of power in a Tesla Model S is something that rarely ever happens. It’s 100% the owner’s responsibility to plan accordingly so that faux pas like this do not occur. Bailing an owner out of this type of situation is not something Tesla Motors has to cover, so as you can imagine we were extra thankful that they came to our rescue and towed us out.