OK. I admit I am sans Tesla.....for now. But I do have a 2000 Honda Insight. And I do have several gas cars. The Honda Hybrid has a gas engine when the battery goes dead. BUT I would NEVER run my gas tank down to 3oz of gasoline (that is three shot glasses full). 3 Oz of gasoline represents 1 mile. What am I missing here that Tesla drivers will run till only one mile is left? I try to get gas in my Lexus when it tells me I have 50 (Fifty) miles of gasoline left. Is the Tesla so reliable that you really think ONE mile is safe????? I dont have sympathy for you.......
For road trips, it will be an issue until Superchargers are located every 25-50 miles. In my one year of driving a 2015 Model S 85, I have thus far encountered three scenarios where relying on the Tesla navigation could have got me stranded.
1.
Road Closure. Driving from Illinois along I-44 to Oklahoma, the interstate was unexpectedly shutdown due to flooding. The shortest detour added 15 miles and 45 minutes to my drive. As others have mentioned, planning your trip to 10-20% arrival charge may not always work when factors outside your control arise (detours, power outages, distance to nearest public charger).
2.
Remote Destinations. Driving to destinations that are not along the interstate. I took a day trip from Peoria, IL to Nauvoo, IL and back. Departing estimate said 15% to arrive back home. When setting out to depart home, the estimate dropped to 5%. Nearest supercharger was 116 miles away (2 hour detour) from Nauvoo, or I could drive 30 miles (40 minutes) out of the way for a 7.7 kw charger that would require another a minimum of 2 hours charging to even make the detour worth the effort. A definite 2.5 hour detour or risk it to make it home? Luckily, we made it home. Not sure if we would have made it had the outside temperature been 10-20 degrees colder.
3.
Inaccurate BMS Range Estimating. My 2015 Model S now has upwards of 65,000 miles on it. On a recent road trip, I found that car is now having trouble estimating the time required to charge above 85%. For example, I set the car to charge to 100% at home before the trip. Two hours after the car should be been done charging (NEMA 14-50), it is still estimating that it needs 1 hour to finish charging.
Similar story as I stop at a Supercharger. I could stop to charge again in 60 miles, or charge up to 95% here and drive 180 miles to the next charger. I choose to aim for the 180 mile charger and set the car to charge to 100% at the Supercharger, it estimates 1 hr 10 minutes to full. Fine, I entertain myself with Netflix and come back 1 hr later, to which it still says 20 minutes remaining. I wait another 10 minutes and it still estimates 20 minutes remaining. To hell with it, it says I should arrive with 10% battery left so I set off with only ~90% charge. For the next 20-30 minutes of driving the estimated range is all over the place. For a few minutes, showing I need to slow down to 55 mph to reach my destination, then saying I will arrive with 15% charge. Once I drive for a bit, and the state of charge gets below 80%, the estimated range settles down and consistently says I will arrive with 7% charge. With conservative driving, I made it to the supercharger with 6% battery remaining.
When the battery is above 80% or below 20%, the range estimate is wildly inaccurate. After searching these forums, I have come to the conclusion that this is a common occurrence for cars with miles on them. This saddens me, as my daily charge routine is to set it 80%. I charge the car to 100% 2-3 times per year for the occasional road trip, and have perhaps 12 supercharger stops per year.
As I said, until Superchargers are located 25-50 miles in every direction and/or Level 2 chargers are available near every place of interest, there will be many circumstances that are out of your control. In my opinion, adding 2+ hours in detours for a road trip to compensate for lack of charging infrastructure is not reasonable. Therefore, there will be lots of people who push the range. Most times you will make it to your next charge sessions, sometimes you will end up stranded.