Hello!, I am seriously considering purchasing a Roadster but I have some reservations about its driving range. I have a commute that is 115 miles one way two times a week. I will have the opportunity to charge the roadster when I reach the destination for a minimum of 5 hours using a 220 outlet. My concern is regarding how fast I can drive. The speed limit on the highway I use is 75mph and is loosley enforced. One can drive 85mph without any problems. In fact this section of four lane highway is known as the autobahn around here as people drive over 100mph. I have read on this forum that driving over 70mph can reduce to range to as little as 100 miles (in standard mode), which is less than my commute . The dilemma is that driving at 60mph would turn my hour and twenty minute commute to a two hour commute:frown: Has anyone tried driving the car at 85+mph to see how far they can get? thanks in advance!

The graphs in here - Tesla Motors - Engineering - will give you an idea of what the range should be at any given speed ... but of course in the real world, quite literally, YMMV.

5 hours is enough time to go from Standard mode empty to Standard mode full at 40 amps. Do you know if you'll be able to plug into a 50 amp RV outlet allowing you to draw 40 amps? You should get 130 miles or so at that speed. Where you may run into trouble (or need the reserve mileage) is if you need to have the A/C or heat on, or worse both for defogging in the cold. That will cost you 10 miles of range during your trip. On those day, slow down to 80 mph and you should be good. Those are my best estimates.

Thanks JohnR and Tdave! So is the range graph based standard mode charging rates? The graph basically says 130 miles at 85mph which cuts it pretty close. 80mph at 150miles seems more realistic. I am assuming I can fairly easily have a 40amp 220V hookup installed at the facility I will be going too but I will look into that. They only other worry is when the battery starts to loose capacity because of use. How many trips can I make (charge/recharge before the battery capacity drops by 10%?

Please tell us more about this 115 one way. Hills? Headwinds? temperatures? Is it 85mph for 95% of the trip? You are very close to hitting need for more than standard range if its 100% 85mph. Add headwinds, hills and high or low temps with the top off and it would be over standard. IMO

You're right that the battery will lose range over the years. For example, you might find yourself having to do the trip at 80 mph after 3 years, at 75 mph after 5 years, and 70 mph after 7 years, at which time you'll be wanting a new battery anway. I have no idea if those numbers are accurate. It's just an off the top of my head guess to give you an idea of what you may be in for.

Realize also that you'll be trying to complete your trip all in Standard Mode. But you ALWAYS have that last 10% of battery in reserve available simply by pulling over and switching into Range mode, to give you another 25 miles of range at 55 mph, if you should need it one day. That will impact your battery life somewhat if you use that reserve. But the point here is that most days you'll be practiced in making it to your destination in Standard mode, but will always have that buffer if you really need it.

I seem to remember a firmware upgrade that allowed you to access that bottom 10% without pulling over. I could be mistaken, though.

Well, if I'm the only one in the car, I'd certainly pull over in order to switch into Range Mode. That's a lot of taps on the touchscreen. I wouldn't attempt that while driving, and definitely not at 85 mph.

When I was in James' 2010, I recall switching from standard to range mode, while driving, and watching the ideal miles left add 25 more... Then we switched back and the 25 "extra" miles went away again.

I wonder whether it's worse for the battery to charge it to 100% and drain to 10%, or charge to 90% and drain to 0. My guess would be the latter (low charge is worse than high), but that's really just a guess based on the warnings that Tesla issued about leaving the battery discharged.

That is a good question, but there are probably other factors to consider... Such as how long it is left at the "bad state". For instance, charging to 100% and leaving it fully charged for long periods of time is not good. If you were driving directly to a charge spot, I bet going down to indicated 0 is probably not as bad if you get straight to charging right away. On the other hand, letting it run down to 0 then parking it for a while before putting it back on charge is probably not good either. It could be a further complicated question by the ambient temps at your start and stop points. Also, your driving habits on the trip. I bet pushing the batteries hard at the extremes is not good. For instance, it may be a good idea to slow down as you get closer to "0" and avoid any more "hole shots" as the batteries may not be in the "mood" to do fast discharge at that point. Possibly too many variables for Tesla to offer real guidance on this sort of comparison.

By my reading of the email from Tesla about battery care, that is the worst thing you can do to the battery and will void your warranty. Given those two choices, I'd definitely vote for charging to 100% and driving down to 10%. On another point, although I haven't tried it, I'll bet you can do 85 mph in range mode. I once broke 80 mph in valet mode going slightly uphill.

I'm all for being able to adjust the valet settings; but I already have a "lend it to my daughter" mode: turned off, in the garage, with the keys in my pocket. Stay out of my car, you hooligan! I've seen how you drive the Prius!