Making my first road trip in an Model S-85. Left Phoenix for Palm Springs. Initially the on board Supercharge display map said I could make the trip to the Quartzsite (AZ) SC with 13% battery to spare. Then, after stopping about half-way at a rest area along I-10, the car recalculated and informed us we didn't have sufficient charge to reach the SC in Quartzsite... or return to the Buckeye SC! We weren't doing any heavy acceleration, in fact, we were using the cruise control most of the time. Well, we just made it to the Quartzsite SC (whew!) with "6 miles" to spare after shutting downs as much battery usage as possible and driving at 55 mph the last 60 miles. Very nerve racking, especially in the middle of the desert.