Dipped into my safety reserve because of higher than normal energy usage. Pre-planning for 70 MPH, a 13% negative , cold weather consumed another 6% and that was with the cabin heat switched off.
I shall allow for this on the next leg by reducing speed at least during the early going. Once I see that distance to go balances with range available I can resume a regular rate.
Even with a garage temp of 45, the OAT Is 19 degrees and the traction battery is marginalized. The battery does not like cold. Observe the yellow dashed lines. These appear during these conditions so as to limit maximum current draw and maximum regeneration, either of which challenges the battery. Normal use creates heat. There is an electric element to provide auxiliary heat if required. When things get up to temp the limiters recede. In the pursuit of battery longevity we see how the system looks after itself.
Planning a trip in an Electric Vehicle (EV) is very similar to fuel planning for a cross-country in light aircraft. Before undertaking a journey you want to know enroute conditions, access performance data, locate fuel stops, have an alternate or a backup plan. EV range, like aircraft range is limited. Fuel stops are few and far between for either. The consequences of miscalculation for either can be serious. If you have aviation experience you will grasp the range planning concept readily.
The variables that can affect range, i.e. shorten or lengthen are:
There are other factors to consider exclusive to the EV such as cabin comfort; heating or cooling (HVAC) uses energy from the battery whereas a light aircraft uses waste energy from combustion exhaust manifolding to provide heat. A battery electric vehicle will suffer from some degree of vampire drain and parasitic energy losses -0.3 range miles for each clock hour vehicle moving or stationary. Wheel and Tire design choices influence rolling resistance and aerodynamic drag. Passenger windows open vs closed can alter aerodynamics.
By far the biggest consideration is speed because of wind resistance. Drag is proportional to the square of speed, and the power needed to overcome that drag is proportional to the cube of speed so if you want to go twice as fast, you’ll have to be eight times more powerful. The following table shows percentage corrections to rated range and is based on driver reports and manufacturer guidelines.
| 45mph | +26% |
| 55 | + 8% |
| 60 | 100% of EPA rated range (at 70 degrees with miniscule HVAC) |
| 65 | – 8% |
| 75 | -26% |
| Clear and dry | 100% of rated range |
| Wet roadway | – 2% |
| Standing water | -10% |
| Light snow | -15% |
| Heavy snow | -25% |
HVAC referencing the outside air temperature (OAT)
| 15 | -25% at full blast, HVAC pulls about 7.5kW — battery heating is ncessary |
| 32 | -13% pre-heat the cabin if possible and then reduce cabin heat temp and use seat heaters. Optional cabin heat switched off (Brrrrrr) but still need battery heat -8% |
| 50 | – 7% |
| 70 | 100% of rated range (HVAC on, but barely in use i.e. vent only) |
| 100 | – 7% |
| 120 | -13% there is energy draw for battery cooling in extreme |
ELEVATION
| Mountain | -10 miles in lost range for each 1000′ of Rise |
| Mountain | +4 miles recovered range for each 1000′ of Descent |
The more cars at the gas pumps in a filling station the lower the pressure. i.e. unleaded may flow more slowly due to reduced pressure. A Tesla Supercharger station is similar but first — how the Supercharger Station is engineered:
The takeaway here is that the 120kW charge rate is a perfect case situation. If others are on the same Teat your rate of flow will vary [lower].
Tesla Model S has a mid year production update which means that if you took delivery before X date your unit has been superseded by something better. This can be expected with any leading edge technology but has the tendency to upset the early adopters. Remember ordering your first Pentium PC only to see the Pentium II intro mere months later rendering your box obsolete? Or smart phone, or tablet or…
First production vehicles are limited to a 90kW rate of charge. These cars have “A” batteries. Word gets out that updated “B” batteries, with the bragging rights of a 120kW hour charging rate have been incorporated into production. Somewhat unfairly, Tesla led folks to misunderstand that the higher charge rate would be enjoyed by everyone after a routine Firmware Upgrade which turned out not to be the case. Suddenly everyone is on their knees to look at the underbelly of their pride and joy to glimpse a factory VIN label 
proclaiming which batteries are installed with hopes that it will say “B”. Some are disappointed. Others find both letters mix and matched. Evidently there may have been a 4 month span when the new batter was ready but there were plenty of the “A” batteries still in inventory. Unfortunately those folks are also limited to the lower standard. Some people have newer car VINs with older style and some owners older VINs with the newer type leading to additional bewilderment.
This charge rate thing is meaningful. If you’ve spent luxury car money and your available time has considerable value, your wait at the charging station is measurable. The higher charge rate ability will get you back on the road perhaps 5-10 minutes before the Tesla owner with the lower limit. He might be left grumbling as you both pit stop and you are able to speed away first. This is a new world to understand. Those of us still consuming petrol don’t give a second thought to refueling. The Tesla owner when away from home base will strive to locate and use a Tesla SuperCharger location and by the way, Tesla’s deal is to provide a network of stations and make the energy available without cost to driver (as in FREE).
It becomes an interesting study in behavior as those first in line to buy the new car must have known that the original design, as wonderful as it is, was bound to be improved upon and enhanced over time.