Submitted by cerjor on April 9, 2012
I need to drive the 1600 miles from Seattle to Phoenix and have been trying to figure out how long it will take. The total time will be the driving time plus the charging time (plus sleeping time). Because I will be getting a 230 mile (60kw-hr) model, I chose an arbitrary 200 miles between stops. I assumed the use of a J1772 charger which is 220V and 70A (Usually only 80% of this current is available.) Thus, the charging rate will be 220*0.8*70 = 12.3kw. The power consumption rate of the car was tabulated according to the graph found at http://www.teslamotors.com/goelectric/efficiency. I calculated the travel time for every 10mph from 10-70mph.
Speed Time Whr/mi kw-hr Charge time Total time Avg Speed Time SEA-PHX
mph Hours used Hours Hours mph Hours
10 20.0 110 22 1.8 21.8 9.2 174.3
20 10.0 130 26 2.1 12.1 16.5 96.9
30 6.7 145 29 2.4 9.0 22.2 72.2
40 5.0 170 34 2.8 7.8 25.8 62.1
50 4.0 200 40 3.2 7.2 27.6 58.0
60 3.3 240 48 3.9 7.2 27.7 57.8
70 2.9 280 56 4.5 7.4 27.0 59.2
For example, if the car was driven for 200 miles at an unrealistic speed of 40 mph the travel time would be 200/40 = 5 hours.
To calculate the charging time, the power consumption/mile was multiplied by the distance traveled. At 40mph the power consumption is 170W-hr/mile (from the graph) so the total energy consumption is 200x170/1000 = 34kw-hr. The length of time required to replenish this amount of energy 34kw-hr/12.3kw = 2.8hr. If you use a different charger, this time will be different.
That means it will take 7.8 hours for a 200 mile segment if using a charger with the above specs and traveling at 40mph. The average speed of travel will be 200mi/7.8hr = 25.8mph. (This seems very slow but if you drive and ICE at 75mph for 8 hours and then stop for the night, your average speed will be only 25mph: 75*8/24.)
Doing these calculations for speeds from 10-70mph yields an unexpected result. On this long trip, it doesn’t look like it matters whether you go 55mph (for maximum range) or 70mph (keeping up with traffic). The difference in arrival time will less than 2 hours. However, after 200 miles at 70mph you will have used up 93% of your charge. I hope there is a charging station waiting.