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My Trip to LA: a real-life range experiment

I drove my Signature Performance to LA on I5 yesterday and decided to take the opportunity to test the actual range of the car at different highway speeds. Here is what I found:

Leg 1, Oakland to Harris Ranch (175 miles): I put cruise control on 55 MPH and because of light traffic, I never had to take it off. Somewhat to my surprise, my average energy consumption was 282 Whr/mi, which equates to almost exactly 300 miles on an 85 Kwh battery (assuming that you can actually pump 85 Kwh into your battery, of course). I had always figured that the 300 mile number was just marketing hype, but guess what? The car can actually get that far, if you happen to be on a 300 mile long flat interstate. At any rate, upon arrival at Harris Ranch I was relieved to see that the single supercharger bay was empty. I did, however find a sign advising me that more charging bays were under construction and would be completed by "March 2013". How are we coming on that, Tesla? Note that, with the exception of Altamont Pass, this leg was essentially flat road. The Grapevine was yet to come.

Leg 2, Harris Ranch to Tejon Ranch (110 miles): On this leg, I set cruise control to 65 MPH and again I never took it off. At this speed, i got 332 Whr/mi, for a range equivalent of 256 miles. Again, the road was almost totally flat. So that extra 10 MPH cost me about 45 miles of range. Moral: If you're getting low on battery, slow down!

Leg 3, Tejon Ranch to Atwater Village (80 miles). Tejon Ranch lies right at the foot of the Tehachapi Mountains, and over the next 15 miles Interstate 5 climbs roughly 4,000 ft. to Tejon Pass. I put cruise control back to 55 and headed uphill. Now, even though the model S has a lightweight aluminum body, it weighs over two tons because of the one ton+ battery. And since a LOT of energy is required to lift two tons 4,000 feet, I was prepared to see some startling numbers. Sure enough, by the time I crested Tejon Pass, my average energy consumption for the leg was totally in the toilet: over 700 Whr/mi. Now, because of regeneration:I knew I would get some of that back on the way down the other side, but I was really amazed to see that by the time we reached Castaic at the north end of the San Fernando Valley, the meter was back down to 285 Whr/mi! In other words, I had recovered essentially all the extra energy required to climb Tejon Pass. The Grapevine turned out to be no problem at all. Oh, by the way, I never touched the brake pedal on the way down.

Note: The model S has a toggle which turns off regeneration, but I have no idea why anyone would ever want to do this -- it just wastes energy and uses up your brake pads for nothing,

Conclusion: The Model S is an amazing car that does essentially everything Tesla says it does.

@david32
thank you for the post. also note that leg 2 is very close to EPA rating 265 mile range

The usable capacity is 83475Wh, judging from the rated range of 265mi and the rated line at 315Wh/mi, so you would get 296mi on a range charge at your rate of 282 Wh/mi. The additional caveat was flat ground, so between even slight elevation changes and winds, that would easily account for the difference.

One other data point - with the cruise on 75, over somewhat hilly ground and cooler but mild temperatures with the heat running, I averaged 380 Wh/mi, which gives just under 220mi range. Even with heavier HVAC use, I expect 210mi range will be readily achievable.

But yes, when I was driving the LEAF and therefore actually needed to worry about range on more than just long trips, it was basically just calculating how fast I could drive to reach my ultimate destination if I happened to be driving further that day. I never drove the car until it "turtled" (shows a turtle and only allows a few mph), but on a couple of occasions I did drive it until the range went to dashes. I would typically drive 80 on the interstate, knowing that I had about a 20mi buffer if I needed it just by driving 60.

@David32,
Very good post and thank you for sharing. Your post is the kind of posts that would perfectly exemplify what the MS can truly deliver with unbiased real driving experience.

@jat

Where do you get the "rated line" of 315 Wh/mi? I was under the impression that the "rated" energy consumption rate was about 307 Wh/mi, which would yield a usable capacity of 81,355 Wh, or about 95.7% of the 85 kWh battery.

I'm leaving tomorrow on a trip from Seattle to the SF Bay Area. No superchargers along the way, but I do plan to use several 70 amp chargers. Someone has computed that, even with the high amperage chargers, driving faster will take more time than driving slower. The reason is that the time gained by speeding is more than offset by the additional time required to charge. With superchargers, driving faster will save time.

Douglas, The best way to think about time saving is that you will lose time if you drive at a speed that takes energy out faster than you can put it back in. So if the charger that you stop at can only provide 50 miles of range per hour than you should be driving no faster than 50 mph. This is why the supercharger makes is possible to ge as fast as you want and make the best time. Although there is a bit of a caveat in that. Your ideal trip will start with a full "tank" and end with an empty one as you will not be charging during your trip for that amount of range.

Theresa

When you make e trips you have written about, do you use full charge?ie 300 miles

@David32

Very helpful post for me, thanks. I plan to do this exact trip when I pick up my car. Seems to me you could have done the first leg more in line with vehicle speeds in California (65-70 mph on interstate 5).

Theresa. I think it's more complicated than that. You need to compute the energy consumption at each speed, and then compute the additional time necessary to restore that energy by charging. For example, driving 100 miles at a steady 25 mph will use about 20 kWh (based on somebody getting 400+ miles by driving that speed). Driving 100 miles at a steady 50 mph will use around 25 kWh (based on a range of 300+ miles at that speed). Let's say you can charge at 10 kW (the rate of a standard NEMA 14-50 outlet). Then, at 25 mph, the drive + charge would take six hours (four hours driving and two hours charging). At 50 mph, the drive + charge would take 4.5 hours (two hours driving and 2.5 hours charging). So it would never make sense to drive at 25 mph if your charger put on miles at that rate. However, driving 55 mph + charging will apparently take more time than driving 75 mph + charging. I have not done the calculation myself, so I can't vouch for it.

@DoulgasR
Congrats on getting that second twin charger. Will you trat us with a travelogue? You should have good weather for a spell. Hope you have a great adventure. Don't forget 7 Feathers Casino if you're feeling lucky and need a charge/suite.

@TeslaTech

Thanks! I am staying at 7 Feathers, at least on the way down. I will probably be mostly incommunicado during the trip, however, as I will not take a computer and I don't plan to type on the touch screen while driving. I will try to keep a log, however, and report back.

But the best data you will find on that same journey are in two long posts by ChadS over at TMC. Very thorough.

david;
Very nice and very important post. Speaks directly to the issue of TM claims vs. the real world. They agree.

@David32, you make same mistake as many other people make, car battery doesn't weigh anywhere near one ton (unless you use lbs as unit). Whole battery pack including supporting structures is somewhere close to 500kg, batteries alone only about 368kg. Whole drivetrain is something like 650kg including cooling fluids, radiators etc. IE not much more than ICE drivetrain that can match Model S performance.

PD - where are you? This thread I believe outlines an earlier exchange. 300 miles is indeed doable in-between 25 MPH and 65 MPH. My take away is that it's not that far off the stated 55 (yes, with flat road, moderate temp,... - hence a give a few more MPH for that allowance).

@DouglasR - looking at the energy graph when the average line is near the rated line. Actually, I think it is about 313 -- today, I saw 314 show the dashed line just above the rated line, and previously 312 was clearly below it.


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