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Two 60+ kWh Similar Road Trips with Rather Different Outcomes

Sep 18, 2012
185
133
San Diego, CA, United States
Weather was nearly identical in both trips and the freeway sections of the routes were identical. Both trips immediately followed a full-range Supercharge (238 mi is what I get on my 2017 75).

Yuma > San Diego > La Jolla

Trip #1 Left the Yuma Supercharger and drove around town for the afternoon doing a couple errands and put maybe 10-15 miles on it. Then drove to San Diego without stopping (170 miles). Drove moderately aggressively (70-75). In the morning, I drove 15 miles to La Jolla VERY conservatively. GPS said I wouldn’t make it – but I got it done easily with a little drafting and keeping it at ~55.

trip1.jpg

Trip #2 Left the Yuma Supercharger and immediately drove to San Diego without stopping (170 miles) Drove very aggressively (75-80). In the morning, I drove 15 miles to La Jolla at a normal pace (with a bit of traffic). GPS said I would make it easily but it ended up being closer than I thought.

trip2.jpg

Question #1: What is the deal with the total kWh burn in BOTH trips. Why am I so far from 75 kwh? I expected the low 70s or, at worst, high 60s. What’s going on? An extra 5-10 kWh would really help me for this scenario. And as the car ages, I won’t be able to do this trip at all. . .

Question #2: Where did the extra 2 kWh to burn come from in the second trip? The second trip was a lot more aggressive so I got less range – but I could have used those precious kWh the first time around. What am I missing?
 

[email protected]

Family, Racing, Karting, MTBing
Sep 25, 2013
918
225
Enschede, NL
Re #1: The 75kWh pack has an actual capacity of (only) 72kWh*. Minus ~9kWh buffer (5kWh for 'reserve' and 4kWh brick-protection) you get close to your 63 kWh.

Re #2: Those errands on your first trip result in some 2 kWh of 'hidden' consumption. The kWh on the trip meter only shows usage while driving, not the idling/systems booting/heating/cooling just before/after those short trips. That usage doesn't show there, but you end up with less kWh for driving until empty.

*) See Tesla’s hacked Battery Management System exposes the real usable capacity of its battery packs for an overview, and info on the 100 here: Pics/Info: Inside the Tesla 100 kWh Battery Pack
 

David99

Active Member
Jan 31, 2014
4,850
7,026
Brea, Orange County
Your car has a 75 kWh battery but only 70 are usable. The rest is kind of blocked out at the low end. Tesla doesn't allow the battery to be discharged all the way to 0 because it would be damaging for the battery. Don't feel bad though. My 85 never even had 85 kWh. It had maybe 81. Now after 160k miles I lost some capacity and the remaining usable capacity I have is aprox 68 kWh. Yes that's not a typo.

Thew difference in energy consumption can come from various variables. One thing most people are not aware of is that Tesla's trip meter does not calculate energy used when the car is standing still. So every time you are waiting at a red light or park it, energy is still consumed but not accounted for in the trip meter. Difference in temperature or moisture in the air can cause the AC to use more or less energy. Some energy ius used by the car regardless of miles driven. A longer trip causes more of that auxiliary energy to be used compared to a shorter trip even when both are the same miles. Battery temperature makes a big difference as well. A warm better is more efficient, a colder battery has higher losses. Tesla doesn't show you the battery temperature, though. I have an app displaying the CAN bus data showing the battery temperature. It has little to no connection to ambient temperatures. If the battery was warmer in one of those trips, that could have caused less energy to be used (because of lower internal losses). Wind is a huge factor as well. Just a few miles of head wind can easily make such a difference.

Bottom line, there are many factors that can cause a 3-4% difference in consumption.
 

tpham07

Active Member
Mar 21, 2017
1,965
2,202
Rhode Island
I get 241 miles at 100% on my S75. 238 is not the most outrageous thing ever. The #s you see on Tesla.com are the EPA official test numbers, not the numbers Tesla is supposed to show you on the dash.
 

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