Jaguar I-Pace EV400 Forum banner
1 - 6 of 6 Posts

·
Administrator
Joined
·
3,125 Posts
Discussion Starter · #1 ·
I live in the SF Bay Area. I have a friend who owns a cabin in the mid-elevation range of the Sierra Nevada on Highway 108 (the one that goes to Sonora Pass, one pass north of Tioga Pass in Yosemite). My wife and I spent the last weekend there, and it was once again awesome; if you ever find yourself there, Sonora Pass is gorgeous and amazing, and there are many recreational opportunities along CA 108. But I digress.

We take the I-Pace to the cabin sometimes. One-way it's a ~150 mile trip with 5600 ft of net elevation change. Coming out of the Bay Area it's all freeway until Manteca (almost exactly half-way) in the Central Valley, and then it's mostly fast-moving two-lane road with appreciable sections of divided highway to the destination, which is Cold Springs, CA.

The trip is a great lesson in applied Physics and the fact that data and measurement should be the basis for discussions around efficiency and range, and how those are affected by knowable parameters: environment (temperature, wind, elevation changes, etc) and driving parameters (mix of fast vs slow, traffic density, etc).

We've done this trip several times with the I-Pace and on this occasion I decided to take some battery readings at the end points, and along the way home. It's a representative trip overall for conditions that are close to ideal for an EV.

Attached is an annotated map of this specific trip. The segments labeled "1" and "2" are the entire trip, "1" is going up to the cabin and "2" is coming back down; the segments labeled A-D are subsegments of the trip home, i.e., coming back down.

I recorded certain standard parameters of the routes (distance, speed, etc) and also took OBD measurements of battery charge and temperature at key waypoints. That's the data upon which some of these simple calculations are based. The calculations primarily address the impact of elevation on consumption, efficiency, and range. NB: my OBD shows about 81 kWh usable capacity; and the car's consumption estimates that you can download from the InControl site almost exactly match those I calculate with my OBD readings, so I trust them.

On a trip like this, net elevation change is the key determinant of range and efficiency. You can see that in the comparison between the trip up (1) vs down (2), where the consumption is dramatically different due to the potential energy required to lift the mass, and regenerated on the downhill. When one subtracts the theoretical contribution of potential energy (last column in the first table), the efficiency of up and down trips become very similar.

Second is how much time is spent driving fast on the freeway and stop-and-go, vs steady average two-lane highway speeds around 50 mph. (Of course, range is very much influenced by battery temperature too but we didn't test that here and it's amply documented elsewhere.)

The overall worse consumption of the trip home was caused by Segment D, which took 28 minutes longer because of extensive stop-and-go and had higher compensatory speeds elsewhere, both of which results in increased consumption per mile.

The most fun comparison is the one between segment A and the others (B,C,D): 6.6 kWh per 100 miles ... I could have gone for another 1000 miles on that charge (on my way to the center of the earth).

In summary, physics works as predicted, which is reassuring philosophically; at a practical level, don't forget to consider your net elevation change in your trip planning. If it's large, range will deviate substantially from expectation, in either direction.

Ecoregion Map World Atlas Parallel


Rectangle Font Line Parallel Screenshot


Font Circle Magenta Number Parallel
 

·
Registered
Joined
·
731 Posts
So basically is took you essentially a full battery (100 to 20%) for you get there and only 100 to 45 to get back. Quite a difference!
 

·
Registered
2019 FE Photon Red
Joined
·
1,005 Posts
Thanks for the data. It would have been nice to see the final climb as a discrete section to compare to section A. With numbers as extreme as section A, it might be possible to tease out the efficiency of the regen - a question that has been asked/discussed on here many times.
 

·
Administrator
Joined
·
3,125 Posts
Discussion Starter · #6 ·
Yeah I didn't think of it on the way up. I'll be doing this trip a few times this summer, I'll try to remember. In principle, however, you don't need the section; the whole trip should work for it as well, it's just that the confounders will influence things more over the 'irrelevant' miles that have no net elevation change.

Back of the envelope: If I subtract the greater AC use and more variable speeds of the return trip especially on segment D, the difference between the trip up and the trip down is almost twice the potential energy for 5600 ft, which means the regen is not much less than 100% efficient.

I have lots of shorter trips that involve a net elevation change of 700 ft, my home to that of a good friend. Altogether I think the regen efficiency is at least 90%, probably slightly better.
 
1 - 6 of 6 Posts
Top