Ascending mountains in the Leaf

[kidjan]

We conducted a test yesterday with our 2014 Leaf in the Olympic Mountains. We arrived at a point, the visitor center, where the road started to climb up with 74% battery. From that point we drove 16 miles and gained about 4000 feet and arrived at the trailhead with 22% battery and 8 miles remaining on the range. On the return trip down we charged up to 38% and 47 miles on the range when we passed that same visitors center. It was 19 miles back home and arrived with 18% battery.

Total distance travelled was 70 miles. Started with a 100% battery and used up 82%.

Interesting--I live in Salt Lake, have a 2015 S. Just the other day I left my house at 4300ft elevation with 100% battery, and drove up to Alta (~8400ft elevation). When I got there, I had ~38% battery left. On the way down the canyon, I regen'd about 15% battery, so exited the canyon with ~53%. Got home with about 45%.

It's really fun driving down the canyon with regenerative braking; you basically don't have to use the brakes. I just swap between B and D mode to speed up/slow down as necessary.

 

[MalcolmReynolds]

We conducted a test yesterday with our 2014 Leaf in the Olympic Mountains. We arrived at a point, the visitor center, where the road started to climb up with 74% battery. From that point we drove 16 miles and gained about 4000 feet and arrived at the trailhead with 22% battery and 8 miles remaining on the range. On the return trip down we charged up to 38% and 47 miles on the range when we passed that same visitors center. It was 19 miles back home and arrived with 18% battery.

Total distance travelled was 70 miles. Started with a 100% battery and used up 82%.

Interesting--I live in Salt Lake, have a 2015 S. Just the other day I left my house at 4300ft elevation with 100% battery, and drove up to Alta (~8400ft elevation). When I got there, I had ~38% battery left. On the way down the canyon, I regen'd about 15% battery, so exited the canyon with ~53%. Got home with about 45%.

It's really fun driving down the canyon with regenerative braking; you basically don't have to use the brakes. I just swap between B and D mode to speed up/slow down as necessary.

How many miles was the trip up? I am curious to the distances we are able to climb before battery runs out.

 

[kidjan]

It's about 47 miles, round-trip. Total ascent/descent is actually about ~5800 ft, because there's some ups and downs on the way there. Interestingly enough it looks like there's an alternate route for me that'd be more like ~5100 ft, but about five miles longer. Now I'm curious what sort of performance I'd see on that route instead.

 

[hyperionmark]

How many temperature bars do you guys see during these mountain runs?

 

[alozzy]

@kidjan

Would be interesting to see what the EV trip planner shows for kWh consumed for your two options. Do you mind running the numbers?

https://www.evtripplanner.com/planner/

For comparing energy use between two routes, you can ignore the variables if you want, but do make sure to choose the "Nissan LEAF Beta" profile, rather than the default Tesla one.

 

[MalcolmReynolds]

Thanks for that link to the trip planner. I just plugged in my adventure to Cripple Creek using that tool and the numbers it is providing looks like I would not make it. How accurate is the trip planner?

It is saying I would climb 3119 ft, 54.4 miles one way, and the trip up would use 15kwh, and the trip down would use 9.8kwh. So looks like I would come up pretty short. For a total trip of 108.8 miles.

 

[alozzy]

It definitely sounds like you won't make it, unless you have a 30 kWh pack. However, the OP was talking about a different route I think, as he said:

It's about 47 miles, round-trip

 

[MalcolmReynolds]

Yes, the OP is doing something different. I was just chiming in on a planned mountain EV assault there locally. LOL Thanks for the link.

 

[alozzy]

No worries

 

[DungenessLeaf]

Let's work this backwards and assume that the re-gen on the Leaf, or any other EV, is 100%. If so, then the distance travelled v/s the percent battery would be the same, but only assuming that one made a round trip and started and returned to the same point in elevation. And that is just about what we found in our round trip up and back down the mountain. Road surface and speed should make a difference so include that.

Our trip was all up a paved road averaging about 30 when going up the mountain. From the foot of the mountain to home was paved, mostly flat, and averaged about 45. If the Leaf computer could let one monitor the temperature in the cooling loop and one could calculate the heat loss, that would give some idea of the efficiency of the re-gen. Maybe one of the apps could do this.

 

[WetEV]

Thanks for that link to the trip planner. I just plugged in my adventure to Cripple Creek using that tool and the numbers it is providing looks like I would not make it. How accurate is the trip planner?

In my experience, EV Trip planner is not very accurate for Leafs. Good user interface, and writes out a spreadsheet that you can improve with better calculations.

 

[remarquian]

The magic of mountain driving in the Leaf is that you get free+ mileage going downhill - not only are you travelling energy-free, you're also regenerating as necessary. I've gotten to the top of Mt. Evans with 6% battery and gotten all the way back down to Denver... with 20% once I got to the bottom!

Where in Denver were you starting from?

I've done both PP and Mt Evans, but charged before going up.

 

[jjgilham]

I really like the elevation test to study regeneration efficiency. The piece that I feel is missing is careful speed control. In an ideal test you would pick a reasonable speed to do the trial at and maintain that speed going up and coming down.

I recognize that this is not always possible due to the amount of regen available and the need to actually drive in traffic safely but I believe it makes a large difference. If on the upward route traffic is slower (say averages 40) mph but on the downward leg (it is faster) say 45 mph that may not seem like that big of a deal, however the losses due to air resistance are proportional to the square of the velocity. So in this example, the drag on the car coming down is 26.5% more than going up (Df is proportional to (45/40)^2 ). At higher velocities the air drag force is by far the largest resisting force on the car.

Here would be my ideal test:

Find a stretch of road (2 or 3 miles) with a gradual hill that gains a few hundred feet in elevation.

Repeat an up-down test at 20 mph - 60 mph going up and going down in 5 mph intervals, (use cruise control to control speed). Use LeafSpy to record the total power used going up and going down at each speed.

I have a 19.6 mile commute for which i start at 480 ft, drop to about 100 ft and then climb to over a 1000 ft and then end at 800 ft. at work. I spend a lot of time thinking about the most efficient use of regen. In the hundreds of tests I've run on this route I find that speed is the biggest overall determinant of efficiency going up and down. I can't really go less than 60 going up most of the climb (70 mph freeway and traffic is even faster going down). When I go another route with the same net vertical for which I can go 35 or 40 the efficiency is much higher (both ways).

As an interesting side fact - I have a power meter on my charger and I keep track of how much energy "out of the wall" is needed to put energy into the battery. In these tests for both Leaf's I've owned I find that the charging efficiency is between 88% and 90%. So coming out of the wall it takes an maybe 29 kWh to get 26 kWh into the battery. I would suggest that this puts an absolute upper limit regen efficiency of about 90%. But note that in practice it will be much worse than this because we will also have the additional inefficiencies of the generator conversion losses to consider. In addition, the energy in the battery isn't delivered back to the wheels with perfect efficiency.

If I had to guess I'd say .9 * .8 * .9 or maybe 65% is about the best you can do. (I'm thinking .9 into and out of the battery and .8 for the generator efficiency. I think a carefully conducted trial of the type I describe here would give us an excellent estimate of the "efficiency of regeneration". I'm really guessing about the "efficiency of the generator" in the Leaf, I'd be interested if anyone has any data on this.

Cool project!