[EVphoto]

I have a 2021 Bolt. I am a hiker and backpacker that loves the Eastern Sierra Nevada; however I live in the San Francisco Bay Area. This means there are mountains to be crossed.
I have done some tests to measure the impact of elevation on range. The challenge is the number of variables: speed, rate of climb and even number of sharp curves.
After numerous tests in the Bay Area doing 1000+ ft climbs where speeds averaged between 25 and 40 mph, I have concluded that 1 additional kWh is needed for each 600 ft of gain; and that descent results in about a 55% capture of spent energy. So for trip planning with Plugshare (which shows the elevations of a trip), in addition to the kWh's for distance traveled, I add on 1 kWh for every 500 ft of gain.

What have others experienced with elevation impact? And how do you plan for it?

 

[AJ-ptmdy]

I can suggest the app ABRP (a better route planner) as a good tool for estimating battery energy needed for the mountain route segments. The elevation changes, assuming the roads are known to whatever mapping this app uses, are included in the app's estimate. The variables of the EV make and model, battery degradation, usual speeds, ambient temps, rain-or-snow -- these are all settings in this app, for the particular trip being planned.

Before I knew about the app ABRP, I had used my desktop PC and Google Map to check my planned highway/road routes for total amounts of elevation gains and total descents. The bicycle option in GoogleMap, being sure to keep the route on the highway (not some alternate paths), shows the elevation totals for the up and for the down. I used basic physics to calculate the battery energy in kWh to lift the Bolt 1000 meters, assuming the Bolt plus some passengers and cargo as a total 2000 kg. Raising a 2000 kg weight 1000 m increases its potential energy about 5.5 kWh and to do that work the Bolt needs to deliver that energy at the tire-road interface. Assuming about 20 percent losses for the dc-to-AC conversion, motor losses, and some more drivetrain loss, I added a guesstimate of 20 percent. This means 1.2 x 5.5 = 6.6 kWh of battery energy was my estimate just for the raising by 1000 m. I would add that to the flat-road energy needed to drive the km of distance. This 6.6 kWh for 1000 m gain is not far from EVphoto's 1 kWh for each 500 foot gain.

Initially I was then estimating the "credit" for the total descents by thinking that the descent was giving back the potential energy, but with some losses and so the energy going back into the battery could be guesstimated as 20 percent less than the basic 5.5 kWh, or an amount 4.4 kWh per 1000 m of descent. Recently I realized that during the descent this assumed 20 percent loss would be reasonable only if the descent was so steep and the speeds such that the driver's screen actually shows some kW of power going into the battery. Most likely the slope and speed (at least at highway speeds) would be such that the forward travel power is more than this "descent power", so the driver's screen still would show that power is going from the battery toward the drivetrain. In that circumstance, the descent energy that the Bolt (plus cargo) is giving back is all going toward reducing the energy needed to drive the Bolt along the road. My observation then is that the Bolt's mass is directly contributing to pushing the car forward on the downward slope, and so reduces the power needed from the battery, by that full amount. Therefore I really should have given the descents the full credit at a value of 5.5 kWh per 1000 m of descent. I realize that there are variables like actual weight of Bolt plus its load, and the road surface, but these estimates did seem to be reasonable, even when I was still doing the descent's credit with my first (false) guesstimate for the descents.

This physics exercise was interesting even without much ability to test my guesstimating, and it did give me the comfort for my mountain highway trip planning in my first years of Bolt driving. Now, I would just use the app ABRP and with experience on my usual highway routes, that provides enough confidence. Also, in recognition that my usual mountain highway routes do not have DCFCs closely spaced, I use a strategy of arriving at a DCFC with enough left to reach the next DCFC station.

 

[greendave]

I have a 2021 Bolt. I am a hiker and backpacker that loves the Eastern Sierra Nevada; however I live in the San Francisco Bay Area. This means there are mountains to be crossed.
I have done some tests to measure the impact of elevation on range. The challenge is the number of variables: speed, rate of climb and even number of sharp curves.
After numerous tests in the Bay Area doing 1000+ ft climbs where speeds averaged between 25 and 40 mph, I have concluded that 1 additional kWh is needed for each 600 ft of gain; and that descent results in about a 55% capture of spent energy. So for trip planning with Plugshare (which shows the elevations of a trip), in addition to the kWh's for distance traveled, I add on 1 kWh for every 500 ft of gain.

What have others experienced with elevation impact? And how do you plan for it?

It's really quite variable, dependent on speed and grade. For example, going up Old Priest Grade from Moccasin to Groveland is a gain of ~1,400 feet, but only required 1.5kWh. But the distance is short - 1.8 miles - and the speed slow.

For the trip you're doing, I can say that if you drive reasonably (basically the speed limit), getting from Oakdale to Bridgeport via Sonora Pass requires ~65% charge, i.e. if you charge to 80% in Oakdale, you'll arrive with 15%. You can always slow down though if things are getting tight. The return trip is much easier.

I wouldn't both going via Tioga Pass. First, you need a reservation to drive through Yosemite 6AM-4PM. Second it's slow (always get stuck behind some RV). Third, there's no fast charging between Bridgeport and Bishop, so you'll likely have to make a detour to one or the other if you're going anywhere between Lee Vining and Bishop.

If you have specific routes in mind, feel free to ask. I've been going out to the eastern Sierra with the Bolt since fall of 2019, before Bridgeport and Bishop even had fast charging...

 

[Sean Nelson]

...I have concluded that 1 additional kWh is needed for each 600 ft of gain...

That's in the same ballpark as the figure I use: 2kWh per 1000 ft. I figure that's a conservative number (i.e., unlikely to get me into trouble for being overly optimistic about how far I can go).

 

[Paul Gipe]

I recently did a test run to Tehachapi from Bakersfield with our new battery. ABRP's estimate was right on the money with highway speeds and 3,500 feet of elevation gain. The GOM is still adjusting since the advent of the new battery.

Paul

 

[jefro]

Takes a ton of energy to lift a Bolt up a hill. You can't recover that. I drive up a long steep hill and the best I can use is 1-2kWh on gauge. Going home I only recover 2/10th or point 2 of a kWh. The slope is ended with another rise that takes all my gain.

Route planners like the GM and others try to include it.

 

[XJ12]

What have others experienced with elevation impact? And how do you plan for it?

Welcome to the forum. Definitely ABRP mentioned above. I had a trip a couple years ago where I had to go through the mountains with about 2,500 feet of elevation change. Before I hit the peak, the car's range estimate was saying I wouldn't make my destination. But I knew better because I had planned the first leg using ABRP and eventually I would be going down hill after the peak. Worked out great. Here's a graph from ABRP of that run through the mountains. Shows state of charge starting at 100% with an estimate of 16% if I averaged 43 mph.

 

[AZBILL]

I have done the trip from Phoenix to Flagstaff, 153 miles and 6000ft elevation change, with my Bolt and with my Mach E. Both cars lost 10% range as compared to flat highway driving. ABRP was way off for both cars, way too pessimistic. The Chevy energy tracker was about 5% pessimistic with respect to arrival SoC.

 

[redpoint5]

Takes a ton of energy to lift a Bolt up a hill. You can't recover that. I drive up a long steep hill and the best I can use is 1-2kWh on gauge. Going home I only recover 2/10th or point 2 of a kWh. The slope is ended with another rise that takes all my gain.

Route planners like the GM and others try to include it.

The Bolt is using that energy pretty efficiently unless the hill is so steep the friction brakes are engaging.

Takes a ton of power to overcome aerodynamic forces at higher speeds. Just because the battery isn’t charging up a lot doesn’t mean that energy isn’t largely being utilized.

Elevation change shouldn’t affect range much unless your starting point and ending points are differing elevations.

 

[jefro]

Find a long uphill road. Track the power at base and then track the power from peak back to base. The Bolt isn't a perpetual machine. There is a lot of loss. I live in a hill country area and I've monitored my use on two EV's over the last 4+ years. Maybe my hills are more energy stingy?

 

[redpoint5]

All theoretical and anecdotal for me.

With an ICE, hilly terrain tends to be more efficient than flat travel, but only if minimal brake use is required.
Of course, the shortest distance between 2 points is a straight line, so hilly terrain is a longer distance than if there were no hills.

 

[Sean Nelson]

With an ICE, hilly terrain tends to be more efficient than flat travel, but only if minimal brake use is required.

HA! You obviously don't live here in mountainous British Columbia with our steep, 2-lane, twisty highways. Brake use is mandatory, not legally perhaps but for anyone without a death wish...

 

[Martin D]

I have done the trip from Phoenix to Flagstaff, 153 miles and 6000ft elevation change, with my Bolt and with my Mach E. Both cars lost 10% range as compared to flat highway driving. ABRP was way off for both cars, way too pessimistic. The Chevy energy tracker was about 5% pessimistic with respect to arrival SoC.

My observations are the same as Bill’s. Going up will use 10% more than you can regenerate when you go back down.

I see a similar result in the acceleration/deceleration cycle. The power consumed in attaining a cruising speed will be mostly returned upon decelerating back to zero.

But the use of friction brakes with no regeneration is a 100% loss.

 

[EVphoto]

It's really quite variable, dependent on speed and grade. For example, going up Old Priest Grade from Moccasin to Groveland is a gain of ~1,400 feet, but only required 1.5kWh. But the distance is short - 1.8 miles - and the speed slow.

For the trip you're doing, I can say that if you drive reasonably (basically the speed limit), getting from Oakdale to Bridgeport via Sonora Pass requires ~65% charge, i.e. if you charge to 80% in Oakdale, you'll arrive with 15%. You can always slow down though if things are getting tight. The return trip is much easier.

I wouldn't both going via Tioga Pass. First, you need a reservation to drive through Yosemite 6AM-4PM. Second it's slow (always get stuck behind some RV). Third, there's no fast charging between Bridgeport and Bishop, so you'll likely have to make a detour to one or the other if you're going anywhere between Lee Vining and Bishop.

If you have specific routes in mind, feel free to ask. I've been going out to the eastern Sierra with the Bolt since fall of 2019, before Bridgeport and Bishop even had fast charging...

Thanks for the information. You are traveling on the same roads as I. I too prefer the 108 Sonora pass route. Have you ventured into Eureka Dunes from Bishop? It looks easy in terms of energy but i am concerned about road condition, especially clearance?

 

[EVphoto]

I have done the trip from Phoenix to Flagstaff, 153 miles and 6000ft elevation change, with my Bolt and with my Mach E. Both cars lost 10% range as compared to flat highway driving. ABRP was way off for both cars, way too pessimistic. The Chevy energy tracker was about 5% pessimistic with respect to arrival SoC.

Interesting data. I have done that drive too but with an ICE. Good to hear that ABRP was conservative; better than too optimistic.

 

[greendave]

Thanks for the information. You are traveling on the same roads as I. I too prefer the 108 Sonora pass route. Have you ventured into Eureka Dunes from Bishop? It looks easy in terms of energy but i am concerned about road condition, especially clearance?

Good question. I've actually never taken Death Valley road south from 168/Big Pine, though I've passed it many times. I can ask my friend who took his Forester out there last year for details, but from what he said, the road was pretty poor. Even if clearance isn't an issue, you'd definitely want a spare tire.

(In 2018, I took an ICEV with no spare to Bristlecone Pine Forest. We made it, but it was a nervous experience. Another vehicle in our group - a pickup truck in fact- did get a flat.)