Ascending mountains in the Leaf

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DungenessLeaf

Member
Joined
Jun 6, 2017
Messages
20
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%.
 
Potential energy (in joules) = m*g*h

m: mass in Kg
g: 9.8
h: net elevation change in meters

kWh = joules / 3,600,000

As a practical matter potential energy is conserved (so long as you avoid slowing down with brakes or regen.)
 
Can you try the same thing with other electric car brands also? :). I just want to know how Leaf's regen is compared to others.

If I buy a Volt in the future, I want to drive it while my wife follows me with the Leaf. Going to the same places at the same speed and (hopefully almost the same) amount of braking. Then I want to compare the regen of both. Someone in this forum said regen of Volt is much better than Leaf. That's why I am curious.
 
It appears from the data that losses due to regenerative charging is minimal, and it was charging all the way down the mountain. Most of the battery energy used to lift the car 4000 feet was returned to the battery on the way down, less the energy to move the car those miles as the loss in the regenerative charging system appears very small. The trip of 70 miles used 82% battery which is about right if it were on level ground at the speeds we travelled.
 
DungenessLeaf said:
It appears from the data that losses due to regenerative charging is minimal, and it was charging all the way down the mountain. Most of the battery energy used to lift the car 4000 feet was returned to the battery on the way down, less the energy to move the car those miles as the loss in the regenerative charging system appears very small. The trip of 70 miles used 82% battery which is about right if it were on level ground at the speeds we travelled.
Regen is quite lossy -- probably around 50%
Your increase in range on the GOM was from not using more juice on the way down. The GOM averages out the Wh/mile consumption rate since the last charge.

If you monitor the batery SoC you can confirm my suspicions.
 
Regen in our 2011 LEAF worked great when the car and battery pack were new, but at ~28% capacity loss, the regen is pretty lame now. With a warm battery at a relatively low state of charge, the regen isn't too bad. But if we charge to 60 - 80% SOC and then want to drive down "our" mountain, we end up having to use the conventional friction brakes quite heavily, which leads to warped rotors and obviously hurts efficiency and brake life. And in cold winter weather, it doesn't matter how low the SOC is, the regen is severely limited.

That's a big reason we don't generally drive the LEAF all the way down the mountain anymore; we just use it locally, between the various mountain communities in our area where the elevation changes are smaller and gentler.

The central issue is that the LEAF's battery pack, in terms of degradation and capacity loss, is arguably the least robust among all of today's production EVs. Early LEAFs were the worst, but even the newer 30 kWh battery seems to have degradation issues. I truly hope that Nissan's planned switchover to using LG Chem batteries will play a role in solving this for LEAF 2.0.

In addition, it seems that the LEAF's software is restricting regen more than necessary on degraded batteries. When we plug into a CHAdeMO quick charger (haven't done so in months, I admit), our charge rate is limited somewhat, but not nearly to the degree that regen is limited. Charging is charging, so why should regen be limited more than CHAdeMO charging?
 
abasile said:
I truly hope that Nissan's planned switchover to using LG Chem batteries will play a role in solving this for LEAF 2.0.
I read that the deal with LG Chem fell through; Nissan continues to use the same factory for supply and I don't get the impression the owners are investing much in battery R&D these days. I'm pretty certain they continue to use the +/- original Li-x chemistry
 
Which trim level of the Leaf do you have? Are you using the B-MODE going down the hill? The 2013 S and 2014 S does not have B-MODE. On 2013 and 2014, only SV and SL has the brake mode.
 
drhlee1 said:
Which trim level of the Leaf do you have? Are you using the B-MODE going down the hill? The 2013 S and 2014 S does not have B-MODE. On 2013 and 2014, only SV and SL has the brake mode.
Yes but on a S model the ECO mode initiates much stronger REGEN than non ECO. Note on Leafs prior to '13 none had the B mode, just ECO which like the S models has stronger regen than non ECO mode.
My '12SL down 2 bars basically has no REGEN, even with ECO on :( OTH my full bar '13S in ECO gives me all bubbles of regen on all but single digit temps and below and high SOC(>95%) when I lose a bubble or two.
 
I use ECO mode and the brakes going down the hill, since our car is too old to have B mode. Still, even with B mode, you're limited by how much regen the car's software will allow.
 
We have an SV with re-gen. I was comparing the battery percent, not the range which is computed based on what it expects on how you have been driving. That is why when we arrived at the trail at 4000 feet, it estimated the range at 8 miles. It was thinking... "if your going to drive some more like this, your only going to get 8 more miles". It was probably right but turned around and went back down and it started to think, "OK, if this is what your going to do, we think you can go much more on the remaining energy". I think the range meter does a good job.

If the re-gen would have a lot of loss, the energy would have to be dumped somewhere as heat. I suspect it is very efficient, just as much as the battery driving the motor. Let's not guess, but try to find the Nissan data. Remember, if it was 100% efficient, you would get all the energy back, minus what it took to drive the car at that speed over that distance. Our numbers were very close to that.
 
I don't know specifics for the LEAF but I've read and calculated for the Prius and the Tesla Model S. The absolute highest number ever seen is 65% regen.

I stand corrected on one point though: you mentioned SoC in your OP so presuming that the numbers on the display are accurate, you did indeed have regen.

Addendum:
I think I can convince you that the display is inaccurate ...

To recap your numbers:
Start at 100% SoC
SoC at 74% at start of climb
SoC at 22% at peak
SoC at 38% after descent
SoC at 18% back home after 70 miles

You can add specific numbers, but for now I'll presume 20 kWh charge with a full battery, and the car+passengers+luggage was 1650 Kg
The 4000 ft climb then is 5.5 kWh potential energy, so 5.5/20 = 27.5% of your total battery energy
Driving the 16 miles down the hill would have required about 16% if level terrain, leaving 11.5% left over to put in the battery at 100% efficiency and an unachievable maximum SoC of 33% after the descent.
 
Interesting. But note... it was 8 miles up and 8 miles down. In 8 miles we went from 22 to 38 % SoC. On the way down there were times when the re-gen meter was pegged at +30 kW.
 
Then I have to recalculate; but first, I'm confused how you ended up with 70 miles total trip ?
(19 miles to the start of the ascent + 8 miles up the mountain) * 2 = 54 miles

Addendum:
8 miles each way on the mountain makes the display numbers even more fishy
If you start the ascent at 74%
Use 27.5% for the climb
Consume 8% to travel 8 miles on level terrain
End up with 22% at the top,
Then 74-27.5-8-22 = 16.5% that is missing somewhere.
 
I can only compare my 2011 Leaf (with new battery at 100% SOH) against my Gen 2 Volt on a road I drive fairly frequently for work: To Mount Wilson and back. My experience has been that the regen in the Volt, in addition to being much stronger, is also more efficient with a larger percentage of energy returned to the pack... YMMV.

oko said:
Someone in this forum said regen of Volt is much better than Leaf. That's why I am curious.
 
Regeneration is more effective on my 2015 with 2 year old battery and almost 43,000 miles than on my 2011 immediately after the battery was replaced. Regeneration is quite efficient because there would be a lot of heat generated in the battery and power electronics if there were significant energy losses.

What is often overlooked is that the losses to move the car at a given speed on the level are present when going up hill and when going down hill. This means that you will never get as much energy into the battery going down hill as it took from the battery to go up the same hill. Going up hill requires the energy representing the change in potential energy plus losses for level driving. Going down hill yields the energy representing the change in potential energy minus the losses for level driving. At 100% efficiency for driving under load and regeneration, the net energy delivered from the battery is two times the energy required to move the car the one way distance on the level at the given speed.
 
Sorry that my first numbers were confusing and wrong. Here is the Google Earth actual distances.

Total one way from house to trailhead 33.5 miles. So that is 67 miles and I rounded up to 70 because of a slightly different route, but it was not as much as I thought. So let's keep it at 68 round trip.

But oops, my error was in the climb distance. The one way distance was 14.8 miles which is from the Visitors Center (150 feet elevation) to Switchback trail (4,444 elevation). So 19.2 level, 14.8 climb, 14.8 descend, 19.2 level.

Between my house and the Visitors Center, there are quite a few climbs and decent of 20 to 30 feet which I am ignoring.

We had three people in the car, a spare tire, and some automotive sediment... about 575 pounds.
 
oko said:
Can you try the same thing with other electric car brands also? :). I just want to know how Leaf's regen is compared to others.

If I buy a Volt in the future, I want to drive it while my wife follows me with the Leaf. Going to the same places at the same speed and (hopefully almost the same) amount of braking. Then I want to compare the regen of both. Someone in this forum said regen of Volt is much better than Leaf. That's why I am curious.

Regen on my Leaf in B mode seems to be limited to around 28kW under ideal conditions. I frequently still use friction braking for limited periods in my daily commute.

Regen on my Volt in L is limited to 60kW. It is rare to need that much regen except when coming to a stop on a downhlll interstate offramp. More typical amounts I've seen are in the 40kW range in normal hilly driving.
 
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!
 
eatsleafsandshoots said:
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!

I am hoping to test this idea out to see how far I can get. I am looking at a journey from Colorado Springs up to Cripple Creek and back. I saw someone else posted they could do that trip in the Leaf so I want to give it a try. However my car is older and doesn't have the fresh new battery that the original poster had at the time. So I am curious if I can make that trip.

As a side note: I see the city of Cripple Creek has a public charging station for the city, and there is a casino there that also has a charging station, but only for customers. Only gambling I intend to do is the drive up there to see if I can make it and then make it back! LOL I looked to see if anyone had posted any reviews on the charging station there, but I don't see anything. So we don't know if the charger is actually there, actually works etc. But I would like to make the attempt and see how far I can get. That is a huge climb from the Springs up there. I might chicken out
by the time I get to Woodland Park. But as others have noted, the drive back down should be a piece of cake balancing regen and coasting on the way back down.
 
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