Maximum Regen - Can Someone Top This?

[Polly Wog]

I've posted a few times about how much regenerative energy I get in my Model S when I descend Haleakala here on Maui, but today I gained a bit more than normal. During the 35 mile drive from the summit (10,000 feet elevation) to the point where the road essentially flattens out (about 100 feet elevation or thereabouts), I gained 9.0 kWh and 31 rated miles. I went from 98 rated miles at the summit to 129 at the base. I'm curious if any other owners have come close to that figure. If so, where and how much? I've attached a few pictures documenting it.

 

[Bullet1]

That's amazing. Bet your trip up showed all red!

I was planning a downhill run on one of our large ranges but it won't top yours as the decent will be max 4000ft. Only way I could beat that is get a tow behind a truck.

 

[FlatSix911]

Well done!

 

[Polly Wog]

...Only way I could beat that is get a tow behind a truck.

Yes, but that would be cheating!

 

[tstafford]

That's awesome!

 

[Brass Guy]

The most I've seen in a single stretch is 15 miles gained, heading east to Sheridan, WY. I don't see mountains often. That was my first trip far enough away to experience RM increase.

Curious - what to you think is the cause of your power restriction in the first photo?
Judging by the SOC and exterior temp (neither low enough), my guess is you recently arrived at the summit using a lot of power for an extended time, and the motor's hot.

Edit - I just looked up Mt. Washington, probably the biggest close mountain to me. The auto road has an elevation change of about 4600 feet, so I won't be challenging your feat any time soon.

 

[msnow]

I've posted a few times about how much regenerative energy I get in my Model S when I descend Haleakala here on Maui, but today I gained a bit more than normal. During the 35 mile drive from the summit (10,000 feet elevation) to the point where the road essentially flattens out (about 100 feet elevation or thereabouts), I gained 9.0 kWh and 31 rated miles. I went from 98 rated miles at the summit to 129 at the base. I'm curious if any other owners have come close to that figure. If so, where and how much? I've attached a few pictures documenting it.

View attachment 193614 View attachment 193615 View attachment 193616

Do you think it had anything to do with a firmware update?

 

[Skotty]

Note the trip info in both pictures ... it's kind of interesting to look at. 541 Wh/mi up, balanced out to 293 after coming back down. -254 Wh/mi coming down (note the negative), which is rather remarkable. Much better than a gas car in this instance.

 

[AudubonB]

That's terrific. I'm pretty sure those Coloradans who have done the Mt. Evans climb will weigh in on how much they are able to gain back.

 

[Ti3034]

Impressive.

Does the 31 degree increase in outside temperature to 87 degrees effect the estimated range?

 

[SageBrush]

Note the trip info in both pictures ... it's kind of interesting to look at. 541 Wh/mi up, balanced out to 293 after coming back down. -254 Wh/mi coming down (note the negative), which is rather remarkable. Much better than a gas car in this instance.

That's terrific. I'm pretty sure those Coloradans who have done the Mt. Evans climb will weigh in on how much they are able to gain back.

My napkin arithmetic says that potential energy down the mountain (using 2600 kg mass) is ~ 22 kWh. Since level driving at low speeds is around ~ 5 kWh over 30 miles the regen efficiency works out to a rather amazing 14/22 = 63.5%

Addendum: arithmetic corrected

 

[ChadS]

Places like Pike's Peak and Mt Evans are taller, but their prominence is only, like, half that of Haleakala. So I would think it would be very tough to top Polly Wog.

That said, there are other elements. It is possible, say, that D cars have more regen than non-D. It also matters how steep the roads are and how fast you descend - if you end up having to use brakes for traffic or turns, or hit wind resistance due to high speeds on a straight, you won't get max regen. And of course it depends on your regen setting.

When I did Pike's Peak I seem to recall that I regained about 30 miles on the way down, but I didn't take pictures or write it down so I could be mistaken.

 

[ibdb]

I think that Polly Wog is in the perfect location to maximize regen. Nowhere else in the world has such a significant elevation change in such a short distance. The twists and turns and generally low speed limits also help.

I know I got some significant regen coming down from Mt. St. Helens, but I didn't track it. I would think that visitors to Mt. Rainier would also do very well on the way back down the park. Most other locations I can think of just can't compete with Haleakala for total elevation change.

 

[Morristhecat]

I have driven Haleakala in a rental car a couple of years ago not long after I first bought my S, and at the time I wondered about how it would work with the S in regen. Thanks for posting.

A few weeks ago I did a similar drive up Meadows in the Sky Parkway, in Revelstoke BC. I recall reaching the top and my wife was asking me if we needed to stop by the nearby supercharger before we go to the hotel, as she noticed our state of charge was quite low compared to when we started. I told her I expect to regain a good chunk of our charge on the way down, and sure enough we did. I think it was about 60km in range that we gained or so... Just checking my TeslaLog trip details of the trip, I have it logged out below. It isn't quite the 10,000ft of Haleakala, but it is 6,000ft of similar switchbacks. In the Trip Stats, the log data gets lost at about 1500m (5000ft) I believe due to loss of 3G signal to the mothership, but you can imagine an interpolation of the data before it gets picked up again on the way down. You can also see on the map where the 3G signal got lost and the road continues up the mountain. Interesting data nonetheless.

 

[aesculus]

Most other locations I can think of just can't compete with Haleakala for total elevation change.

The ideal place is one with the largest slope that does not exceed the regen brake capability. Not sure what that is. And any hairpin turn that forces you to apply the brakes would hurt your efficiency too. If I remember, Haleakala has plenty of those. But if you came down the mountain at a speed that never required you to touch the brakes on those turns, no problem.

 

[aesculus]

over 30 miles the regen efficiency works out to a rather amazing 14/22 = 63.5%

I am not following the math. Where did the 14 come from?

I thought the recovery (purely from elevation gain/loss and no wind resistance, rolling resistance, temp or other factors) was more like 89%.

 

[SageBrush]

I am not following the math. Where did the 14 come from?

9+5
9 kWh added to battery
5 kWh used for level road, low speed driving over ~ 35 miles

 

[CmdrThor]

I have averaged -496 Wh/mile, but over a shorter distance. Only about 6 miles, ~2000 ft elevation drop.

Oh, and it was in my Model X towing a 3,000 lb trailer

 

[Polly Wog]

Do you think it had anything to do with a firmware update?

@msnow, I don't believe so at all. I was stuck behind a Forest Ranger and had to go slower than normal for about 8 miles, which I know helped a bit. Also, I hit green lights on the lower portion of Haleakala Highway (you know, the parts where you can "legally" go 55 mph), which rarely seems to happen for me.

@Brass Guy, the car had "cold soaked", if you can call it that, for about 10 hours, so the outside temperature is indeed the reason for the restriction at the top. It went away within about 2 miles, though.

 

[Polly Wog]

@aesculus, I actually made it down just over 27 miles before I had to touch the brakes for the first time. I've driven down enough times now that I seem to be pretty good at knowing when to take my foot completely off of the accelerator pedal in order to make the hairpin turns without using the brake, or flying out of my lane!