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Using more energy than expected downhill. Trip Planner underestimating energy use.

Having some issues with energy use while going downhill. I have had my Model 3 (2018 LR AWD, 18" w/ aero covers) for just over 2 years. At first, I would be able to match or beat the trip planner. I put a set of DWS06 tires on it and started to notice an increase in energy use when doing the long downhill into CA, but I chalked it up to not having the eco-focused tires. I recently put on a set of the OEM MXM4 tires and had an alignment done at the SC where they got it dialed in to factory specs. I am still using way more energy downhill than the trip planner is estimating.

On a recent drive from Truckee, CA to Sacramento, CA (starting at about 5,800ft to donner pass at 7,100 to Sacramento at 100ft or so) I used about 50% more energy than the trip planner estimated (elevation shows nearly 10% more SOC used than expected). I started the drive in Reno, NV and supercharged in Truckee, so I had a warm battery. No regen limit dots, tire pressures 42-44, speed mostly around 70, 75 once closer to Sacramento, and almost all on autopilot. I have done this drive many times and ever since that first tire change I have been having this issue regardless of season, weather conditions, or speed. I have included a picture of the trip planner at the end of my drive and you can see that it really starts to deviate during the downhill portion when the car was expecting the SOC to increase or stay about the same (starting at mile 10 or so and becomes very pronounced around mile 30).

It is strange because I can get fairly close to the estimate during level or uphill driving, it is just going downhill where I begin to deviate from the planner. I also want to note that I have the wheel settings in the car computer set to 18" without aero covers which should be planning on more energy use in general.

Any ideas on what might be causing this? It is making long road trips harder with the increased energy usage and the uncertainty of how much to charge up at the superchargers.
 

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KenC

Active Member
Sep 4, 2018
4,869
4,642
Maine
One, it's a new feature, and so it may not yet be optimized. Two, I too have noticed the elevation figs aren't quite spot on, but I'm looking at just hills, not thousands of feet of elevation drop. I'm using more energy due to elevation than I expected.

Having said that, you drove 99 miles, even with a lot of elevation drop, you only used 26.8%, which is still very good. Do you know what your normal usage would have been at your speed?

The projected estimate is around 13%, 75% down to 62%. For 100 miles, even with elevation drop, that seems a bit insane. Just punching in some figs into ABRP, it says you should use about 24.8kWh, 242Wh/mile, so about 33% SOC. Your 26.8% looks better than ABRP's estimate. It's the elevation projection that seems to be screwing things up.

One more thought, the elevation estimate shows you got -13.9%, so you added ~42miles of range by going down a mile in elevation. According to the car's estimate, you should have saved 23.2% going downhill or ~70miles! That seems like a lot to save by going down from Donner Pass.
 
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One, it's a new feature, and so it may not yet be optimized. Two, I too have noticed the elevation figs aren't quite spot on, but I'm looking at just hills, not thousands of feet of elevation drop. I'm using more energy due to elevation than I expected.

Having said that, you drove 99 miles, even with a lot of elevation drop, you only used 26.8%, which is still very good. Do you know what your normal usage would have been at your speed?

Even with the old energy app it would be the same story. Before the first tire change the trip planner would be spot on with the estimate. I used to be able leave Reno at 90% and get to Sac with around 65%. That's about the same battery use but with 35 extra miles and starting at 4,500ft instead of 5,800ft.

I attributed the increased energy use at first to the other tires I had on it, but now with OEMs and a fresh alignment I am thinking it might be something else causing this.
 
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Even with the old energy app it would be the same story. Before the first tire change the trip planner would be spot on with the estimate. I used to be able leave Reno at 90% and get to Sac with around 65%. That's about the same battery use but with 35 extra miles and starting at 4,500ft instead of 5,800ft.

I attributed the increased energy use at first to the other tires I had on it, but now with OEMs and a fresh alignment I am thinking it might be something else causing this.
downhill Usage should be at or near zero 50% more than that isn’t much, has regen felt different? Tires properly inflated? Alignments are an art not saying yours is wrong but it may be a place to start since downhill uses no energy and that’s where you place your issue at.
 
Also want to add that I use ABRP and the reference consumption updates itself as I drive. When I first got the car, the reference consumption was pretty stable at around 200 wh/mi @65 mph, the DWS06 tires fluctuated between 225-235, and now with the MXM4s it is 260(!!)

I am not a new owner and have put about 30k miles on the car and am familiar with how speed, temperature, wind, etc. affect the range. I am not expecting to get the rated range but wow my efficiency right now is pretty poor and it's crazy to me to use more than twice what the car is estimating and what I used to use in the past.
 
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downhill Usage should be at or near zero 50% more than that isn’t much, has regen felt different? Tires properly inflated? Alignments are an art not saying yours is wrong but it may be a place to start since downhill uses no energy and that’s where you place your issue at.
Regen hasn't felt different. I got the spec sheet after the alignment at the service center and all the measurements are dead center or very very close to what they should be.
 

ucmndd

Well-Known Member
Mar 10, 2016
10,194
20,033
California
1) It's cold. It's also been very windy with the recent storms blowing in. When was this trip, what were the weather conditions? A good headwind would easily account for your observation, even driving downhill.
2) Expect the MXM4s to have significantly higher energy consumption for the first 1,000 miles or so. How recently did you put them on?
 
Much already stated but the newer software now looks at temperature, winds (headwind, tailwind) number of passengers, change in elevations. On older model 3 is regenerative braking on? Also tire pressures (I prefer 2 PSI ABOVE factory setting). Projected energy usage is looking at speed limit for calculation then adjusts as you drive to what you are actually doing. This is why on long trip if driving above limit estimated remaining percentage will keep dropping. Conversely, if reduce to say 2 MPH below lint, arrival percentage starts increasing. If you drive continuously above limit and the arrival percentage remaining drops below a certain threshold, a popup message will appear saying "reduce speed to XX to make next charging stop (or destination). I have noticed with the new feature of integrated braking with regenerative braking (to give same regenerative feel at or near 100% and lower charge level) there won't be any regeneration dots BUT the green line of generation once it extends to a certain point will be gray. I presume this mean no regeneration is taking place but the brakes are being applied to simulate the same result. This feature can also be switched off in one of the settings.

From release notes on 2022.40.4.1 "Your vehicle can now automatically apply regular brakes for consistent deceleration when regenerative braking is limited due to battery temperature or state of charge. To enable, tap Controls > Pedals & Steering > Apply Brakes When Regenerative Braking Is Limited."

I'll add this as a maybe - have you done the annual brake service? It is primarily for winter climates but part of it is removing corrosion from the brake caliper guide pins and lubricating. Perhaps a brake is not fully releasing and dragging?
 
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Much already stated but the newer software now looks at temperature, winds (headwind, tailwind) number of passengers, change in elevations. On older model 3 is regenerative braking on? Also tire pressures (I prefer 2 PSI ABOVE factory setting). Projected energy usage is looking at speed limit for calculation then adjusts as you drive to what you are actually doing. This is why on long trip if driving above limit estimated remaining percentage will keep dropping. Conversely, if reduce to say 2 MPH below lint, arrival percentage starts increasing. If you drive continuously above limit and the arrival percentage remaining drops below a certain threshold, a popup message will appear saying "reduce speed to XX to make next charging stop (or destination). I have noticed with the new feature of integrated braking with regenerative braking (to give same regenerative feel at or near 100% and lower charge level) there won't be any regeneration dots BUT the green line of generation once it extends to a certain point will be gray. I presume this mean no regeneration is taking place but the brakes are being applied to simulate the same result. This feature can also be switched off in one of the settings.

From release notes on 2022.40.4.1 "Your vehicle can now automatically apply regular brakes for consistent deceleration when regenerative braking is limited due to battery temperature or state of charge. To enable, tap Controls > Pedals & Steering > Apply Brakes When Regenerative Braking Is Limited."

I'll add this as a maybe - have you done the annual brake service? It is primarily for winter climates but part of it is removing corrosion from the brake caliper guide pins and lubricating. Perhaps a brake is not fully releasing and dragging?

Thanks, I didn't realize it needed the annual brake service. I will try that this weekend and see if it improves at all. It could be that it's dragging just enough where I don't really notice it under load but it could make a difference on the downhill regen. We do get some snow and colder temperatures here in the winter and it probably hasn't been done in the 4 year life of the car.

I don't have the integrated braking with regen feature turned on.
 
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Thanks, I didn't realize it needed the annual brake service. I will try that this weekend and see if it improves at all. It could be that it's dragging just enough where I don't really notice it under load but it could make a difference on the downhill regen. We do get some snow and colder temperatures here in the winter and it probably hasn't been done in the 4 year life of the car.

I don't have the integrated braking with regen feature turned on.
When they do the service (about $65 when Tesla mobile does it) you can examine and measure the brakes pucks. See if equal or if one unusually worn.
 
I *think* the estimate uses your very recent consumption as a reference in its estimate. Recently I had to speed up considerably to get rid of an annoying driver on the highway just a few miles before stopping at a supercharger. The estimate for the next leg required a surprising SOC to me but I charged as it suggested. As I suspected, while driving the estimate at arrival continuously went up. I left the SC with a 4-5% arrival SOC to arrive with more than 12% at home. Flat terrain. The estimates were almost spot on for all the rest of that 1400 mile trip.
 

KenC

Active Member
Sep 4, 2018
4,869
4,642
Maine
Also want to add that I use ABRP and the reference consumption updates itself as I drive. When I first got the car, the reference consumption was pretty stable at around 200 wh/mi @65 mph, the DWS06 tires fluctuated between 225-235, and now with the MXM4s it is 260(!!)

I am not a new owner and have put about 30k miles on the car and am familiar with how speed, temperature, wind, etc. affect the range. I am not expecting to get the rated range but wow my efficiency right now is pretty poor and it's crazy to me to use more than twice what the car is estimating and what I used to use in the past.
The efficiency was ~200Wh/[email protected] on the OEM tires?!? Wow, that's amazing. I think mine was about 235Wh/mi. I switched to the Vredestein Quatrac5 and it was the same.
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,807
11,501
Boise, ID
When I first got the car, the reference consumption was pretty stable at around 200 wh/mi @65 mph, the DWS06 tires fluctuated between 225-235, and now with the MXM4s it is 260(!!) [...] but wow my efficiency right now is pretty poor
As a longtimer, it still amazes me how far we've come in efficiency. We are discussing figures like 260 Wh/mile being "poor", when it's not unusual for me to average about 360 on my old 2014 Model S during some of the year.
 
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Hah, I can do better than that. My average for the 3 years I've had the car is 328wh/mile, January this year was 484wh/mile. LR AWD 2020 Model 3 :cool:

EDIT: And I don't find that wrong, my car isn't broken...
I think we are getting too focussed on miles/WH and range, Agreed these are relevant parameters, but we also need to enjoy our drive, just like ICE folks who never measure their range after every trip.
 
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SageBrush

REJECT Fascism
May 7, 2015
14,153
19,667
New Mexico
Interesting story.
The energy graph lines do appear to diverge on the downhill portions. If you have 'Scan my Tesla' you will be able to monitor the regen power and recouped energy. I would not think twice about this if a single event but if it the new behavior of the car then either there is more friction than usual or (less likely) the regen is impaired.
 

KenC

Active Member
Sep 4, 2018
4,869
4,642
Maine
Having some issues with energy use while going downhill. I have had my Model 3 (2018 LR AWD, 18" w/ aero covers) for just over 2 years. At first, I would be able to match or beat the trip planner. I put a set of DWS06 tires on it and started to notice an increase in energy use when doing the long downhill into CA, but I chalked it up to not having the eco-focused tires. I recently put on a set of the OEM MXM4 tires and had an alignment done at the SC where they got it dialed in to factory specs. I am still using way more energy downhill than the trip planner is estimating.

On a recent drive from Truckee, CA to Sacramento, CA (starting at about 5,800ft to donner pass at 7,100 to Sacramento at 100ft or so) I used about 50% more energy than the trip planner estimated (elevation shows nearly 10% more SOC used than expected). I started the drive in Reno, NV and supercharged in Truckee, so I had a warm battery. No regen limit dots, tire pressures 42-44, speed mostly around 70, 75 once closer to Sacramento, and almost all on autopilot. I have done this drive many times and ever since that first tire change I have been having this issue regardless of season, weather conditions, or speed. I have included a picture of the trip planner at the end of my drive and you can see that it really starts to deviate during the downhill portion when the car was expecting the SOC to increase or stay about the same (starting at mile 10 or so and becomes very pronounced around mile 30).

It is strange because I can get fairly close to the estimate during level or uphill driving, it is just going downhill where I begin to deviate from the planner. I also want to note that I have the wheel settings in the car computer set to 18" without aero covers which should be planning on more energy use in general.

Any ideas on what might be causing this? It is making long road trips harder with the increased energy usage and the uncertainty of how much to charge up at the superchargers.
So, just another comment. As I don't have a lot of experience with these long downhills, but is it normal for the car to have used net zero miles between mile 8 and mile 85? Or is it even possible to regenerate so much SOC, to go from about 67% at Mile 32 to peak at about 73% at Mile 52?
by default 2022-11-16 at 2.36.57 PM.jpg

Just looking at the elevation/SOC chart in ABRP, it shows some short flat SOC stretches, around the Mile 8-10 area, and even some short sections that actually gain some SOC, like Miles 20 and 25 and Mile 45, but these gaining SOC sections tend to be no more than a few miles, and are the steepest drops on your trip. So, I'm still wondering if the elevation estimate of Tesla's latest software is just overestimating things.

As I mentioned in my first post, what drew me to your post was the fact that I have noticed some odd elevation figs in the latest software, where it always says I'm using too much energy due to elevation. My elevation changes are quite modest around my area, and I'm having a hard time understanding how I should be doing better, so I naturally assumed the software's elevation estimate is wrong.

Just looking at ABRP's estimate compared to your actual, it looks pretty good. Starting at 75%, it drops to 44% at the finish, where you ended with 48%. Maybe, I had your speed wrong, as I used 108% of limit; otherwise, ABRP's estimate looks good.

I mean, your comment seems like your estimate issue began 2yrs ago, when you had your first time change?
 
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