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1000+ Wh/mi readings in early driving

1000+ Wh/mi readings in early driving

Hello all,

I'm getting extremely high consumption numbers over the first few minutes of my drive. It usually regulates if I get on the highway, but I live in NYC so the highway isn't always an option.

By high energy, I mean 1000+ Wh/mi to start. That slowly (sometimes very slowly) creeps down to 500 Wh/mi, and eventually regulates to +/- 200 Wh/mi once I'm going 50mph or more. I am very aware of the factors that affect energy, and I'm not abusing any of the known culprits:

- I'm often going <30 mph, and rarely drive over 70 on the highways around NYC.
- A/C fan is usually on 2. I still get high readings when A/C is off (I've tested it all)
- I get these readings regardless of whether or not I pre-condition the cabin temp.
- I'm not accelerating in an aggressive way
- My tire pressure is perfect, approximately 48psi as recommended

I've read every forum and watched every video I could find (within reason), and I haven't seen anyone with this particular problem. A consumption surge of 1400 Wh/mi when I'm driving 20 mph with no A/C just isn't normal.

I have a two year old in the car, and I need to know that my energy readings are reliable and that my battery isn't malfunctioning in a potentially dangerous way.

No snarky comments, please. I understand the basic science of the car and the physics of driving. :)

r1200gs4ok | 30. juli 2019

I just noticed this on Monday.......started out and was 975 wh/mi.....could nit believe my eyes....pulled over and looked at every setting....all the same from the previous day....outside temp was 70F and overcast....dont know what is happening.....have a mobile service scheduled for Thursday...will ask them

CST | 30. juli 2019

Pre-cooling the car?

jdcollins5 | 30. juli 2019

AC load when cooling down a hot car. I see it every time I start the car in the summer. Same thing for heat in winter.

Bighorn | 30. juli 2019

Normal. Small denominator issue. I’ve seen 8000 Wh/m after driving off with AC on in the driveway. Has always been the case.

Bighorn | 30. juli 2019

And please don’t occupy service with a normal car

RoadDevil | 30. juli 2019

Likely there is upward slope at the beginning, you may not notice it, but it plays a big role in energy efficiency, especially in a short period of time span you pay attention to, I suggest that you test by start in opposite direction , and read the efficacy after driving the same distance and or time to see it still give you high reading

kutoroff | 30. juli 2019

Same observation on hot days, but if you go to the Energy display showing 15 mile average all is well.

wiscy67 | 30. juli 2019

I usually start the day about 1200 Wh/mi as I leave the 'hood but it quickly comes down to low 200's after a mile or two. Nothing to worry about.

Bighorn | 30. juli 2019

It's just an artifact of starting energy divided by a small denominator. Nothing to see here.

Joseb | 30. juli 2019

Where are you seeing this? is this the energy app? If it tries to calculate it real time, yeah is pointless (i.e. what does it show in a very long down hill? like -50 Wh/mi?)

I only use the trip computer (the one you swipe from bottom left)

Bighorn | 30. juli 2019

@jluis
If you have your trip card up, you see efficiency starting at 0.1 miles into your trip.

wiscy67 | 30. juli 2019

I use the trip meters and not the energy app. The trip meter for current trip and Last charge are the main two I use. The current trip shows the high values right out of the gate but quickly equalizes.

CRAIGJFIFTY3 | 31. juli 2019

Bighorn has it right. It’s watthours per mile. When you get in the car it starts using energy, but you haven’t covered any ground. By the time you get moving, you’ve used a few watthours. When you start moving you use high amounts of energy, but the display won’t show the results until you reach .1 miles. Just ignore the early readings.
I seen it start as high as 1800wh/mile. Can’t wait to see what happens this winter using the heating.

Lorenzryanc | 31. juli 2019

something something math. If 30 min in your above 400 in the Summer, I'd say there MAY be an issue. Winter will be higher so if this is your first upcoming winter, you'll see about 50-75 kw/hr higher than summer. Heat is a (relatively) big drain. I have a hill coming out of my development and I like to floor it to see how high I can get. It lasts for about 30 seconds before I come back to 220-280.

Techy James | 31. juli 2019

I see those readings when I first start with the drive of the day. Especially after pulling out of driveway and start going. I think it's simple physics here. After sitting the car is prepping the battery along with going from stop to moving which is also the point any vehicle regardless of source of energy uses the most to get car moving. But they always drop even if not leaving town speeds of 25-35 mph.

h2ev | 31. juli 2019

That's just the way it is, until it averages out over a longer distance. Regen plays a huge role to average out your wh/mile figure.

My drive out of my subdivision is about a 1 mile drive. The wh/mile figure will be about 1000 when I get out of the house and reach the top of the hill, about 1/4 mile. By the time the road flattens out, it'll drop to about 400 after about 1/2 or so. And then comes a long downhill, and when I have 100% regen, by the time I reach the bottom, I've seen it go to a negative number, as high as -25 or so, but typically during spring and summer it'll be around 50 wh/mile by the time I get out of my subdivision.

There's nothing wrong with your car. It's just NYC driving, with no long stretch for regen until you get to highway speeds.

andy.connor.e | 31. juli 2019

When i start my gas car, the average mpg of my trip starts out at about 3mpg as i back out of my driveway. When i get to work, its at 38mpg or higher.

Bighorn | 31. juli 2019

Everything has an outsized effect in the first mile because of the short distance (small denominator), including regen. Over the course of a longer trip, not so much, including regen. Losing altitude is where gains are derived, with or without regen.

hokiegir1 | 31. juli 2019

Short distances usually have low efficiency. It takes a lot of energy to get 4000 pounds rolling in any direction, but less to maintain it once it's going. Usually, this will level out over 5-10 miles (depending on how much "stop" is in stop and go traffic).

charles.a.braun | 31. juli 2019

You mean like this: https://drive.google.com/file/d/1bgS4Axy0GAxImlTlAr1ZJzQBzNiEA7XB/view?u...

Just a normal day and me just trying to get out of my parking garage at work. No excessive HVAC use.

Usually I am in the 900s but for some reason (no abnormal conditions) on this day I exceeded 2000. I thought it was interesting so I took a picture.

andy.connor.e | 31. juli 2019

Ya, thats because you traveled 0.1 miles in 4 minutes. Like everyone has been saying, when you start the numbers will be absurd. As you travel further they will even out.

charles.a.braun | 31. juli 2019

I understand the reason for the high number. What I thought was curious about 2,333 was that I have parked in the this parking garage and usually in the same exact parking spot now approximately 350 times in my 19 months of ownership. Of those 350 times I have generally noticed about 900 Wh/mi. Well with 1 exception, which is the picture I took.

Every time, including this 1, of course the numbers leveled out as I made the 50-75 mile drive home, depending on my chosen route.

Bighorn | 31. juli 2019

@charles
Your car was on for 4 minutes before you traveled a tenth. Whatever energy you consumed in that time is factored in. A sum total of 233W, so something drawing about 3 kW. Like I’ve said, I’ve seen 8000 Wh/m after the air ran a few minutes before departure.

IHaveArrived | 31. juli 2019

Are you starting out in reverse? I see high consumption rates in reverse.

johnw | 01. august 2019

Perfectly normal. I get this from time to time as well when first driving, but my overall wh/mile in the summer are less than EPA even though I'm a lead-foot.

gmr6415 | 01. august 2019

I've noticed the same, but what I notice at the same time is driving only a mile or two, yet losing 3 or 4 miles off of the battery indicator in that distance. The beginning energy usage seems to be catching up with some of the capacity loss from when the car was sitting still, which in my case is most likely battery cooling while sitting in the sun.

The battery indicator doesn't show tenths, so you can lose a mile pretty quickly once you start moving. "IF" that's being accounted for in your energy graph calculations that's going to result in an initial higher than actual Wh/mi usage.

Secondly if you are pulling off after the car has been sitting overnight the motor and gear box are still relatively cool as compared to normal operating temperature. I've read that the lube in the Tesla gear box is ATF. ATF is much more dense at moderate to low temperatures than at operating temperature, so it may be 90˚ outside but the gear box has overnight temperature saturation, and it will maintain those temps (while parked) much longer than the rest of the car simply because it's close to the ground and shaded.

As a result, no matter how hot it is outside if the car has been sitting long enough for the gear box to cool down after the last use you are going to use a lot more energy propelling the car until the gear box lubricant reaches operating temperature and the viscosity becomes less dense.

https://ibb.co/H49zTWx

majassow | 01. august 2019

You can even see this effect with the climate off:

Ke = 1/2 mv^2

Getting the car up to 75mph takes about 300Wh of energy (that gets added to your normal Wh/m consumption due to friction losses), and becomes kinetic energy.

Assume it takes you 1 mile to go from 0 to 75mph, and your normal Wh/m reading is 300 at a constant speed, then you would see about double that, or 600Wh/m. If you get to 75mph faster (and in a Tesla, 75mph in one mile is considered sedate :-)), then you'll see higher Wh/m numbers. You'll see this any time you start from park and accelerate to high speeds.

The good news: most of this kinetic energy is recoverable through regen, and why the numbers will drop back down when you arrive at your destination.

Try this science experiment at home: Find a freeway with on/off ramps about a mile apart. Turn off climate and reset your trip meter while stopped prior to the on-ramp. Accelerate to 75mph (observing all traffic laws, people!), note Wh/m reading. It should be 2-3x normal (depending on how much lead in your foot).

Get off freeway and come to a complete stop, using all regen. Note the final reading. It should be relatively close to your "normal" Wh/m numbers.

Your daily physics lesson is over.

andy.connor.e | 01. august 2019

Most people never understood just how inefficiently they drive. Now that their car is telling them, they think something is wrong with the car. Definitely not your driving habits, must be the manufacturer.

majassow | 01. august 2019

andy: seeing those instantaneous high Wh/m numbers is not necessarily an indication of driving efficiency. Just physics. For example: you can probably achieve 75mph from a standing start in about 0.1 miles. It takes a little over 300Wh to do that (Ke of 300Wh + average friction for 1/10th mile, for grins, lets say 30Wh). So 330Wh per 0.1 mile. The display will display 3300Wh/mile since it just divides your current consumption by the current distance.

But when you slow down via regen, you get 90+% of the Ke back in battery charging, negating most of the inefficiency. Much of the observed inefficiency in lower Wh/m from driving aggressively comes from either: 1) more use of physical brakes, or 2) higher average speed (where wind resistance is an efficiency killer)...

gballant4570 | 01. august 2019

Don't cycle service. Get to know your car instead. When I leave my house, I see anywhere from 1200 to 1600 wh/m at the onset. I go down a 2.5 mile hill, and the number can go negative. Its a very simple 5th grade math kind of thing.

andy.connor.e | 01. august 2019

Ya i mean this really isnt a new thing. If you ever owned a car that tells you your trip average mpg, it always starts off low. When i get to the end of my driveway, im running 2mpg. At the end of my first road about half a mile, its at 15mpg. But when i get to work about 10 miles, its always over 38mpg.

ReD eXiLe ms us | 01. august 2019

This whole conversation reminds me of the people who insisted there had been a Year 0 A.D. twenty years ago. They wer unconsolable and could not be reasoned with.

Bighorn is always right.