Apps for mileage comparison

[Late2theparty]

Hi there We've had our M3 RWD for about 2 weeks now and just loving it. On my ICE vehicle I track the mileage with an app called Fuelly, I've managed 27.5mpg for over 100,000 in our 2017 Chrysler Pacifica and it's just sorta "how I drive". But with the M3 it's like....what's my mileage? What is this wh/mile? Is there a way to track it or compare it? We got our wall charger installed a few days ago and charged to 100% then went on a drive and coaxed the projected range up to 385 miles, that was kinda fun. Anyway....is there a way to do this? Thanks

Joe

 

[Late2theparty]

Gotta admit, it's tough getting the mileage on the screen. Yesterday we drove 90 miles with a mix of interstate, rural, and city driving and went from 190 mile range to 95 mile range....and I was sorta trying to conserve energy. I'm sure it's possible if we didn't need the A/C and if we drove slower across the board...but still, not easy to match it. Coming out of a store on a hot day and jumping into a cool car has consequences. As does enjoying the incredible acceleration, the quiet ride at 75mph, and a cabin temp of 72 degrees!

Who likes coaxing the max miles from their batteries? Got any tips, apps, or suggestions?

Joe

 

[Konicom04]

It uses a lot of energy for the first few miles.
Long continuous drives will result in much better wh/mile.

 

[zoomer0056]

What is this wh/mile?

First, change your battery reading to show % instead of range in miles. Wh/mi is what you're interested in minimizing, its the way with an EV. Track it using the trips screen in your car. Rename trip B to lifetime and never reset it. Then use Current Drive, Since Last Charge and Lifetime to track usage. You can also search TMC for Wh/mi and you will get more than you wanna know. Many many threads on this subject.

 

[joebruin77]

There are third party apps that show what I believe you are looking for. For example, I use and recommend Stats: For Model s/x/y/3. This app shows you all sorts of stats, including your average MPGe. You can find it in both the Apple App Store and the Google Play Store.

 

[WhtLghtning]

Tessie will show your "real world" range based on how you drove over the last 30 days. Works very well.

 

[Late2theparty]

Checking our Stats and Tessie now, thanks Also switched Trip B to lifetime so that's super helpful too. Finally, the wh/mi search has yielded a ton of stuff.

I got the hitch mounted to the car today and put two bikes on a tray style hitch mounted carrier. Drove a little under the speed limit, still ended up about 10% over on miles so the car coming off of the back of the car really matters!

One quick one....so as you all know these cars accelerate super fast right? If you accelerate from 0 to 60 fast or slow....why does it take more total energy to go fast? Shouldn't it be the same? I mean...more power but less time so total energy to get the mass up to speed is the same. But it's not. What am I missing here?

Joe

 

[WhtLghtning]

Accelerating quickly requires more energy than accelerating slowly

 

[Late2theparty]

Yes...but why? You spend less time accelerating if you do it quickly. Why doesn't it cancel out the increased energy?

 

[zoomer0056]

Yes...but why? You spend less time accelerating if you do it quickly. Why doesn't it cancel out the increased energy?

I know it takes more energy, it's taught in high-school. I asked ChatGPT to explain it for you.

ChatGPT
When accelerating more quickly, you're essentially changing your velocity over a shorter period of time. This requires a higher force to be applied, which in turn demands more energy according to Newton's second law of motion (F=ma). The increased force and energy expenditure are needed to overcome inertia and reach the desired acceleration rate promptly.

 

[dafish]

I would call chatgpt a fail.

OP:

the answer is time. Efficiency drops at greater power outputs. In particular when the front motor is called for. Since you want more force in less time you must sacrifice efficiency. Were that not the case you would be correct, they should be equal

and yes, Tessie. Data downloads would let you maintain as much history as you wanted too

 

[Late2theparty]

I would call chatgpt a fail.

OP:

the answer is time. Efficiency drops at greater power outputs. In particular when the front motor is called for. Since you want more force in less time you must sacrifice efficiency. Were that not the case you would be correct, they should be equal

and yes, Tessie. Data downloads would let you maintain as much history as you wanted too

Ah so maybe it's about efficiency? As in when we have two situations that result in the same total power expenditure (accelerating the same mass to the same speed just over different times) that the high power/short duration situation is less efficient than the low power/long duration? That would make sense. However....I thought with electric motors the efficiency was about the same high or low power? Or maybe pushing a large amount of power creates heat or something and that's where the loss happens?

 

[Late2theparty]

The amount of energy is, in fact, the same. Let's go with a 10kg mass from 0 to 20 meters/second (about 45mph) and let's accelerate it at 10m/s2 and 5m/s2. It's not f=ma we need to use, it's how much kinetic energy do we need to put into the mass to get it to 20m/s? That formula is E=1/2mv2 and it doesn't matter how long it takes to get there, it's the same amount of energy.

Now the power isn't the same....just like the time isn't the same. Power is energy/time so first let's calculate the energy E=1/2mv2 so 1/2 X 10 X 20E2 = 2,000 joules.

Now the time....velocity = acceleration X time so time = velocity/acceleration = 20m/s / 10m/s2 = 2 seconds at 10m/s2. It's 20m/s / 5m/s2 = 4 seconds at 5m/s2 so that makes sense, 2 seconds to get there at 10m/s2 and twice as long or 4 seconds at 5m/s2.

Back to power....Power=2000J/2seconds=1,000 watts for 2 seconds to get to 45mph at 10m/s2 and
Power = 2000J/4 seconds = 500 watts for 4 seconds to get to 45mph at 5m/s2

Now....with the 4s acceleration at 5m/s2 you have an average speed of 10m/s or about 22mph. With the 10m/s you have an average speed of 17.5m/s or 39mph. So I'm thinking maybe that's the difference....not in energy to get up to speed but it takes more power because when you accelerate fast you are simply averaging a higher speed. And maybe (?) some efficiency losses too.

Joe