Tesla confirms Model 3 will have less than 60kWh battery option

[Yanquetino]

It would be interesting to see how that list becomes re-ordered by these factors, because that would reveal the relative efficiency as far as EV tech.

Okay... as you wish. Here is the same comparison table, but with a new column for curb weight, sorted from heaviest to lightest:

In general it appears that, when an EV's curb weight drops below 3,000 lbs., its EPA energy efficiency rating starts to exceed 3.5 MPkWh. IF that pattern holds true, to achieve a whopping 4.267 MPkWh, the Model 3 with a 75 kWh pack would need to weigh at least 35% less than a Model S 75D. As I said, that would be an amazing level of efficiency.

Hope this helps!

 

[Cyclone]

LA Times reported in 2014 that over 25% of Tesla buyers were transitioning from a Toyota manufacturer car, most were Prius models, so this makes sense.

Many of us finally have the ability to get a Tesla.

I came from a 4Runner than would get about 350 miles on a tank.

 

[zenmaster]

IF that pattern holds true, to achieve a whopping 4.267 MPkWh, the Model 3 with a 75 kWh pack would need to weigh at least 35% less than a Model S 75D. As I said, that would be an amazing level of efficiency.

For some reason I was using a longer range value for the 75D than your table indicated. Was also considering the the Model 3 weighing roughly 25% less at 3500lbs.

 

[stopcrazypp]

As we all know, miles-per-kWh is the key factor to speculate about battery size and range. Perhaps it would be helpful to compare the MPkWh of the current EVs on the market. This table lists the EPA results, lowest to highest:

There is one major problem with this chart. It describes nominal capacity, not usable capacity. This would not matter if all EVs used the same usable percentage, however this is far from the case. For example, the 2015 i3 has a usable capacity of 18.7kWh out of 22 kWh (85% usable). This bumps your MPkWh (usable) number to 4.325.

Tesla uses a 95% usable capacity (for example 4kWh brick protection out of 85kWh pack).

 

[SageBrush]

We cannot escape physics. If all else is equal, more battery weight will increase drag and the proportional increase in weight for more battery will be more than the proportional increase in range.

 

[zenmaster]

We cannot escape physics. If all else is equal, more battery weight will increase drag and the proportional increase in weight for more battery will be more than the proportional increase in range.

The drag will be a function of speed rather than weight.

 

[SageBrush]

The drag will be a function of speed rather than weight.

The drag equation:

m*g*CRR + 0.5*Rho*CdA*v*v

In metric
m: mass in Kg
g: gravity
RR: tyre rolling resistance in Kg/tonne
Rho: density of air in Kg/meter cubed
Cda: cross sectional area in meters squared
v: velocity in meters/second

 

[zenmaster]

The drag equation:

m*g*CRR + 0.5*Rho*CdA*v*v

In metric
m: mass in Kg
g: gravity
RR: tyre rolling resistance in Kg/tonne
Rho: density of air in Kg/meter cubed
Cda: cross sectional area in meters squared
v: velocity in meters/second

That equation would be the *total* forces operating against the moving car, in addition to drag force, which is indicated by 0.5*Rho*CdA*v*v.

 

[SageBrush]

You say toe may toe -- which is WRONG. It is Toe mah toe

Drag is drag, and not just aero drag. FWiw though, the equation does not include mechanical drag. Just aero and road.
Back to the point: increased battery weight will increase drag and e.g. a 20% increase in useable battery will not be a 20% increase in range unless other changes to the car improve mechanical efficiency or reduce one of the other variables in the drag equation.

Physics

 

[zenmaster]

Drag is drag, and not just aero drag.
Physics

You're simply misusing the term "drag" to somehow include separate or orthogonal resistive forces. These forces indeed additive, and are important when considering the power required to overcome, but they are not all considered "drag". In case you want more info on the drag force in particular:
Drag (physics) - Wikipedia, the free encyclopedia
And more info here:
Automobile drag coefficient - Wikipedia, the free encyclopedia

 

[Topher]

The benefit of range is for road trips where you wouldn't have to stop multiple times instead of just 1 in 500 miles. These stops add hours.

Two stops of 20 minutes is not longer than 1 at 40 minutes. And quite frankly, I can't drive anywhere near that far without stopping.

Further, to get any decent range on the Model S, you must drive much slower than traffic.

Nonsense as stated.

Thank you kindly.

 

[MP3Mike]

Two stops of 20 minutes is not longer than 1 at 40 minutes. And quite frankly, I can't drive anywhere near that far without stopping.

It is if you assume it takes ~7 minutes to get to/from each stop. Making your total time to charge and get going again 68 minutes vs. 54 minutes. Depending on charger location it can be better, or much worse than that.

 

[zenmaster]

Two stops of 20 minutes is not longer than 1 at 40 minutes. And quite frankly, I can't drive anywhere near that far without stopping.

This is getting ridiculous. In my car I stop 1 time to fill up on a 500 mile trip. That stop takes about 7-10 minutes, for a total trip time of 7hrs 25 minutes.

In a Model 90D, I'd use 154.3 kWh and have to stop for 2 hours for a total trip time of 9 hrs, 21 minutes.

Nonsense as stated.

Every 5 mph over 65 reduces your range by 15-20 miles. If you drive at normal traffic speeds at 80mph, guess what happens to the range?

 

[Topher]

It is if you assume it takes ~7 minutes to get to/from each stop. Making your total time to charge and get going again 68 minutes vs. 54 minutes. Depending on charger location it can be better, or much worse than that.

And if you assume that there is good shopping at both stops, it will be much higher.

So, saving 14 minutes per road trip is worth $13k?

Thank you kindly.

 

[Topher]

Every 5 mph over 65 reduces your range by 15-20 miles. If you drive at normal traffic speeds at 80mph, guess what happens to the range?

Nope. Power goes as velocity *cubed*, not linearly.

Thank you kindly.

 

[zenmaster]

Nope. Power goes as velocity *cubed*, not linearly.

You can draw a line through the curve and that's basically what you get for that limited range of speed.

 

[Cyclone]

In my car I stop 1 time to fill up on a 500 mile trip. That stop takes about 7-10 minutes, for a total trip time of 7hrs 25 minutes.

Which works for you. I cannot drive like this. On a recent trip from Charlotte to Greenville (90% -> 50% range on my S), I had to stop partway through for a bio break and to stretch my legs. The S didn't need to stop, but I did.

Two months ago I had to drive an ICE from Miami to Charlotte. I did the drive non-stop in 11.5 hours. I've done the same trip in my S, non-stop (once, most of the time I plan an overnight) and it took me just over 14 hours. Yes, longer, but I was in much better shape at the end of my S drive vs. the Lexus drive because of the breaks.

 

[zenmaster]

Which works for you. I cannot drive like this. On a recent trip from Charlotte to Greenville (90% -> 50% range on my S), I had to stop partway through for a bio break and to stretch my legs. The S didn't need to stop, but I did.

Two months ago I had to drive an ICE from Miami to Charlotte. I did the drive non-stop in 11.5 hours. I've done the same trip in my S, non-stop (once, most of the time I plan an overnight) and it took me just over 14 hours. Yes, longer, but I was in much better shape at the end of my S drive vs. the Lexus drive because of the breaks.

You're actually making an argument that because the recharging time may also happen to afford the driver a long break time, there is no disadvantage from the imposed delay? The longest I would stop in that distance would be once, for about 45min (to eat). How long does it take a person to stretch? I'm not going shopping or something when I'm on my way to a vacation destination.

My 500-mile numbers were taken from here: EV Trip Planner for a trip from Atlanta, GA to Cocoa Beach, Fl. This is assumed to be accurate. I encourage anyone to simply see how long the trip must take and if you would really otherwise stop for that long for a "break".

 

[SageBrush]

Definitely something to think about if you drive long trips daily.
A couple times a year ? Who cares

And certainly for me, a 15 minute break for every 2-3 hours of driving on a loonnng trip sounds like a VERY GOOD IDEA (tm)
No Pulmonary Embolism, and I arrive at my destination somewhat less toasted.

 

[wdolson]

Okay... as you wish. Here is the same comparison table, but with a new column for curb weight, sorted from heaviest to lightest:

In general it appears that, when an EV's curb weight drops below 3,000 lbs., its EPA energy efficiency rating starts to exceed 3.5 MPkWh. IF that pattern holds true, to achieve a whopping 4.267 MPkWh, the Model 3 with a 75 kWh pack would need to weigh at least 35% less than a Model S 75D. As I said, that would be an amazing level of efficiency.

Hope this helps!

I think estimates for the Model 3's weight are around 3900 pounds. It's not going to be a light car.