P3D+ 250 mile range with non-aggressive driving

[Daniel in SD]

Same energy different power. Yes I agree. I think people trying that "hyper-mile" by feel are at most just inadvertently going slower, losing aero losses on the way up and then starting slow at the top again. Might as well just go slower 100% of the time, perhaps saving even more energy.

edit - but you didn't put a unit for drag. Energy or power, it matters. Power is cubed.

The unit for drag is force. Energy consumption due to drag is proportional to speed. It takes twice as much energy to travel twice as fast (assuming you’re traveling the same distance!). The power draw is quadrupled but of course it takes half the time.

 

[khraiv]

All companies that sell vehicles in the US have to be certified by the EPA. Tesla isn't over-inflating numbers, they're relying on a system (as is everyone else) that can't cover all real world driving conditions.

Take it up with the EPA.

The issue has nothing to do with EPA rating. Tesla knows your actual usage, it knows where you're going, and routes you to various superchargers based on EPA data instead of the actual data it knows. It's an opportunity for improvement in future software updates.

 

[Glamisduner]

On my volt I get better efficiency popping it into neutral and letting it accelerate downhill than I do letting it regen downhill when on the freeway. Every time you transfer energy there is a loss in heat, so it would only make sense that this is the case. I only do this on long downhills where my acceleration will won't be too far over the speed limit and there are no cars in front of me going slow.

If you have to stop or slow though, regen is FAR better than braking, but just rolling in neutral is actually better (so long as you never brake).

Can you do this in the model 3?

 

[clostridium]

Sure if you slow down going uphill it will be more efficient. It would also be more efficient to drive slow downhill. However it will take longer to reach your destination! It is optimal to go a constant speed to minimize loss. Unless you're using regen on the downhills, then it's better to go a little faster downhill since the regen has loss.

You kind of mixed things together in your reply. I wasn't saying to drive slower on the downhills, I was suggesting that you allow the car to go faster which you mention is a good thing vs. using regen but then you go back to saying constant speed is best. Note that cruise control would use the regen and then brake to maintain the speed you selected on those downhill runs. Which is wasteful.

Level roads no traffic - constant speed is best so cruise control is best
Up and downhills - accepting variance in speed to make best use of car's momentum is best choice which means cruise control isn't always best.

The car is going to slow down and waste the conversion of potential energy into kinetic energy on downhill runs if you use the cruise control on hills.

 

[Xenoilphobe]

The 20s with summer tires will also reduce range

 

[clostridium]

The faster you drive the faster you get there. While you might need to stop more often, you will spend less time charging because you will be charging at a higher rate due to a lower state of charge.

Actually this is a lot more complicated than you've made it out to be. You are right that driving faster gets you there faster but it also causes energy consumption to go up faster than the linear decrease in the time it takes to get there. You are also right that the car charges faster on a supercharger at lower SOCs. The interaction of the two is what matters. There is a tradeoff in traveling speed vs. charge time that can be calculated for different EVs.

Here is an older example of this for the Model S that I picked because it specifically looked at what happens with different SOCs because that impacts supercharging rates so much (i.e. charging from 10->40% is much faster than 50->90%), I couldn't find it for the Model 3:
Driving & Charging Time

Arriving with lower SOCs results in a higher optimum traveling speed.

The Model 3 seems to charge to a higher SOC before tapering off when supercharging which leads me to believe that the curve will be shifted and it would favor faster travel more than the S but I don't know how much. If anyone can find that information please share.

 

[chronopc]

Actually this is a lot more complicated than you've made it out to be. You are right that driving faster gets you there faster but it also causes energy consumption to go up faster than the linear decrease in the time it takes to get there. You are also right that the car charges faster on a supercharger at lower SOCs. The interaction of the two is what matters. There is a tradeoff in traveling speed vs. charge time that can be calculated for different EVs.

Here is an older example of this for the Model S that I picked because it specifically looked at what happens with different SOCs because that impacts supercharging rates so much (i.e. charging from 10->40% is much faster than 50->90%), I couldn't find it for the Model 3:
Driving & Charging Time

Arriving with lower SOCs results in a higher optimum traveling speed.

The Model 3 seems to charge to a higher SOC before tapering off when supercharging which leads me to believe that the curve will be shifted and it would favor faster travel more than the S but I don't know how much. If anyone can find that information please share.

This thread has good discussion on the topic. The conclusion is that for the Model 3 the faster you drive the less time it takes to get to your destination taking into account the time it takes to charge.

Ideal travel speed in RWD?

 

[clostridium]

This thread has good discussion on the topic. The conclusion is that for the Model 3 the faster you drive the less time it takes to get to your destination taking into account the time it takes to charge.

Ideal travel speed in RWD?

As far as I can tell they didn't take into account the supercharger taper in this calculation. So this approach is valid for the part of the supercharging curve that is pretty flat up to about 50%

This post starts with a nice demonstration of the curve:
Supercharger speed: 116kW

In their example it took 15 minutes to get from ~5% -> 46%
Then 25 more minutes to get from 46% -> 79%

So assuming that a maintained constant supercharging rate is only valid in the first half of the battery.

 

[chronopc]

As far as I can tell they didn't take into account the supercharger taper in this calculation. So this approach is valid for the part of the supercharging curve that is pretty flat up to about 50%

This post starts with a nice demonstration of the curve:
Supercharger speed: 116kW

In their example it took 15 minutes to get from ~5% -> 46%
Then 25 more minutes to get from 46% -> 79%

So assuming that a maintained constant supercharging rate is only valid in the first half of the battery.

Yes, but if you're trying to get there faster you don't want to charge fully. You want to take advantage of the faster speed you get when you have a lower SOC. So you would want to make more stops and charge to a lower %.

 

[chinnam3]

There are times on autopilot where you will be behind a car going below the speed limit then that lead car will give way. AP will then quickly accelerate to the set speed which will hurt your range efficiency.

Not only because of how aggressive EAP accelerates and decelerates, but also consumes some more energy to put complete steering effort for constant adjustments and processor effort (however small it may be).

Ofcourse assuming we maintain similar speeds with EAP vs without EAP. EAP does not see to far to take advantage of gradual slow downs. For example it will accelerate fast to gain set speed and apply hard braking to slow down behind a car, Where as we generally don't accelerate in that scenario as we know car is stopped ahead and/or light is red.

I for certain gotten better range than EAP when I drive conservative (ofcourse same speed).

 

[clostridium]

Yes, but if you're trying to get there faster you don't want to charge fully. You want to take advantage of the faster speed you get when you have a lower SOC. So you would want to make more stops and charge to a lower %.

If wherever you are going there is enough of a charging infrastructure that you can charge every ~140 miles and those chargers are at most a few minutes off the road you are traveling then driving super fast and charging often will be the winning strategy.

If even one of those isn't true it's not a winning strategy.

 

[chronopc]

If wherever you are going there is enough of a charging infrastructure that you can charge every ~140 miles and those chargers are at most a few minutes off the road you are traveling then driving super fast and charging often will be the winning strategy.

If even one of those isn't true it's not a winning strategy.

Definitely true. Driving up and down CA where there are a ton of supercharger locations, this strategy is great.

 

[VLTWGGN]

Glad someone made a thread for this. My beautiful P3D+ has averaged 295Wh/mi in its first 1000mi. On long highway stretches I'll be looking at 310Wh/mi at 75mph, but in stop/go traffic, I've never achieved less than 254Wh/mi.

 

[Daniel in SD]

You kind of mixed things together in your reply. I wasn't saying to drive slower on the downhills, I was suggesting that you allow the car to go faster which you mention is a good thing vs. using regen but then you go back to saying constant speed is best. Note that cruise control would use the regen and then brake to maintain the speed you selected on those downhill runs. Which is wasteful.

Level roads no traffic - constant speed is best so cruise control is best
Up and downhills - accepting variance in speed to make best use of car's momentum is best choice which means cruise control isn't always best.

The car is going to slow down and waste the conversion of potential energy into kinetic energy on downhill runs if you use the cruise control on hills.

What I meant is that if you're not using regen it's best to go a constant speed up and down hills because it minimizes aerodynamic losses. The efficiency of the drivetrain is pretty much constant so there is no additional drivetrain loss by doing this. If the downhills are steep enough to be using regen then it's a much more complicated problem. It's definitely better to go faster downhill then but how much faster would require calculating the additional aerodynamic losses vs. the regen losses vs. how much slower you can now go uphill with the time you saved downhill.
It would be fun if someone wrote an app to tell you the optimal speed at each point in a route vs. travel time.

 

[Daniel in SD]

If wherever you are going there is enough of a charging infrastructure that you can charge every ~140 miles and those chargers are at most a few minutes off the road you are traveling then driving super fast and charging often will be the winning strategy.

If even one of those isn't true it's not a winning strategy.

I was playing around with abetterrouteplanner and it looked like the optimal speed was greater than 100mph for a Model 3LR from here (San Diego) to Seattle. So, driving slowly definitely doesn't save time if you can use the supercharger network.

 

[SageBrush]

The car is going to slow down and waste the conversion of potential energy into kinetic energy on downhill runs if you use the cruise control on hills.

Exactly.

I don't know why this is so hard for some people to understand.

 

[UnknownSoldier]

Just to go back to @khraiv's original point... The data he saw is exactly aligned with what @Troy published based on the EPA data aligned to just highway driving and not a mix:

Tesla Model S/X/3 range at 65/70/75/80 mph

Looking at that chart, a P3D on 20" wheels doing between 70-75 mph would be expected to have a range of 240-260 miles, which is exactly what @khraiv saw. That car would be expected to have about 25 miles of additional range for every 5 mph reduction of speed (at least down to 55 mph per the chart).


View attachment 330096

Is this chart accurate for P3D- (no PUP) with 18" wheels? I feel like I really dodged a bullet by getting the P3D- instead of the P3D+ if it is because the range difference is absolutely enormous between the 18" wheels (especially if you put the aero caps back on for a road trip) and the 20" wheels. I'm actually surprised it can be such a gigantic difference, what's different between 18" and 20" wheels which change the range so much?

 

[SageBrush]

It's definitely better to go faster downhill then but how much faster would require calculating the additional aerodynamic losses vs. the regen losses

Regen probably loses 40%.
Aero is ~ 50% of total frictions
Figure the sqrt(1.8) = 1.34x speed increase

 

[Knightshade]

On my volt I get better efficiency popping it into neutral and letting it accelerate downhill

FWIW that's actually illegal in many states. Including yours.

California Vehicle Code 21710 states, “The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such a vehicle in neutral.”

 

[lolder]

Efficiency of the whole system drops as current grows. Probably dumping 100kW of heat just inside the battery pack at full tilt.

Not even close to 100 kw. The battery is about 95% efficient so at even 400kw that would only be about 20 kw.