[Gtdude]

I’m new to the EV game. Wondering what has the biggest impact on efficiency other than the obvious things like tires, weight, and driving habits. Does running heat and a/c have a significant impact? I know about the drive modes, but just curious how much or little cutting down on normal driving functions impacts an EV.

 

[O. horridus]

I think the biggest thing that's under your control is speed. Aerodynamic drag increases in proportion to the square of the velocity. So if you drive at 70mph instead of 60mph (for example), your speed is 17% higher but your drag is 36% higher (70/60 = 1.17, and 1.17 x 1.17 = 1.36). So small increases in speed can reduce your range by a lot, and small decreases in speed can increase your range.

Anything that increases drag, e.g. bikes mounted on the roof, or towing a trailer, will have a disproportionate effect.

All of this also affects ICE vehicles the same amount, but most people are unaware of it because they don't have a large range readout to reinforce their latent range anxiety.

 

[sciencegeek]

I all depends on the driving situation you're in. Drag matters most at freeway speeds, which is when range also matters the most (because you're more likely to go long distances if you find yourself on the freeway). So I agree with O's comments above. Other things:

Around town (when efficiency matters less because range is less of a concern), i.e. at speeds where drag matters less, your driving style makes a big difference. If you always punch it off the line and brake hard to slow down your efficiency drops a lot.

Going uphill takes a lot of energy (90% of which you'll get back on the way down, assuming same speed). Lifting an R1S with 100 kg of driver and stuff for 1000 ft takes 2.7 kWh, or about 2.15% or your usable capacity of a large battery pack (which I assume to be ca. 125kWh). So if you drive to the mountains from sea level to say Lake Tahoe (ca. 6000 ft) it'll cost you an extra 13% of battery (more if you're loaded up with stuff).

Towing is stupidly expensive.

Resistive heating takes a lot of energy, more than AC. Plus on warm days when you use your AC your battery is also nice and warm, and you have more juice in the tank compared to cold days. In my I-Pace the heater can pull as much as 6kW, though once the cabin is warm it's less than that. But it makes a difference ... one hour of heating at say 4kW is 4kWh, or 5% of my I-Pace's usable battery capacity.

Seat heaters / coolers use a lot less than cabin heat / AC ... almost negligible.

Radio, lights, etc are negligible.

 

[Old Paul]

I’m new to the EV game. Wondering what has the biggest impact on efficiency other than the obvious things like tires, weight, and driving habits. Does running heat and a/c have a significant impact? I know about the drive modes, but just curious how much or little cutting down on normal driving functions impacts an EV.

Recently viewed a YouTube video on an Out of Spec range test on the R1T. Very informative. You may find it helpful.

 

[St00k]

I think the biggest thing that's under your control is speed. Aerodynamic drag increases in proportion to the square of the velocity. So if you drive at 70mph instead of 60mph (for example), your speed is 17% higher but your drag is 36% higher (70/60 = 1.17, and 1.17 x 1.17 = 1.36). So small increases in speed can reduce your range by a lot, and small decreases in speed can increase your range.

Anything that increases drag, e.g. bikes mounted on the roof, or towing a trailer, will have a disproportionate effect.

All of this also affects ICE vehicles the same amount, but most people are unaware of it because they don't have a large range readout to reinforce their latent range anxiety.

Look at this, cars see up to a 28% reduction in fuel economy with a bike rack. That's dramatic.

How Bike Racks Affect a Car's Fuel Economy

To find out how bike racks affect a car's fuel economy, Consumer Reports tested a roof rack and a trailer-hitch rack loaded with two adult-sized bicycles on a 2019 Nissan Altima and a 2019 Toyota RAV4 going 65 mph.

www.consumerreports.org

 

[sciencegeek]

Look at this, cars see up to a 28% reduction in fuel economy with a bike rack. That's dramatic.

Yeah, roof racks really increase the coefficient of drag (and also the surface area by a little).

 

[kizamybute']

Speed, temperature, wind, hills. Drive through 80 degree weather on relatively level freeways and maintain 55-60 MPH (often the flow of traffic in L.A.), and your range will likely be close to EPA figures. However, if you head out to Arizona in winter on a cold night (high 20's or low 30's), dealing with some of the steep hillsides that exist, common desert head-winds and keep up with the common flow of traffic on wide open desert freeways at 80 MPH and you'll likely end up with about 55-60% of the rated range. Slap a trailer on it and you'll be fortunate to make it 100 miles on a full charge. Without the trailer, probably in the 170 to 190 mile range. Likewise, if you end up on a basically level side road in good weather (over 70 degrees) with no wind at a steady pace of around 40 MPH, likely would get in the 400 mile range, without AC on.
Also, per manufacturers, wheel size impacts range. Naturally, if the truck is loaded to capacity, that will impact range too. Tonneau cover open will likely create drag and impact range. Lower ride height on highways will improve range. Using the Heater sucks up A LOT of battery. AC, not quite as bad. Tire pressure. If you go off-roading a lower your pressure down into the 20's or 30's, will adversely impact your highway range versus the recommended pressure at around 48 psi.

The list goes on and on. So many things can impact range. Those are the most common ones. When travelling, I always plan my trips based on about 60% as I'm not one that wants to drive conservatively (hyper-mile). I want to drive like I would in any other vehicle. So, my rule of thumb for long highway trips is around 60% of rated range and I'm usually pretty close.

 

[TessP100D]

I all depends on the driving situation you're in. Drag matters most at freeway speeds, which is when range also matters the most (because you're more likely to go long distances if you find yourself on the freeway). So I agree with O's comments above. Other things:

Around town (when efficiency matters less because range is less of a concern), i.e. at speeds where drag matters less, your driving style makes a big difference. If you always punch it off the line and brake hard to slow down your efficiency drops a lot.

Going uphill takes a lot of energy (90% of which you'll get back on the way down, assuming same speed). Lifting an R1S with 100 kg of driver and stuff for 1000 ft takes 2.7 kWh, or about 2.15% or your usable capacity of a large battery pack (which I assume to be ca. 125kWh). So if you drive to the mountains from sea level to say Lake Tahoe (ca. 6000 ft) it'll cost you an extra 13% of battery (more if you're loaded up with stuff).

Towing is stupidly expensive.

Resistive heating takes a lot of energy, more than AC. Plus on warm days when you use your AC your battery is also nice and warm, and you have more juice in the tank compared to cold days. In my I-Pace the heater can pull as much as 6kW, though once the cabin is warm it's less than that. But it makes a difference ... one hour of heating at say 4kW is 4kWh, or 5% of my I-Pace's usable battery capacity.

Seat heaters / coolers use a lot less than cabin heat / AC ... almost negligible.

Radio, lights, etc are negligible.

Going uphill takes a lot of energy (90% of which you'll get back on the way down, assuming same speed).

no sorry, but you will not get 90% back coming down hill. Not even close.

 

[sciencegeek]

Of the potential energy that is required to lift the weight you will get ca 90% back. Of course you won't get the energy back that you used to travel the associated distance. In other words, if you use 10kWh "extra" to lift the car X number of feet, you'll get about 9kWh back when you drop the car the same number of feet.

 

[ERivTruck]

In this video, the biggest factor for their range would be the tire pressure setting. I thought he said in an earlier video the recommended tire pressure was 48 psi. In this video, he stated he set the tire pressure to 38 psi. Couple that with that they ran with the 20" AT tires and wheels, those would be the biggest hitters for the decreased range on this test.

So in summary, if you want 314 miles, get the 21" aero wheels + tires, maximize the pressure setting, and keep weight and accessories to a minimum. You should be able to get it.

 

[thebishman]

Cold weather will reduce range versus 80dF by 25%-33%; driving into a strong headwind; higher average speeds; towing a trailer; having a roof box on the vehicle; all of the above will reduce the EPA ratings, some markedly.

 

[ColeAK]

Of the potential energy that is required to lift the weight you will get ca 90% back. Of course you won't get the energy back that you used to travel the associated distance. In other words, if you use 10kWh "extra" to lift the car X number of feet, you'll get about 9kWh back when you drop the car the same number of feet.

Not even close if you are talking about regen braking to get used energy from the battery during the uphill back on the downhill. I’ve got 8 years in teslas in Alaska. From my house to “town” I descend ~800’ over about 4 miles and my drive to work is 7 miles top speed 45 mph. In my current model 3 LR most days I average ~325 Wh/mi round trip, use 1-2% driving to work and 4-5% going home. On flat ground same driving type I’m more like 225-240 Wh/mi.

under full regen you at best get 50% back. That is under full force regen. Going down Hatcher pass 2800’ in 15 miles I can gain 1-2% but lose 10-15% going up.

Now from what I find effects range.
Like others have said speed is #1. ICEs tend to be more efficient on the highway. EVs are more efficient around town. In the teslas I can get rated range or better running 55-60 mph. 65-70 10-15% range reduction, 70-75 more like 20-25% reduction.

up hill, like mentioned uphill is a huge hit.

cold weather. I don’t notice any real reduction in cold aside from running the heat. Sunny day clear roads 20F heat off I easily get rated range.

running the heat, It depends. First off EVs never feel warm and cozy inside when compared to an ICE. Keeping the heat set at 60-62F, I don’t notice much of a difference until if gets <0F. <0F like 25%, when it gets down to -20-30F more like 40-50%. But at those temps there are multiple factors contributing. Now if you crank the heat to 70+ Even with temps in the 20’s it can cut range by 25-40%.

headwinds make a large difference. 30-40mph headwind can cut range by 30-40%

snow covered roads. Lose fresh snow can cut range by 50%.

rain, rain that is enough to wet the roads can cut range by 20%. Heavy rain more like 40-50%.

Snowing, loose fresh snow, temps <0F, I’ve had days where I average 900-1000+ Wh/mi. That is like a 75%range reduction.

that said I’ve had teslas in Alaska for 8 years and prior to last November my closest supercharger was >2000 miles from my house. Never run out of battery.

 

[Jhawk]

I’m new to the EV game. Wondering what has the biggest impact on efficiency other than the obvious things like tires, weight, and driving habits. Does running heat and a/c have a significant impact? I know about the drive modes, but just curious how much or little cutting down on normal driving functions impacts an EV.

As a 5+ year Model S owner, my best advice to you is to forget about all the various impacts wind, rain, snow, etc…. can have on the vehicle. Over the long term just count on the vehicle being able to deliver a worry free driving range somewhere around 55-60% of the rated dash range. Yes you will have days that vastly exceed this, but the novelty of plotting a travel course like you’re flying a single prop Cessna really loses its luster over time. I still fall into the trap of looking at the weather conditions all along my route, pushing the limits to see if I can make it and each time I pull into a SC with 5mi on the dash I tell myself I’m never doing it again (and no I have never been stranded).

My wife just did a 650mi round trip route in our Model S yesterday and it took her a little over 14hrs of driving/charging. She too was worried about how much to charge at each SC so I just gave her a list of stops, included the miles to the next SC, and gave her a dash range to charge to that was 40% higher than the actual mileage to the next SC. She made the entire trip with no range anxiety. Stopping to charge 7 times I think created a little anxiety but she has a fun story to tell and can brag that she holds the record in our house for most miles traveled in a day in our car .

Range is king. Give me my Max Pack

 

[TessP100D]

As a 5+ year Model S owner, my best advice to you is to forget about all the various impacts wind, rain, snow, etc…. can have on the vehicle. Over the long term just count on the vehicle being able to deliver a worry free driving range somewhere around 55-60% of the rated dash range. Yes you will have days that vastly exceed this, but the novelty of plotting a travel course like you’re flying a single prop Cessna really loses its luster over time. I still fall into the trap of looking at the weather conditions all along my route, pushing the limits to see if I can make it and each time I pull into a SC with 5mi on the dash I tell myself I’m never doing it again (and no I have never been stranded).

My wife just did a 650mi round trip route in our Model S yesterday and it took her a little over 14hrs of driving/charging. She too was worried about how much to charge at each SC so I just gave her a list of stops, included the miles to the next SC, and gave her a dash range to charge to that was 40% higher than the actual mileage to the next SC. She made the entire trip with no range anxiety. Stopping to charge 7 times I think created a little anxiety but she has a fun story to tell and can brag that she holds the record in our house for most miles traveled in a day in our car .

Range is king. Give me my Max Pack

Well said. Range is King.

GO MAX PACK.

 

[sciencegeek]

Why seven charging stops for 650 miles in a Model S? Four should have done it with no sweat broken unless there were highly unfavorable conditions (or the battery is severely degraded, or she drove it like she stole it)

Max Pack (vs large pack) won't help with total amount of time spent charging unless you're in a sweet spot where you're able to skip one charging stop compared to Large Pack, and then the difference in total time spent won't be large. That's because the amount of time you use for charging is dependent on how much energy you used, and not on how big the vessel is that holds the energy.

For those who question how much potential energy one 'gets back' going downhill after going uphill the same vertical distance: if there were no loss due to inefficiencies you'd get back 100%. That's just physics. I don't believe that Tesla's motors are so inefficient that they only get 50% back ... get back to me with the Tesla numbers once you have sat down and recorded multiple trips of the identical route with exact numbers of energy consumed in kWh and some plain algebra to give me a percentage ... I've done it with my I-Pace on multiple routes and the empirical number is 90%. Which is consistent with first principles and the approximate efficiency of electrical motors and battery charging.

 

[ColeAK]

Why seven charging stops for 650 miles in a Model S? Four should have done it with no sweat broken unless there were highly unfavorable conditions (or the battery is severely degraded, or she drove it like she stole it)

Max Pack (vs large pack) won't help with total amount of time spent charging unless you're in a sweet spot where you're able to skip one charging stop compared to Large Pack, and then the difference in total time spent won't be large. That's because the amount of time you use for charging is dependent on how much energy you used, and not on how big the vessel is that holds the energy.

For those who question how much potential energy one 'gets back' going downhill after going uphill the same vertical distance: if there were no loss due to inefficiencies you'd get back 100%. That's just physics. I don't believe that Tesla's motors are so inefficient that they only get 50% back ... get back to me with the Tesla numbers once you have sat down and recorded multiple trips of the identical route with exact numbers of energy consumed in kWh and some plain algebra to give me a percentage ... I've done it with my I-Pace on multiple routes and the empirical number is 90%. Which is consistent with first principles and the approximate efficiency of electrical motors and battery charging.

you are thinking of the very basic science of it in terms of KE and PE. Like EVs are perpetual motion vehicles, which they aren’t. You are saying that I could go 100 miles uphill then on the way back down get 90 miles for a net using 10 miles for a 200 mile trip. Absolutely no way. If so why not just drive up and down hills all day to increase range? You get much better Wh/mi on flat roads then going up and down. Also most conditions of you completely let off the accelerator to get full power regen you will stop even if fairly steep grades. I think Tesla quotes~70% is max effect, but typically to modulate to the correct speed I’m only using 25-50% of that 70%.

in a few weeks when I take my winter tires off and switch regen back to full (I run regen in low all winter) I’ll get in my Tesla and drive up to prospect heights then down to Anchorage and post pictures of the energy graph from both trips and the round trip.

 

[Jhawk]

Why seven charging stops for 650 miles in a Model S? Four should have done it with no sweat broken unless there were highly unfavorable conditions (or the battery is severely degraded, or she drove it like she stole it)

Max Pack (vs large pack) won't help with total amount of time spent charging unless you're in a sweet spot where you're able to skip one charging stop compared to Large Pack, and then the difference in total time spent won't be large. That's because the amount of time you use for charging is dependent on how much energy you used, and not on how big the vessel is that holds the energy.

For those who question how much potential energy one 'gets back' going downhill after going uphill the same vertical distance: if there were no loss due to inefficiencies you'd get back 100%. That's just physics. I don't believe that Tesla's motors are so inefficient that they only get 50% back ... get back to me with the Tesla numbers once you have sat down and recorded multiple trips of the identical route with exact numbers of energy consumed in kWh and some plain algebra to give me a percentage ... I've done it with my I-Pace on multiple routes and the empirical number is 90%. Which is consistent with first principles and the approximate efficiency of electrical motors and battery charging.

It’s a 2013 P85 with 19s, 220mi rated range on the dash with 112k miles on the odometer. Once you leave home fully charged, you don’t want to spend time trying to charge above 60% and the older the battery the steeper the charge curve. So yes, theoretically you could do 4 stops but you don’t want to because it’s 75-100mi between SCs so you stay want to pull in with the lowest states of charge possible to get the fastest replenishment.

It was an average March day here in the Midwest, temps in the low 30s in the morning and a 10-15mph crosswind to start the day, warming up to low 60s and tailwind later. I think she averaged 320-390watts/mi over the trip. That’s about the typical stats we see driving here with interstate speeds of 75mph.

 

[sciencegeek]

You are saying that I could go 100 miles uphill then on the way back down get 90 miles for a net using 10 miles for a 200 mile trip.

Oh I see where the misunderstanding is coming from. Nah that's not what I'm saying, haha. I'm saying that you get 90% of the potential energy back (and of course much less of the energy that you need for propulsion because of losses to drag and tire hysteresis). It's quite remarkable actually how well the empirical measurement corresponds to theory.

 

[TessP100D]

Oh I see where the misunderstanding is coming from. Nah that's not what I'm saying, haha. I'm saying that you get 90% of the potential energy back (and of course much less of the energy that you need for propulsion because of losses to drag and tire hysteresis). It's quite remarkable actually how well the empirical measurement corresponds to theory.

Big fancy words. Very impressed.

in the end as I said, regen does very little to range. range is king.

 

[sciencegeek]

Haha you guys are funny. Lack of evidence trumps truth, eh?