Putting some numbers on the factors that affect range

[TonyWilliams]

Interesting thread, since over the past 18 months or so, the Supercharger network is booming, the CHAdeMO adaptor is near availability, and percentage wise, fewer people are buying EV's who would bother with calculating range.

With that said, I'll add some of my thoughts:

Longest Range Pointers


1) Drag - Wind resistance - high elevation and hot ambient temperatures thin the air, making it easier for any object to pass through the air. In the airplane business, we call this calculation "density altitude". Here's an easy to use online version: Density Altitude Calculator - English/Metric. The most "aerodynamic" vehicle will cut through the air with the least resistance.

2) Drag - Rolling resistance - drag from everything that rotates to move the car; tires, wheel bearings, u-joints or cv-joints, gears and bearings, gear lubricant. Generally, the hotter the lubricant, the lower its resistance; the higher the tire air pressure, the lower the tire resistance.

3) Gravity and Mass equals Weight - as long as there is gravity, it will take energy to accelerate mass and energy to propel mass at speed. Obviously, it also takes significantly more power to lift the mass away from the gravitational pull while driving uphill. Quite simply, lighter is better.

4) Ideal speed - every vehicle has a speed where the intersection of the power required to overcome drag and weight is the least. Heavy cars with high drag tires (but extremely aerodynamic) like a Tesla tend to be most ideal in the 20-25mph range and small, lower mass cars like LEAF and Spark EV are probably in the 10-15mph range. Obviously, anything that uses power that isn't being used to overcome drag and weight is a waste; the heater, a/c, etc.

5) Hot batteries store more energy - the hotter the better, however, this same heat tends to significantly shorten their life (Nissan LEAF in Phoenix) and in some cases (Boeing 787), make the battery fail. Obviously, the Tesla chemistry is closer to the B787 than the LEAF, so its batteries must not be allowed to get too warm.

That's it! Hit the ideal speed, at the lowest weight with the least drag and the most stored energy and that will give you longest range in your car.

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ELEVATION GAIN

It's a straight forward calculation to determine the additional energy required to go up a hill, however down the hill is far more complicated.

One kilowatt hour = 2,655,224 pound feet of energy.

Driving your 4000 pound Electric vehicle up a 1000 foot elevation requires 4000 * 1000 = 4,000,000 foot pounds of energy divided by 2,655,224 equals 1.5kWh of energy to lift the car.

1.5kWh of energy at an economy of 4 miles per kWh (250 watts per mile) = 6 miles of range used to drive up 1000 feet for a Nissan LEAF type car.

For a 5000 pound Tesla Model S (just two occupants) equals 5 million foot pounds to go up 1000 feet.

5 million divided by 2,655,224 equals 1.883kWh of energy to lift the car.

1.833kWh of energy at an economy of 3 miles per kWh (333 watts per mile) = 5.5 miles of range used to raise the car 1000 feet.

*****************

METRIC

One kilowatt hour = 367.0978 meter kilograms of energy.

1.5kWh of energy is used to gain 300 meters at an economy of 6 km per kWh (167 watts per kWh) = 9 km of range used to raise the car 300 meters.

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NISSAN LEAF RANGE CHART:

There have been apps produced (LEAF Energy for Apple, ?? for Android) based on this chart for the LEAF. It might offer some insight to help somebody with their Tesla:

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Range Chart for Toyota Rav4 EV with Tesla drivetrain:

Miles Gained per Hour Charging @ 87.5% charger efficiency
70F Ambient temperature - hotter or colder will decrease miles gained
Amps/Volts -- Where ---- City Drive ----- 65mph
-------------------------- 2.7 miles/kWh -- 3.4 miles/kWh
-----------------------370 wattHours/mile - 295 wattHours/mile

12 / 120 ------- Any ------ 2.8 miles ------ 3.5 miles (supplied cable with car)
16 / 120 ------- Any ------ 3.8 miles ------ 4.7 miles (JESLA with NEMA 5-20)
12 / 240 ------ Home ----- 6.8 miles ------ 8.6 miles (EVSEupgrade.com mod)
16 / 208 ------ Public ----- 7.5 miles ------ 9.5 miles (2013 LEAF EVSEupgrade)
16 / 240 ------ Home ----- 8.9 miles ----- 11.2 miles (2013 LEAF EVSEupgrade)
20 / 208 ------ Public ----- 9.4 miles ----- 11.9 miles (2013 LEAF EVSEupgrade)
20 / 240 ------ Home ---- 11.0 miles ----- 13.9 miles (Clipper Creek LCS-25)
24 / 240 ------ Home ---- 13.6 miles ----- 17.7 miles (JESLA w/NEMA 14-30 or 10-30)
30 / 208 ------ Public ---- 14.8 miles ----- 18.7 miles (typical public J1772)
30 / 240 ------ Home ---- 17.1 miles ----- 21.6 miles (rare public J1772)
40 / 208 ------ Public ---- 18.5 miles ----- 23.4 miles (Tesla Roadster/Clipper Creek)
40 / 240 ------ Home ---- 22.7 miles ----- 28.5 miles (JESLA w/NEMA 14-50 or 6-50)

 

[wycolo]

as long as there is gravity, it will take energy to accelerate mass

Even without gravity too!!
--

 

[Eggplant]

Yeah, I was laser focused on that comment too. Stupid Higgs boson.

 

[ChadS]

HERE is a thread that discusses losses to due to roof-top box. Of course it varies by box and mounting system, but he got 15-22% reduction based on how fast he was going. Which happened to be very close to the reduction he got by going 20kmph faster. So slow down 20kmph if you have a rooftop box and you should be fine.

 

[David99]

Cheapest way to increase range is to inflate the tires a little higher than recommended.

From the 'mythbuster' test:
Recommended pressure: 35 psi
tyres at 10psi = 3.7% increase in consumption
tyres at 30psi = 1.2% increase in consumption
tyres at 40psi = 6.2% decrease in consumption
tyres at 60psi = 7.6% decrease in consumption

According to many people that have done this for years reported that their thread wear on the tires is very even, so no worries about uneven tire wear.

 

[John Vig]

Chad, your original post in this thread is great..., THANK YOU, but, as Larry Chanin's question indicates, it could be even better if you labeled the graph and the tables. The first time I looked at the graph, it took me too a while to figure out what the green shaded area meant. It also took me a while to figure out what the column 2s were in the tables. For example, the +25% at 15 degrees F was not immediately obvious; +25% of what? I assume it means that, at 15 deg F, 25% more energy (or range) is consumed as compared to the energy (range) that would be consumed at 70 deg F, provided that the battery and cabin are fully warmed up at the start?

If the battery is at 15 deg F at the start, then, is it not true that the +25% becomes a lot higher? About what would the number be during the first few minutes of such a trip, and, how long would it take, say, at 65 mph, for the percentage to decrease to +25%? About how long would it take at a lower speed, say, at 45 mph, average?

 

[xy46]

I am new to Tesla having picked up my P85D just over a week ago. I initially put 650 miles on it over four days of mainly highway driving. This week, it's been extremely cold here in Michigan (6-20 degrees), and my daily commute to work is just slightly over 1 mile each way. I have a HPWC in the garage, but due to a mix-up between the electric company and my electrician it isn't functional yet, so I am using a 110V/20 amp plug for charging overnight in an unheated garage. I have been searching the forums for the answers to the questions below, so I apologize if the answer to these questions have already been documented else where.

In the mornings, I preheat the car for approximately 20-30 minutes, then drive the one mile to work. Car sits outside and not plugged in for 8-10 hours. I preheat it again for 20-30 minutes and then drive it one mile back home. I have done this for the past two days. Energy usage graph image is below:

My commute yesterday morning is the energy use between the 5th and 4th mile hash mark, and my commute home last evening was between the 4th and 2nd hash mark (I ran a short errand on the way home which added the extra mile). This morning's commute to work is between the 2nd and 1st harsh mark obviously, and the drive home tonight between the 1st and 0 hash mark. As you can see, I am utilizing greater than 1,000 Wh/mi in what I assume is energy being used to further heat up the battery even after my 20-30 minutes of preheating.

So my questions are: (1) Is it normal to use > 1,000 Wh/mi in warming up the battery? and (2) how long do I need to preheat in my garage to avoid this as it seems like I still get it even when preheating the car for 30 minutes? (3) Finally, I also notice that after turning on the car with the cold battery that my dash shows usage of approximately 10 kW of electricity while sitting still (see image below). Is this reflecting the energy currently being consumed to heat the battery?

Thanks for the help! By the way, I love my P85D!

 

[dsm363]

xy46: That's probably normal since it gets cold soaked sitting outside for 10 hours. Are you still charging in the morning right before you take off? That should help keep pack warm. 30-60 min of preheating should help too so you are doing right thing there.

The main problem (nice problem actually) is you have such a short commute to work so pack doesn't have a lot of time to beat up.

 

[Zextraterrestrial]

pretty sure that 10kW is the heating power.
looks more like 6kW though. you might be able to see it change a little if turn on and off heater/AC

 

[xy46]

Thanks for the advice dsm363 and Zextraterrestrial. Experimented tonight and indeed the power use slows slightly on the dash when I shut the heater off. Kind of cool that it shows you the real time use like that. I also preheated the cabin for 60 minutes and that seemed to help, too with power use while driving. It wasn't dramatically better but still better. Tonight I scheduled the battery charging so that it finishes just as I am leaving in the morning, so will see how much of a difference that makes. Since I am only currently using a slower 20 amp service, I wonder if it will really make that much of a difference. Is there a way to turn on the battery heater on ahead of time while it's still plugged in to power?

 

[stevezzzz]

Make sure the car's not in Range mode while plugged in: that defeats any battery preheating, though I'm pretty sure you need to be plugged into 220/240V to get any battery heating.

 

[xy46]

I definitely have range mode off for that reason. I should have my 80 amp HPWC up and running within the week and am anxious to see if I will get better battery heating then. Sounds like from what you are saying that may be what's making the difference.

 

[Ugliest1]

I definitely have range mode off for that reason. I should have my 80 amp HPWC up and running within the week and am anxious to see if I will get better battery heating then. Sounds like from what you are saying that may be what's making the difference.

I'm guessing (ok, a very strong guess based on my car's behaviour) that your HPWC will make all the difference in the world. You'll still be using a fair amount of electricity anyway due to the cold-soaking but either timing your charge to start (overnight) so that it ends (at 70, 80, 90%, whatever you set) just before you need it in the morning will have the battery at operating temperature. That will take some guessing on start time (1am? 2am?) and depends on rated range left.

The other way to heat the battery, is charge normally on plugging in the night before, then using the smartphone app turn on cabin heating about 30 min before you want to leave. Cabin heating (with the HPWC) will also warm the battery. You may need to do that twice (i.e. cabin heat an hour before, then re-turn on again 30 min before) depending on how cold the car gets overnight. The beauty of the HPWC is, the car will take power from the wall, not the car battery when plugged in. At your office parking spot, pre-heating the cabin will pull from the battery (no choice there).

Sorry if you knew most of this already, thought this might help re your earlier questions. The cabin heating appears to run for about 30 minutes. YMMV.

 

[jerry33]

The cabin heating appears to run for about 30 minutes. YMMV.

That has apparently changed recently. It's now 15 minutes if you start it with the App.

 

[xy46]

I'm guessing (ok, a very strong guess based on my car's behaviour) that your HPWC will make all the difference in the world. You'll still be using a fair amount of electricity anyway due to the cold-soaking but either timing your charge to start (overnight) so that it ends (at 70, 80, 90%, whatever you set) just before you need it in the morning will have the battery at operating temperature. That will take some guessing on start time (1am? 2am?) and depends on rated range left.

The other way to heat the battery, is charge normally on plugging in the night before, then using the smartphone app turn on cabin heating about 30 min before you want to leave. Cabin heating (with the HPWC) will also warm the battery. You may need to do that twice (i.e. cabin heat an hour before, then re-turn on again 30 min before) depending on how cold the car gets overnight. The beauty of the HPWC is, the car will take power from the wall, not the car battery when plugged in. At your office parking spot, pre-heating the cabin will pull from the battery (no choice there).

Sorry if you knew most of this already, thought this might help re your earlier questions. The cabin heating appears to run for about 30 minutes. YMMV.

Thanks - this is really helpful. I have noticed that while preheating with the car plugged into my garage's 110v/20 amp outlet that the car has to take energy out of my battery as I assume the 110v/20 amp can't provide enough energy at that rate. I am glad to learn that once I get the HPWC active that it will be be more effective at preheating the battery while I simultaneously preheat the cabin. I assume that this preheating of the cabin works because it's using the heat pump to circulate heat to the battery as well as the cabin during the warming process. With the help everyone has provided me here, I scheduled my battery charging to complete as I was departing this morning. Additional I preheated the vehicle for two cycles of 30-minutes each just prior to departure. This all helped because when I left this morning for my 1 mile drive to work, I only averaged approximately 650 Wh/mi vs. >1,000 Wh/mi as I had been doing previously in the same temperatures.

That has apparently changed recently. It's now 15 minutes if you start it with the App.

I have read this elsewhere, but it appears that mine is staying on for the full 30 minutes.

 

[Robbo]

I have a 20 month old S85 and had a nail biter this weekend. Left Saturday morning with the car fully charged up in trip mode (stated 247 mile range) and drove it 105 miles at an avg 65 mph mostly highway trip. Weather was cold (mid-20s). When I arrived the car showed 102 miles of range left. Put the car in energy save mode and left it parked outside for about 37 hours with temperatures dropping into the low teens. Sunday night began the 68 mile trip to the nearest Supercharger. Temperatures were in the high teens and there was about 1/2 inch of snow on the ground. The range now showed 97 miles and the NAV showed a yellow drive slowly message. I put the car into range mode set the heat down in the mid-60s and got on my way. Given the bad weather, I had no problem driving slowly and set the cruise control at 50mph. The snow turned to freezing rain and my range started to converge down to my travel distance. By the time I hit the SC, my range was down to 6 miles. So 105+68 (distance) + 6 (remaining range) = 179 or spot on Chad's numbers.

Not a pleasant experience though-- in addition to having to deal with the lousy weather and driving conditions, the stress of worrying about running out of battery and getting stuck in a nasty storm at midnight on a Sunday was palpable (my jaw hurt from all the clenching). I have run this route a half dozen times before but never in weather this bad. Based on experience I had always figured on a 20% "loss" to range but this time pushed the loss ratio up to 33%. The funny/stupid thing is I could have stopped at the SC on the outbound trip and topped up for 15 minutes and not have had any stress at all.

 

[ecarfan]

I am amazed you only lost 5 miles of range over the 37 hour time the car was sitting unplugged in temps in the 10 to 20 F range. Or perhaps I am not reading your post correctly!

I assume the "drive slowly" message was due to the battery being very cold.

 

[hiroshiy]

Thanks for the info, Robbo! I always use 30% rule - if I want to to X miles (well, kilometers for us), I need 1.3x miles of Rated range (ours say Typical range), or charge up to a little over 1.3x miles. It seems our Typical is at 320wh/km, so I might be OK to have only 20% buffer.

 

[xytor]

When I was driving my Roadster big distances on the road trip, I found I could reliably use less miles than the "Ideal Miles" indicator by doing a few things:

1) Always using cruise control. This is important because it eliminates all the little accelerations that I -- as an imperfect human -- make while driving.
2) Set the cruise to 56 mph. I could probably get even more miles by driving slower, but I found it was a good compromise for the next point.
3) Follow a big truck. This one is tricky because I never want to follow too close due to debris causing windshield cracks. But even with 7-10 Roadster-lengths away from the truck, it helps. At 56 mph, there is usually at least one slow, steady truck driving this speed that I can get (not too close) behind.
4) This only works on flat-ish roads. Elevation gain obviously uses more ideal miles than actual.

Also, I often find that ideal miles go pretty quickly from the 210-170 range, about as fast or faster than actual miles traveled. Then, from 170 down, they slow down and I can get about 1.5 actual miles per ideal mile used.

 

[Hans (Amsterdam)]

Range of the 70D is not bad at all, especially when driving 50mph with 90 degrees Fahrenheit. Model S | Tesla Motors