Hypermiling techniques?

[bhzmark]

Suppose you are zero battery at the top if the hill and you just barely make it doing a full on neutral coast at a max speed of 40 tapering down to zero as you just barely make it to the supercharger.

What if the speed limit is 25 so have to use regen to stay under the speed limit. Do you think you will still make it?

 

[Chris TX]

Suppose you are zero battery at the top if the hill and you just barely make it doing a full on neutral coast at a max speed of 40 tapering down to zero as you just barely make it to the supercharger.

What if the speed limit is 25 so have to use regen to stay under the speed limit. Do you think you will still make it?

Yes, because you can go 15 miles past zero

 

[Candleflame]

Huh? You might need to go back to engineering school. But either way, ICE and EV have very different characteristics here. But for ICE, just look up "pulse and glide" - hint - glide is in neutral or clutch in.

Now it does get complicated with newer cars that can cut the fuel on coasting but you still have more parasitic loses. Glide in neutral with ICE off can't be beat.

this just isn't practical for driving. and also illegal.

 

[mspohr]

What recommendations are there for best mileage when going up/down steep hills/mountains?
(where its not possible to stay under 30kW, maybe there is a max speed target that isn't going to have too much wind adding on)

Rough rule of thumb:
Regen captures about 80% of the power (round trip).
Going 10 MPH faster uses an extra 20% energy due to aerodynamic losses.
So... if you are coasting and speed up by more than 10 MPH, you are wasting more energy due to aerodynamic losses than you would with regen. It would be better to use regen.

 

[bhzmark]

Rough rule of thumb:
Regen captures about 80% of the power (round trip).
Going 10 MPH faster uses an extra 20% energy due to aerodynamic losses.
So... if you are coasting and speed up by more than 10 MPH, you are wasting more energy due to aerodynamic losses than you would with regen. It would be better to use regen.

Those Rough rules are fiction and thus worthless. Why do people just make stuff up? I suppose it is good news that the Tesla buyer demographic has expanded so dramatically.

Aerodynamic drag is not a constant -- it increases with the square of speed. At low speeds it is trivial; at high speeds it can kill efficiency.

 

[InsaneDriver]

I have a 2007 Yukon Denali XL, the best mileage I was ever able to get out of it was when I followed an 18 wheeler up I-5 from Olympia WA to Seattle. I was able to achieve 25 MPG (Insane I know). I think not only did it block the wind it also created a 'suction' and pulled me along. The same think would have to help any vehicle, drafting like bike racing, nascar etc..

Get behind a truck. You don't have to tailgate at all (it's dangerous, anyway), but just being being an 18-wheeler, or any tall truck, reduces wind resistance tremendously. I learned this the first week I had the car when I was charging with a 110v outlet and had to conserve every Wh. There was nothing better for conserving energy than getting behind a truck on the highway (at any speed) and letting the truck take the brunt of the wind resistance. The only downside is you are generally going to go slower than you otherwise would because trucks drive slower than cars, on average, and you don't want a truck throwing off debris and hitting your car!

I'm convinced that someone who wants to hire a truck to drive at 50 mph in front of his could hit the 400 miles/charge challenge from Elon. I don't have the time or inclination to try this, but it definitely fits the bill.

 

[Paul Carter]

I was trying to see if I could assist AutoPilot hypermile a little.

Last night I discovered using the car length controls on the cruise control stalk can help. If its tracking a car in front of you, when going up hill and/or you know you'll have to slow down shortly, quickly turn it all the way towards you (setting 7). The car goes into regen to back off. When going downhill turn it back to your prior setting. Will play with this a bit more, but liking what I've seen it do so far with that.

 

[David99]

Rough rule of thumb:
Regen captures about 80% of the power (round trip).

I know that's on Tesla's blog, but it is very misleading. The motor and inverter are about 85-90% efficient and the battery is also about 90% efficient. So, yes regen puts about 80% of the energy back. But that's just looking at an incomplete picture. You still have rolling resistance and wind drag and everything else, both times. A more realistic picture would be to measure the amount of energy used to drive up a hill and then measure the amount of energy recaptured going down again. You get maybe 20% back if at all.

 

[doctorwho]

I know that's on Tesla's blog, but it is very misleading. The motor and inverter are about 85-90% efficient and the battery is also about 90% efficient. So, yes regen puts about 80% of the energy back. But that's just looking at an incomplete picture. You still have rolling resistance and wind drag and everything else, both times. A more realistic picture would be to measure the amount of energy used to drive up a hill and then measure the amount of energy recaptured going down again. You get maybe 20% back if at all.

I agree with your hill comments. On the way down the car 'recovers' almost all of the expected range lost during the ascent but almost none of the battery percentage charge

 

[joeytree]

I have not done hard math (it's been too long since my engineering days), but David99 has the right of it from my experience. While wind resistance and rolling resistance (if I recall correctly) both increase with speed, I think it unlikely that the increased energy lost to these factors is greater than the energy lost when using regenerative breaking since it is only 70% to 80% efficient (I don't know the exact number for the Tesla's cars). In addition, since nothing is 100% efficient, you loose additional energy when you try to pull the regenerated energy from the battery to the wheels. So regenerative braking should never be more efficient than coasting down a hill.

And I speak from experience. My first EV was (and is) a LEAF, and my efficiency drastically increased by (1) only using power to accelerate or maintain a lower speed than before (now 55 instead of 65) and (2) coasting down all hills (unless the grade of the hill was too small to maintain or increase speed) and continuing to coast at the bottom of the hill until I started to approach my maintenance speed again. This bumped me from consistently below 4.0 mi/kWh (250 Wh/mi) on my round-trip highway commute to consistently above 4.0 mi/kWh. With a few other adjustments (e.g., allowing some deceleration up hills along with the coasting acceleration down hills, and trying to anticipate slow traffic and potential red lights ahead), I almost never get less than 4.0 mi/kWh, even at single-digit-Fahrenheit temps (once or twice a winter tops, I'm in northern NJ). I now average 4.2 mi/kWh (238 Wh/mi) in the fall/winter (i.e., starting when more than one low-temp warning pops up in a week) and average 4.6/4.7 mi/kWh (217-213 Wh/mi) in the spring/summer (i.e., starting when I get one or fewer low-temp warnings in a week two weeks in a row). And while my highway speed fluctuates from 50 mph (going up a steep hill) to 75 mph (going downhill), my average speed is still roughly the same as it was before (the LEAF calculates that too) since I end up braking far less frequently.

Now for my question. I recently ordered a Model S60D with a 218-mile EPA range, and am wondering what fuel efficiency other MS owners have been getting in the winter. Basically I'm trying to figure out how likely it is that I'll be able to make the 205-mile trip from my NJ home up to Lake George, NY in the winter without having to stop at one of the Supercharger stations along the way. If at least 90% of the battery is accessible for driving (I think it's actually more than that, but I can't recall the number), then an efficiency of 250 Wh/mi would take me 216 miles, and should be sufficient (between the underestimation of accessible battery percentage and extra 10 miles or so in rage) to get me up there in one shot. That's 4.0 kWh/mi, which I've consistently hit as a minimum in my LEAF in the winter. Has anyone managed to get that efficiency consistently with the MS in below-freezing winter temps?

 

[jerry33]

It's hard to give a real winter estimate because conditions vary so much--a few cm of fresh snow will really eat range. Here's what you can do to maximum efficiency:

1. Set the charge timer so that it ends about the time you're going to start a trip.

2. Preheat the cabin to maximum using the App.

3. Use range mode.

4. Insure that your tires are properly inflated. (gas shrinks in cold weather, so you have to add more to compensate).

5. Keep the speed down.

In the worst winter conditions, an S85 gets about 175 miles (-20, wind, cold start) according to those who live much further north than I do. So on a 205 mile trip in very bad conditions, I'd expect to charge once in my S85. Note there is a big difference between local driving starting from a warm garage and highway speed driving with few buildings to block the wind. Now my lifetime average is 248 Wh/mi, but there's no way I would expect to get that in bad winter conditions.

 

[hiroshiy]

If @joeytree is hypermiling Leaf then would be able to achieve at least 300Wh/mile in summer. Note in Tesla world we use reciprocal of that of Leaf... not sure why. So 300 means 1000 / 300 = 3.3mile/kWh. You could drive like Jerry but he is a serious hypermiler

In winter, please divide the numbers by 1.2 or 1.3. So in mild winter no snow, you'll get 2.8, and with snow 2.6. Headwinds not included. Hope this gives you some idea. Note that these numbers are 65mph highway speed, so if you can do 55mph all the time you get much higher efficiency.

 

[joeytree]

Thanks @Jerry 33 and @hiroshiy! I typically use power to maintain 55 mph (coasting downhill to obtain increased speeds). Preheating in winter sounds like a given, since the car will be plugged in at that time. So it sounds like I might be able to make it in one shot if there's no snow (I forgot about the effect snow and rain can have on range). In the worst case, there's a Supercharger station on the trip about 72 miles from me, and another about 95 miles later, with Lake George being only another 55 miles after that (actual distances should actually be a bit less). So I should be good to go even in the worst inclement cold weather.

I do have a second question. It doesn't relate to hypermiling, but it does relate to making long trips. My dad ordered a Model 3, but my mom would be the one to drive it to Lake George if they use it instead of their Prius to make virtually the same trip. My mom refuses to go less than 70-75 mph on that trip to make it in as close to 3 hours as she can. So I was planning on doing the same thing in my future S60D so my Dad will have an idea of the decrease from EPA range, thus letting him know the size battery needed. I am planning to stop at both SC stations on the way north (likely necessary), but am planning to see if I only have to charge 10 minutes per station, since charge rate is inversely related to the state of charge at any given time. Does that sound feasible, or should I plan longer charges at each of the two stations?

 

[jerry33]

I do have a second question. It doesn't relate to hypermiling, but it does relate to making long trips. My dad ordered a Model 3, but my mom would be the one to drive it to Lake George if they use it instead of their Prius to make virtually the same trip. My mom refuses to go less than 70-75 mph on that trip to make it in as close to 3 hours as she can. So I was planning on doing the same thing in my future S60D so my Dad will have an idea of the decrease from EPA range, thus letting him know the size battery needed. I am planning to stop at both SC stations on the way north (likely necessary), but am planning to see if I only have to charge 10 minutes per station, since charge rate is inversely related to the state of charge at any given time. Does that sound feasible, or should I plan longer charges at each of the two stations?

What I do is charge till the trip graph is green. That typically takes 15 minutes or less depending. Note that the "you have enough energy" alert will go off before the trip graph turns green. The trip graph takes speed limits and hills into consideration, so if 75 is higher than the speed limit, you will need to charge longer.

For myself, I don't see why rushing and ending up tired at the end of the trip is better than taking it a little slower and arriving relaxed, but I know many people don't think that way (especially when driving an ICE or hybrid).

 

[stevezzzz]

Sounds like you've got a good handle on hypermiling techniques, joeytree. I will point out that here in the West the mountains are bigger and there is no way to avoid regen on the longer, steeper downhills. You, at 55mph on shallow downhills, aren't incurring the drag penalty I would see at 100mph+ freewheeling down from the Eisenhower tunnel on I-70; besides, it's not safe or legal. I routinely set the cc at 65 or 70 mph and accept the 2kWh+ that regen puts back in the battery pack on the downhill.

As to your last question, you may find that 10 minutes per supercharger is adequate for that Lake George trip, particularly if you arrive at a low SOC and are not sharing a SpC cabinet with another Tesla who plugged in before you, but don't forget to consider the time lost in getting off and back on the highway: it can be considerable. With two Superchargers as close together as they are on that route, you may find your optimum strategy is to start out from home at 100%, skip the first SpC while driving as fast as necessary to arrive at the second with as low an SOC as you're comfortable with, and charge only long enough to give you an adequate buffer for those last 55 miles. I assume you've got destination charging lined up at Lake George?

 

[bxr140]

So regenerative braking should never be more efficient than coasting down a hill.

Only to a point.

If you're just talking little inclines like most of NJ (I'm from there, that's not a dig), yeah, coasting down and increasing speed by a few mph is probably more efficient. Especially on long downhills though, regen at cruise speed is the most efficient solution.

It's all about potential/kinetic energy management. At some point you're wasting more of your energy to the increased air/rolling resistance than you're wasting to the less-than-100%-efficient regen cycle.

Certainly the effect is more pronounced at freeway speeds. Gut feel says the inflection point is probably 6-8mph increase in speed.

 

[Ed Hart]

This is a fun string. I think a big factor is the rate at which the batteries can absorb energy. For sure, a higher percentage of energy will be absorbed for reuse when decel is modest than when regennig down a steep hill. On the open highway, we drive 70-75 mph almost all the time. As you can see in the attached file, when we crossed the country in our single-motor Model S, we averaged 304 watts per mile. Around town, it is about the same. After a few months of ownership, I quit thinking about it. See link to file:

Yorba Linda Vacationers First To Go Coast To Coast Mostly by Autosteer

 

[hiroshiy]

Thanks @Jerry 33 and @hiroshiy! I typically use power to maintain 55 mph (coasting downhill to obtain increased speeds). Preheating in winter sounds like a given, since the car will be plugged in at that time. So it sounds like I might be able to make it in one shot if there's no snow (I forgot about the effect snow and rain can have on range). In the worst case, there's a Supercharger station on the trip about 72 miles from me, and another about 95 miles later, with Lake George being only another 55 miles after that (actual distances should actually be a bit less). So I should be good to go even in the worst inclement cold weather.

I do have a second question. It doesn't relate to hypermiling, but it does relate to making long trips. My dad ordered a Model 3, but my mom would be the one to drive it to Lake George if they use it instead of their Prius to make virtually the same trip. My mom refuses to go less than 70-75 mph on that trip to make it in as close to 3 hours as she can. So I was planning on doing the same thing in my future S60D so my Dad will have an idea of the decrease from EPA range, thus letting him know the size battery needed. I am planning to stop at both SC stations on the way north (likely necessary), but am planning to see if I only have to charge 10 minutes per station, since charge rate is inversely related to the state of charge at any given time. Does that sound feasible, or should I plan longer charges at each of the two stations?

Hi, @joeytree, just my 2 cents to your first question. Even if you keep 55 mph and try to hypermile, Model S is a big car and it's going to be difficult if you use any heat during the trip. So even from 100% charge I would say going 218 miles can be cutting very close in summer, maybe impossible during winter in NY, with no charges in between. There is a thread where people show off lifetime data on hypermiling (or lack thereof) on this forum and @jerry33 is I think #2 in the world with around 250Wh/m. And he is in Texas.

There's a hypermiling calculator on Tesla's website only available on PC so do some simulation for varying speed and heat.

On your 2nd question if your mom speed over 75mph that will really negatively affect range. I personally feel 70+ mph eats range fairly quickly. There's I believe no report on Supercharging speed on S60D, which would be the fastest car to supercharge, but 10 minutes might not be enough.

In this video 85kWh battery charges 90km = 56 miles of charge from almost 1% SOC in 10 minutes (this car is European so 320Wh/mile based). If you have 54kWh at full charge and drive at 300Wh/m your range would be:
54kWh / 300 = 180
56miles / 300 x 320 = 60
So your maximum range in Summer with 10 min SC at 75mph could be 240 miles, if you plan to arrive at SC at very low SOC. In winter 240 / 1.2 = 200 miles.

IMHO getting 300 is not that easy at 75mph. Could be possible at 70mph. Choose smaller wheels and narrower tires with low rolling resistance.

 

[joeytree]

Thank you all for your input! It's really helpful! I agree with all of you, and didn't realize that I was already accidentally taking into account @stevezzzz comments about coating to too-high speeds. I hate getting pulled over for speeding (takes you longer to reach your destination than if you had been going slower, and point suck). I already started driving slower when we got the Prius (being replaced with my future S60D), and even more so when we got the LEAF (the car I predominantly drive). So I'm usually at 55 mph at the top of regular hills, and at 50 mph when I reach the top of a big hill (there's one I allow myself to slow to just over 45 because you gain back so much speed on the other side). I then coast down and will start regenerating if my speed gets between 75 and 80 mph (for safety and to avoid getting pulled over). So I incidentally never had to worry about drag at 100+ mph.

@jerry33, I completely agree with taking it slow and relaxing. I didn't realize the benefit until I started doing 55 mph on the highway in the LEAF. I don't have to be on constant vigilance like I did when trying to maintain 65 and continually trying to pass people. Now I get to enjoy my surroundings and whatever music I'm listening to. I think I can make to to Lake George in one shot in all but the winter, even accounting for the extra weight, since I take it slow. Though I might have to start following trucks again.

I'm really looking forward to seeing what mileage I can get in the S60D. I realize the increase in weight from the LEAF means my numbers will take a hit, but that gives me a goal to reach. I want to try and at least hit my cold-weather LEAF average of 4.2 mi/kWh (238 Wh/mi) as my warm-weather Tesla average, and try to hit or beat 4.0 mi/kWh for long highway trips in warm weather. And winter might not be too bad if I preheat the car. It was close to or at single digits when we test drove the MS this past February, and with my wife and two kids in the car with me creating extra body heat, we pretty much only needed the seat warmers. So I think we'll be able to only use heat intermittently when going up to Lake George just to keep our feet warm. That's really the only part of me that gets cold when driving the LEAF without heat in the winter. Hat, leather mittens, earmuffs, and seat and steering-wheel heaters take care of everything else. I fully realize though that my 5.0+ mi/kWh (200 Wh/mi) warm-weather local driving average is pretty much a pipe dream in the MS. The real trick in the winter will be seeing what snowboards on the roof will do to the range. I'm hoping to at least make it the 159 miles to the Albany SpC station in one shot, though I realize I may have to stop at the one in Newburgh first.

As for my mom, she's a bit stuck in her ways at age 71. So i just need to determine what EPA range they'll need in order to make it up in one shot in the winter (she might be willing to get off at Albany and charge it it would only take 10 minutes to get enough juice for the last 55 miles or so).

And yes, I have destination charging. Not ideal (just a regular outside outlet right now), but they're looking into getting a 50amp, 240-volt outlet installed. Either way, since we always stay at least one night when we go up, even a trickle charge would be enough to get us back to Albany on the way home. Strike that, just looked at the SpC map and Tesla just added one in Queensbury in the last couple of days, which is right by my parent's place in Lake George! In fact, it's right by the entrance we use to get onto I-87 to come home! Score!

 

[WannabeOwner]

My mom refuses to go less than 70-75 mph on that trip to make it in as close to 3 hours as she can

That may actually be the best policy - unless your Mom wants to avoid stopping altogether.

Best range is at 25 MPH ... of course it takes you ALL day to get there! Drive at 100 MPH and increased air resistance means you use far more fuel, so have to stop more,and overall it takes you longer.

I believe the sweet-spot is somewhere around 70-75 MPH. You will have to stop, but the time-to-charge, at that average speed, is the same as the driving time - whereas extra time to charge with average speed of 100 MPH is longer than the driving time, and at 25 MPH time-to-charge is much quicker than the driving time. It does depend on arriving at chargers "close to empty", because the battery charges faster when empty, compared to nearly full, and it may be different for S60 than S90, because the bigger batteries add more range, per unit of charging-time.

Starting at 100% SoC and arrive at destination at close to 0% will also help - so on the final leg, once you know you have enough "fuel" to reach your destination (line on the Trip Graph is all green), you can speed up. Just be prepared to slow down if the trip graph starts to show yellow (you will need to show your Mom how to program the supercharger stops into the SatNav, and how to use the Trip Display)