Miles per KWH at highway speeds (65 mph)

[mkjayakumar]

Are you saying that 0.4 miles/kwh penalty is more than what one should expect for the LEAF? I thought that was pretty reasonable. 10 miles penalty on a full charge is of course my extrapolation.

Tony: what is there to fix in climate control ? If I don't want the AC all I have to do just turn it off and still have the fan ON pumping in outside air. Maybe from heating perspective which I haven't used it even once.

 

[TonyWilliams]

Are you saying that 0.4 miles/kwh penalty is more than what one should expect for the LEAF? I thought that was pretty reasonable. 10 miles penalty on a full charge is of course my extrapolation.

Tony: what is there to fix in climate control ? If I don't want the AC all I have to do just turn it off and still have the fan ON pumping in outside air. Maybe from heating perspective which I haven't used it even once.

Go to http://www.EVSEupgrade.com" onclick="window.open(this.href);return false; and buy their fix, where you can run the fan without the heater or a/c.


Please do that test, and post those results.

EDIT: here's the way I'd like the data presented so we can eliminate guessing and 20 questions as much as possible:


EDIT: here's the way I'd like the data presented so we can eliminate guessing and 20 questions as much as possible:


Checklist before the data collecting run:

1. (your answer) Any changes to car from stock (different tires, bike rack, Texas cattle horns, etc)
2. (your answer) Tire pressures set, heater and air conditioning off, car at 100% charge, cells allowed time to balance
3. (your answer) Gross vehicle weight? 3350 pounds plus operator, passengers, spare tire, bags, concrete, etc
4. (your answer) Route, length, elevation, hills if any, general conditions (dry, concrete/asphalt, etc)
5. (your answer) Assumed or measured battery temp (from LEAFscan tool)
6. (your answer) Ambient air temp
7. (your answer) Gid count at start, if available
8. (your answer) SOC, if available (from LEAFscan)
9. (your answer) Starting total voltage (should be 393.5v from GidMeter or LEAFscan tools)
10. (your answer) Accept CarWings on Nav screen startup by pressing OK

Data to record:

1. (your answer) Outbound steady speed (confirm with cruise control on)
2. (your answer) Outbound observed steady speed miles/kWh from Nav adjusted -0.1
3. (your answer) Inbound steady speed (confirm with cruise control on)
4. (your answer) Inbound observed steady speed miles/kWh from Nav adjusted -0.1
5. (your answer) Miles at Low Battery Warning
6. (your answer) Miles at Very Low Battery
7. (your answer) Overall miles covered to Turtle
8. (your answer) Overall miles/kWh from dash economy display
9. (your answer) Calculated battery useable energy (miles / miles/kWh = battery kWh)
10.(your answer) Ending pack voltage, SOC, and Gid (350v-ish from GidMeter or LEAFscan tools)
11. (your answer) Go to a computer (usually the next day) and report the CarWings kWh and miles used

 

[Herm]

Inflating to 44psi might give you an extra 10% in range.. try it.

Didn't you mean to say 0.10%? :lol:
Note to new readers: Herm is an extremist on this - as on a few other things.

Try it.. a couple of runs at 44psi wont kill you or ruin your tires.. you never know and may be pleasantly surprised. Send me a PM when you post your results please.

 

[EVDRIVER]

Inflating to 44psi might give you an extra 10% in range.. try it.

Didn't you mean to say 0.10%? :lol:
Note to new readers: Herm is an extremist on this - as on a few other things.

Try it.. a couple of runs at 44psi wont kill you or ruin your tires.. you never know and may be pleasantly surprised. Send me a PM when you post your results please.

One year at 52 PSI and my range is always excellent, even on the freeway.

 

[TonyWilliams]

Inflating to 44psi might give you an extra 10% in range.. try it.

Didn't you mean to say 0.10%? :lol:
Note to new readers: Herm is an extremist on this - as on a few other things.

Try it.. a couple of runs at 44psi wont kill you or ruin your tires.. you never know and may be pleasantly surprised. Send me a PM when you post your results please.

I'm guessing you seriously think TEN percent is possible, and to that I say absolutely NO.

BTW, I run 44 psi.

 

[Herm]

I'm guessing you seriously think TEN percent is possible, and to that I say absolutely NO.

Try it, do a few runs at 32psi and see what you get, perhaps no difference at all.. after all at one time you thought 100 miles range was not possible

 

[TomT]

Some time ago, I did a test at 36 versus 44. This was done at 45mph since rolling resistance affect decreases with speed (it is a constant but becomes less of the overall picture as aerodynamic drag increases). This was on the old crap-o-matic Ecopia tires; I have not redone the test since I went to the Michelins... I made a number of 2 direction runs on the same road to average out variations and to confirm I was getting consistent and valid data. I no longer remember the exact numbers I obtained but the percentage improvement at 44 pounds was just over 1 percent. This convinced me that there was no great merit to increasing tire pressure simply to decrease rolling resistance, at least with those tires on a Leaf. Thus, I settled on 40 pounds as a good number for me. YMMV.

Try it, do a few runs at 32psi and see what you get, perhaps no difference at all.. after all at one time you thought 100 miles range was not possible

 

[DeaneG]

...the percentage improvement at 44 pounds was just over 1 percent.

Tom, there you go again... confusing the issue with actual data. I think many would prefer to just wake up in the morning and believe they'll get a 10% improvement for inflating their tires to a glassy hardness.

 

[TonyWilliams]

I'm guessing you seriously think TEN percent is possible, and to that I say absolutely NO.

Try it, do a few runs at 32psi and see what you get, perhaps no difference at all.. after all at one time you thought 100 miles range was not possible

I never thought 100 miles was impossible, just not practical. I absolutely stand by that.

Deflating the tires below 36 psi and then jacking it up to something else is not what I, or I believe others, are referring to. Why not put 5 psi? Or 2. Or take the wheels off and roll on the disc brakes. Then claim 83849% increase with tires on at 909 psi.

 

[aqn]

Re: tire pressure.

Leaf tires are rated at 44 psi (the usual). I run them at 38. It is a bad idea to have them at 44. Your center tread will thin out faster then the sides, and your steering will feel too loose. I will lower the pressure to 36 in summer as tires do swell when hot (i.e. increase the pressure). That's why you measure your tire pressure cold and in shade.

Your experience is quite different from mine. I have run mine at 44 psi for the past 3200 miles. (The first 4381 miles I ran at 36 psi.) So far, there is no difference in wear. Time will tell.

There might have been a different in steering feel; there is no difference in traction. The tires' compound (hard wearing: warrantied for 65K miles) and construction (65 aspect ratio) pretty much guarantee little difference in performance (or lack thereof) no matter the pressure.

And yes, you do get much better mileage with proper pressure.

I'd say "may get better mileage" rather than "do get better mileage". There are just too many variables involved. If you live in SoCal or Phoenix or some locale similarly flat, little things like tire pressure and air conditioning use (cooling, not heating) would probably make a difference to energy economy. For me, it's not as clear cut. My theory is that I live in a quite hilly area, and the inconsistency of energy use going up hills (and to a smaller degree, the energy re-gen'ed going down) dwarves any changes caused by changes in tire pressure, A/C use, etc.

That said, I have been recording data since new (dash mi/kWh, odometer, temperature, D/ECO, A/C used, heater used, average speed, and PSI), since last April, total of 232 charge events:
D, no A/C, no heat: 44 psi yields 4.8% better economy (28 events at each PSI, averaging the middle values, throwing away top/bottom five values.)
ECO, no A/C, no heat: 44 psi yields 2.5% WORSE economy! (69 events at 36 PSI and 51 events at 44 psi, averaging the middle values, throwing away top/bottom five values.)

These figures are not final, since the time I ran 36 psi was during the summer (Apr-Nov 2011), and the 44-psi period was over the winter/spring (Nov-now), so it'll take another year of doing the opposite (PSI, D vs ECO, etc.) before I would feel confident making claims about effect on energy economy of pressure, D vs ECO, A/C use or not, etc.



(It may appear that my method lacks... precision and control. To that I say: unless you can drive a 60-mile loop (or a reasonable distance, i.e. not 10 miles!) repeatedly under exactly the same conditions, how do you isolate the effect of one change? Other than on a closed track with no elevation change, with banked turns or very open turns to enable a constant throttle setting, no traffic lights, no traffic, where you can drive multiple consecutive 60-mile loops, how can you be sure that your finding is reliable and repeatable? Outside of that environment, can you guarantee that you can do two runs and believe that the results are both within the margin of error? How would you know what the margin of error is from only a few runs? Where can you drive dozens of miles without having encountering stop signs, traffic lights, other traffic, etc.? And if you cannot, how do you know that you accelerate and decelerate consistently?

So, the alternative for me is recording lots of data point to "flatten" out the variables (traffic condition, how I drive/brake, different routes, speeds, wind conditions, etc.). Over a large number of data points, those variables will trend to a reliable average because, well, that's how averages work. Then, by changing one factor (pressure, A/C use, heater use, etc.) over two equal time periods, any difference in results is directly attributable to that change.)

 

[TonyWilliams]

(It may appear that my method lacks... precision and control. To that I say: unless you can drive a 60-mile loop...

You don't have 60 miles to drive in Texas? One day at 36psi, next day with similar temps, wind, etc, do it at 44psi?

An hour out of each day.

 

[planet4ever]

I've only had my Leaf a few days. I have a 30-mile commute, and I was hoping to only charge after a round-trip (60 miles). But I live in western PA, so the terrain is fairly hilly, the weather has been pretty cold (~30°F in the morning), I usually have to have my headlights on, and it rains a lot so the windshield wipers have been running half the time.

After charging to 100%, I was down to ~18% after the round trip. I've only been driving 55mph on the highway. I was hoping that I could get away with charging to only 80% regularly, but this now seems unlikely. I haven't used the heater yet. I'm getting about 4.2-4.3 m/kWh. I have to say I'm a bit disappointed.

This post has been bothering me for two days, so I guess I am going to have to respond to it. First, let me say that, yes, if you are charging the battery at 30°F, then 60 miles at 55 mph is stretching it on an 80% charge. But if you were able to charge in a 60°F garage, and you varied your speed on the hills to optimize battery use, it should be doable. The headlights aren't much of a load if you keep them on low beam. I doubt if the windshield wipers make any significant difference at all. There can be a real effect from tires rolling on a wet road, and rain often means wind. That can be a killer.

However, if you are getting 4.2-4.3 m/kWh at 55 mph you can't be hurting too badly from wind or hills or wet roads or headlights. If you are charging the battery at 30°F, though, you are only starting out with something between 18 and 19 kWh at 100%. 18 kWh * 4.3 m/kWh = 77 miles, which does leave you with only about 22% left.

The thing that has been bugging me, though, is how do you know that you are down to ~18%? You certainly can't tell that reliably from seeing a number like 18 on the big miles remaining number, which we call the GuessOMeter. And I hope you aren't assuming that each bar represents 8%, so calculating that two bars and a bit of the third one would be 18%. It's possible that you have been looking at Tony's chart, and knew that you were just on the verge of getting Low Battery Warning, which he says should be around 17%.

So tell us, garsh, where did you get that 18% number?

Ray

 

[aqn]

(It may appear that my method lacks... precision and control. To that I say: unless you can drive a 60-mile loop...

You don't have 60 miles to drive in Texas? One day at 36psi, next day with similar temps, wind, etc, do it at 44psi?

An hour out of each day.

Not 60 miles without obstructions like traffic lights, stop signs, traffic, deer, etc. Acceleration and deceleration can't be good for reliability of energy economy data. (60 miles is a third of a way from Austin to Houston.) And even if I do find such a stretch/loop, I would want to do more than just two runs. If two runs show differences, I don't know if it'd mean anything other than "yes, there is a difference". I wouldn't want to believe in the magnitude and repeatability of that difference.

 

[garsh]

So tell us, garsh, where did you get that 18% number?

That's just the number that appears on the owner's portal under "state of charge". I had two bars remaining at the time.

 

[Herm]

Deflating the tires below 36 psi and then jacking it up to something else is not what I, or I believe others, are referring to. Why not put 5 psi? Or 2. Or take the wheels off and roll on the disc brakes. Then claim 83849% increase with tires on at 909 psi.

I have seen 10% differences going from 28 to 40psi in the past, granted not in a Leaf and not with LRR tires.. BTW, 32 psi on the Leaf may be unsafe, its such a heavy car..

In any case, test it and report.. with so many of you now using guid-o-meters it should not be hard to document minute changes... you probably wont need a 60 mile run either.

 

[TonyWilliams]

In any case, test it and report.. with so many of you now using guid-o-meters it should not be hard to document minute changes... you probably wont need a 60 mile run either.

Small changes need the longest runs, with the most isolated conditions, for most repeatable accuracy.

 

[planet4ever]

So tell us, garsh, where did you get that 18% number?

That's just the number that appears on the owner's portal under "state of charge". I had two bars remaining at the time.

Oh. Actually, it must have said 17%, not 18%. That is a very misleading number. The only thing that website knows is that you had two bars. It simply calculated 2/12 = 0.1666... and rounded that to 17%. That gives you the impression it is accurate to 1 part in 100, when it is really only accurate to about 1 part in 10. Tony's chart says that when you have two bars left your battery is somewhere between 26% and 31% full.

Ray