# Miles per KWH at highway speeds (65 mph)

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#### mkjayakumar

##### Well-known member
[If there is a topic for this mods please move it, but I couldn't find..]

Now that we all know how much one can get at speeds less than 40 mph, which is around 5.0 miles/kwh, or a range approaching 100 miles to a full charge., I am more interested in knowing what one should expect if I were to drive at a constant highway speed of 65 mph. More than the range, I think the miles/kwh is a better parameter for us to evaluate than the the actual range, because that parameter can tell you with reasonable accuracy how much one can drive on a specific SOC %.

On a test drive today I got 3.8 miles/kwh with the following parameters:

- Cruise control driving at 65 mph
- relatively flat TX 121 in DFW area
- no climate control.
- ECO mode

Is 3.8 miles/kwh a good number for the Leaf ? If so can I assume that on a full charge given that the usable capacity is no more than 21 KWH, I can expect a range of 21*3.8 = 79 miles to VLB ?

Will I get better with or without Cruise control ?

-Jay

mkjayakumar said:
Is 3.8 miles/kwh a good number for the Leaf ?

Cruise control will not make much difference in your scenario, one way or the other. At 65 I'd expect about 3.6 so you did well with 3.8.

Can I assume Tony's chart uses ACTUAL speed, i.e. one should be careful to adjust the Leaf's speedometer reading (especially at the higher speeds)?

Try it again with the tires at maximum sidewall pressures, or higher.

MikeD said:
Can I assume Tony's chart uses ACTUAL speed, i.e. one should be careful to adjust the Leaf's speedometer reading (especially at the higher speeds)?

No, it's not that high tech yet. It started out "simple".

When we have LEAFscan this summer, we will recompile all the data with external GPS derived speed, raw battery data, etc.

No dash mounted gauges, no CarWings, no Fuel Bars, no GoM, no BS.

I have to disagree. Going above the maximum rated cold tire pressure on the sidewall of a tire is NOT a safe or recommended procedure. If an individual wants to do so on their own and understands the possible risks and downsides inherent in such an overinflation, that is fine, but we should not be making such a recommendation carte blanche.

Herm said:
Try it again with the tires at maximum sidewall pressures, or higher.

A couple of PSI over is not going to create a risk but will maximize mileage.

I understand tire 'pressure', but what is tire 'sidewall pressure' ?

I have seen Tony's chart and I am also aware of many folks who have achieved those miles/kwh and ranges in lower speeds. I was just curious to know if people have seen those numbers at higher speeds of 60mph and above, driving atleast 30 to 40 miles in those speeds.

I ran a test this past weekend with the following results:

- Cruise control 60 mph for 20 miles and cruise control 65 mph for 40 miles. Only time I slowed down was for a couple of off-ramps and on-ramps.
- Perfectly flat terrain and no wind
- No climate control. Temperature 70 degrees
- Drive mode

Went from 100% charge to LBW in 62 miles and registered 3.9 miles/kwh on the car's readout.
I didn't push it all the way to VLBW. Completed the test at slower speeds at 71 miles.

Sometimes I wonder if my car's battery capacity is a bit less than it should be (the car's only four months old and has less than 3,500 miles on it), but since I, typically drive around 40 miles per day at slower speeds, I'm ok with getting 62 miles at somewhere around 63 mph.

That's a good test, but for us in colder states with heater on the same test would result in <50 miles...

IBELEAF said:
That's a good test, but for us in colder states with heater on the same test would result in <50 miles...

South Florida is an ideal location for electric cars (too bad the locals don’t know that).

Weatherman said:
Sometimes I wonder if my car's battery capacity is a bit less than it should be (the car's only four months old and has less than 3,500 miles on it), but since I, typically drive around 40 miles per day at slower speeds, I'm ok with getting 62 miles at somewhere around 63 mph.

That's not typical, as sounds more like this car.

If you can, could you perform this test next, or at the bare minimum, beg, borrow, buy, or steal a Gidmeter.

The only true method to determine how far your car will go is to actually drive the car from 100% to Turtle. The important parameters to consider are listed in the notes in the bottom of the range chart (link in my signature line).

If you ever think your battery is experiencing an abnormality try a test drive with climate control off, as there are too many variables there, and I suggest as level highway as can be found in your area.

Temperature is easy to match, but an important note is BATTERY temperature. If you just used a DC quick charger 6 times in a row, and the ambient air is 55F, your battery might be 120F. Conversely, if your car is left sitting outside in the freezing cold overnight, but it's now 70F in the afternoon, your battery is not at 70F. This is a typical southern California winter weather pattern.

So, level terrain if possible (level terrain and steady speed will eliminate the variables of regeneration, because there won't be any), no heater or a/c (for hopefully obvious reasons), record vehicle weight and road conditions (should be dry). The end result should give you a baseline to compare your performances to consider battery degradation. Some great tools for data collection are Gidmeter or LEAFscan tools !!!

To compensate for any wind and to compensate for elevation variations (you absolutely will be returning to the same elevation when you pull back in your driveway at the end of the test), I recommend 40-ish miles out, and return of 40-ish miles in the opposite direction, all at 60mph. If you can't travel at 60mph, match whatever speed you use with your estimated range; for example, 50mph steady speed can go about 97 miles per the range chart, so drive outbound about 45-47 miles before turning around for the return.

You need to reset your odometer and miles/kWh economy meter on the dash at the beginning of your run, but don't reset this data until you've collected the data at the end of the test. You should use the Nav economy meter (which reads 0.1 high with the present firmware) to get steady speed data. Get your car at the stable target speed (again, let's choose 60mph) and then reset the Nav economy meter while at that target speed to (hopefully) get the target miles/kWh at that speed. For instance, while on the outbound 40-ish mile leg, at 60mph with cruise control, hit reset on the Nav economy screen reset, and at the end of a continuous 40-ish miles while still at 60mph, expect to see 4.0 miles/kWh on that meter before you start slowing down to reverse course. Then subtract 0.1 to match the console date, to get 3.9 miles/kWh.

Then do the same on the return run. Get to speed, then reset Nav economy gauge, and read the result at the end BEFORE you change the speed. Again, if there's any wind, or elevation changes, or both, you'll get two different numbers for each direction. Again, do not reset the dash economy meter until you've recorded that data for the entire trip, from 100% charge to Turtle mode. Naturally, the dash miles/kWh number won't match your two way averaged 60mph Nav data (even when corrected -0.1), since you weren't driving 60mph the entire trip, like in your driveway, and through the neighborhood to the highway that your test was conducted on.

Its not so important to note fuel bars (but you can) as they are a variable In energy capacity per unit (but not as crazy as the GoM). For instance, the fuel bars will show 12 units at "100%" charge, even if the battery is -20C with 50% degradation. Important "hard data" landmarks are the mileage readings at Low Battery Warning, Very Low Battery, and subsequently Turtle. You don't need to drive the car to dead, just Turtle mode.

Check the tire pressure before a run! 36psi is recommended, many of us run right up to the 44psi limit specified by the tire manufacturer. Reset both economy meters and odometers. Do not attempt this on windy days. Do NOT use the GoM (that's just dumb) or CarWings (current firmware is off 2.5% for mileage). DO NOT USE AVERAGE SPEED.

BALANCE THE BATTERY CELLS FIRST!!! That means, charge to 100% and let the car sit for 4 hours after the car reaches 100% while still plugged in. Or, if you observe a top off charge between one and four hours after reaching 100%, you can then consider the cells balanced (as much as is possible). You don't have to do anything else. The LEAF's automation will take care of all the dirty work.

Checklist before the data collecting run:

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

Data to record:

1. Outbound steady speed (confirm with cruise control on)
3. Inbound steady speed (confirm with cruise control on)
5. Miles at Low Battery Warning
6. Miles at Very Low Battery
7. Overall miles covered to Turtle
8. Overall miles/kWh from dash economy display
9. Calculated battery useable energy (miles / miles/kWh = battery kWh)
10.Ending pack voltage, SOC, and Gid (350v-ish from GidMeter or LEAFscan tools)

Post all this data on here for our crack team of LEAFers to decode, but plug the car in to recharge first!

Tony

mkjayakumar said:
I understand tire 'pressure', but what is tire 'sidewall pressure' ?

Its the maximum pressure printed on the sidewall of the tire, many drivers routinely exceed it since tire manufacturers have vast safety reserves (over 100psi). The higher the pressure the less drag your car will experience, just like a bicycle tire. With modern radial tires you will not see any abnormal wear with this higher pressure... if you are an aggressive driver you may even see LESS tire wear with higher pressures.

You will feel every bump on the road, but your tires will run cooler since they are not flexing as much as they normally would. Low tire pressures are extremely dangerous in a heavy car like the Leaf.

Weatherman said:
South Florida is an ideal location for electric cars (too bad the locals don’t know that).
Some of us locals do.

This, of course, is pure conjecture since such a disclaimer is not printed nor documented anywhere that I am aware of. Manufacturers do not simply pull such numbers out of thin air but, rather, determine them with careful analysis and design review. Some tires might be just be fine at 100 pounds, whereas others might disintegrate or suffer some other failure mode at 46; you simply have no way to know, and that is the point. Therefore, it is simply reckless to suggest that someone runs higher than the manufactures stated maximum pressure.

Herm said:
mkjayakumar said:
I understand tire 'pressure', but what is tire 'sidewall pressure' ?
Its the maximum pressure printed on the sidewall of the tire, many drivers routinely exceed it since tire manufacturers have vast safety reserves (over 100psi).

TomT said:
Therefore, it is simply reckless to suggest that someone runs higher than the manufactures stated maximum pressure.
+1.

Besides, the actual extra range is probably very small making it a high risk, low returns venture.

Also true, which makes it even sillier... Plus, there is a negative impact on braking, handling, and ride at such high pressures. About the only thing that DOES improve somewhat is hydroplaning speed... (In MPH it's roughly proportional to the square root of the tire pressure times ten. That is but one reason why aircraft use special tires designed to run very high tire pressures.)

evnow said:
+1.

Besides, the actual extra range is probably very small making it a high risk, low returns venture.

Here is a result of my next test at the same speed but for a longer duration.

- 70 miles traveled at exactly 65 mph, at an impressive 4.2 miles/KWH.. Note: I reset the miles/kwh in the dash only after getting into the freeway and reaching a steady state of 65 mph. And this 4.2 was when I pulled out of the freeway just before the off-ramp.

- LBW at 76 miles with 8 miles left in the GoM. I then pulled out of the freeway into city streets. This means if I had continued driving at the same speed (65mph) and I would have seen VLB at 83 miles.

Questions:

- While the range pretty much matches with Tony chart, the miles/kwh I got was much higher. How is that possible ?

- If the 4.2 miles/Kwh was indeed the efficiency, then assuming a conservative 21KWH usable capacity, I should have got a range of 90 miles with sustained speed of 65 mph. But in reality, If I had continued driving at 65mph, I would have got no more than 83 miles. Where did the 7 miles go? battery capacity degradation ?

mkjayakumar said:
- While the range pretty much matches with Tony chart, the miles/kwh I got was much higher. How is that possible ?

- If the 4.2 miles/Kwh was indeed the efficiency, then assuming a conservative 21KWH usable capacity, I should have got a range of 90 miles with sustained speed of 65 mph. But in reality, If I had continued driving at 65mph, I would have got no more than 83 miles. Where did the 7 miles go? battery capacity degradation ?

You can't use the range shown on GOM as definitive. There is "hidden" miles after GOM shows zero.

Ofcourse, you can't drive at 65 mph after sometime as the power gets reduced. I'd say, 83 miles @ 65 mph is fantastic. 10 miles more than EPA combined city + highway range. What more can you ask for ?

BTW, long time back Perry told me we would get about 70 miles @ 70 mph. Sounds quite accurate.