Texas heat affecting my range.

Well, I don't have any hard-core scientific numbers for you but I've noticed the last few weeks with the 100 degree weather here in Texas that my range has gone down. Of course, I expected that would happen with the heavier usage of the A/C. Anyone else noticed this?

For example, I drove to this store on the other side of town with a full battery two months ago at night so there was very little usage of A/C. I got back home with 35 miles remaining. Took the same trip in the day time, same route, same speed, etc. Got home with 23 miles remaining.

I've also noticed just my daily commute of 12 miles seems to also be showing less and less range remaining on the estimator the hotter it gets outside.

In the mornings on my way to work I just leave the windows down. But it is too hot on the way home, so I have to use the A/C.

Has anyone done any experiments to see if it is more efficient on the Leaf during highway driving to leave the windows down and the A/C off or the other way around?

adric22 said:

Has anyone done any experiments to see if it is more efficient on the Leaf during highway driving to leave the windows down and the A/C off or the other way around?

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Mythbusters have made a couple of attempts to test this, but with an ICE vehicle. Aerodynamics are, I suspect, more important with the Leaf than with the boxier vehicles they used, but generally the faster you go the more it skews toward keeping the windows closed.

Pre-cooling your cabin while the car is still plugged in might help if that allows you to hold off on the AC use for a while, but the target temp for that is not configurable (71?), and the time before it heats back up might not be useful.

As far as your specific commute - best answer would probably be reached by doing the experiment yourself.

The high temperature may be having an impact unrelated to your AC usage - specifically higher electrical resistance in the system?

adric22 said:

For example, I drove to this store on the other side of town with a full battery two months ago at night so there was very little usage of A/C. I got back home with 35 miles remaining. Took the same trip in the day time, same route, same speed, etc. Got home with 23 miles remaining.

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Two months ago you may not have had the new firmware update installed. I'm assuming that you do now. The update changes the range estimates and adds an invisible buffer on the bottom. For example, now when it shows 8 miles remaining you (typically) have more like 14 left - a 6 mile buffer. Subtract that from your figures (35 - 23 - 6) and you're left with another 6 miles - which sounds about right for A/C loss over a full charge. So, I'm gonna go out on a limb and say my guess about the firmware update is about correct. Is it?

adric22 said:

For example, I drove to this store on the other side of town with a full battery two months ago at night so there was very little usage of A/C. I got back home with 35 miles remaining. Took the same trip in the day time, same route, same speed, etc. Got home with 23 miles remaining.

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Are you driving slightly slower at night but not realizing it, and thus had a better estimate?

GeekEV said:

Two months ago you may not have had the new firmware update installed. I'm assuming that you do now. The update changes the range estimates and adds an invisible buffer on the bottom. For example, now when it shows 8 miles remaining you (typically) have more like 14 left - a 6 mile buffer. Subtract that from your figures (35 - 23 - 6) and you're left with another 6 miles - which sounds about right for A/C loss over a full charge. So, I'm gonna go out on a limb and say my guess about the firmware update is about correct. Is it?

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You know, I hadn't thought about that, but yes - I did get the firmware update in between those two trips. But my lower range on my daily commute has been more noticable the last few weeks. And an interesting side note. In the morning when I leave my garage in ECO mode, it usually shows like 106 miles. I keep the windows down and my commute is mostly on 30 mph streets. When I get to work I've usually only dropped like 1 mile from the range estimate even though I will have driven 4 or 5 miles. But on my way home when I fire up the A/C, by the time I get home the range estimate has dropped to like 86. So the car can definitely tell that I'm using a lot more power. Of course, the A/C is operating at full load at that point because the car is so hot. So I would imagine on a longer trip, the car would get cooled down and the A/C would cycle down some.

I think I'll do an experiment. Now that I think about it, this should be pretty easy. Since one of the screens on the Leaf's NAV display will show exactly how many KW the vehicle is using in real time, it shouldn't be that hard to drive down a flat piece of highway and check the difference in KW between running with the windows up and the A/C on and then again with the windows down and the A/C off.

Lithion ion batteries presumably don't like high temperatures and I'm wondering if this is perhaps affecting your range as well.

surfingslovak said:

Lithion ion batteries presumably don't like high temperatures and I'm wondering if this is perhaps affecting your range as well.

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While I'm sure this was his original hypothesis, I believe it would need to be MUCH hotter to affect range; cold affects these batts much more than heat. I think the firmware update plus the (obvious) use of A/C is the culprit.

I thought the heat was affecting my range,
http://www.mynissanleaf.com/viewtopic.php?f=9&t=4154&start=50
and also thought I had read something in the manual about it, but I can't find that now,
so if I can get 5.3 mKwh when it is 75 outside and only 4.3 mKwh when it is 100 outside,
would it make sense that that is just due to A/C use? (pretty much same trip at same speed, but maybe not exactly)

Interesting question, and it's plausible that this is due to A/C use alone. I found an old research paper from NREL and on page 4 they state that range reduction of 16% is to be expected. If my math is correct, you are seeing 18% range reduction.

An electrical air-conditioning load of 1000 W, which might meet steady-state air-conditioning requirements for a small sedan, reduces SC03 range by 16%.

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There's only one way to be sure. Someone's going to have sweat for science and make a no AC drive in the heat for comparison purposes.

Heat and humidity will lower air density, this should increase range.. perhaps the pavement and tires get sticky with the heat and this will increase tire drag.

A hot battery will produce more power.

I've noticed the same thing. But credit it to increased use of the A/C. When starting a drive in the afternoon the enegy screen even shows a significant increase in kwh for climate control. On my 25 mile trip home it seems to settle down about half way with recycled air but by then the damage is done to my range. Texas heat is just brutal. The morning drive always has reasonable range results.

While conducting your experiments, don't rely on the "turn climate control off for +x miles" reading. It is heavily damped and will take a good while to adjust to changes in the a/c settings. For example, of you set it to manual mode, a/c off and drop the temp to 60 so it's not trying to heat the outside air, you'll see the energy usage drop to zero immediately, but the +x miles readout won't drop for quite a while.

I've been driving in over 110 degree heat the past few days (112 today) and I still can obtain over 6m/Kwh with the A/C. After the A/C adjusts (maybe close to ten minutes or less), the KW meter goes way down and it only makes a 1-2 mile difference with it on.

only way you can really get a good estimate on range effects is to make several round trips on the same day or on days as close to it as possible.

i find that even on repeatable routes like my work commute, the figures can vary greatly from day to day. temps, wind speed and direction, road conditions (dry/wet) and traffic all play a part.

best thing to do is track your performance over several weeks and see if you can see anything from that

on my commute in the morning, i have very little traffic, lights easy to judge, etc. so it should be consistent but its not. there is still a range variance of at least 20% in seemingly identical conditions. i also tracked daily trips in the Prius as well and found the same large variance. now my commutes were 7.1 miles one way when i was tracking the Prius and 9.1 on the Leaf. (moved so now its 6 miles)

LEAFfan said:

I've been driving in over 110 degree heat the past few days (112 today) and I still can obtain over 6m/Kwh with the A/C. After the A/C adjusts (maybe close to ten minutes or less), the KW meter goes way down and it only makes a 1-2 mile difference with it on.

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I see the same behaviour driving in the heat in DFW, very little mileage differance. I keep my AC set to 80F/Auto since that keeps the car more than cool enough, so after the initial cool down the dash shows climate control using very little and only shows 1-2 mile difference. Prior to settling on 80F I messed around with the AC (non-auto, lower and full blast on the air) and climate control was using 2-3Kw/hr and showing a +9 mile difference in range.

Correction: 4-5 miles when I leave it set to 80F/Auto vs 8-9 when I mess with it. Kept an eye on it today and it is what looks like 750W vs 1.5kW

adric22 what climate control setting are you using?