Range vs. air temperature according to AAA

I'd start with this thread when computing range: http://www.teslamotorsclub.com/show...some-numbers-on-the-factors-that-affect-range.

The calculator on Tesla's website includes the effect of temperature on range:

Your Questions Answered | Tesla Motors

Battery heating has a big impact when temperatures are below 50F. You'll get less range from short intermittant trips than a long continuous trip since the pack needs to be warmed up to 50F at the start of each drive.

To be clear, the battery itself is not losing range in the cold. It's storing the same amount of energy. You just typically have other draws that consume energy (and the battery cannot put out as much *power*--or receive as much using regen--when cold).

In the Model S you can enable "Range Mode", which will prevent any active heating of the battery unless it's REALLY cold (and 20°F does not qualify as REALLY cold). Instead, the battery pack very slowly warms up passively from the small losses in power production. Range mode will help you save considerably on range.

If you feel you need to heat the battery, you can preheat the battery while plugged in before you leave using power from the wall. Same goes for the cabin heating.

There are other things about winter that increase energy use that have nothing to do with EVs:

-The air is more dense, therefore drag is higher.
-It is generally windier in the winter--therefore higher drag forces.
-There is often more precipitation (rain, snow) and less traction (rain, snow, ice) which contributes to losses.

So, there are plenty of things you can do to reduce energy loss in the winter for those drives when you need the range:

-Preheat the battery pack while plugged in.

-Preheat the cabin to a warm temperature while plugged in. The materials in the cabin will store some of the heat and give it back while you drive.

-Use the seat heaters to reduce the cabin heating needs.

If you follow these tips, I've found a loss of about 20% range in the winter (temps around freezing).

Todd Burch said:

In the Model S you can enable "Range Mode", which will prevent any active heating of the battery unless it's REALLY cold (and 20°F does not qualify as REALLY cold).

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Huh, range mode does that? I wonder if I'm doing any long term damage to my battery by leaving it in range mode all the time (by not letting it control the temp of the battery as tightly as it wants)... I was under the impression that all range mode did was limit the climate control, and I've been leaving my car in range mode all the time simply because the higher fan speeds are really, really loud.

kjl said:

Huh, range mode does that? I wonder if I'm doing any long term damage to my battery by leaving it in range mode all the time (by not letting it control the temp of the battery as tightly as it wants)... I was under the impression that all range mode did was limit the climate control, and I've been leaving my car in range mode all the time simply because the higher fan speeds are really, really loud.

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I'd say in the Bay Area, you have absolutely no worries. It is only pack heating that is limited, and only in moderate cold. When it gets really cold, the pack heater will protect the battery power delivery. Also, bear in mind that a cold battery is a happy battery. It might be less powerful, but it is also chemically degrading very very slowly. High heat is the killer.

You are absolutely fine leaving the car in range mode. Cold is fine for the battery (better, as Vger pointed out). If the battery is hot, it will still cool it as necessary. If it is REALLY cold, it will still heat it as necessary.

Todd Burch said:

To be clear, the battery itself is not losing range in the cold. It's storing the same amount of energy. You just typically have other draws that consume energy (and the battery cannot put out as much *power*--or receive as much using regen--when cold).

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Well, in a battery without temperature control (like the LEAF), the capacity is reduced by cold and increased by heat.

We use a rule of thumb of minus 1% per 4F degrees below 70F and plus 1% per 8F above 70F.

So, a 30F battery has 10% less stored energy for you to consume and a -10F has 20% less stored energy.

The Nissan LEAF has 21.3kWh of usable stored energy when in new condition at room temperature.

I'm kind of stuck on the 57% number in the OP. Where did that come from? From my experience, 57% is way more than I would expect to see. Well maybe in Frozen Monkey Bay, Alaska... Tony's numbers are more in line with my expectation.

By the way, 50F is a very sharp cut off for non-range mode. The other morning it was 48F in the car and I got 380 wh/mi. Same day mid morning, it was 54F and the exact same route and basically same driving style yielded 322 wh/mi. 48F was 18% worse, I assume mostly due to battery heating.

Oh and a slight semantic point - a cold battery doesn't have less stored energy, it's just less usable energy. If you warm it up, the usable amount increases.

AAA apparently took a Leaf and put in a temp controlled room and tested the range to at those numbers. Certainly don't apply to the Model S to that degree.

dsm363 said:

AAA apparently took a Leaf and put in a temp controlled room and tested the range to at those numbers. Certainly don't apply to the Model S to that degree.

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EV Trip Planner does a pretty good job at calculating the needed power to keep the cabin and battery warm. Go simulate some of your trips in winter, spring, and summer; see what the results are.

I've found the biggest help for winter range is to preheat the battery by charging just before you leave without being in range mode, and preheating the cabin. In fact, before leaving on a winter hypermile trip, or at winter Supercharger stops, I will often set the cabin heat up to 85˚ F. with the app to store extra heat in the interior of the car.

Cottonwood said:

EV Trip Planner does a pretty good job at calculating the needed power to keep the cabin and battery warm. Go simulate some of your trips in winter, spring, and summer; see what the results are.

I've found the biggest help for winter range is to preheat the battery by charging just before you leave without being in range mode, and preheating the cabin. In fact, before leaving on a winter hypermile trip, or at winter Supercharger stops, I will often set the cabin heat up to 85˚ F. with the app to store extra heat in the interior of the car.

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Has anyone seen a 57% hit in the winter though in a Model S?

dsm363 said:

Has anyone seen a 57% hit in the winter though in a Model S?

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I've been through some pretty good winter drives and have seen nothing like this. See Realistic Range Expectations in Crummy Winter Weather - Hypermiling in the Winter...Brrr]

From that post:

dsm363 said:

Has anyone seen a 57% hit in the winter though in a Model S?

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I drove from Springfield to Salem in deep and some packed snow and I had to sit stopped on I-5 near Salem in low 20F temperatures for 2 hours. this was 70 miles total and I only saw 435 Whr/mi average. most of the drive was ~ 45 mph though (any more and I was fishy...the guy that passed me was stuck in the shoulder- 3-4' of powder shortly after)

hauling ass half way / half way in snow to Springfield from Grants Pass was ~ 400Whr/mi (42F down to 28F)

PhilBa said:

By the way, 50F is a very sharp cut off for non-range mode. The other morning it was 48F in the car and I got 380 wh/mi. Same day mid morning, it was 54F and the exact same route and basically same driving style yielded 322 wh/mi. 48F was 18% worse, I assume mostly due to battery heating.

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I don't debate your numbers, but I am suspicious that it's from a change from 48F to 54F. Winds are usually light in the mornings as an inversion layer often sets up. As the sun heats up the surface for a few hours, this inversion layer bakes off and stronger winds aloft start to break down to the surface.

Even if you didn't notice significantly stronger winds or gusts, a light breeze or the occasional light to moderate gust can have significant effects on Wh/mi. I'd put my money more on the reason being slightly stronger surface winds than a 6 degree change in temperature. I doubt there's any battery heating at 48F.

dsm363 said:

AAA apparently took a Leaf and put in a temp controlled room and tested the range to at those numbers. Certainly don't apply to the Model S to that degree.

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And they likely ran the cabin heater. So, the battery "usable" losses from cold are well known and quantifiable.

The HUGE consumption of energy from the heater is well known, too.

dsm363 said:

Has anyone seen a 57% hit in the winter though in a Model S?

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Over the long haul I haven't. But I've certainly seen individual trips where I've averaged over 500 Wh/mi (e.g. in snow and ice). I've seen my commute (10 mi round-trip) cost me well over 400 Wh/mi in the winter, although not every day. Lately in milder weather I've been getting closer to 290 Wh/mi. The problem, of course, is that's a pretty short trip so I'm sure the measurements are far less accurate.

Todd Burch said:

I doubt there's any battery heating at 48F.

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The target temperature for the battery heater is 50F, so it's possible that heating is responsible for the difference.

Model S Overall Thermal Management

It is possible AAA tested an older Leaf with resistance cabin heating. The Tesla (and newer Leafs) have a heat pump. Pretty big difference.

As far as the loss of range in the heat, the AAA test is obviously seriously flawed. Reduced air density and more usable energy from the battery more than makes up for a/c use in my experience. I get about 100 mile range at 95 degrees in a Leaf.

AAA has no credibility in regards to changing the automotive paradigm. This article was a hit piece on EVs in general