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A new AAA study finds that when the thermometer dropped to 20 degrees Fahrenheit, range fell by an average of 41 percent on the five models it tested… Some EV drivers recently found that range can drop by half when the mercury tumbles into negative territory.

https://www.cnbc.com/2019/02/06/aaa-confirms-what-tesla-bmw-nissan-ev-owners-suspected-of-cold-weather.html

Date: 2019-02-08 12:36 am (UTC)
From: [identity profile] misha-b.livejournal.com


There are several reasons the range decreases:
1. Cold battery is not efficient and pre-conditioning (warming it up) takes energy.
2. Heater use.
3. The actual range loss.

(3) is much smaller than 40% and the other two are relatively small on longer trips where range makes a difference.

Date: 2019-02-08 02:24 am (UTC)
From: [identity profile] ny-quant.livejournal.com

Откуда это известно?

Date: 2019-02-08 02:27 am (UTC)
From: [identity profile] misha-b.livejournal.com
Много откуда, в том числе из личного опыта.

Date: 2019-02-08 04:25 am (UTC)
From: [identity profile] misha-b.livejournal.com

What is exactly your question? These are pretty basic facts about EV's. I don't have an exact analysis with full breakdown depending on your usage pattern. I am sure you can find them if you search online.

Date: 2019-02-08 06:23 pm (UTC)
From: [identity profile] ny-quant.livejournal.com
The question is why would I believe your opinion more than AAA study?

Date: 2019-02-08 06:50 pm (UTC)
From: [identity profile] misha-b.livejournal.com

There is no opinion here. Those are facts. The study seems to confuse different sources of energy drain. Your actual range depends greatly on your usage profile, if you are simply driving on a highway it will be much closer to the rated range (see the link I gave you).

Date: 2019-02-08 07:43 pm (UTC)
From: [identity profile] ny-quant.livejournal.com
// The study seems to confuse different sources of energy drain

How so?

Date: 2019-02-08 07:22 am (UTC)
From: [identity profile] misha-b.livejournal.com
Here is an example: https://insideevs.com/tesla-model-3-road-trip-in-bitter-cold-2-feet-of-snow-video/

33% loss of range in much colder weather + snow on the ground.

Date: 2019-02-08 06:25 pm (UTC)
From: [identity profile] ny-quant.livejournal.com
Thus your claim about "(3) is much smaller than 40% " is already debunked.

Date: 2019-02-08 06:51 pm (UTC)
From: [identity profile] misha-b.livejournal.com
What do you mean debunked? Those conditions were much worse than in the AAA study. Much colder + snow on the road.

Are you saying that the car must drive close to its rated range under _any_ conditions? That is physically impossible and not true for ICE cars either.
Edited Date: 2019-02-08 03:53 pm (UTC)

Date: 2019-02-08 07:22 pm (UTC)
From: [identity profile] ny-quant.livejournal.com
debunked means shown to be incorrect but maybe it is indeed not apples-to-apples comparison

No, I'm not saying this. IC engines powered cars also don't but it's much less of a problem for obvious reasons.

Date: 2019-02-08 08:33 pm (UTC)
From: [identity profile] misha-b.livejournal.com

Everything depends on your usage pattern. If you are charging at home or at work, the range loss on a daily basis can be significant, but is not something you notice at all (at least with a reasonably long-range EV, such as Tesla or Bolt) (I suppose there are a few people commuting >200 miles daily for whom it is an issue).

If you do not have a place to charge during the day or overnight, the range loss can be a serious inconvenience.

Finally, if you are driving long distance, the expected range loss is typically smaller than what they report (perhaps ~20-30% in cold weather with heater on, depending on conditions). However one has to be aware of it and plan accordingly. That is the usage where EV is most difference from ICE cars.


Date: 2019-02-08 06:04 am (UTC)
From: [identity profile] agasfer.livejournal.com
DoE оценивает ежегодный перерасход топлива из-за езды на недонакачанных шинах в более, чем миллиард галлонов. Поскольку зимой народу влом докачивать, половина машин ездит на спущенных шинах и перерасходует бензин. Для электрических эффект должен быть таким же. Кстати, поскольку на холоду резина жестче, расход энергии на трение в покрышках зимой больше.

Вот и еще одна причина.

Date: 2019-02-08 06:24 am (UTC)
From: [identity profile] misha-b.livejournal.com
That's a good point. When it is cold the pressure in the tires is lower and few people are going to bother pumping them up. In fact, if you drive long enough the tires will warm up from friction and the air pressure goes up significantly improving your range.

Date: 2019-02-08 06:50 am (UTC)
From: [identity profile] agasfer.livejournal.com
Hence, for fair comparison, tire pressure must be the same for all vehicles involved both in summer and in winter.

Date: 2019-02-08 04:57 pm (UTC)
From: [identity profile] misha-b.livejournal.com
Yes, that shows why accurate comparisons are tricky.

Date: 2019-02-08 06:31 pm (UTC)
From: [identity profile] agasfer.livejournal.com
One more consideration, completely unaccounted for so far, is that in the cold it takes less energy to recharge the battery. To simplify the model, when the battery is charged, the energy is used to convert chemical A into chemical B (there are several chemicals involved, of course, but just to make it simple); then this energy is discharged into electric current when B converts back to A. If the battery is cold, you still have the same amount of chemical B in the battery, meaning, you have the same amount of energy stored. So why it gives back less energy in winter?

The reason is, if in the summertime the battery is discharged to 100% A and 0% B (ideally), in the cold it stops working at about, say, 75% A and 25% B. So, if you warm up the battery, it can go on discharging to 0% B, but in the cold it just stops working when not completely discharged. However, this also means you need to convert only 75% A back into B, not 100% A, when you recharge the battery again.

Thus, in the wintertime you have to recharge the battery more often but every time you are recharging you use less energy. This leaves the same reasons to use more energy in winter as with the combustion engine vehicles.

Date: 2019-02-08 04:15 pm (UTC)
From: [identity profile] affidavid.livejournal.com
Зимой стоит держать давление в покрышках пониже из-за снега и льда. Докачивать не стоит.

Date: 2019-02-08 04:56 pm (UTC)
From: [identity profile] agasfer.livejournal.com
Едва ли это чем-то поможет, только ускорите износ. Лучше менять резину на зимнюю.

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