Study Says Fast Charging Takes Longer When It’s Cold Out

AUG 11 2018 BY MARK KANE 50

Cold batteries severely slow down electric car fast charging capabilities

The latest Idaho National Laboratory’s study – Empirical analysis of electric vehicle fast charging under cold temperatures – confirms various reports that low temperatures (especially below 32°F / 0°C) impact fast charging.

The test done for the Nissan LEAF taxis (previous generation we believe) over 500 DC fast charges shows that fast charging can take some three times more than the usual 30 minutes to 80% when the battery is very cold.

The reason for this is electrochemical reactions within the cell, which can’t be done at low temperatures, and onboard battery management systems that limit the charging rate to avoid damage to the battery.

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“Motoaki and his colleagues analyzed data from a fleet of Nissan Leafs operated as taxis over roughly 500 Direct Current Fast Charge (DCFC) events. Temperatures for the charging events ranged from 15 to 103 degrees Fahrenheit.

The researchers found that charging times increased significantly when the weather got cold. When an EV battery was charged at 77 degrees, a DCFC charger might charge a battery to 80 percent capacity in 30 minutes. But at 32 degrees, the battery’s state of charge was 36 percent less after the same amount of time.

And, the more the temperature dropped, the longer it took to charge the battery. Under the coldest conditions, the rate of charging was roughly three times slower than at warmer temperatures.”

The problem for EV drivers could be limited if they use garage or drive without the need for fast charging (are satisfied with AC Level 2 at several kW), but if someone is on long-distance travel and needs to fast charge along the route during cold weather, he/she should be prepared for both – extended time for charging and higher expenses (if charging fees are related to length of session). The cars that are equipped with an efficient thermal management system should be less affected.

The difference between winter and summer could also make a big difference for taxi drivers, so they need to recognize the EV performance in the worst case scenario to not be surprised after purchase.

““Battery researchers have known about the degradation of charging efficiency under cold temperatures for a long time,” said Yutaka Motoaki, an EV researcher with INL’s Advanced Vehicles research group.

But most of the current knowledge comes from experiments with smaller batteries in the lab, not data from large, electric vehicle batteries in real-world conditions. Further, EV manufacturers often provide consumers with only rough estimates of charging times, and they typically do not specify the range of conditions for which those estimates apply.

“We wanted to ask the question: What is the temperature effect on that battery pack?” Motoaki said. “What is the effect of degradation of charging efficiency on vehicle performance?””

Source: Idaho National Laboratory

Categories: Charging

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50 Comments on "Study Says Fast Charging Takes Longer When It’s Cold Out"

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Obviously. It is well known that batteries need to be heated for performance.

Cold weather is the Achilles heel of ev’s. You get hit double, range is reduced and charge time increases. That makes long trips impractical in a car like the Bolt when it’s winter in the Midwest or Rockies. I would argue that we need larger batteries i.e. 120kwh-150kwh to fix both range and charging issues.

It is only a problem for taxi drivers, not for long distance trips. If you drive 200 km contiguously on highway speed the battery is warm enough to accept full fast charging speed. Only if you try to fast charge after a cold night of standstill you are seeing much slower charging speeds.

Not at -10F. No amount of driving warms the battery much. Only a warm garage. I lived this.

Obviously you haven’t, at least not in a nominal Leaf-type vehicle. At freeway speeds from DC charger to DC charger around 10° F this winter, my 2013 Leaf will typically be around 6 battery temp bars between the rapid discharge and rapid charge. Range is reduced somewhat, but there is little effect on charging at that battery temperature.

Although it adds some, use EV Trip Planner and set the temps and speeds and make sure to select the Model 3 Long Range and it still does pretty good in the winter. Yes, it will cost more and be slower, but still useful for long range travel. I don’t know if it models for a cold battery, but the battery should actually stay fairly warm on a trip with frequent fast charging.

What’s long trip to you? Bolt is probably good for 180 miles in cold, 150 miles if you go nuts with heater and open the windows. That’s 2 hours of driving in highway. That’s enough range for almost everyone, and 1 hour longer that tolerable when kids are whining in back seat.

My weekend drive is 280 miles round trip (one day). With a range of about 150 miles at 75 (speed limit) the bolt doesn’t work. I take another car to avoid the hassle of having to charge. In the summer it’s easy, maybe 20 min to charge. Winter, I keep my trips under 150 miles or take a different vehicle.
No way I could go home for the holidays. 850 miles in a day. Only 12hrs in my TDI or Volt. Who knows in a Bolt, but I don’t want to find out.

If you drive more than 2 hours in one sitting, Bolt isn’t the car for you, especially if you drive that much often.

SparkEV did 650 miles in 16 hours, and the guy was leisurely driving and charging. Bolt with 160 miles range extra to start, you can probably do 850 miles in 17 hours.

850 miles in 12 hours is average speed of 71 MPH. You’re not resting much at 75 MPH speed limit. Frankly, I like 2 hours drive (or 1 hour with kids) and 30 minutes rest schedule even in gasser. As such, my trip time would be similar with gasser or EV. Provided, of course, there’s no waiting for free chargers.

We do 3-3.5 hours before stoping

How about a 80 kw battery that is tuned for weather environments

A relatively efficient car with a well insulated 80 kWh pack that charges at a 2C rate (or around a 150 kW charge rate) would work for most people, even for moderately long roadtrips. And I don’t think that BEV’s should set their goals to please the longest range drivers right now, work to satisfy 80% of the car buying public. The drivers that want to drive 4 hours, refuel in 5 minutes and drive another 4 hours aren’t numerous enough to be worth pursuing. 60 kWh packs are a bit short ranged. The Bolt would be a slightly better choice if it looked less like a clown car and had more comfortable seats, but gaining 1/3 more AER would be huge. 300+ miles of AER make roadtripping much easier than 238 miles of AER, plus it pushes back the point at which the charge taper is going to kick in, allowing you to fast charge (without as much tapering) to around 80% and have a comfortable 240+ miles of AER in the pack.

Why would a larger battery push back tapering?…

“The problem for EV drivers could be limited if they use garage”

I have never seen any DCFC in enclosed garage. But even a garage must be heated to have an effect. Otherwise, it’ll be almost as cold as outside.

No need to heat garage.
Just close the door when you do not drive in or out.
Greetings from Austria.

Do they have DCFC inside where you can close the garage door in Austria? There’s none like that in US. Sound to me like lots of hanky panky could go on after the door is closed while using DCFC.

Hey, when you are in your garage… can you see the stars? That’s probably why it’s not working for you even if you close the door

Do you have DCFC in your garage? You must have more money than sense.

“But even a garage must be heated to have an effect. Otherwise, it’ll be almost as cold as outside.”

Nope. Obviously science isn’t your forte. You might want to read up on “thermal mass”, as well as “passive heat sink”.

Precondition the battery

How do precondition a LEAF battery?

I don’t believe they are referring to the Fast charger being inside, that would have no impact on an arriving vehicle with a cold battery.

They meant keeping the car in a garage overnight to avoid the coldest temperatures which helps with charge speed when you do arrive at a rapid charger. My garage is unheated but is typically 20-30 degrees F warmer in the dead of night (as long as I keep the doors closed).

Another study where science proves the obvious.

I do long distance in winter at temperature around 0°F (-18°C). My car sleep outside and only my first fast charging is slower since the battery heat up on the first leg. It’s no more than 30 minutes. After that the battery continues to heat up. By my 3thrd fast charging the battery is as hot as in summer and take the same time. I don’t see how a taxi driver will be impacted if he’s fast charging multiple times a day.

In other breaking news, the sun rose this morning.

Fake news

Blog entry I wrote about the Bolt and fast charging in the winter. While the blog is specific to my experiences in the Bolt, the issue of fast charging cold batteries in the winter is not.

Good post

Someone at GM should get fired for that. The Bolt has temperature management, but in the cold, they decided to stop that temperature management when the battery is low. Many complaint about it in Quebec last winter as temperature often hit -25C/-17F last winter.

Anyhow, with my 2014 i3, the only time I saw weather impacting charging was when my i3 stayed idle/parked in the cold for an extended period. But on the highway, I always get the same DCFC charging rate, they only reason I take more time in the winter (and when I say longer, it’s like 5 minutes more) is because I’m heating the cabin while charging. And I can do 4 to 5 DCFC in a row… no #rapidgate here 🙂

Rain is more likely when there are clouds in the sky too.

I see this was with Leaf. Whatever happened to battery warmer in Leaf that people boast about?

The battery heater kicks in when the battery gets cold, it can’t be turned on by the driver or set to a higher threshold temperature. Its set by Nissan to turn on at -4F to prevent damage to the battery, not for the convenience of the driver.

I have found charge speed is limited once the battery gets below 40F, a long way away from the battery heater turning on.

Did not know it was not adjustable by the driver. Thanks for the explanation. Maybe this should be adjustable especially if the car’s plugged into DCFC. When the ambient is 32F or even 64F, there’s really no need to worry about battery heating issue.

In other news: Water is wet in a certain range of temperatures.

It shouldn’t be news to anyone with even an average grade school science education that batteries store electrical energy via chemical reactions, and that chemical reactions are greatly slowed at low temperatures.

It’s pretty silly to point out that it take three times as long to charge a battery at or below freezing temperature. While true, that’s mostly irrelevant to any EV owner.

That merely points out the necessity for a battery heater to be part of any EV’s battery pack. If the electric power from a charger is directed to the battery heater for a few minutes, then the rest of the charging can proceed at normal rates, and after that it certainly won’t take “three times as long” to charge the battery pack!

More complexity to the car. Switching a radiator for a battery warmer

Not necessarily. Tesla Model 3 effectively solved this in software. (By using the drive motor / inverter as a heater.)

Admittedly, a heat pump should be more efficient… I’m not aware of any vehicle using a heat pump for battery heating, though.

The problem is, this is not true for all EV. Some EVs do have proper temperature management. Tesla, BMW i3, Kia Soul, Ionic, the soon to arrived Kona. The Bolt has one, but GM doesn’t seem to think you are driving EV in the cold.

They probably shouldn’t have used Nissan Leafs as their metric for battery charging performance. Sure cold weather charging will be less efficient for EVs but I don’t think using the Leaf as the representative for all EV fast charging is very scientific. It is just one data point.

The effects of cold weather are so great that a cold weather performance category should be added in addition to City and highway range. MPGe is not that helpful.

MPGe is the most useless data ever

Just give me AER, City Range, Highway Range, Cost of kw per hour

MPGe is used to manipulate the CAFE standard, and manufacturers find it very useful. Consumers would find MPGe$ more useful, which isn’t available without some calculations.

Yes that would be a good idea. Then it would become obvious to the average consumer that the LEAF has poorer winter performance while a Tesla isn’t impacted to the same degree.

This is nothing new and it is not a big problem for distance travel.

If you drive some distance in the cold and your destination doesn’t have a charger, charge at the nearest public quick charge at the end of the drive while the battery is warm. It will take much longer next morning at freezing temps and close to forever at below 0F. So don’t try to quick charge next morning.

If at the start of a long drive you have a full or close to full charge (or even half), then drive at least 50-60 miles at highway speeds before charging. The battery will be warm and charge at full rate. On a long trip after the first charge the battery will be hot, but not have any issues with getting too hot since it is easy to cool things with a below freezing ambient.

Water is wet and the sky is blue

To be precise, water is wet between 0C and 100C at sea level on the planet Earth. 🙂

I do agree however the article states the obvious.

Sky is black. Light scattering in earth’s atmosphere is blue in absence of much “dust”. With presence of more “dust” and angle of incidence, sky is red. Los Angeles sky before 1980’s was brownish gray.

We needed a study for this?