Does cold weather damage the batteries used in an EV?

Hi.

    Supposedly, cold weather reduces the rate of chemical reactions inside a battery, so they don't perform as well either as something to provide power or to accept a charge.    Sometimes there is some more obvious permanent damage such as a cracked battery case or crystaline structures that have formed inside the cells and remain there for ever after, usually short-circuiting a cell.   
     This leads to two questions:

1.     Does it usually get back to normal when a warm day returns?
2.     If a rechargeable battery loses some capacity (in the sense of KWh of electrical energy it can store or deliver)  in the cold weather,  where does that energy go?    Suppose you charged it to full on a warm day, then a cold day arrives and you used it only to find it lasted just half the usual time  -  does the other half of the time just re-appear when you warm the device up again?

    Relevance / Background:   Like a lot of people, I'm thinking of getting an EV (Electric Vehicle) soon.   How many (British) winters will the batteries last?   Have we had EV's for enough years to know how well they last?  Also, how much range for the vehicle will usually be lost on the cold days?

Best Wishes.

Battery efficiency generally decreases at low temperatures, the effects being summarised as an increase in internal impedance. Thus more energy is lost to internal heating when work is done. Oddly, when starting an internal combustion engine at low temperatures it sometimes helps to crank the starter motor a few times and wait: the warmer battery can now deliver enough current to spin the motor fast enough to start the engine.

Some early BEVs had a battery preheat cycle but I think battery performance now tolerates at least UK winter conditions without it.

You can estimate the cold weather range loss from the cabin heater specification. You generally need about 5 kW to keep  the windows clear in a small car at 0 deg C, and maybe 20 kW on a really cold day.  The advantage of an internal combustion vehicle is that  hot air is an inevitable waste product, so thanks to increased air density, it actually goes further on a cold day!

Hi.

    Thanks for your reply @alancalverd .    I know very little about batteries or real world engineering.

..... the effects being summarised as an increase in internal impedance.....

   Is that really a fair summary?
    I've found a few webpages suggesting the internal impedence of a Tesla battery is very low:   approx.   30 milli-Ohms     to   46.1 mΩ

[reference:    Tesla motors club,    https://teslamotorsclub.com/tmc/threads/model-x-100d-battery-internal-dc-resistance.108682/      and also a website from  circuitdigest dot com -  but the latter seems to be filled with adverts and strange links you must click,  I wouldn't want to list that actual website address and risk people causing problems to their computer ].

    Anyway, even if this internal impedance doubles in the cold weather, it hardly seems significant compared to the resistance of the motor and/or any other electrical equipment attached  (car radio,  or the heaters   etc.).

     I'm not a real-world engineer, as I keep saying, but this is a back-of-the envelope calculation that seems relevant:
According to one website,  a Tesla motor provides  220 KW power when driven at 320 V  and rotating at 5000 rpm.   I'm going to guess that's typical rpm.
   So  P = V² /  R         =>         R =  V² / P    =   320² / (220 x 10³)   =   0.47 Ohms   ≈   465  milli-Ohms.
    Let's drive just the batteries internal impedance and the motor.    So, let's assume   these are the only two things of relevance connected in series (so a current, I, passes through both).
The total power used =  I² R_total  =  0.51  I²
Power used to heat the battery =  I² R_{internal battery}  =  0.04 I²
Ratio of power lost as heat in the battery :  total power  =   0.04 : 0.51   =>    7.8% of the total battery capacity (in KWh) is wasted as heat in the battery.

Do a similar calculation with the battery internal resistance doubled (for a very cold day) and we have: 
Ratio = 0.08 : 0.55     =>  14.5% of the total battery capacity wasted as heat in the battery.

    I'm going to assume that on typical driving, 1 KWh of energy used in the motor will move the car  X amount of miles.   I know you'd go further downhill etc. but let's just assume that on typical driving,  total energy delivered to the motor is linearly proportional to the number of miles the car will move.   Is that a reasonable assumption?  Probably.... it seems that car manufacturers are making an estimate like this when they show the increase in range  vs.  the choice of a larger capacity battery.  If it takes 100 Joules of energy to move 1 mile, it takes 200 J to move 2 miles etc.
    So, very roughly,   we get 92.2% of the battery capacity converted to range on a wam day  and  85.5% on a cold day.   Hence,  a drop in range of  6.7% of the battery capacity   (of which we were only getting  92.2% even on the warm day),  so a change of  6.7 / 92.2    ≈  a 7% reduction in range on a cold day compared to the warm day.
     Is that a reasonable back-of-the envelope calculation or have I made a mistake?  Are these estimates reasonable?

You can estimate the cold weather range loss from the cabin heater specification. You generally need about 5 kW to keep  the windows clear in a small car at 0 deg C, and maybe 20 kW on a really cold day.

     That does make sense.   The power demand to keep the window clear and the driver sufficiently alive and responsive may be the more significant power drain in cold weather.
      I've noticed that some top-of-the-line EV's are offering a heat pump as a means of heating the car.   This is the most efficient way of heating the car and will provide a bit more range on the cold days.

The advantage of an internal combustion vehicle is that  hot air is an inevitable waste product, so thanks to increased air density, it actually goes further on a cold day!

     I don't live right up in the highest hills.   The air is fairly dense most of the time  (I would have thought).  I would imagine a modern car with a turbo to ram the air in and suitable electronic clever bits would be able to get enough oxygen into the engine on every stroke.   I mean if it put too much oxygen in, then the ratio of fuel to oxygen is too weak and then you'd just be losing power again.
    Do you really get more  m.p.g. on a cold day?    Perhaps you were talking about the hot air waste product?   On a cold day, I suppose that will go further (further up) every second.   However, my vehicle wouldn't be a hot air balloon and that sort of vertical mileage wouldn't be something I want.

    ----------
    Anyway, I know very little about EV's or real world engineering in general.    If anyone has some data about the real world longevity of EV batteries after a few cold winters  and/or  the typical loss of range on a cold day, please let me know.   This is a science forum, not a help site just for me but I would argue that every government is putting all of us under pressure to go electric soon and so this sort of information is of value broadly.   However, any moderator is free to move the discussion somewhere else - like the "just Chat" section if they wish.

     Looking at the diagrams of modern EV's  the batteries seem to be really low down, often just under the floor that the passengers stand on.   I would be guessing that changing the batteries is an expensive piece of maintenance.   Do you have easy access from underneath or does everything have to be taken out to get to the batteries?   I don't know....
In terms of realistic cost, is the car dead as a whole once the batteries lose their ability to hold a sensible charge?

Best Wishes.

Relevance / Background:   Like a lot of people, I'm thinking of getting an EV (Electric Vehicle) soon.   How many (British) winters will the batteries last?   Have we had EV's for enough years to know how well they last?  Also, how much range for the vehicle will usually be lost on the cold days?

I'm waiting for sodium ion, they have none of these problems, should be far cheaper too. As for the cold weather performance dealers I have spoken to in a non customer situation tell me in winter they expect half the advertised mileage at present from evs but thats not a problem really for most in the UK. I suppose all of that hard accelleration and braking doesn't help.

First of all, cold means salt, and especially Tesla hasn't shown any obvious awareness of the need to protect parts from corrosion.  That's an issue since batteries are at the bottom of the car where the salt is.

2.     If a rechargeable battery loses some capacity (in the sense of KWh of electrical energy it can store or deliver)  in the cold weather,  where does that energy go?

Capacity and energy are different things.  Sure, you put X energy into the car, it gets cold, and now there's less energy available. It went away with the heat?  Does the full charge return if it warms up or do you need to top off a full battery if it's been cold and it's warm now?  I don't know the answer to that one.

1 KWh of energy used in the motor will move the car  X amount of miles. 

Estimate 3 - 5 miles per kWh. It's not quite linear with battery capacity for a given car as the bigger battery weighs more!

There is of course battery university, which says than lithium ion cannot be charged below 0C unless it is a specific chemistry, but I imagine that would lower the capacity, as all the various lithium chemistries seem to, so I doubt anything claiming high distance/power would be, such as the current set of wheeled crematoriums . Lots more on here about batteries on all types, far more than I understand but it's where I go to.

https://batteryuniversity.com/article/bu-410-charging-at-high-and-low-temperatures

Hi.

   

There is of course battery university, which says than lithium ion cannot be charged below 0C unless it is a specific chemistry...

   I have just checked this.  I think it's that Li-ion batteries should not be charged below freezing rather than that they cannot be charged.    According to your suggested Batteryuniversity site,  charging them below freezing temperature is always slow and would usually cause permanent damage resulting in lower battery performance.
    That's not something that Tesla ever seem to mention - and it does seem that they use Li-ion batteries of some variant or another.  Even with some clever technology it seems you would still be well advised to charge them at a small fraction of the usual rate when the temperature is below 0.    So, taking a long trip in the winter and putting your vehicle onto a fast charger along the way may be very bad news for the batteries.

Best Wishes.

Hi ES, I have never worked with battery tech and apart from a primitive understanding of how batteries work I find I have little to add. The ever increasing stored energy in these batteries and the potential for sudden release of this energy does alarm me- I raised this concern before to mixed replies. I am sure you have seen some of the fires involving lithium batteries.

Battery cars are a victim of the availability heuristic: if something springs to mind more readily it will be perceived as more probable, BEV fires make news but ICE fires don't. People are used to the idea that petrol catches fire, it's not news, but for the best part of a century people have seen batteries as innocuous and harmless, so the idea that they're no longer so benign is more sensational. Everyone jumped to the conclusion that the Luton airport car park fire was a BEV when it wasn't.

Stats on the subject are still thin on the ground, but ICE cars are between 2 and 20 times more likely to catch fire than a BEV.

The only car I've ever watched burn was a Mk3 Cortina (electrical, not the petrol tank), although my Carlton came quite close to it one morning (again, electrical).

The perceived difference in risk is due to the fact that ICEs don't spontaneously combust. The usual point of unintentional ignition occurs when a poorly-maintained vehicle has been running fast and hot, the fuel line comes adrift or the carburettor (remember those?) floods, and a backfire on overrun blows flames out of the air intake.

However well-maintained a BEV may be, early lithium batteries gradually developed in an internal short circuit and self-immolated entirely at random. The problem was occasionally reported in phones and computers but really hit the headlines when Boeing Dreamliners  became a fire hazard. I  think the problem has been  largely eliminated, but the fact remains that a burning BEV is very difficult to extinguish and almost impossible to salvage, which is one reason that insurance premiums have doubled in the last few years.

The Ford Pinto, a petrol(gasoline) car was prone to self cremation, as far as I remember.

Stats on the subject are still thin on the ground, but ICE cars are between 2 and 20 times more likely to catch fire than a BEV.

Certain chemistry electric batteries catch fire, such as high performance tesla's, many are now different chemistries that are not a fire risk, so I would like to see figures on EVs that have dangerous batteries. Whilst safety in a car is one thing, safety in a house whilst sleeping is quite another, li ion batteries that catch fire are extremely destructive. I believe all large energy storage batteries for houses are of the non flammable type, there are many of those around and you never hear of 1 catching fire, even though they would burn a house down within seconds.

Hi.



   I have just checked this.  I think it's that Li-ion batteries should not be charged below freezing rather than that they cannot be charged.    According to your suggested Batteryuniversity site,  charging them below freezing temperature is always slow and would usually cause permanent damage resulting in lower battery performance.
    That's not something that Tesla ever seem to mention - and it does seem that they use Li-ion batteries of some variant or another.  Even with some clever technology it seems you would still be well advised to charge them at a small fraction of the usual rate when the temperature is below 0.    So, taking a long trip in the winter and putting your vehicle onto a fast charger along the way may be very bad news for the batteries.

Best Wishes.

As for the batteries, you would need to know the car specifics, if it has a battery heater, if it monitors it's temperature if it has different chemistries, I should email the manufacturer. I would call damage a "can not" Evan, technically you can directly use very high voltage power lines to recharge the battery, unfortunately it will probably damage the battery and possibly yourself. Just a matter of time?

I ran across this comment from Blair Korchinski on Qora, comparing petrol and electric cars in the Canadian cold... (he obviously likes EVs)
https://www.quora.com/If-electric-cars-are-not-good-in-extreme-cold-then-why-do-people-keep-buying-Teslas-in-Canada


Q: If electric cars are not good in extreme cold, then why do people keep buying Teslas in Canada?
A: As the owner of two gasoline-powered pick-ups and the driver of a diesel at work, questions like this always make me laugh.
In the cold an EV (Electric Vehicle) loses 40% of its capacity. In the best conditions, the very best ICE vehicle reaches 40% efficiency [loses 60%].
When it?s cold here in Canada we plug in our ICE vehicles so they will start. Double block heaters, like in my 2004 Chevrolet Silverado, suck about as much electricity as the average commute uses in an EV.
Gas mileage goes way down in the winter in ICE vehicles. Most of us warm up our cars for 10?15 minutes twice a day. The engines don?t run as efficiently, so even warmed up fuel mileage suffers. Then there are problems with fuel lines freezing, cars not starting. Then there?s extra wear and tear caused by thick oil not lubricating properly until the oil warms up. Catalytic converters don?t get hot enough to do their jobs, so we pollute even more.
Diesels, well diesels suck in the cold. The fuel doesn?t atomize properly, the batteries get so weak they won?t run the glow plugs or engine heater, and in the bad cold, the fuel gels up. DEF (Diesel Exhaust Fluid) tanks freeze solid and the little heater in there can?t keep up, so you get emissions alarms. The heaters don?t put out enough heat, you have to leave them idling for extended periods. Stop for fuel and the damned pumps freeze up so it takes forever to fill the tanks.
Go to an area where there are lots of diesels when it?s -30 ?C and you can smell the half-burnt diesel in the air. That?s how inefficient they become in the cold.
All of that is just an average winter day for guys like me. We?re so used to it, we barely think about it as we stand out there in the cold with our booster cables.
So the question shouldn?t be why we buy EVs, but why we don?t buy more of them. The modern technology makes way more sense here than ICE vehicles do.

There is probably nothing incorrect in that ode to the EV but it paints a misleading picture. Okay, an ice will max out at ~40% but the other 60% is available for heating the vehicle whereas an EV which is already 40% down in these cold temperatures will have to use a lot of battery power just to maintain a survivable environment- just what the range will be I don't know but it will be impaired. I cannot imagine fuel consumption increasing during a cold snap unless road conditions prevent the vehicle from reaching an efficient speed/gear ratio. Cold dense air generally improves the efficiency of an ice.

The Ford Pinto, a petrol(gasoline) car was prone to self cremation, as far as I remember.

Pintos caught fire because the tank ruptured in a rear end crash. There was famously the scandal when the cost-benefit memo was leaked showing that it was cheaper to keep paying compensation to the victims than modify the car.
https://en.wikipedia.org/wiki/Ford_Pinto#Cost%E2%80%93benefit_analysis,_the_Pinto_Memo

The perceived difference in risk is due to the fact that ICEs don't spontaneously combust. The usual point of unintentional ignition occurs when a poorly-maintained vehicle has been running fast and hot, the fuel line comes adrift or the carburettor (remember those?) floods, and a backfire on overrun blows flames out of the air intake.

I doubt that. I'd say more fires are fairly spontaneous electrical faults (unless the regular servicing schedule entails checking every electrical contact in the car for corrosion/looseness/overheating).

"Electrical faults with the 12-volt battery system are the most common cause of car fires, according to the AA's technical expert Greg Carter."

The fire I watched in the Cortina started after the owner had already reported an electrical fault, and the garage mechanic had thought he'd managed to fix it (everyone watching was expecting the fuel tank to explode, but judging by the way the fire brigade behaved, they knew it wouldn't). The near-fire in my Carlton was the heated rear window fuse incinerating the fuse box. Then there was the spate of Zafira fires which were also faulty maintenance of the electrics.

There is probably nothing incorrect in that ode to the EV but it paints a misleading picture. Okay, an ice will max out at ~40% but the other 60% is available for heating the vehicle whereas an EV which is already 40% down in these cold temperatures will have to use a lot of battery power just to maintain a survivable environment- just what the range will be I don't know but it will be impaired. I cannot imagine fuel consumption increasing during a cold snap unless road conditions prevent the vehicle from reaching an efficient speed/gear ratio. Cold dense air generally improves the efficiency of an ice.

He seems to be confusing a low efficiency with a large variation in efficiency with temperature change.

Personally, when I look at the state of cars these days, BEV or ICE, I'm glad I gave up driving.

Q: If electric cars are not good in extreme cold, then why do people keep buying Teslas in Canada?
A: As the owner of two gasoline-powered pick-ups and the driver of a diesel at work, questions like this always make me laugh.

So given the choice, he sticks with ICE!

The problem of diesel turning to glue should have been solved years ago: JETA1 is essentially similar to diesel and works down to -40 C all day every day. Preheating diesel isn't beyond the wit of man, and as 40% of the energy of fossil fuel appears as heat once the engine is running, you can do a lot to reflow the exhaust over the catalytic converter if you need to.

The power required to heat the cabin is exactly the same regardless of the source, but as I pointed out in reply #1, it is "free" with an ICE but reduces the range of a BEV.

AFAIK Antarctic scientists use properly specified ICE vehicles with no real problems, and most Scandinavians seem to get around OK on ICE snowmobiles. There's much to be said in favor of aircooled engines at low temperatures, though aircooled diesels haven't found much favor in the light aviation business.

Hi.

    Thank you to everyone who has replied.   I hope everyone has had at least one "thank you" mark put on their post.   I may be paying less attention to this thread from now on.

    I think I've found a partial answer to my earlier question about where the energy goes on a cold day.  @Halc was the only one who tried to address that question.   Specifically it seems you could charge the battery to full on a warm day but get much less than the full battery capacity displayed when you use it on a cold day.    The explanation seems to have two important points:
     1.    Most of the on-board sensors and computers are just trying to calculate the range and battery capacity that you have as best as they can.   Many will know what the ambient temperature is and some computers will adjust the figures that get shown on the drivers display according to some algorithm.   A very cold battery just won't deliver such a high voltage and this will usually appear to the sensors as if the battery capacity is lower than it actually is    etc.      Overall, it only appears as if some energy has just simply gone but actually it probably hasn't.   If it warms up again, the battery should still be at about full charge.
      2.     Many of these EV's monitor the battery temperature and they will heat it up, often called pre-conditioning of the battery.   The phrase "pre-conditioning" is usually applied to something that happens while the vehicle is plugged in and before the journey even begins.   For example, most of these EV's can be programmed to know when you start your morning commute to work and they will get everything pre-conditioned automatically.   However, it seems that this sort of conditioning for the battery doesn't completely stop when the vehicle is being driven.   I can only guess while this is still called "pre-conditioning" instead of just "active and current conditioning" but I suppose they would argue it's something that is done BEFORE more power is available from the batteries.   Most EV's will not allow the batteries to get too cold while you are driving.   Obviously if you do also put some heat into the cabin area, then the range is reduced even more.   While you could choose to let the driver freeze and wear winter gear inside the car, you simply cannot choose to let the batteries stay too cold.   So, inevitably, you will get less range on the cold days.

     NOTE:   I don't yet own an EV and claim no expertise.   I'm not really getting straight answers from most of the car salesmen.  I suspect that's because we just haven't had EV's for long.   Any comments I have made are just the best sense I can make out of it at the moment.

Best Wishes.