Maximum safe temperature for Lithium Ion Batteries - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: October 07, 2024, 04:59:53 am
content: Is it safe to leave my power bank that uses 16850 Li_Ion batteries in my car where temps get up to 120 degrees Fahrenheit?Thanks

author: K5_489
author_rank: Regular Contributor
timestamp: October 07, 2024, 07:26:10 am
content: Safe as in they won't cause your car to blow up? Sure. I have battery equipment in my work truck that routinely sees temps above 140*F.Reality is that you'd have to really try to get a battery hot enough to be a serious safety risk in a storage environment. But repeated exposure like that is definitely going to have a noticeably negative effect on cycle life. Anecdotally, the cordless power tool batteries in my work truck here in Phoenix typically are trash within 9-12 months. The same style/brand batteries at home? Still going strong after 5 years and the home batteries see FAR more cycles than the work ones.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 07, 2024, 07:55:51 am
content: The decomposition does not happen below 60 °C (140 Freedoms). In a car in direct sunlight you can easily go above 60 °C.Don't leave li-ion batteries in cars.

author: fixit7
author_rank: Regular Contributor
timestamp: October 07, 2024, 08:17:17 am
content: Well gentlemen, you have conflicting stories.:-)

author: Gyro
author_rank: Super Contributor
timestamp: October 07, 2024, 08:24:44 am
content: From what I have seen, the instructions that come with all Li_Ion battery containing products specifically warn against leaving them in hot cars. I would be surprised if your power bank instructions do not.

author: Psi
author_rank: Super Contributor
timestamp: October 07, 2024, 08:40:51 am
content: Your dash will get pretty damn hot. but I doubt the glove box gets all that hot, or a pocked in a door.But it really depends on where you live and how hot it gets.I would feel ok putting a lithium battery in the car somewhere like the glove box, but not putting it on the dash in the hot sun. That being said, the glove box does contain a lot of nicely combustible paper.Most dash cameras have lithium batteries in them. They are usually mounted up high near the top of the window glass, so they are away from the hot dash area, but still in mostly direct sun.

author: CosteC
author_rank: Regular Contributor
timestamp: October 07, 2024, 08:42:55 am
content: Primary question is bit imprecise.There is number of Li-Ion batteries chemistries, each with different limits.LiFePO4LiCoO2Li4Ti5O12LiNiMnCo02Just to list most popular.Each supplier has separate limits due to peculiarities of constructions and expected lifetime.Maximumstorage temperatureis higher thanmaximum operation temperature, which is higher thanmaximum charging temperaturetoo.Most of Li-Ion operational temperature is +80'C but cause lifetime degradation, with recommended +50'C.Temperature in car is also quite a topic. North Canada, Germany, California or maybe Egipt? Anyway in many countries black dashboard can reach 105'C easily. (221 in unprofessional units used in three countries or Farenheit)

author: Psi
author_rank: Super Contributor
timestamp: October 07, 2024, 08:45:41 am
content: Quote from: CosteC on October 07, 2024, 08:42:55 am'Freedom units' are now known as 'Corruption units'. Since there's now more corruption than freedom.

author: K5_489
author_rank: Regular Contributor
timestamp: October 07, 2024, 08:10:16 pm
content: Quote from: Gyro on October 07, 2024, 08:24:44 amLargely because the heat can have a severe negative effect on lifespan, not because they will tend to become bombs. High heat has been the enemy of batteries since batteries became a thing. It's not limited to lithium, and lithium aren't inherently any less safe compared to other chemistries in the heat.Not that I'm suggesting that everyone should run out and stack some batteries on their dash, but lets be real here - if 120*F was enough to cause safety concerns, there would literally be thousands of stories from people in Phoenix having phones and power tools blowing up in their cars.Virtually every work truck out here has a stack of much bigger Li_Ion batteries in them than any 18650 based power bank. My own truck has about 100Ah worth of Li_Ion batteries in it at any given time that live in the cab and the service body bays. My Toughbook sees multiple hours outside baking in the sun, and gets to the point that it's too hot to touch with bare hands frequently, and has been left in the cab for days in the summer. People leave cell phones in the car all the time. I've personally measured temps of over 150*F inside the cab with the truck off and in the sun.One of my coworkers has had an office duster can explode in his truck, become a missile, and leave a good dent in the cab roof...from the inside. But in the 20 years I've been working in this field, I've never once heard "My (insert lithium device here) exploded in the truck!"

author: TimFox
author_rank: Super Contributor
timestamp: October 07, 2024, 08:26:00 pm
content: Note: if you must disparage Fahrenheit since you think it’s icky, you should try to spell it correctly.Otherwise, you look petty.

author: fixit7
author_rank: Regular Contributor
timestamp: October 07, 2024, 09:49:24 pm
content: Quote from: Psi on October 07, 2024, 08:40:51 amThanks. I have had the power bank for at least 5 years.I moved and went from 700 sq.ft to 200 sq. ft.So I had to store a lot of stuff at my daughters house.It included a resistors, capacitors, chips, circuit boards, soldering station , to name a few.If I get back into it, would this website be good?

author: amyk
author_rank: Super Contributor
timestamp: October 09, 2024, 12:28:19 am
content: https://pubs.rsc.org/en/content/articlehtml/2014/ra/c3ra45748fAround 150C is when they start going into thermal runaway.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 09, 2024, 06:04:27 am
content: Proper li-ion cell is certainly safe in car inside temperatures, even if they get higher than your mentioned ~50degC. But remember that random fail-quality crap may catch fire on their own, and I could well imagine higher temperature would increase the risk.Then again even if the cell survives without catching fire, the lifetime will be dramatically reduced so it's not a good idea.

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2024, 06:38:21 am
content: Quote from: fixit7 on October 07, 2024, 04:59:53 amLi-ion batteries are designed to operate optimally between 15°C and 35°C. Exposure to temperatures around 50°C can be harmful, and in a car left under direct sunlight, the internal temperature can easily exceed 100°C, further exacerbating the risk of damage.

author: Psi
author_rank: Super Contributor
timestamp: October 10, 2024, 09:50:31 pm
content: Quote from: Siwastaja on October 09, 2024, 06:04:27 amYeah. The vast majority of fires caused by lithium batteries are from:- Badly manufacture cells that are simply crap quality and prone to internal shorts or thermal runaway.- Badly assembled battery packs. Minor external damage from an insignificant drop/impact/vibration, which does no visible damage, causes things to move around inside and create shorts, or slowly wear through insulation making the risk of shorts higher and higher.Badly assembled battery packs is a big problem because if a pack gets at an obvious hole in the side then everyone knows that's bad and the pack should not be used and disposed of safely. But if it looks totally fine people expect that it *is* totally fine.- Gross misuse or physical damage.The number of times quality lithium cells, used within their rated temp range, decide to go into thermal runaway on their own is pretty small.

author: fixit7
author_rank: Regular Contributor
timestamp: October 07, 2025, 03:57:09 am
content: I need temps in the Fahrenheit.The U.S. and England rebelled against the metric system.As a chemist, I dealt with the metric system.If you want to help me, please post in Fahrenheit.To convert Celsius to Fahrenheit, the easy trick is to double the Celsius temperature and add 30, which gives a close approximation. For an exact conversion, use the formula: Fahrenheit = (Celsius × 1.+ 32.

author: Psi
author_rank: Super Contributor
timestamp: October 07, 2025, 08:53:09 am
content: Australian forum, Australian units

author: mikerj
author_rank: Super Contributor
timestamp: October 07, 2025, 11:05:50 am
content: Quote from: fixit7 on October 07, 2025, 03:57:09 amVery few people use Fahrenheit in the UK. Whilst we haven't adopted metric units for everything (road distances, speed limits, beer etc.) almost everything in an engineering context will be using metric.

author: MrAl
author_rank: Super Contributor
timestamp: October 07, 2025, 11:47:42 am
content: Quote from: TimFox on October 07, 2024, 08:26:00 pmHi Tim,Thanks for the humor, I love comedy."Different" spellings can make for some pretty funny stuff sometimes

author: MrAl
author_rank: Super Contributor
timestamp: October 07, 2025, 12:18:21 pm
content: Quote from: fixit7 on October 07, 2024, 04:59:53 amHello,Did you mean the 18650 battery cell?First you should look at the aging factor, then reconsider how you want to store them, then consider the possibility of thermal runaway.To start, as the temperature increases the cell ages faster and faster. This can be modeled as an exponential:rate=A*e^(-E/(R*T))This means for lower temperature T the rate is low, but as T increases, the rate increases very fast meaning that the reaction is very temperature dependent. That is referred to as the Arrhenius equation that you might find useful.What this means for battery life is that as the temperature rises, the cell life degrades faster and faster meaning it will decrease to 1/2 (and of course lower) of the capacity much faster. That means the cell will have to be replaced much sooner. This alone tells you something important.However, that's not the end of it. The higher the temperature the higher the risk of a heat related problem like thermal runaway. That causes some big problems like fire.If the car gets direct sunlight, then the cells have to be in a place that is ventilated so they can keep cooler. If the car is in the shade there is less risk.If the cell is being charged then that's an even higher risk when the temperature goes up.You can find max temperature limits in data sheets, but they probably will not show the cycle life decrease with elevated temperatures, which as stated above, are extreme. The battery could become unusable in a much shorter time.As you probably know, you should really keep these cells as close to room temperature as you can, and hope that in the future we get a better technology for batteries we use as much as this kind.