Are Lithium polymer batteries are safe in extreme heat or cold

[GTA Driver]

Few days ago, bought my first Battery pack at a small electronic shop in a mall I work. Its a Belkin Pocket power 10k. If this works out, I may get additional battery packs from amazon.ca

It will charge in my home never in my car. Its "Lithium polymer". I see some people, most notably @Dashmellow have had battery packs for some time. Are Lithium polymer safe in extreme heat and cold?

We have had a few days approaching record temperature. Three days at 35c. In the winter, evening at -30 c. My SUV is black and I can not park in the shade when I am working.

edit: according to http://www.belkin.com/us/p/P-F7U020/

THE SAFETY TRIANGLE​

Belkin batteries include sensors monitoring heat, voltage and circuitry so the power bank (a.k.a. portable charger) will not overheat and harm your devices. Excess heat, voltage fluctuation or circuit abnormalities activate an override that shuts the battery down immediately for ultimate safety.​

​

 

[Nigel]

There are very few reports of Lipo USB power banks being dangerous, so yes they are safe as long as you don't physically damage them.
High power lipo packs used for model aircraft do sometimes burst into flames, but they are put under far more stress, both electrically and physically, than a USB powerbank ever will be.

The temperature limits are -
For charging: 0C to 40C, it is important to stick to these limits.
For powering a dashcam: -40C to 60C, from 60C to 85C isn't going to be dangerous but will reduce the lifetime significantly.

A good powerbank will have high and low temperature cutoffs to protect itself, but it might be worth testing it to check.

If you are worried then you can put them in a "lipo charging bag" which will contain any flames and stop a fire spreading. A good idea if charging them unattended, although almost nobody bothers and there are millions, maybe billions of them in use, some of them very poor quality.

Note that a USB powerbank shouldn't get hot in use from it's own heat, should only ever get a few degrees C warmer than ambient, if it does get hot then don't use it, so it is safe to use one in a car with 60C ambient, although your dashcam may not survive!

 

[Nigel]

Never leave it in direct sun, and in the summer don't place it near the roof, run a cable down to where it is relatively cool, but maybe not on the floor because then it may get flooded which is definitely bad!

 

[Dashmellow]

Lithium-Polymer batteries are essentially the same chemistry as Lithium-ion batteries with the exception that polymer batteries have a gelled electrolyte, a somewhat different separator and foil pouch enclosure instead of a hard tubular shell like you would see on any common 18650 cell.

Although lithium batteries have improved dramatically over the last several years in terms of safety there is still a need to exercise caution in how and where you use them. This is why we have strict regulations on shipping them or storing and using them on airplanes. The safety issues with lithium batteries come about when they are subjected to stress for extended periods of time, especially during periods of charging or discharging. Automobiles are considered high stress environments for lithium batteries due to temperature extremes, vibration and shock. Charging a cell phone on your desk with a battery bank is different that powering one or more dash cams full time in a moving motor vehicle where there are vibrations, shocks from bumps and changing temperatures. Stress also dramatically reduces longevity of lithium-ion cells meaning that they will have less and less of an ability to accept and hold a charge. They will take longer to charge each time and put out less current for shorter periods of time.

All lithium battery banks today have protection circuitry for short circuits, temperature, voltage etc. that will shut off power if it detects and issue. The safety issues come about when the battery cells themselves suffer from internal damage from the build up of lithium metal and dendrites than can cause an internal short circuit. If this happens then any protection circuitry in the power bank becomes useless.

Lithium Polymer type battery banks tend to have an slightly improved safety profile over lithium-ion cells. The reason is that if a problem occurs the foil package they are in can expand quite a bit before bursting. Lithium-ion cells where the battery chemistry is inside a metal tube can build up enormous pressures inside if there is an internal problem which can cause it to explode, even though they do have some ability to vent before they reach that state. Many of the so called battery "explosions" we hear about in the news are really more about excess gasses from a run-away electro-chemical reaction inside metal battery tubes or inside sealed smartphones that build up enough pressure to burst. Once these expanding, hot, volatile gases come into contact with the air (oxygen) they catch fire and as it is a chemical fire it is difficult to extinguish. So Li-Po batteries tend to be less likely to actually "explode" and can take a bit more abuse until they catch fire as compared to sealed metal battery cells.

I've had the opportunity to test a variety of power banks over a period of four and a half years now and have not encountered any serious problems during this time despite using them under fairly extreme conditions. Nevertheless, it is important to use caution and common sense. It is also important to use good maintenance and charging practices.

I use power banks on hot days but I am careful to place the banks under my seats in a position where they are slightly off the floor and air can circulate around them. I will use them for a few hours like this but avoid leaving them baking in a hot vehicle all day. I crack the windows slightly in my vehicle and I monitor the cabin temperature of my vehicle. If at all possible I try to park under some shade. Although it can get pretty hot inside my dark blue truck, the temps might occasionally get "near" 50˚ C, but I've never seen anything close to 60˚ C. In cold temperatures like we experience here in northern New England lithium cells have a reduced capacity but they still perform well. Lithium cells should never be charged in sub freezing temperatures.

I do NOT recommend leaving lithium battery banks discharging inside any sort of bag. Although lithium battery cells do not get hot during discharge (you should dispose of them if they do), the internal circuitry that controls charging, discharging, safety features and LED displays does get warm, especially under heavy load. Each battery bank I've tested seems slightly different in this regard. Some have circuitry that gets quite warm, even a little hot during discharge and some hardly show any noticeable heat at all. Some of the apparent heat is a function of the design and material use in the housing of the battery bank and some seems to be a product of circuit design.

Rest assured that even if a battery bank doesn't seem to be getting warm to the touch, it is indeed producing some heat. If you put the battery bank in a sealed bag, this heat will be trapped and will start to build up. When discharging, especially in an automotive environment battery banks should be stored in as cool a location as you can find, out of direct sun and in a position where as much air as possible can flow around them.

I can speak of this from direct experience. I am a long time regular blood donor. (7.2 gallons!) They always hand out some sort of free 'thank you" swag to blood donors and one time they were giving out these nice Red Cross foil lined insulated lunch bags, kind of like a cross between a lunch bag and cool looking piece of hiking gear. On a sunny and warm June afternoon when the donation was over and I was heading out to my truck, I thought, "Hey, this insulated bag should be just the thing to keep one of my battery banks cool when I'm running it in my vehicle on a hot day". So, I placed the battery bank in the bag with two USB cables running out of it going into two cameras and went about my usual business. It was probably running for slightly less than an hour by the time I got home. When I reached into the bag to remove the power bank it felt like I was sticking my hand in a hot oven and the power bank was almost too hot to touch! Yikes, this was a shocking eye opener! I surely won't try this again!

Battery banks that don't seem to be putting out much if any heat at all are actually putting out more heat than you may realize. So, it's just not a good idea to use them under heavy load in ANY enclosed bag inside a hot car, even un-insulated ones.

Edit: I should mention that the power bank that got so hot inside the insulated bag is now almost four and a half years old and until recently has been in almost daily service running dash cams in my vehicle. It no longer has the charging capacity it once did but still has the capacity to run two dash cams for quite a few hours and it survived the severe overheating abuse it endured inside the insulated lunch bag without bursting into flames.

 

[GTA Driver]

Interesting replies. I was out of town on short vacation and the internet was poor at the hotel I was staying at.

I had the pack running from 6:30 am Friday to 7:30 Saturday with perhaps a four hour break as it appeared to shutdown at one during my 5 hour trip and I switched back to the cigarratte lighter. I got my destination at 6:30 pm on Friday, switched back to the battery pack and on Saturday morning my DC was still running. If I have an arsenal of these things, my DC’s will be running much of the time, with no drain on my car battery.

On my Rav the space between the seat and the console is just a little bit wider than the battery pack and the pack sits nicely there.



I can push it between the seat and console close to the ground. It will not be in direct sunlight and there will be some circulation.



I never gave the air circulation end of it much thought until @Dashmellow ‘s reply. I was going to place the battery pack in the rear of my 2012 Rav4in what I call the “smugglers compartment “ where it would NOT be under direct sunlight and insulated. The “smugglers compartment” is storage under the floor at back. Underneath the “Bed” or cargo area.. In 2013 or 2014 models, Toyota moved the spare tire from the back door (gate) to under the floor like many cars have in the trunk. I suppose for safety reasons as many drivers don’t sufficiently tighten the spare tire back on the rack on the door and the tires fall off.

Here is a photo on the web on 2013 or later Rav.



Mine is a similar size but without the tire.


It possible to have cable running out of false bottom rear storage that I have and I was going to have two battery packs if I ever get side cams for both sides of the vehicle in addition to the rear camera. This would be out of the sun, but the circulation is a concern.

What I could do is prop the door on the smugglers compartment maybe a half inch to let air in and out but I have cargo liner which would interfere with that.

I estimate this compartment to be close to 4 feet to 2 and half with a 2 and half foot depth. Perhaps with it empty, it should be ok for circulation.

If don’t use the smugglers compartment, I may be able to place the packs behind the rear sides before the cargo area.

 

[Nigel]

Interesting replies. I was out of town on short vacation and the internet was poor at the hotel I was staying at.

I had the pack running from 6:30 am Friday to 7:30 Saturday with perhaps a four hour break as it appeared to shutdown at one during my 5 hour trip and I switched back to the cigarratte lighter. I got my destination at 6:30 pm on Friday, switched back to the battery pack and on Saturday morning my DC was still running. If I have an arsenal of these things, my DC’s will be running much of the time, with no drain on my car battery.

On my Rav the space between the seat and the console is just a little bit wider than the battery pack and the pack sits nicely there.

View attachment 39831

I can push it between the seat and console close to the ground. It will not be in direct sunlight and there will be some circulation.

View attachment 39832

I never gave the air circulation end of it much thought until @Dashmellow ‘s reply. I was going to place the battery pack in the rear of my 2012 Rav4in what I call the “smugglers compartment “ where it would NOT be under direct sunlight and insulated. The “smugglers compartment” is storage under the floor at back. Underneath the “Bed” or cargo area.. In 2013 or 2014 models, Toyota moved the spare tire from the back door (gate) to under the floor like many cars have in the trunk. I suppose for safety reasons as many drivers don’t sufficiently tighten the spare tire back on the rack on the door and the tires fall off.

Here is a photo on the web on 2013 or later Rav.

View attachment 39835

Mine is a similar size but without the tire.
View attachment 39836

It possible to have cable running out of false bottom rear storage that I have and I was going to have two battery packs if I ever get side cams for both sides of the vehicle in addition to the rear camera. This would be out of the sun, but the circulation is a concern.

What I could do is prop the door on the smugglers compartment maybe a half inch to let air in and out but I have cargo liner which would interfere with that.

I estimate this compartment to be close to 4 feet to 2 and half with a 2 and half foot depth. Perhaps with it empty, it should be ok for circulation.

If don’t use the smugglers compartment, I may be able to place the packs behind the rear sides before the cargo area.

A USB battery pack should not generate much heat, yes it will be a problem if kept in a well insulated container designed to retain heat/cold and would be a disaster inside a thermos flask! But your wheel well should not be an issue. People put quite large lipo packs in quite small lipo charging bags to charge without issues, although the lipo charging bags probably conduct heat quite well, they are not insulated and generally made from glass fibre fabric which conducts heat much better than polyester/nylon/etc. The 12v to 5v converter providing power to the USB battery pack will get hot and you should make sure the heat from that has a way to escape, maybe by clamping it firmly to the metal car body to take the heat away and maybe keep it in a separate space to the batteries since it will probably be happy to operate at 90C.

 

[Dashmellow]

Conflating the process of charging lithium-ion power banks with the process of discharging them is a red herring that merely confuses the issue at hand. "Charging bags" are for charging and are used because that vast majority of lithium-ion battery mishaps occur during the charging process.

One way or another operating a power bank in an automobile during high discharge in an small enclosed space like a bag or glovebox is a fool's errand.

That said, @GTA Driver, I think using a power bank inside your “smugglers compartment" storage area might be OK......But then again, it might not. I have a suggestion. Place a small MIN/MAX thermometer in the compartment on a typical summer day and see what results you get. Then try the same experiment with your power bank running for several hours inside the “smugglers compartment". See if the temperatures inside the compartment seem suitable for a power bank in general, and then see if using a power bank under load inside this enclosed space causes the temperature to rise significantly compared to not using it. As I've stated, some power banks produce more heat during discharge than others depending on their circuit design.

 

[GTA Driver]

I have a couple thermometers I can use for this.

 

[kamkar]

Today with 32 deg C weather outside i saw 46 deg C in my glove box.
It will probably not change much where i plan to install a backup battery a little bit lower in my car.

And tonight i took a look at the 26650 cell i have in my car flashlight, it still have the same fit though the flashlight have been there in my car on a permanent 1A outlet ( when car running ) since April.
It is mounted on the R side of my center console, so the tip of the flashlight do see some direct sunlight.
I have only seen smoking / burning lipo batteries in relation to charging, and one time due to physical damage ( as seen on youtube videos where some guy stab a cell with a screwdriver or something.

 

[Deleted member 37895]

I had a Mobius set up as a home security camera in a light grey ABS plastic box, and after a few months the battery swelled up. It's been 100F+ and it's in direct sun during the afternoon

 

[SawMaster]

Safety is relative. Used and cared for correctly these are very safe, but not perfectly safe. The real issue is in how the failure mode occurs which can be catastrophic. People get caught out not understanding this and device manufacturers deemphasize this if they mention it at all for fear of losing sales.

I'm probably more nonchalant with mine than I should be, but not when charging. Then I can be nearly obsessive, for I know that things can go from apparently fine to a thermal runaway during charging in a minute or two. I'd venture that if they would ban the cheap chargers, half the major problems would disappear.

Stay within their limits always, and you will have to be very unlucky to have problems with them. Exceed their limits even slightly and you might induce the most unlucky day of your life.

Phil