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I'm looking to buy a portable jump-starter power bank that's rated for up to 140°F.

I'm wondering how dangerous it would be to store it in the car (trunk or globebox) if I know outside temperatures might occasionally peak at ~105°F.
(Note this is outside air temperature. I don't know how hot inside a car can get.)

I know it can result in reduced lifetimes but I do not care about that. I just don't want there to be a risk of fire, is all.

It's 14000 mAh and the thought of a lithium battery fire scares me, but I can't imagine that it wasn't designed for this use case. Would this be dangerous or safe?

Bonus points if you could describe the safety mechanism(s) that are typically employed to protect against this. It may help me understand the risks better.

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  • \$\begingroup\$ At 95 degrees outside a car will get to be 140 degrees inside in 1 hour. So no. \$\endgroup\$
    – Passerby
    Mar 5, 2017 at 18:14
  • \$\begingroup\$ @Passerby: It's not that straightforward is it? They call the 140 degrees an "operating temperature". What if I don't operate it at that temperature? etc. \$\endgroup\$
    – user541686
    Mar 5, 2017 at 20:54

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An old thread but just ran into it ..

The issue of storing jump starters in car (where they should be stored frankly) seems to pose some risk as consumer reports state below. Unfortunately it is still very hard to find products with relevant storage temperatures.

"All of the jump starters we tested had a maximum recommended operating/storage temperature, ranging from 120 degrees Fahrenheit for ... up to 185 degrees for ....

That's a major concern: According to the National Highway Traffic Safety Administration (NHTSA), the temperature inside of a car parked in direct sunlight can reach between 131 and 172 degrees Fahrenheit when the temperature outside is between 80 and 100 degrees. In hot desert areas, the inside temperature can rise even higher.

Unfortunately, the device manufacturers were guarded on the potential consequences of storing these units at high temperatures. Complicating matters, it's the fact that most of the units list their temperature ranges (operating or storage) in the instructions, but not on the product packaging"

https://www.consumerreports.org/cro/jump-starters/buying-guide/index.htm

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Depends on what type of 'lithium' battery is inside the jump-starter. Lithium-ion/Lipo batteries start to go into thermal runaway at about 60ºC (140ºF). LiFePO4 is safe up to much higher temperatures because it doesn't 'cook off' until over 220ºC (at which point the interior of your car would already be melting!).

The problem is finding out what type of battery your jump-starter has. I found one that supposedly has an LiFePO4 battery, but many others do not specify the exact type (and even they did, can we believe them?).

A vehicle interior can get much hotter than ambient if not well ventilated. Dark objects in direct sunlight get hottest and heat rises, so the glovebox might not be the best choice. I would store it in the trunk, as low down as possible and covered up.

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  • \$\begingroup\$ +1 Thanks! It claims Li-Ion (as I had in the question tag), but I don't know details beyond that. I've been considering getting a LiPo-safe bag to keep it in, but given it's a whopping 14 Ah I'm not sure how if the bag would be much help in the case of thermal runaway... \$\endgroup\$
    – user541686
    Mar 5, 2017 at 6:26
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After tons of research I was unable to find a battery-based jump starter with sufficient high storage temperature (140F+) capability. Even the LiFePo4 chemistry battery ones seemed to have unusually low temperature guidelines for storage, despite the battery chemistry being traditionally rated for much higher storage temps.

I ended up going with a "super capacitor" starter. They have much higher and lower storage temp tolerances, the one I got is OK from -40C to 70C. They don't hold a charge while stored, it seems like you can either charge it using the trickle that is available from your "dead" battery, or from USB or DC lighter cord.

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