Portable jump starter
 

Does anyone have/use a portable jump starter in their car?

This is amazon 'best seller'.

Those are actually pretty dangerous because your storing a high current capable lipo battery fully charged in your car. Once your car heats up in the sun the battery voltage will rise with temperature and potentially cause a lipo explosion/very hot fire gas stream. I would never store one in my car.

As a counterpoint to the above, I've had one in my car trunk for over 2 years with zero issues. I live in Houston, so it gets plenty hot here. A properly designed one shouldn't be an issue.

I do, however, recommend sticking with a name brand that's proven, rather than a knockoff. After a bunch of research and reading of review, I went with one from Antigravity Batteries.

I have a Cobra JumPack that I keep in the trunk - so far no explosion. I only used it once to start another car that was blocking my exit from a parking garage. My concern is about leaving in the trunk when I am parked at the airport this winter and the temps drop to like 10 degrees F. I keep the JumPack in a small insulated lunch bag and hope this will help keep it warmer. I was also thinking of putting the bag on the front floor when leaving the car at a cold place like the airport, the warming effect of daylight sun might help in keeping it warmish/less cold; a trunlk can be a dark really cold place I am thinking. Any thoughts on the issue of cold?

That is pretty hard to believe since they are really not much different than the battery in your phone. At my work we aren't allowed to bring phone in so our parking literally has thousands of phones inside cars under hot sun for 8 hours per day every single day. Never heard of any explosion.

Yes but cell phone lithium ion batteries have very low current capabilities. Even still I'm sure you heard of the note 7 fiasco. That was due to an effort to squeeze more milliamp hours out of the cell by lowering its amp handling capacity. It's a matter of science that voltage of batteries rises with temperature. I come from lots of experience with lithium polymer batteries from my model airplane hobby. We use large high current lipo batteries in our high performance aircraft. Countless guys have had lipos go into thermal runaway (no more recognizable car) when leaving charged packs in there car for a flight after work. Lipos swell and puff up under high temps and this can cause a puncture from the housing they are mounted inside of, once oxygen reaches inside the cell.... fire. Just giving you guys a heads up. It's not pretty when they go off.

Here's a list of well documented lipo fires by cause:

https://www.rcgroups.com/forums/showpost.php?p=1936756&postcount=4

Yes I work for a DOD contractor and no cell phones allowed as well. But everyone has poor cell phone battery life as a consequence of the high temps inside the car reducing the effective capacity of the batteries. Cell phone Lipos luckily are relatively low risk compared to the much more powerful high amperage capable Lipos.

Cold isn't an ememy as long as your not trying to charge or use the battery. Cold alone will only serve to slow aging and preserve the battery. But don't try to charge or use to jump while cold. Wait until the battery is 75-95 F

I've got one of these, had to use it half a dozen times in the last couple of months, and it's worked every time:

I had an Antigravity XP-10 jump starter swell up so badly that it broke apart its plastic case. This was in the summer, and it did not catch on fire. When I called the company to see if it was still covered under warranty (it wasn't), they didn't seem surprised to hear about the problem. An Antigravity Micro-Start Sport has been working fine for a couple of years. I also have a PowerAll PBJS16000RS which I just used last weekend to jump start a 1.6L engine.

Something I've considered for long-term parking is the Goal Zero Maintainer 10 Trickle Charger which you can suction cup to the inside of a window and connect to the battery terminals.

https://www.goalzero.com/shop/trickl...ickle-charger/