Advice needed for buying a jump starter

[RMcG]

I would like advice about the type of jump starter to buy to carry in my Yaris in case of a dead/rundown battery.

QUESTIONS:

1) Do Lithium battery jump starters carried in a car withstand high heat exposure (e.g., 120 to 160 Fahrenheit/49 to 71 C) that can occur inside a car during very hot summer weather, such as is seen in some parts of the U.S?

2) Do Lithium battery jump starters withstand such high heat exposure better than the older sealed lead acid battery jumpers?

I am thinking of buying a Lithium battery jump starter to be carried in the car during the summer and a sealed lead acid battery jumper for the winter.

3) Do you think Lithium Polymer jumpers are safer than Lithium Ion jumpers?

Any other comments will be welcomed.

Thanks,

R.

More background if interested

I am starting a new job back in Montana and will need my car to be working reliably. Unfortunately my headlight on reminder alarm just failed (after working well for 14 years). I have become used to it reminding me to turn off my headlights, so I am concerned that I will forget at times and let my battery run down.

A reputable independent repair shop I use told me that only a dealer can fix the broken alarm problem. And estimates from two local Toyota dealers indicates a bill of about $200 just to diagnose the problem, with another $200-$400 likely to fix the problem after diagnosis.

It seems that a good economical solution is to carry a jump starter with me. But in researching jump starters, it is clear that the newer lithium battery jump starters do not work in cold weather; see, for example, this thread Lithium Ion Battery Jump Starters started by tmontague from Canada. The temperatures in Montana are extreme: well below zero F (-18 C) in the winter and above 100 F (38 C) in the summer. The temperature inside a car that is carrying a jumper during the summer in 100 F (38 C) weather can reach 160 F (71 C).

The older (heavier & bulkier) sealed lead acid jumpers work better in cold weather. But in reading about sealed lead acid batteries & jumpers, it sounds like they get degraded if exposed to extremely high temperatures. On the other hand, lithium batteries & jumpers seem to handle high temperatures better than sealed lead acid batteries & jumpers. But I would like to confirm this, and see what the experience and thinking of others on this forum is.