Power Pack Jump Starter

DrewE wrote:

fj12ryder wrote:
So there is kind of a "sweet spot" temperature wise with these things? I've known that cold weather is hard on batteries, but never really considered hotter weather being an issue. How hot would be too hot? In a closed car during the summer reduce it's life expectancy?

What kind of battery are you talking about? The effects of temperature on various chemistries is rather different.

For lead-acid batteries, their capacity and current surge capability goes down when the temperature goes down (and as it gets colder engines require more power to start as the oil is thicker etc.), so the battery needs to be in better condition overall in cold weather for it to do its job. However, the rate of self-discharge also goes down very considerably, and with it the rate at which the battery ages chemically, so for plain storage colder is generally better. The rule of thumb I recall is that the rate of self-discharge roughly doubles or halves for every ten degrees celsius of temperature difference. Lots of geeky information may be found here.

Empirically, car batteries seem to typically require replacement sooner for vehicles that are in hot climates than for those that are in comparatively cold climates. I don't know if that trend continues for extremely cold (as in truly arctic) climates.

NiCd batteries don't have too much capacity or current change at lower temperatures. I don't know offhand how Li-Ion batteries or NiMH batteries do. Chemical reactions in general slow down at lower temperatures, so most batteries will have reduced capability in the cold.

When I asked I was referencing the Lithium batteries that have been talked about in this thread. I know lead-acid batteries will not work as efficiently in the cold, but was curious about how the power pack jump starters will perform.