Where'd you get the 50° number from? I looked at the manual for mine and it does recommend an ideal storage temperature of 68°, but that's not a limit by any means. It's a lead acid battery, not terribly different from your truck's battery. It'll be diminished somewhat at lower temperatures, but there's not a jump pack out there that wouldn't be. The JNC jump packs are the top dogs, don't bother with anything else.
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