Chill the batteries? Heat the pack? Both?
More importantly, for those using rechargeables, do you actually find that they work or last at all? I really hate throwing away used up batteries, but I've never had a rechargeable battery that I thought had a reasonable life either in use or in storage. Avalanche transceivers display a battery 'percentage' remaining when you power them up. The one time that I installed a freshly charged pair of reusable AAs in my beacon, I saw 75% the first time that I turned it on! I've been reluctant to use them in anything that I care about ever since…
Dave