Maybe this will help (if you've not looked it up already yourself).
greenbatteries.com said:
Putting batteries in the freezer or refrigerator doesn't necessarily prolong their life
Alkaline batteries stored at "room temperature" self discharge at a rate of less than two percent per year. So normally refrigerating or freezing them will only help maintain their charge by a tiny amount. Hardly worth the effort of chilling them. However, if alkaline batteries are stored at higher temperatures they will start to lose capacity much quicker. At 85 degrees F they only lose about 5% per year, but at 100 degrees they lose 25% per year. So if you live in a very hot climate or are storing your batteries in a very hot location, it may be worthwhile for you to store your alkaline batteries in a refrigerator instead.
NiMH and NiCd batteries self discharge at a MUCH faster rate than alkaline batteries. In fact, at "room temperature" (about 70 degrees F) NiMH and NiCD batteries will self discharge a few percent PER DAY. Storing them at lower temperatures will slow their self discharge rate dramatically. NiMH batteries stored at freezing will retain over 90% of their charge for full month. So it might make sense to store them in a freezer. If you do, it's best to bring them back to room temperature before using them. Even if you don't freeze your NiMH batteries after charging them, you should store them in a cool place to minimize their self discharge.
Some people will claim that freezing rechargeable NiCD or NiMH will help reduce "memory charges" in a battery and allow it to resume it's once full charge. This was a popular with many laptop owners of the day, before Li-Ion phased the remainder of NiCD/NiMH batteries out. "Charge Memory" happens when these batteries are not charged completely before usage or they are drained severely to a specific point, there is a chemical change that can render these batteries to provide less charge than they was designed to.
