Is this a good idea? While opening the fridge to get a battery, I relized something. That I have always kept them it there, simply becasue while I was a kid my parents do so.
Does this really make them last longer? I think when I was a kid there was not alkaline batteries, does that make a difference? I am now 43 years old.
It does keep alkalines and most rechargeable types from self-discharging if you intend to keep them around for a long time without being used. You do have to allow them to warm to room temperature before using them, however, since cold batteries can’t supply very much current. It isn’t really necessary, most of the time, though, since alkalines have a 5-year or longer shelf life.
Here’s one answer. Executive summary: It should help a bit, but not a lot.
If you want to keep batteries for a long time, I suspect you’re better off getting lithium batteries, which have a longer shelf life (on the order of 10 years before they lose significant power).
I am reluctant to post an “IME” in GQ that often nowadays, but I think it applies.
At a time when I was using helmet lanterns fairly frequently (for inspections and other reasons) I too was keeping batteries in the fridge to extend their life, then letting them warm over a day or two before use.
I found, experimentally, that the fridge batteries seemed to have MUCH less life than non-fridge batteries from the same bulk packs left out of the fridge. So much so that I even did experiments on this, and found that after full warming, name-brand alkaline D cells from the same pack had about 0.25-0.3V less voltage than batteries left out the whole time. And as a result, I got less light out of them and for a shorter duration, too.
I realize that most "reputable " sources say it should help them keep their charge, but this has not been my experience. I did not set up a detailed experiment with controls and such, mind you.
Here’s one take on the situation:
http://www.straightdope.com/mailbag/mbattcharge.html
Looks like the answer might be no.
hmmmm
In the USAF we kept ordinary batteries on hand for many uses. And we had an ordinary fridge for storing them. It was also against regulations to put any food in that fridge. Why?
The stated reason was that mercury vapor could leach out of the batteries (we’re talking a couple hundred AA through D cells) and would be soaked up by any food kept in there.
I’m not sure of the scientific validity of the regulation, but at least one US Gov’t agency believes that storing food & batteries together is not a good idea.
Personally, I’d rather not run the risk; mercury is nasty stuff biologically, and nothing else in batteries is much healthier for you. The miniscule potential benefit of increasedbattery life isn’t worth the (perhaps) small risk of heavy metal poisoning.
YMMV
If the fridge is good, why are the batteries in the flashlight that I keep in my car always dead!
There isn’t any. Batteries do not, I repeat do not contain mercury anymore, and haven’t for many years. I’m not 100% certain, but I’m fairly sure that it is not even legal to sell batteries containing mercury anymore in the US, because of disposal concerns.
Q.E.D., I fear that that answer is not correct. Mercury batteries are available in many regions of the world, and thanks to the Internet grey market and people who travel a lot, are often shipped to places where their production is banned.
Example: http://www.pcs-chromex-batteries.com/batts.htm
In fact, here’s a safety sheet for them from Energizer: http://data.energizer.com/datasheets/psds/pdfs/mercury.PDF
FWIW, AFAIK it is not illegal to buy, sell, trade, or import for personal use into the US. Mainly to manufacture and import for commercial purposes.
I should add “or sell commercially in the US” to the above.
I meant to say “in the US”, of course. I don’t know the battery situation in every little hole-in-the-wall country on Earth. 
Just note that this does not apply to the rechargeable lihium-ion batteries. They have a notoriously bad shelf-life and will lose half their storage capacity in two-three years.