It has been long rumored that storing batteries in the refrigerator can extend the lifespan of the battery and, apologies for the obvious food-storage joke, keep them fresh. Does it actually help? Is there any legitimate reason for putting your batteries in cold storage?
First, let’s look at why people are even putting their batteries in the refrigerator. The underlying principle (which is actually scientifically sound) is that the colder temperature slows the rate of energy discharge. Every battery has a rate of self-discharge, the rate at which it loses a percent of its stored energy while just sitting there doing nothing (e.g. in the package, tossed in the junk drawer, etc.)
This self-discharge occurs because of what are known as “side reactions”, chemical reactions that occur within the battery even when there is no load applied to it. There is no way to avoid self-discharge, but improvements in battery design and manufacturing have significantly reduced how much energy is lost during storage. Here’s how much common battery types typically discharge per month at room temperature (around 65F-80F).
Alkaline Batteries: These are your most common disposable batteries: the kind you buy, use until they’re discharged, and then dispose of them. They’re quite shelf-stable and typically lose 1% or less of their charge per month.
Lithium-ion Batteries: Found in laptops, high-end portable power tools, and mobile electronics, lithium-ion batteries have a discharge rate of around 5% per month.
Nickel-Cadmium (NiCa) Batteries: Although not widely used today, nickel-cadmium batteries were the first widely adopted rechargeable battery. You can still find them on some portable power tools and in other applications, but few consumers are buying them today for light home rechargeable use. The discharge rate on nickel-cadmium batteries is typically around 10% per month.
Nickel Metal Hydride (NiHM) Batteries: Nickel metal hydride batteries largely replaced NiCa batteries for consumer use (especially in the small battery market). Early NiHM batteries had a rather high rate of discharge and could lose up to 30% of their charge per month. Low self-discharge (LSD) NiHM batteries were introduced in 2005 and have a discharge rate around 1.25% per month, which is on par with the low discharge rate of disposable alkaline batteries.
Looking at the discharge rates, it makes sense that in some applications some people would want to put batteries in the fridge. If you were a photographer that needed to store a bunch of early generation NiHM batteries for your flashes, for example, it might have made sense to charge them all at once, put them in the fridge, and then throw them in your gear bag the morning of a big event.
Practically speaking, however, there’s next to no reason to put your batteries in the fridge. Whatever gains you might get in shelf-life using the technique would be offset by potential problems. Micro condensation on and inside the battery can damage it and cause corrosion. Extremely low temperatures (such as a very chilly portion of the fridge or placing them in a freezer as some people erroneously advise) can further damage the batteries. Even if you don’t outright damage the battery, you have to wait for the battery to warm up to use it and keep it from gathering condensation if the room is humid.
In essence, you’re risking ruining your batteries to squeeze a few months of storage out of them and, further, the batteries that benefit most from cold storage are rechargeable and could have just been recharged prior to your intended use. So the best way to store your batteries is to buy a storage box, and keep it in a cool, dry, and non-refrigerated location.