Storing Batteries in the Fridge – Test of AA Cells and Science Behind it

Wondering if you should store batteries in the fridge?

This is a topic that has some truth, quite a lot of misconception and some confusion sprinkled on top of it.

Let’s first see the quick version and then proceed to in-depth analysis of storing batteries in cool environments.

Myth: Storing all batteries in the refrigerator will increase their lifespan.

Fact: Some battery chemistries may benefit from it but the benefits do not outweigh the cons so you are probably better off not putting your batteries in the fridge, let alone your freezer. Freezing batteries does not work if your goal is to extend their lifespan. Furthermore, freezing them could damage them by changing their chemical structure. The fridge may help but the freezer is not a thing to try.

Test: To further prove the point I tested putting a zinc-carbon battery in the fridge and compared its voltage with the battery from the same package that was not refrigerated and the results are as expected. No significant gain. The test is below.

Testing the theory of refrigerating the batteries

Image of a voltmeter and batteries for performing a refrigeration test.

For the sake of this test I bought two zinc-carbon batteries because this is the battery chemistry type that can benefit the most from being put in the fridge. I bought Two AA 1.5V batteries from Varta.

They both had equal voltage upon opening the package. Both cells had 1.627V. While voltage is not directly indicating capacity it comes pretty close to it if we are making an isolated test like this when the batteries are not under load.

I placed one AA battery in the fridge for 30 days while the other battery was kept at a room temperature in my drawer (a typical household battery storing scenario).

Here are the test results:

Battery that was kept in fridge

Image of voltmeter testing a battery that was kept in the fridge
Image of a battery that was kept in the fridge for 30 days and its voltage.

The battery that I placed in the refrigerator at the temperature of 40°F (5° C) for 30 days kept a slightly higher voltage. It lost only 0.001V which can be considered as a win when compared to the room temp. stored cell but not necessarily considering the fact that this cell will probably corrode or leak easier. Also, this is a tiny voltage save so it is really not worth the trouble.

Battery stored at room temperature

Image showing a battery kept at room temperature and its voltage being tested.
Image of a battery that was stored at a room temperature for 30 days in the drawer and its voltage.

The battery kept in the drawer had lost a higher voltage than the refrigerated cell. It lost 0.003V which may sound like a 300% increase but these are still tiny voltage losses that are expected to happen with batteries. Refrigerating them only to save yourself a 0.002V loss per month is not worth it.

But why do people put batteries in the fridge then?

Image of two AA batteries in the refrigerator.

Putting batteries in the fridge is an attempt to utilize the underlying principle that if batteries are kept cool they will lose less of their energy. This is scientifically correct and especially for certain chemistries.

All batteries are prone to self-discharge when sitting idly. There is nothing that can stop a battery from the self drain. Thankfully, as the battery technology advanced, the self-discharge rate became smaller and smaller.

If the battery is stored at a cooler temperature then the self-discharge rate will be even smaller.

Now let’s see why you shouldn’t attempt prolonging the battery life by putting them in the fridge.

Moisture, corrosion, leakage and other problems associated with freezing of the batteries

You don’t want your battery to leak don’t you? Or to corrode?

Then don’t put them in the fridge let alone the freezer.

While some batteries will benefit of being in the fridge this is definitely not a good idea.

A cold battery will attract humidity from the air. This significantly increases the chances of internal corrosion and battery leakage. This is why you shouldn’t refrigerate the batteries. The moisture will build upon the cell and the only way to avoid that is to keep it in a plastic bag to prevent that.

Additionally, prior to using the frozen battery, you will need to let it reach room temperature and that becomes an additional hassle. The battery will not be ready when you need it. And if you put the cold battery in a device, the condensation may accumulate on the battery which can also damage the device.

What battery chemistries benefit from being in the refrigerator?

While batteries in general prefer a slightly cooler environment than the room temperature most chemistries will do best if kept at the room temperature (around 68-78 F degrees).

However some chemistries would in theory benefit from refrigeration if we ignore the problems discussed above.

The Zinc-Carbon batteries

image of a zinc-carbon battery

Zinc-carbon or heavy-duty batteries are one of the chemistries that would experience quite a benefit of being refrigerated when not in use. The zinc-carbon battery would retain up to 80% of its capacity four years down the road if stored at a temperature between 40° and 50° F (5-10C°).

Compare that to the same cell kept at 70°F or 21°C that would retain only about 65% if its capacity and you will see the obvious difference.

The Zinc-carbon is a battery that people in the past refrigerated the most. It is old chemistry and was widely used. Today it is still used for low draining devices.

Alkaline battery

image of an alkaline battery from Energizer

Alkaline household batteries like AA or AAA will experience no special benefit if refrigerated. Alkaline batteries do not last longer in the refrigerator. They should be stored at room temperature in a dry environment.

The refrigerator itself is too moist for them and since there is no benefit of keeping alkaline batteries in there you shouldn’t do it.

Lithium-ion battery

Lithium-based batteries will often have a lower self-discharge rate if stored at a temperature around 32°F (0°C). Putting them in the fridge is, however, definitely not recommended. Lithium-ion batteries are dangerous and any damage to their internal structure due to condensation and corrosion could damage them and your device.

Nickel metal hydride and Nickel Cadmium batteries NiMH and NiCd

image of a NiMH battery from Eneloop

The NiMH rechargeable batteries pretty much completely replaced the NiCd battery which is toxic for the environment. The NiMH at first had a pretty bad self-discharge rate but thankfully this has significantly improved over the years and now they are almost on par to alkaline cells. The NiMH batteries are meant to last a long time, some even more than 1000 charge cycles, so it is not a good idea to freeze these batteries. You will just risk them being damaged.

Besides modern NiMH like cells from Eneloop are so good at keeping their charge when in storage that it is just pointless to risk damaging them.

What if you really must put your battery in the fridge

Image showing batteries in the air-tight container.
Don’t forget to put them in the air tight container!

If you really decided to try this yourself and save a few battery capacity points then this is how to do it.

How to refrigerate batteries:

  • Keep them away from food.
  • Don’t do it if you have small children, pets, old people in the house who have access to the fridge.
  • Put batteries in the vacuum plastic bag.
  • Set the temperature of the fridge to the appropriate temperature.
  • Don’t freeze the batteries in the freezer because this can change the battery chemically and damage it.
  • Don’t put them in the fridge if you are unsure of what you are doing. This is especially true for any advanced battery chemistries like Li-ions, LiFePo4s, Li-Po or similar.
  • When getting them out leave them in the vacuum bag until they reach room temperature prior to using them. This way you may avoid condensation build-up.

Conclusion

Look, putting batteries in the refrigerator is not worth it despite of the possible small gains in energy retention. The increased likelihood of battery damage will cost you more and especially if we are talking about lithium based cells or nickel based household batteries like AA.

Myths should stay where they belong and the facts should rule the day. Fact of the matter is that the batteries are meant to be on the room temperature and even the battery manufacturers will agree on this.

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