This is one of those stories that has a great deal of myth, a little bit of fact and a generous sprinkling of confusion.
The zinc alkaline difference
Zinc-carbon batteries powered almost all portable devices for nearly 50 years after their invention in the late 1800s and zinc-carbon batteries do indeed last longer if stored at between 40 to 50°F (5 and 10°C).
After four years at this temperature, a zinc-carbon battery will still maintain 80% of its capacity compared to 65% for a unit stored at 70°F (21°C). Zinc-carbon batteries are disposable, once they are flat they are of no use, and so the practice of keeping batteries that were not in use in the fridge became widespread.
Alkaline batteries, commercially available from the 1950s, became a popular replacement option for zinc-carbon. Alkaline, however, shows almost no improvement in self-discharge when chilled or frozen. However for many people a battery is just a battery and so the practice of chilled storage was often continued.
Over the years some inquiring minds tested the fridge storage idea but often just testing ‘a battery’ without understanding the different chemistries. From the 1950s onwards ‘a battery’ was usually alkaline, the results showed no improvement and this lead to speculation that the whole fridge storage idea was a myth.
Cold storage issues
This was coupled with the fact that a battery will drain faster if you take it straight out of a cold environment and start using it. In the case of zinc-carbon, all those self-discharge savings are quickly lost if the battery is used straight from the chiller!
On top of this, many people experienced batteries which rusted faster and then leaked due to the condensation caused by cooling and/or warming of the batteries too quickly. This was also caused by using them straight away where the heat the battery generated caused the condensation.
This all then lead to the general advice that fridge or freezer storage of batteries was a bad idea and there was nothing to be gained from it.
Lithium likes it cool
However, research into lithium ion batteries (introduced in the 1990s and rapidly replacing Alkaline in many applications) found that they, like Zinc-carbon, did also benefit from cold storage. Their self-discharge could be reduced from 4% per month to 2% per month if stored close to 32°F (0°C).
Contradictory advice now abounds, even from the most respectable of sources.
A clear example is Energizer. Their Non-rechargeable batteries: Frequently Asked Questions document specifically states that “storage in a refrigerator or freezer is not required or recommended for batteries produced today” but their Carbon-Zinc application manual provides data proving that their own range of carbon based batteries benefit from reduced self discharge and states “The storage of carbon zinc batteries at temperatures below 21°C will increase their service maintenance” before going on to demonstrate that “storage at 5 to 10°C is effective“.
You would be forgiven for thinking that if a company like Energizer has mixed messages … who really knows?
What to, and what not to, chill
So here’s the definitive guide:
- If the battery is zinc-carbon (including zinc-chloride) or lithium based, its self discharge rate can be reduced if kept refrigerated.
- Your fridge needs to be a dry environment (some older fridges can be damp), or the battery casing or terminals may rust causing toxic leaks that you really don’t want near your food.
- Do not use a battery straight from the fridge, allow it to warm up gradually to room temperature (a few hours is needed for a unit to warm right through).
- Don’t try to accelerate this warming process (say by putting it beside a sunny window), as this will cause the outer parts of the battery to become too hot and excessive heat accelerates self-discharge.
- While the battery is warming up, keep it in a well ventilated area to avoid condensation which could cause shorts or rusting.
- For everyday usage, don’t get too hung up on it. The benefits are very small unless you are talking about commercial storage to extend shelf life.