Why Do Batteries Leak?

How many of you have encountered a corroded battery compartment in one of your consumer devices? No doubt that most of you have seen the ‘white fluff’ of battery corrosion. It migrates into the battery terminals. Typical aa battery corrosion. It creates a mess and may ruin the electronic device all-together.

– Here’s Why battery corrosion happens.
– How to prevent battery corrosion.
– How to clean it up.

I’m referring to typical consumer batteries such as AA or AAA size.

(See below for Car Batteries / corrosion)

Energizer Guarantee | No Leak

UPDATE, Energizer guarantees that these particular batteries will NOT corrode. I made the switch and can attest that none of them have leaked:

As of this writing, the best price I’ve seen for these batteries:
Energizer max AA
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What is the White Fluff Corrosion on the Battery?


Potassium Carbonate is the white fluffy corrosion that develops at the ends of the battery. It’s most often seen at the Negative ( – ) end of the battery.

The “alkaline” of the battery is potassium hydroxide. It’s the alkali equivalent of acid’s hydrochloric acid. This will leak out, forming a white “fluff” of potassium carbonate.  It typically leaks on the negative end of the battery cell. Why? Apparently the positive end is vented better.

Why Do Batteries Leak?

Hydrogen gas out-gassing | poor battery seals

As batteries discharge, the chemistry changes and some hydrogen gas is generated.

This out-gassing process increases pressure in the battery.

Eventually, the excess pressure may rupture the insulating seals at the end of the battery, or the outer metal canister, or both. Again, the Energizer Max battery claims no-leak (perhaps better seals than other brands).

Dead Batteries may Leak (AA | AAA)

All batteries will slowly gradually self-discharge over time. This will occur whether they are setting on the shelf (a much slower process) or installed in a device (which often occurs much quicker). And dead batteries may eventually leak, resulting in the “white fluff” corrosion.

High Temperatures

High temperatures can also cause batteries to rupture and leak (hot, summer environment).

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Why Do Batteries Corrode If Left Installed?

Consumer alkaline batteries (such as the common AA or AAA) can eventually leak and corrode while on the shelf. With that said, batteries that are left installed in devices are more likely to leak. Here’s why…

Self Discharged & Parasitic Drain

These batteries will gradually and naturally self-discharge. They will discharge even quicker when small trickle currents slowly drain the battery (‘parasitic drain’). Consequently this leads to a dead battery (or batteries) which will out-gas and corrode.

A slow parasitic battery drain is common in many devices. It will slowly discharge the batteries until they’re ‘dead’. As a result, the batteries may eventually leak.

A device that is left unattended for long periods of time (with the batteries installed) may drain down slowly and kill the batteries.


A clock display screen on a portable radio is one good example of parasitic drain. When the device is turned off, the clock continues to draw down the battery, albeit very little. A ‘find me’ dimly lit LED is another example. Many modern devices have active circuitry which is always ‘on’ to some extent. This will slowly drain the batteries while you may not even realize it.

How To Prevent Battery Corrosion In Electronics

Purchase Energizer MAX brand batteries (shown above). They’re guaranteed not to leak.

Related article: Batteries That Won’t Leak Or Corrode

And/Or, Remove the batteries from electronic devices that will not be used for a significant period of time.

This will prevent a slow discharge of the batteries and therefore prevent leakage when the batteries get low or go dead. Dead or low batteries are more likely to leak.


You might have a portable radio set aside for emergencies. Or maybe you haven’t used it for months and months. You should remove the batteries from the battery compartment to prevent a potential slow discharge and the resulting leak and corrosion.

How To Clean Battery Corrosion


Alkaline Batteries:

To clean up the corrosion ‘fluff’ caused by leaking ALKALINE batteries:

– Vinegar or Lemon juice.
– Soak and swab a Q-tip over the terminals.

Car Batteries:

Batteries with an ACID makeup (e.g. car batteries), how to clean up battery corrosion:

– Mix a solution of baking soda and water to make a sort of paste solution.
– This will neutralize the acidic corrosion of the battery terminals.

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Continue reading: Best Jumper Cables ( Size & Gauge )

Best Rechargeable AA, AAA Batteries

(This article has been updated to reflect the latest information. Since switching to Energizer MAX, my battery corrosion problems have disappeared.)

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