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 us have seen the ‘white fluff’ of battery corrosion which has migrated into the battery terminals creating a mess or even ruining the device all-together.

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

(See below for car batteries / corrosion)

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


What is the white fluff corrosion on the battery?


Potassium Carbonate is the white fluffy corrosion that develops at the ends of the battery (most often the negative end).

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 will eventually leak.

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

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?

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.

AA battery caddy:


Why do batteries corrode if left installed?

Consumer alkaline batteries (such as the AA battery shown above) can leak and corrode while on the shelf. With that said, batteries that are left installed in devices are more likely to leak.

These batteries will gradually and naturally self-discharge, or discharge even quicker because of small trickle current drains put on the battery (sometimes called ‘parasitic drain’). 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. The drain will slowly kill the batteries. 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. This occurs while the device is turned off. A ‘find me’ dimly lit LED is another example. Many modern devices have active circuitry which is always ‘on’ to some extent and slowly draining the batteries while you may not even realize it.


How to prevent battery corrosion

Simply remove the batteries from devices that will not be used for some 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.

Example: 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.

Best reviewed jumper cables:

Related: Best Jumper Cables ( Size & Gauge )

Related articles:

Batteries That Won’t Leak Or Corrode

Best Rechargeable AA, AAA Batteries