I only recently realised that batteries (like AA, AAA, C, D, etc.) have a best before date when I accidentally bought an out of date pack and couldn’t figure out why it they wouldn’t work! Why do they lose charge, despite not being connected to anything, or one another?
In: Chemistry
Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes or any external circuit. Self-discharge decreases the shelf life of batteries and causes them to initially have less than a full charge when actually put to use.
Self-discharge is a chemical reaction, just as closed-circuit discharge is, and tends to occur more quickly at higher temperatures. Storing batteries at lower temperatures thus reduces the rate of self-discharge and preserves the initial energy stored in the battery. Self-discharge is also thought to be reduced as a passivation layer develops on the electrodes over time.
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