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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. Self-discharge decreases the shelf life of batteries and causes them to initially have less than a full charge when actually put to use.
How fast self-discharge in a battery occurs is dependent on the type of battery, state of charge, charging current, ambient temperature and other factors. Primary batteries, which aren't designed for recharging between manufacturing and use, use battery chemistry with much lower self-discharge rates than rechargeable batteries, since they must have an economically practical shelf life.
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.
Typical self-discharge by battery type
|Battery chemistry||Rechargeable||Typical self-discharge or shelf life|
|Lithium metal||No||10 years shelf life|
|Alkaline||No||5 years shelf life|
|Zinc–carbon||No||2–3 years shelf life|
|Lithium-ion||Yes||2–3% per month; ca. 4% p.m.|
|Low self-discharge NiMH||Yes||2–3% per month|
|Lead–acid||Yes||4–6% per month|
|Nickel–cadmium||Yes||15–20% per month|
|Nickel–metal hydride (NiMH)||Yes||30% per month|
- Wu and White, "Self-Discharge Model of a Nickel-Hydrogen Cell." Journal of the Electrochemical Society, 147 (3) 901-909 (2000)
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