There are two ways of judging how long a rechargeable battery can last. "Cycles" are the number of times a battery can be used and discharged before it will no longer function. "Life" is the maximum length of time a battery will stay usable if left in storage. Life and cycle amounts differ, depending on the type of battery used. The three most common rechargeable batteries are nickel cadmium, nickel metal hydride and lithium ion. Nickel cadmium, or "NiCd" batteries, has a fairly high cycle rate. It is around 1,500 cycles, meaning that it can be recharged more than a thousand times before failing. The life of NiCd batteries is around 2 years. However, conditions such as temperature have an effect on the length of time they can be stored.
Nickel Metal Hydride
Nickel metal hydride batteries, or "NiMH," can hold higher a capacity charge in the same amount of space, compared to nickel cadmium batteries. These types are common in electric vehicles and consumer electronics applications. NiMH batteries can typically be cycled 1,000 times before they need replacing. However, this can sometimes become shortened if the battery is not discharged and recharged properly. Nickel metal hydride batteries have a life of around 2 or 3 years. Again, temperature and other factors play a major role in shelf life. Storing these types of batteries in an area below room temperature can help extend shelf life.
Lithium ion or "Li-Ion" batteries are commonly used in advanced electronics, such as laptops and digital cameras. Because of the chemistry used in these batteries, they have a low loss of charge when in storage. Normally, Li-Ion batteries can be cycled up to 1,200 times. While several other types must be completely discharged to retain their capacity, lithium ion batteries do not have this issue and can be charged at any time. Life on the shelf for lithium-ion batteries is usually around 3 years. Older Li-Ion batteries typically will not hold a charge as effectively as fresh cells.