A rechargeable battery is a battery that can be recharged and used many times over. It is otherwise known as a storage battery because it is able to accumulate and store energy which then becomes available to the user when he puts the battery to use. A rechargeable battery is sometimes referred to as a secondary cell as well, which is opposed to the non-rechargeable variety which is a primary cell.
When a battery is discharged, it goes through electrochemical changes. In a non-rechargeable battery, these changes are irreversible. A rechargeable battery, however, has the ability to efficiently reverse the chemical changes that occur during discharge when electrical energy is applied to it. In this manner, it is restored to full charge and fit for use once again.
The ability for reverse reaction, however, is not the sole characteristic of a rechargeable battery. It must also be able to undergo the reverse reaction both efficiently and safely many times. For example, some batteries can be recharged but because the chemical reactions are not completely reversed, they are only able to undergo the recharging process a few times, and their performance each successive time is less efficient. In addition, dangerous gases are sometimes built up, causing explosions or ignition either during or after recharging.
One of the first applications for rechargeable batteries was the car battery. Today, many electronics use rechargeable batteries, among them cellular phones, laptops, MP3 players, video cameras, and cordless power tools. In fact, many modern products are designed to only use rechargeable batteries.
Rechargeable batteries come in a variety of forms. Lead and sulfuric acid, as well as alkaline batteries can be rechargeable. Nickel cadmium (NiCd) batteries are an older type of rechargeable battery which were later surpassed by nickel metal hydride (NiMH) batteries. NiCd batteries had a memory with a capacity that tended to decline over time. NiMH batteries are much less susceptible to memory loss. Lithium ion (Li-ion) and lithium ion polymer (Li-ion polymer) batteries are two other types of rechargeable batteries.
Although a rechargeable battery is generally more expensive than the disposable type, in the long run it is more economical as it can be used hundreds, if not thousands of times over. Furthermore, rechargeable NiMH or Li-on batteries work much longer on high-drain electronic equipment per charge than do single-use alkaline batteries.
There are also environmental benefits for using rechargeable batteries. Since one rechargeable battery can take the place of hundreds, even thousands, of single-use batteries, much less waste is generated. Dramatically reduced as well are the toxic materials sent to the landfill.
The limitations of rechargeable batteries, such as availability of a variety of sizes, are quickly diminishing. Rechargeable batteries are being manufactured in more sizes than previously. Battery capacities are increasing, self-discharge rates are getting longer, recharging times are getting shorter, and prices are decreasing. In addition, battery chargers are getting smarter. Some have microprocessors that can read the type of battery that is placed into the charger and that prevent the user from undercharging or overcharging batteries.