What is Electric Battery ?

Automotive lead-acid rechargeable batteries have a much harder life. Because of vibration, shock, heat, cold, and sulfation of their lead plates, few automotive batteries last beyond six years of regular use.

Automotive starting batteries have many thin plates to provide as many amps as possible in a reasonably small package, and are only drained a small amount before being immediately recharged.

Care should be taken to avoid deep discharging a starter battery, as the recharging process melts a small amount of the lead from the plates. When holes form in the plates it results in less surface area for the chemical reaction, which results in less measured voltage.

Leaving a lead-acid battery in a deeply discharged state for any length of time allows the sulfate to become more deeply adhered to the plate, making sulfate removal during the charging process difficult

This can result in less available plate surface and the resulting lower voltage, shortening the battery's life. "Deep-Cycle" lead-acid batteries such as those used in electric golf carts have much thicker plates to aid their longevity.

The main benefit of lead-acid is its low cost, the main drawbacks are their large size and weight per a given capacity and voltage.

Lead-acid batteries should never be discharged to below 20% of their full capacity as internal resistance will cause heat and damage when attempting to recharge them.

Deep-cycle lead-acid systems often use a low-charge warning light or a low-charge power cut-off switch to prevent the type of damage that will shorten the battery's life.

Special "reserve" batteries intended for long storage in emergency equipment or munitions keep the electrolyte of the battery separate from the plates until the battery is activated, allowing the cells to be filled with the electrolyte. Shelf times for such batteries can be years or decades. However, their construction is more expensive than more common forms.

A battery explosion is caused by the misuse or malfunction of a battery, such as attempting to recharge a primary battery, or short circuiting a battery. With car batteries, explosions are most likely to occur when a short circuit generates very large currents.

In addition, car batteries liberate hydrogen when they are overcharged (because of electrolysis of the water in the electrolyte). Normally the amount of overcharging is very small, as is the amount of explosive gas developed, and the gas dissipates quickly.

However, when "jumping" a car battery, the high current can cause the rapid release of large volumes of hydrogen, which can be ignited by a nearby spark (for example, when removing the jumper cables).

When a battery is recharged at an excessive rate, an explosive gas mixture of hydrogen and oxygen may be produced faster than it can escape from within the walls of the battery, leading to pressure build-up and the possibility of the battery case bursting.

In extreme cases, the battery acid may spray violently from the casing of the battery and cause injury.
Additionally, disposing of a battery in fire may cause an explosion as steam builds up within the sealed case of the battery.

Overcharging—that is, attempting to charge a battery beyond its electrical capacity—can also lead to a battery explosion, leakage, or irreversible damage to the battery. It may also cause damage to the charger or device in which the overcharged battery is later used.

From a user's viewpoint, at least, batteries can be generally divided into two main types—rechargeable and non-rechargeable (disposable). Each is in wide usage.

Disposable batteries, also called primary cells, are intended to be used once and discarded.

These are most commonly used in portable devices with either low current drain, only used intermittently, or used well away from an alternative power source.

Primary cells were also commonly used for alarm and communication circuits where other electric power was only intermittently available. Primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible.

Battery manufacturers recommend against attempting to recharge primary cells, although some electronics enthusiasts claim it is possible to do so using a special type of charger.

By contrast, rechargeable batteries, or secondary cells, can be re-charged after they have been drained. This is done by applying externally supplied electrical current, which reverses the chemical reactions that occur in use. Devices to supply the appropriate current are called chargers or rechargers.

The oldest form of rechargeable battery still in modern usage is the "wet cell" lead-acid battery. This battery is notable in that it contains a liquid in an unsealed container, requiring that the battery be kept upright and the area be well-ventilated to ensure safe dispersal of the hydrogen gas which is vented by these batteries during overcharging.

The lead-acid battery is also very heavy for the amount of electrical energy it can supply. Despite this, its low manufacturing cost and its high surge current levels make its use common where a large capacity (over approximately 10Ah) is required or where the weight and ease of handling are not concerns.

A common form of lead-acid battery is the modern wet-cell car battery. This can deliver about 10,000 watts of power for a short period, and has a peak current output that varies from 450 to 1100 amperes.

An improved type of lead-acid battery, called a gel battery (or "gel cell"), has become popular in automotive industry as a replacement for the lead-acid wet cell.