Construction

• Lead-acid batteries are composed of lead plates designed to act as positive and negative terminals in the battery. The positive lead plate is generally in the form of lead dioxide, and the negative plate is pure lead in a spongy form. The plates are submerged in an electrolytic gel that is not prone to sloshing around and therefore increases the safety and versatility of the battery. Sealed lead-acid batteries is divided into cells; a 12-volt sealed lead-acid battery will be composed of six cells connected in series, each generating roughly two volts.
  
  

Usage

• Because the electrolyte is in gel rather than liquid form, a sealed lead-acid battery, unlike its unsealed counterpart, does not need to be kept upright. This means that they can be used in situations where orientation needs to be flexible -- for example, in submarines or aircraft. In many cases, they can be used in the same ways as ordinary lead-acid batteries, such as in electric vehicle motors or as the 12-volt battery in an internal-combustion automobile. Sealed lead-acid batteries are also used in closed environments where adequate ventilation is not possible; indoor batteries like those in a computer's uninterruptible power supply (UPS) are designed with sealed lead-acid batteries in mind.
  
  

Comparison to Non-Sealed Batteries

• Compared to a non-sealed 12-volt lead-acid battery, a sealed battery has the advantage of increased safety, due to the fact that the volatile electrolyte fluid cannot leave the battery case. However, they are more susceptible to damage from deep discharging, and will break if subjected to it -- a 12-volt sealed lead-acid battery should never be discharged below 10.5 volts. They are also more vulnerable to temperature variations, and lose voltage quickly at higher temperatures; at 95 degrees Fahrenheit, the battery's service life is cut in half.
  
  

Disposal Requirements

• Lead-acid batteries contain toxic materials and are therefore considered hazardous waste; they must be recycled to prevent the heavy metal lead from entering the environment. Because the government has been so proactive in sponsoring recycling programs (which recycle 97 percent of battery lead), the store that sells you a replacement sealed lead-acid battery may be required to take your old battery in for recycling; check the laws in your state for more details. If you're not replacing the battery, contact a battery retailer for further information about disposing of a sealed lead-acid battery.