A Sealed Lead Acid (SLA) Battery is a type of rechargeable lead-acid battery that is sealed and does not require the user to perform maintenance, such as topping up with electrolyte and refilling. SLA batteries are offer longer life than disposable batteries and are typically used for backup and emergency power sources, as well as for portable devices such as wheelchairs and children's ride-on toys. SLA batteries are constructed from plates of lead and lead dioxide that are suspended in a solution of sulfuric acid and water. As the battery is discharged, the sulfuric acid is converted to water and the plates produce a form of lead sulfate. This process is reversed when the battery is recharged and the original components are restored. Sealed lead acid batteries are relatively efficient, but their capacity is limited and they must be recharged frequently.