Valve Regulated Lead-Acid (VRLA) batteries – also known as Sealed Lead-Acid (SLA) or Maintenance- Free – are the most commonly used with UPS installations.
A VRLA battery is made up of cells consisting of lead alloy plates immersed in an electrolyte of dilute sulphuric acid. This liquid (or gel) fills the space between the positive and negative plates, forming a closed circuit of cells. The chemical reaction creates DC current, which can be stored for later discharge.
VRLA batteries incorporate a valve that opens and relieves the pressure if an excess of hydrogen gas builds up inside the block. VRLA battery cases tend to be manufactured from flame retardant polypropylene or Acrylonitrile Butadiene Styrene (ABS) plastic.
