The Role of the AGM Separator in Batteries
The AGM (Absorbent Glass Mat) separator is a thin, non-woven mat of micro-fibrous glass that sits between the positive and negative plates of a valve-regulated lead-acid (VRLA) cell. It immobilises the electrolyte, enables ion transport and provides electrical insulation between the plates. Typical glass fibres are 0.25-4 µm in diameter with a mean length near 1 mm, producing a highly porous, acid-wettable structure with low internal resistance – key to high-rate discharge and reliable cycling.
Core functions
- Prevents short circuits between the positive and negative plates.
- Immobilises the electrolyte so the battery can be installed in different orientations.
- Provides channels for hydrogen-oxygen recombination during charge and discharge, preventing active-material shedding.
- Slows the formation of lead dendrites and reduces electrolyte loss.
- Makes the battery maintenance-free, or reduces maintenance, extending service life.
Why AGM separators perform well
The material’s key properties are excellent corrosion resistance, fast electrolyte absorption, uniform thickness, good insulation, high porosity and a long service life. These characteristics give AGM batteries low internal resistance, strong high-rate discharge and dependable standby performance – the reasons AGM is the standard for UPS, telecom and start-stop applications.