Sealed VRLA

VRLA stands for valve-regulated lead-acid and is the designation for low-maintenance lead-acid rechargeable batteries. Because of their construction, VRLA batteries do not require regular addition of water to the cells. VRLA batteries are commonly further classified as:

  • Absorbed Glass Mat battery (AGM)

Fill with liquid electrolyte.

  • GEL battery

Fill with a gel substance, referred to as a gel electrolyte

Zelus, A classic GEL battery

Zelus is a VRLA battery with a gelified electrolyte; the sulfuric acid is mixed with silica fume, which makes the resulting mass gel-like and immobile. GEL batteries virtually eliminate the electrolyte evaporation, spillage (and subsequent corrosion Issues) common to the wet-cell battery, and more features like greater resistance to extreme temperatures, shock, and vibration. The valve regulation system allows for gas to be expelled. They are the same as wet (non-sealed) batteries except that the antimony in the lead plates is replaced by calcium. This preserves the mechanical characteristics but renders the construction far less prone to gassing.


  • Structure

Effective mechanical design presents robust structure and higher energy density.

  • Separator

High temperature stability, mechanical strength and low acid displacement.


  • GEL Electrolyte

Gelified electrolyte suspends acid stratification, does not need to be replenished, because it does not evaporate.

  • Ventilation

High quality vent valve with low tolerances in opening and closing pressure reduces gassing rate significantly.