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.
Effective mechanical design presents robust structure and higher energy density.
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.
High quality vent valve with low tolerances in opening and closing pressure reduces gassing rate significantly.