B.B. Battery batteries Zelus GFT series is a VRLA Front-Terminal 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.