A gel cell or gelled electrolyte is a sealed battery containing semi-solid electrolyte and may also be identified as a sealed lead acid, AGM (absorbed glass mat) or VRLA type battery. AGM batteries are sometimes referred to as starved electrolyte because the fiberglass mat contained within the cell is saturated only 95% with acid and there is no excess liquid. Nearly all AGM batteries are VRLA or valve regulated. VRLA batteries are designed with a valve that allows the battery to keep a slight positive pressure.