Entirely maintenance-free, closed VRLA batteries (Valve Regulated Lead Acid). Batteries in which the electrolyte is enclosed in a silicon gel structure. This solution guarantees high reliability and safe operation, even during cyclical operation. VRLA battery technology has been on the market for a dozen or more years. VRLA cells are used wherever space is limited and the stricter ventilation requirements of classic battery installation cannot be met. Apart from the possibility of using the external gas recombination system plugs for open cells, the primary advantage of VRLA batteries is the amount of space they occupy. There are two distinct technologies for the production of closed cells: with a gel-based electrolyte and with an electrolyte in combination with AGM (Absorbing Glass Matt).