The rechargeable batteries are lead-lead dioxide systems. The dilute sulfuric acid electrolyte is absorbed by separators and plates and thus immobilized. Should the battery be accidentally overcharged producing hydrogen and oxygen, special one-way valves allow the gases to escape thus avoiding excessive pressure build-up. Otherwise, the battery is completely sealed and is, therefore, maintenance-free, leak proof and usable in any position. Absorbent Glass Mat (AGM) technology for efficient gas recombination of up to 99% and freedom from electrolyte maintenance or water adding. Not restricted for air transport-complies with IATA/ICAO Special Provision A67. UL-recognized component. Can be mounted in any orientation. Computer designed lead, calcium tin alloy grid for high power density. Long service life, float or cyclic applications. Maintenance-free operation. Low self discharge.