Absorbent glass material made of 100% microglass fibre is a well-known separator for valve regulated lead acid (VRLA) batteries and has been in use for around 20-year period. As the VRLA battery market and demands of the customer continue to grow; electrical performance, productivity and reliability of VRLA batteries are being enhanced. This is achieved through a combination of process, quality assurance, materials and electrochemical engineering. Reliability and electrical performance of the battery is linked to the AGM glass material. Properties of the AGM material impact the assembly route, defect rates, productivity, product cyclability, life, reliability and recharge performance. Bernard Dumas in partnership with Enersys has developed a specific product containing 8% synthetic fibres for thin plate application. Enough data have now been gathered to guarantee that this type of separator is giving electrical performance equal to or better than 100% glass AGM and has increased battery productivity. The electrical performance of the batteries manufactured with synthetic loaded separator paper was equal or better than the AGM counterpart as demonstrated by capacity testing, cycling and accelerated float life (AFL) tests. Tear-down investigation after accelerated float life testing at 55°C showed no degradation of the synthetic separator paper.