The electrolyte in a flooded deep cycle battery is a solution of acid and water. Using distilled water for inverter battery is recommended because it is free from additional minerals you would find in water such as regular tap water. Adding chemicals and minerals can significantly decrease the life of batteries.Presence of such chemical ions may drastically reduce the lifespan of the battery. ... Distilled water contains no dissolved minerals, salts, organic and in-organic compounds that may harm the battery. Therefore battery manufacturers recommend distilled water for better performance and longer battery life.