Flooded deep cycle batteries are lead batteries that have been designed to provide sustained power over an extended period of time. These batteries have the capability to run reliably until it’s discharged up to 80% or more. The fluid in a flooded deep cycle battery is called electrolyte and is a solution of sulphuric acid and deionized water. Deionized water is recommended for use because it is free from additional minerals that are usually found in tap water. Unwanted chemicals and minerals in water can significantly decrease the life of flooded deep cycle batteries.