Deep Cycle refers to applications that typically discharge 60 to 70% or more of the battery capacity. An automotive battery is an SLI battery (Starting, Lighting & Ignition.) Its plates are designed to deliver maximum power for a short duration. Starting an engine typically discharges an SLI battery 3% or less. When an SLI battery is used in a deep-cycle application or in a vehicle with heavy accessory loads, the battery life will be shortened proportionally to how deeply and frequently it is discharged.
The OPTIMA Deep Cycle battery uses a different chemistry for the plates' active paste material, and a slightly stronger acid. This chemistry allows for a much longer life in deep cycle applications with only a slight reduction in maximum power output.