The secret of battery runtime lies in the capacity. Capacity defines the energy a deep cycle battery can hold. The definition for capacity is usually given in ampere-hours (Ah); it specifies the elapsed time when discharging a battery at a calibrated current to the end-of-discharge voltage. Portable batteries commonly use a one-hour discharge; larger batteries are rated at either a 5 or 20-hour discharge.
  Lead acid batteries come in two basic architectures: deep cycle and starter types. The deep cycle battery is designed for maximum capacity and high cycle count. This is achieved by installing thick lead plates. Typical applications are golf carts, wheelchairs, people movers, scissor lifts and RVs. Starter batteries, in comparison, are made for maximum CCA (cold cranking amp). The battery maker obtains this by adding extra plates to get a large surface area for maximum conductivity. Capacity and deep cycling are less important for automotive because the battery is being recharged while driving. If continuously cycled, the thin lead plates of the starter battery would wear-down rather quickly. As a rule of thumb, the heavier the battery, the more lead it contains and the longer it will last.