Specifications and capabilities commonly compared for marine batteries include cold cranking amps, reserve capacity in amp hours, battery size, terminal type and type of battery. Most marine systems, except those with pull-start motors, require both a starting battery and at least one deep cycle battery each to maintain on-board systems. Starting batteries are compared strictly based on battery size and cold cranking amps. Larger vessels require higher cold cranking amp ratings to effectively engage and start the engines.
Deep cycle marine batteries are designed to withstand a nearly complete discharge and are typically compared by amp hour reserve capacity. The reserve capacity measures the length of time in minutes the battery discharges a set amperage. Marine batteries with higher reserve capacities enable more electronic draw while the engines are not running without interruption. Typically, batteries with greater reserve capacities also cost more than those with lower reserve capacities.
Marine batteries can also be compared based on construction. Traditional lead acid batteries with unique formulations are used for many marine batteries with special outer cases designed to minimize leaks and spills. High-end marine batteries use gel or absorbent glass mat materials, both of which are designed to hold charges for longer, discharge more slowly, and are spill- and leak-proof.