Batteries & Onboard Power

For engine cranking, the best battery is a marine start battery. For batteries that provide power for everything else onboard, a deep cycle marine battery is best. Start batteries are designed to provide a short burst of high power during engine cranking, while deep cycle batteries are constructed to provide continuous power output over longer periods of time.

Automotive start batteries are designed to provide a short burst of high power during engine cranking, after which the alternator takes over to provide power for accessories such as lights or a radio. While some marine batteries can be used for starting, they are also often required to provide power to onboard accessories after starting. Marine batteries feature more robust construction against vibration and thicker internal lead plates, which allows them to provide power over a longer period of time.

A marine battery should have thick internal lead plates, which allows it to provide power over longer periods of time. Thicker lead plates also allow it to withstand more charge and discharge cycles without damage. The battery housing should be large and robustly constructed to provide greater protection against the vibration and shock marine batteries are subjected to aboard boats.

For engine cranking, the best battery is a marine start battery. For batteries that provide power for onboard accessories, such as lights or a radio, a deep cycle marine battery is best. For boats with two batteries, a start battery and a deep cycle battery work well. For smaller boats with a single battery installed, a deep cycle marine battery is the best choice to both start the engine and provide power to accessories afterward.

A storage battery should typically be mounted in a level, upright position. Some types of batteries, such as AGM (absorbed glass mat) are sealed and can be mounted in most any position, based on the manufacturer’s installation recommendations.

The average lifespan of a properly maintained marine battery is around four years, although under some circumstances they can last a few additional years. Improper use, excessive heat, incorrect charge voltages, and lack of maintenance charging are key issues that can reduce battery service life.

Battery technology is developing rapidly to meet many different needs. Absorbed glass mat (AGM) is only one such development. Gel cell, Lithium-Ion, Lithium-Sulphur, lithium-nickel-cobalt-aluminum (NCA) and other types are being developed or experimented with. Stay tuned to these developments, but remember, your boat presents a unique and potentially dangerous environment for battery survival and safety. Let other users do the experimenting first, and be sure that whatever you get is appropriate for your boat and its specific needs.