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Basics of Boat Battery Selection

What size battery do you need? Measure the battery compartment and check the Group Size, which is the industry standard for the physical size of batteries. Here’s what else you need to know about the basics of battery selection.

For starting batteries-the most important feature to consider is cranking amps (CA). That is the discharge load that a fully charged battery can provide in 30 seconds. That’s about the time a battery needs to be at peak performance to start the engine. The owner’s manual or your dealer can tell you how much CA is needed for your boat.

For deep cycle batteries—those used to power all your onboard gadgets throughout your outing—you need to consider amp hours (Ah). That is the amount of energy charge that will provide one ampere of current flow for one hour.  Knowing how many amps you need is very important with today’s high-powered, amp-thirsty electronics.

Amps are important, and so is the reserve capacity (RC) of the battery. That is the number of minutes a fully charged battery can manage a load of 25 amps before falling below 10.5 volts at a given temperature. RC is like the backup, or reserve power, for batteries designed for deep discharge, like those used to power accessories.

Beyond those basics, avoid mixing and matching battery types or brands throughout the electrical system. The battery charger will operate more efficiently as a result. Also, replace all batteries in a system at the same time. If you don’t, the older batteries in the bank will place a drag on the newer batteries, shortening their life span.


Lead Acid Batteries

Lead acid batteries have been around as long as the engines used to power them. Find them in automobiles, boats and just about any other machine needing an electrical crank.

Pros: They can’t be beat for their cost per watt. Inexpensive, reliable and effective.

Cons: Can be high maintenance when compared to the newer types. They are more fragile. Internal damage can result on hard impact.


AGM Batteries

Absorbed glass mat (AGM) batteries contain electrolytes in a woven roll of fiberglass. That prevents the electrolytes from spilling, even if the battery housing is damaged or turned upside down.

Pros: No terminal corrosion because acid is not used. Higher CA and RC rating. Quicker and longer-lasting charges than lead acid batteries.

Cons: Overcharging can shorten life expectancy. Need to keep charged to at least 50 percent capacity for best performance.


Gel Batteries

Gel cells use a blend of sulfuric acid and silica to create a fixed gel-like substance. The immobilized gel means they don’t need to be mounted upright.

Pros: Sturdier and can withstand hard impacts, e.g., pounding waves. Holds deep cycle charging longer than other batteries.

Cons: Need a specific charger.


Lithium Ion Batteries

You have a smaller version in your cell phone. Lithium ions transfer electrons at each end of a cathode and anode.

Pros: Up to 70% lighter than lead acid batteries (think improved fuel economy and engine performance), more environmentally friendly and have longer lifespans.

Cons: More expensive than other types of marine batteries. Slower chargingType your paragraph here.

A Guide to

Choosing the Best Boat Battery