DIY Marine Battery Care Tips

As boating enthusiasts prepare for warmer weather, many assume the do-it-yourself (DIY) task of recommissioning their watercraft. Attention to the boat’s marine battery and its care is an important part of this annual practice. Not only must marine batteries start engines, but they are also responsible for powering onboard accessories. Known as house loads, these accessories can include communications equipment for monitoring weather and contacting emergency services, if needed, as well as electronic devices for convenience and luxury travel on the water.

Marine Batteries and Their Care

Some marine batteries are meant only to start the engine, while a separate battery powers the trolling motor and house loads. Other marine batteries are dual-purpose: that is, they provide both cranking power and deep cycling. Most dual-purpose marine batteries are Absorbed Glass Mat (AGM) batteries, which feature lead plates that are separated with absorbent fiberglass mats. The mats are compressed and saturated with electrolyte. AGM batteries are sealed and require no watering, making them virtually maintenance-free, as well as shock- and vibration-resistant.

As an advancement in AGM design, EnerSys® offers its line of ODYSSEY® Marine Dual Purpose batteries that feature proprietary Thin Plate Pure Lead (TPPL) technology. These batteries provide greater energy density and power than comparatively sized conventional flooded lead acid batteries.

The reliability of the battery for both starting and deep cycling depends upon proper care. Battery care involves inspection, cleaning, testing and charging, all of which the owner can do independently.

When working with marine batteries, wear protective gear on the eyes and hands, and use insulated tools. As always, be sure to follow the manufacturer’s guidelines for battery care and handling and direct any questions to your battery professional.


Examine the marine battery’s exterior for signs of damage or extraordinary wear, the cables for fraying, rust and corrosion, and the connections for deterioration and unsecured mounting. Corrosion can appear as a thin white powder or a blue-green growth on the terminals.

If the marine battery is a conventional flooded lead acid battery, check the electrolyte to ensure that it is between the minimum and maximum levels indicated on the side of the battery. For an accurate reading, the marine battery should be on a flat and even surface. If the electrolyte level is low, add distilled water, taking care to avoid overfilling the cell.

Replace damaged cables and clamps, but if terminals or the case are damaged, typically with cracks or leaks, replace the marine battery itself.


Dirt, acid, corrosion and other contaminants that accumulate on the case or terminals can cause small current leaks. When cleaning, disconnect the battery, and remember to wear protective gear.

Clean away deposits on the terminals with a battery terminal brush and neutralize acid accumulation with diluted ammonia or a paste of three parts baking soda and one part water. Clean away grime from the terminals and case with water. Rinse and dry the battery before reconnecting it.

Once the marine battery is reconnected, coat the terminals with anti-corrosion spray, grease or petroleum jelly to minimize deposits from reoccurring in the future.


Keeping the marine battery charged will reduce the risk of sulfation, which is the accumulation of lead sulfate crystals on the negative plates. Sulfation can prevent the battery from holding a charge. Testing will determine the marine battery’s State of Charge (SOC).

A digital voltmeter measures a battery’s Open Circuit Voltage (OCV). For an accurate reading of the battery’s OCV, the engine should be off for at least six hours to ensure that the surface charge is gone. The battery manufacturer’s specifications will indicate what OCV corresponds to 100 percent SOC, as well as what charge is needed. When OCV readings are lower than specifications require, the battery is likely defective. If so, consult a mechanic or battery specialist to determine the next course of action.


When charging a marine battery, the current must be high enough for a full charge, but if it is too high, it can overheat the battery and damage it. Be sure to follow the manufacturer’s guidelines for proper charging.

Parasitic loads can drain the marine battery to the point of not starting the engine and needing a charge to restore the full SOC. With flooded lead acid batteries, the drain can be enough to permanently damage the battery.

If the engine will be idle for more than a few weeks, connect the marine battery to a trickle charger so electronic devices, like clocks and security systems, do not drain the battery. If a trickle charger is not available, disconnect the battery when the engine is not in use.


TPPL technology helps to prevent a low State of Charge (SOC) that is common when batteries are used infrequently. ODYSSEY® Marine Dual Purpose batteries remain reliable, even after being idle during winter storage. They can be stored for up to two years at temperatures of 77°F (25°C) or lower before they need recharging. They also offer slower self-discharge and faster recharging than conventional lead acid batteries.

ODYSSEY® Marine Dual Purpose batteries can start the engine and power trolling and house loads, as well as simplify storage and recommissioning between seasons. With the proper care and use, they should deliver consistent performance throughout years of motorboating.

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EnerSys, the global leader in stored energy solutions for industrial applications, manufactures and distributes energy systems solutions and motive power batteries, specialty batteries, battery chargers, power equipment, battery accessories and outdoor equipment enclosure solutions to customers worldwide. Energy Systems, which combine enclosures, power conversion, power distribution and energy storage, are used in the telecommunication, broadband and utility industries, uninterruptible power supplies and numerous applications. Motive power batteries and chargers are utilized in electric forklift trucks and other industrial electric powered vehicles requiring stored energy solutions. Specialty batteries are used in aerospace and defense applications, large over-the-road trucks, premium automotive, medical and security systems applications. EnerSys also provides aftermarket and customer support services to its customers in over 100 countries through its sales and manufacturing locations around the world. With the NorthStar acquisition, EnerSys has solidified its position as the market leader for premium Thin Plate Pure Lead batteries, which are sold across all three lines of business. More information regarding EnerSys can be found at