Article by Capt. Steve Katz
Power at Sea: A Guide to Marine Batteries
As Memorial Day week arrives, marking the unofficial start of summer here in Ocean City, Maryland, we at Ship To Shore want to take a moment to acknowledge the significance of this day. It's a time to pause and honor the courageous men and women who have made the ultimate sacrifice in service to our nation. Their bravery and dedication are the foundation of the freedoms we cherish, and we believe it's important to reflect on their invaluable contributions.
This week, alongside our remembrance, we also want to emphasize the importance of proper care and maintenance for your marine batteries. Ensuring their health is key to a trouble-free and enjoyable boating season. As the lifeline of your vessel's electrical system, their condition directly impacts your safety and convenience on the water.
As you likely know, a fully charged 12-volt standard lead-acid marine battery (whether traditional flooded, sealed, or AGM) should read around 12.6 volts when not under load. For a 24-volt system, this reading should be approximately 25.2 volts. It's worth noting that a 12-volt battery measuring just 12.0 volts at rest is already at a 50% state of discharge. Allowing a battery to remain in a discharged state for an extended period can lead to sulfation, a major cause of premature battery failure.
Sulfation is the buildup of lead sulfate crystals on the battery plates, occurring when a battery doesn't receive a complete recharge. This buildup hinders the battery's ability to convert chemical energy into electrical power. Fortunately, sulfation is largely preventable by consistently and correctly charging your batteries after each use.
Staying alert for potential battery problems is also crucial. One sign to watch for is a rotten egg smell emanating from the battery compartment, especially when the engine or a battery charger is operating. During these times, the battery voltage should typically be between 13.7 and 14.7 volts. This odor indicates the presence of hydrogen sulfide gas, produced when the battery's sulfuric acid electrolyte overheats or the battery is overcharged. This gas is colorless, poisonous, and flammable. If you detect this smell, immediately stop charging, ensure the area is well-ventilated, and keep a safe distance until the odor dissipates completely.
While most marine batteries typically last three to five years, depending on usage and maintenance, AGM (Absorbent Glass Mat) batteries are known for their superior resistance to charging and discharging cycles, making them a high-performance option, though they generally have a higher initial cost.
Regarding recharging, if your boat's engine alternator is your primary charging source, ensure it's functioning correctly. Most alternators produce around 14 volts of DC power, with varying amperage output. While voltage is easily monitored with your boat's gauges, measuring amperage is more complex. However, a consistent and stable voltage reading, generally about 2 volts higher than your system's rating, often indicates the correct amperage output. If you notice a voltage drop during a trip, it's wise to investigate the cause, as modern marine engines rely on a stable electrical supply.
If your boat has an onboard battery charger, it's an excellent way to maintain fully charged batteries when the engine isn't running. Many modern chargers include a float charge feature, automatically reducing the charging rate as batteries reach full charge, preventing overcharging and potential damage. Be aware that older chargers without this feature may pose an overcharging risk.
Regularly checking your batteries' condition and ensuring proper maintenance throughout the boating season is key to a reliable power source for all your onboard systems.
We hope these tips help you keep your marine batteries in top condition.
