As summer approaches, boats often get a spring cleaning where the vessel gets washed, engines get tuned, and seals get inspected. Most often, the vessel’s batteries were removed for storage, but that doesn’t mean they should simply be plugged back in without checking them as well.
Most boats have two types of batteries on board, one for starting the engine(s) and a deep-cycle marine battery for powering accessories such as troll motors, lights, radio, navigation, etc. All of the vessel’s batteries should have been fully-charged before long-term storage, but deep-cycle batteries use for powering accessories need some additional maintenance to keep them working reliably.
Most boats will have a single 12-volt or a series of six-volt flooded lead-acid (FLA) deep-cycle batteries. These are the most cost-effective type of battery versus an AGM or maintenance free batteries. To get your FLA batteries in shape for summer boating, put on some rubber gloves and protective eyewear and remove the vent caps on the batteries to check the level of the electrolyte. The lead cell plates of the battery should be completely submerged in the electrolyte. If not, add distilled water to the point when the plates are fully submerged, usually, 1/4-inch below the bottom of the fill well in the cell cover. Do not overfill.
Once you are sure the battery cell plates are properly submerged in electrolyte the batteries should go through a full charge cycle. Once completed, check the electrolyte levels again and add distilled water to any of the battery cells that may need it.
Check for corrosion on the battery terminals and wiring. Corrosion can be cleaned by spraying a solution of baking soda and water to neutralize the electrolyte, then using a wire brush with a plastic or wood handle, the terminals and battery connectors can be cleaned. Use a silicone spray to keep the terminals and connectors clean and to prevent additional corrosion from building up.
Once your deep-cycle batteries are clean and fully charged, it’s a good idea to make sure you do not discharge the batteries past 50-percent. This dramatically reduces battery life. Battery manufacturers also recommend giving your deep-cycle batteries an equalization charge. This is an extended, low current charge performed after the normal charge cycle. It helps keep all the cells in balance. Actively used batteries should be equalized once per month and most battery chargers will have this function built into it. If you have an automatically controlled charger that doesn’t have an equalization function, you can unplug it and reconnect it after completing a charge to give an extra equalization charge.
Once you’ve provided the proper maintenance to your deep-cycle marine battery(s), they should give you optimum performance throughout your boating season. Occasionally, check the condition of each battery charge by using a hydrometer to test the cells and determine the state of charge indicated on the hydrometer and the battery manufacturer specifications. Keeping your marine batteries in shape will make them last much longer and allow you to enjoy your time on the water.