The Best Way to Maintain A Marine Battery

A marine battery is usually a hybrid between a deep cycle battery (used for long light loads like lights, electronics, trolling motor, etc..) and a starting battery (used for heavy quick loads like starting an engine). Marine batteries are designed this way so a single battery can be used to crank the engine and run the electronics without drawing the energy out of the marine battery too quickly. Some boats, especially larger ones, may have two batteries, one dedicated starting battery and a dedicated "house" (deep cycle battery) battery. This article will not discuss that situation as maintenance on the two different types of batteries will be slightly different.


Taking care of a marine battery is pretty simple, but there are a few key items you must do to keep them in their best shape.The first key item is protection from the elements. You can do this by keeping your marine battery in a battery box. A well ventilated compartment in the boat will work as well, but a marine battery inside a box, placed inside a ventilated compartment would be the best solution. Rain, spray, and sun are bad for the lifetime of the battery and will cause the battery to prematurely go bad. Make sure the battery compartment is ventilated as batteries can expel harmful gases in certain situations and these must be ventilated to prevent their build up.

Now that the marine battery is protected from the elements, you want to make sure the battery is securely attached to the boat. It is bad for the life of the battery and the safety of the passengers to have a battery sliding around in a rocking boat. This can easily be accomplished with a strap and some attachment points in the floor of the boat.You may also want to place a small wood frame around the base of the battery to help keep it from sliding. This frame would have to be attached to the boat with epoxy or fiberglassed in for a more permanent solution. It isn't required, but it helps keep the battery secure in it's mounting location.


If your motor has an alternator, make sure it is working properly. The alternator will charge the marine battery while the motor is running and prolong the lifetime of the battery by keeping the charge state higher. You can check this with a voltmeter. Compare the voltage while the engine is off with the voltage when the engine is running. If the voltage is higher with the engine running, then your alternator is charging the battery. (Sometimes the engine has to be above an idle speed for the alternator to supply a sufficient charge.)

Use a smart battery charger to "top off" the battery after each trip. A marine battery will last much longer if it is stored in a fully charged state. You can use a portable charger, but on-board chargers are much more convenient. They stay constantly attached to the battery and are simply plugged in once the boat is parked. While plugged in, they will do the work of maintaining a full charge on the marine battery so it is ready to use for your next trip.


  • Check the marine battery at least once a year to make sure the water level is correct. If it is low, fill it to the appropriate level with distilled water, being sure not to overfill the battery or spill any of the acid on yourself or the boat. This step can be skipped if you own a maintenance free battery.
  • Make sure the battery terminals are clean and free of any corrosion. This will eventually cause voltage problems which lead to bigger electrical problems down the road. The wires that attach to the terminals should be tight as well. Loose connections will cause the battery to possibly spark, creating a dangerous situation when flammable fuel is on-board.
  • Attempt to never discharge the battery more than 50%. Deep discharges cause chemical changes in the battery and will eventually cause the battery to go bad. When a battery goes bad, it simply won't hold a charge anymore. You may be able to tell when your battery is starting to fail because it won't run items as long as it used to. If this is starting to happen, it might be time to start looking for a new battery. Most auto parts stores will check your battery for free by applying a load test.


Congratulations, if you followed this guide you'll have a well maintained marine battery that will provide you years of trouble free service. Now get out there and catch some fish or cruise in comfort knowing you've got a good strong marine battery to get you home!

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