How Should I Care for My Boat's Battery?

Batteries are required to do more and more on modern boats, including starting engines and powering radios, radar, lights, pumps and other electronics. Batteries have a finite life, which depends in part on the quality built in by the manufacturer. Regardless of the type of battery in your boat, there are some basic steps you can take to keep it working properly.

  • Make sure the battery is securely mounted. Batteries must be securely held in the battery box. Shock and vibration can seriously decrease battery life and lead to premature failure. Hold-downs should also be tight and free of corrosion.
  • Clean battery surfaces. Keep the top surface of the battery clean, as dirt can conduct electricity and silently rob your battery of stored energy. The electrical connections must be kept clean and corrosion-free. Use grease or a cleaning spray to prevent algae growth.
  • Check battery cable connections weekly. Make sure all connections are tight and free of corrosion. When accessories are added to a boat, additional wires should never be connected directly to the battery. Connections must be made to the power panel, through fuses or circuit breakers properly sized for the type of wire used to carry power.
  • Visually inspect all cables. Battery cables must be kept clean and properly supported along their run to the power panel. Look for cracks, breaks, tears or other damage to the cables. Check end connections for gaps between the connectors and coating. If you notice corrosion on the wires in the cable, replace the cable. Clean the posts regularly and coat with a corrosion retarder.
  • Inspect all starter connections. Regularly check the connections between the battery and starter switch, and between the starter switch and the starter itself. Check the starter mounting bolts for tightness. Lubricate starter bushings and/or bearings when necessary.
  • Check charging circuit connections. Inspect all connections between the battery, regulator and alternator. Make sure connections are tight and corrosion-free. Inspect the wiring for cracks, worn spots or general deterioration.
  • Check electrolyte levels and state of charge. If your battery has cell caps that can be opened, check the level of the electrolyte in each cell monthly. If the level is low, add distilled water. Some batteries (such as “maintenance free” types) are built with sealed cell covers and sufficient fluid to last the lifetime of the battery. The only way to check the condition of these sealed batteries is with a load test, carried out with a specialized piece of test equipment.
  • Track discharging levels. If you are using the battery to run things when the engine or generator is not operating, don’t discharge the battery below 12.2 volts. Never discharge a battery below 11.8 volts. Use a digital voltmeter to check battery voltage. Recharge the battery promptly after using it, as leaving it in a semi-discharged state will shorten its life.

Battery fluid is diluted sulfuric acid, so remember to always use caution when working with batteries. Wear protective goggles and try not to splash acid on clothing, the top of the battery or nearby surfaces. If any acid is spilled, replace the battery cell covers and wash the top of the battery with plenty of fresh water. Periodically clean the top, using a mixture of water and bicarbonate of soda to neutralize any acid residue. Dry the battery top after cleaning it.

With proper care, most moderate quality batteries used on commercial boats can be expected to last at least three years, while premium quality batteries can last for more than seven years. There are no bargain batteries. Finally, make a note of the date on which your battery was installed and post it near the battery where it can be seen each time you check the battery. Time flies and what you may think of as a relatively new battery may be years older than you thought.


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