Introduction to Marine Batteries
A Lead-Acid Storage Battery Primer
Recreational boaters for the most part use lead-acid storage batteries in their vessels. Compared to the alternatives available, lead-acid batteries are inexpensive to purchase and easy to maintain. These benefits are offset to some degree by weight, hazardous material used in construction and generated by use, and a short lifespan. There are two broad categories of batteries used on boats, starting and deep cycle. Battery may be of wet cell, gell cell or adsorbed glass mat construction. Any boater that handles or maintains a lead-acid battery needs to practice safety first.
Safety - Lead-acid batteries use an electrolyte composed of sulfuric acid that can cause chemical burns to eyes and skins. It easily ruins the clothes it contacts. Batteries contain plates made with lead, which is a toxic heavy metal. Properly handled batteries should never pose a lead poisoning risk. Trouble comes when there is improper disposal of batteries were their cases are broken. A battery under charge produces explosive hydrogen gas. Hydrogen ignites easily and violently. Lead-acid storage batteries can deliver electrical current in the hundreds of amps. A short circuit causes several safety concerns including sparks that ignite explosive environments, melting wires and fire. If this isn't enough, the things are heavy.
Precautions - Boaters need to wear safety goggles and acid resistant gloves during cleaning or servicing batteries. Remove metal jewelry. Battery compartments must be ventilated to prevent the buildup of hydrogen. Dispose of batteries properly and recycle them. Ask for help before you lift that 8D battery out of your boat.
Battery Construction - The components are:
- An acid resistant case – usually made of polypropylene
- Positive and negative plates made of lead
- Porous synthetic separator plates that go between the lead plates
- An electrolyte based on sulfuric acid
- Lead terminals to connect the battery to a load
Starting or Cranking Batteries - These batteries have more and thinner plates to provide high, short-term amount of engine cranking power. Many boats carry both starting and deep cycle batteries wired to take advantage of their designed purpose.
Deep Cycle Batteries - Deep cycles are built for long-term delivery of power. They use thicker plates and are able to withstand repeated discharge cycles. Deep cycles allow the use of electronic devices onboard without continuous use of a generator.
Most recreational vessels use a flooded or wet cell batteries. Gel cell and absorbed glass mat batteries are specialty products. Many confuse maintenance free batteries with gel cells. They are quite different and have different charging requirements. With a little care, lead-acid batteries are safe to use, will provide good and long life. Remember to treat batteries with respect and follow safety precautions. Hire a professional mechanic if you have any doubts about handling batteries. Your mechanic should be happy to show you how to safely maintain your vessel's batteries.
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