Professional Reel and Downrigger Repair and Service by Cris Lane
Selecting a Marine Storage Battery
Types of batteries
Batteries on your boat handle two basic kinds of tasks, starting an engine and running electrical loads like lights, electronics and accessories for longer time periods. To choose a battery, first determine the battery’s application and then choose from one of the three battery chemistries: Flooded, Gel or AGM.
Starting Batteries: Starting batteries, which crank the starter of your boat’s engine, are the sprinters of your electrical system. They deliver between 75 and 400 amperes for 5-15 seconds, and then are recharged in short order by your engine’s alternator. Like all lead-acid batteries, they are constructed with alternating layers of negative and positive plates with insulation between them. Starting batteries have thinner and more numerous plates, providing extra surface area to generate high amperage bursts of current. The two drawbacks of this construction are that the plates are relatively fragile in high-impact environments, and that starting batteries do not tolerate deep discharges, which reduce their operating lifespan.
Deep Cycle Batteries: Your boat’s House battery bank uses Deep Cycle batteries, the marathon runners of the storage system. They power the electrical loads on your boat when no charge source (shore power charger, engine alternator, wind generator or solar panel) is available. Consider them a kind of savings account into which energy is deposited or withdrawn.
Compared to starting batteries, which deliver high bursts of energy for short periods, deep cycle batteries recover fully after being heavily discharged over longer periods because their design features thicker plates with a high content of antimony. Overnight, their use might deplete 50-70% of the battery capacity, depending on the house loads of the boat. When the batteries are recharged, energy is re-deposited into the bank, and the process, or cycle, starts over.
Dual-Purpose Batteries: We generally advise that you choose either a deep cycle or starting battery for best performance and battery life, but dual-purpose batteries work well in some applications. With large thick plates containing more antimony than starting batteries and an active lead paste chemistry, dual-purpose batteries are a good compromise, tolerating deep discharges that would ruin a typical starting battery. Since they have lower storage capacity than comparably sized deep cycles, we recommend them for the following applications:
- Runabouts or other small powerboats using a single battery for both starting and running loads with the engine turned off.
Article courtesy of West Marine
