ArticleBoatingService Repair

Juice is Juice, Isn’t It?

When it comes to your boats onboard systems it’s no surprise that the vessel’s electrical power source is likely the least understood, and that needs to change. As technologies advance, boaters are finding themselves adding larger multi-functional displays, more powerful radar and fish finding systems, underwater lights and extensive entertainment systems. While all of these aftermarket additions add to your comfort and success on the water they also demand a more reliable and powerful battery system.


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Be sure that your house battery bank is capable of withstanding your anticipated daily needs. Photo: FSF Mag

Marine batteries are your lifeline on the water, so it is important that before you leave the dock you understand that the most common cause of dead batteries is utilizing the wrong type, size or quality battery for your particular application. What is also crucial is that you are aware of the fact that marine batteries come in many types and sizes, and that you fully comprehend their different uses and benefits. For an introductory look into the complex world of marine-grade batteries we contacted Kaylan Jana, the Development Support Manager for EnerSys, a global leader in stored energy solutions.

The most important aspect that determines battery type and performance is the thickness and composition of the battery plates.

FSF: What special features do marine batteries offer?
EnerSys: All batteries are built with lead plates that are immersed in an electrolyte solution, but in marine batteries the plates are better suited for the harsh marine environment by being constructed with a special bonding process. When deciding what battery is right for your particular application it’s best to first determine what type of power your battery needs to provide. The most important aspect that determines battery type and performance is the thickness and composition of the battery plates. These factors also have a direct correlation to cost.

High resistance to shock and vibration is certainly one desirable characteristic of a marine battery. Having true dual-purpose capability is also very helpful because the mariner will have the flexibility to use the same battery for both engine starting and cycling. However, one must be careful not to discharge the battery to such a low level that it becomes difficult for the battery to crank the engine.

FSF: What are the differences between deep cycling, starting and hybrid batteries?
EnerSys: Deep cycling refers to a situation where the user continuously charges and deeply discharges the batteries. In general, a discharge is considered to be deep if 50-percent or more of a battery’s amp-hour capacity is extracted during a discharge. Typically, in these applications the discharge is at a fairly low rate but the discharge duration is of the order of hours. The plates in a deep cycle battery have a large surface area and are spaced further apart, which allows the plates to withstand higher temperatures that occur when current is drawn for long periods of time.

In contrast, starting batteries are required to deliver high amperage pulses for a few seconds, just long enough to turn over the engine and fire it up. Because the amp-hours delivered by batteries in this type of application are very small, starting applications are not considered to be cyclic in nature. Starting batteries are constructed with numerous thin lead plates that are stacked close together. This design enables better bursts of energy for rapid and powerful cranking power.

A hybrid battery is rare because batteries are usually designed either for deep cycling or engine starting applications, but not for both. The exception is thin plate pure lead batteries as they are true dual-purpose batteries; they not only deliver very high engine cranking pulses but are also capable of delivering hundreds of deep discharge cycles.

FSF: What is the expected lifespan of a marine battery?
EnerSys: This largely depends on how the battery is used. For example, if the battery is repeatedly deeply discharged it is possible to run the battery to its end of life in less than 18-months. On the other hand if used exclusively for engine starting purposes a high-quality marine battery will last approximately 5 to 8-years. Of course, all of this assumes the batteries are properly cared for, particularly in terms of charging parameters.

Now that you have a basic understanding of marine batteries, lets talk about the different ratings to make note of. All batteries are given a rating for the specific duty they are designed to perform. Marine Cranking Ampere (MCA) ratings refer to the number of amps a battery can support for 30-seconds (at a temperature of 32-degrees) until the voltage drops to 1.2 volts per cell.

The storage capacity of a battery is defined as the amp hour (AH) rating. For example a battery that is rated as a 100Ah battery, at the 10-hour rate of discharge, is capable of delivering 10A for 10-hours before the terminal voltage drops.

Before making a final purchasing decision, remember that you get what you pay for. The saltwater marine environment is very unforgiving. Figure out how much money you’re willing to invest and then select the battery that offers the highest rating for your desired application.

Tips For Maximum Battery Performance

  • Keep batteries clean, cool and dry.
  • Regularly check terminal connections to avoid loss of conductivity.
  • Don’t mix old batteries in the same bank as new ones. Old batteries have the tendency to pull down new ones to the deteriorated levels.
  • Use the correct size and type cables and terminal fittings.

Marine Battery Manufacturers



Lifeline Batteries

MK Battery



Universal Power Group