All batteries degrade over time and will eventually need replacement. While for most household appliances you simply replace them with other types of batteries, it is rarely that simple with marine batteries. When the marine batteries in your boat are life-expired and it's time to replace them, you can't simply walk into your local supplier and select any marine batteries that happen to fit your boat. It is important that you choose marine batteries that will be suitable for the way in which you use your boat.
How will you use your battery?
Think about how you use your marine batteries. Is the primary function of the battery going to be to start the boat, or do you want a battery that can power the lights and other boat electrics for long periods of time while you are at anchor? Remember, the battery is only charging while the engine is running, so all the time that you are using the boat electrics, you are draining the battery — so you could find yourself stranded and unable to start the engine if you fit the wrong battery.
What types of marine batteries are available?
There are three primary types of marine batteries which you will be confronted with when you visit the marine supplies store.
The starting (or cranking) battery: The starting battery is designed to provide a burst of current for a short while to provide the kick needed to start your boat engine when the boat ignition is engaged. It is designed with lead plates that have a large surface area so that it can provide the needed power.
The deep cycle (or power) battery: This is the battery you will need if you want to power all of the electrics on your boat while you are at anchor. The thicker lead plates found in the deep cycle battery are designed to release energy over a long period of time. The long discharge time of this battery will be able to power your electrics for as long as you are likely to want to be at anchor in your boat.
The hybrid marine battery: The hybrid battery has been designed as a compromise between the deep cycle and the starting battery. It combines the properties of both types and could be the right solution if the way you use your boat varies. What you will normally notice with hybrid marine batteries is that while they are often an acceptable compromise, they rarely perform as well as two separate batteries would.