If it’s time for a new battery for your boat, the main decision you’ll have to make is: wet cell or AGM?
The most common – and least expensive choice – is a wet, or flooded cell battery. They provide lots of cranking amperage, making them excellent choices as starting batteries. Wet cell batteries are available in many sizes and terminal configurations. Similar to the batteries in most cars,however, these require periodic maintenance and are best installed where you can get to them easily. They can be damaged by excessive vibration, must be kept in an upright position, and can be permanently ruined if left discharged.
At something like four times the cost of wet cell batteries, AGM (absorbed glass mat) batteries will normally last longer and deliver much higher power and efficiency. AGM’s are heavier than wet cells, but they can operate in any orientation and won’t spill, and they are quite impact and vibration resistant. When stored, AGM batteries typically lose less than 3 per cent of their charge per month at room temperature.
For opinions about when to change your battery, you might want to start with this thread on The Hull Truth. If you have any questions, or would like more information, please contact Chris at (508) 563-7136, or by email at firstname.lastname@example.org.