Battery types

Batteries come in many types and sizes depending on the needs of the owner. Here is a review of the various types of batteries used on voyaging boats:

Flooded or wet cell
The most common and often the most economical batteries are the standard lead-acid or flooded type. These are made up of lead composite plate in a water-acid solution. This type of battery has been around for a long time and is fairly forgiving to overcharging. They are not sealed and require maintenance. Their life span in charge cycles is also lower than most other types of batteries.

Gel cell
Gel batteries replace the liquid acid with a gel, allowing them to be sealed. This makes them spill proof and they require less maintenance. They still have pressure vents to prevent overpressure due to overcharging, so charging regulation is a bit more important. These batteries generally have a slightly higher life span than wet cells and, as one would guess, are a bit more expensive to purchase.

AGM (absorbed glass mat)
AGM batteries feature fine, highly porous microfiber glass separators compressed tightly between the battery’s positive and negative plates. These plates are saturated with just enough acid electrolyte to allow the battery to function. Like gel cells, AGMs are sealed with only overpressure vents. Thin plate pure lead (TPPL) and carbon foam are two other types of AGM batteries. The advantage of AGMs is that they have a higher density internal structure, allowing for greater efficiency. This efficiency also allows for faster bulk charging. The initial cost is higher but reduced charging times may help offset that.

Lithium iron phosphate (LiFePO4)
These are the somewhat new technology in batteries. They are lighter and smaller, offering as much as 70 percent savings for the equivalent wet cell. They can be discharged to a deeper level without damage to the battery, and controlled charging can bring them back to full charge quickly. Additionally, these batteries can have a greater charge/discharge lifespan. Their major drawback is their initial high cost along with needing to have the right equipment for proper charging.

Within these types are different physical sizes along with amp ratings. Some batteries are designed for strictly engine starting while others are designed for deep cycling. Selecting the right battery and doing a proper installation is an important part of any vessel outfitting.