The most popular types of marine batteries use lead acid technology. There are three main kinds available, namely wet cell, gel cell, and glass mat designs. They continue to be popular because their sulfuric acid electrolyte allows them to store large amounts of electricity. However, their lead grids make them heavy and relatively unwieldy to store.
Flooded / Wet Cell Types of Marine Batteries
These continue to be the most popular marine applications, since many different size and design options are possible. The plastic containers hold the lead grids and acid electrolyte. The design is mechanically weaker since the plates only receive support at the edges.
These types of lead-acid marine batteries generally incorporate open cells, so the user can replenish electrolyte vented during charging. Hence, care is necessary to avoid acid burns, or chlorine gas if the sulfuric acid mixes with water. Hydro caps may help recover moisture lost during recharging.
Types of Marine Batteries Using Gel Cells
Gel cell batteries, commonly sealed lead-acid batteries have sulfuric acid made thicker by the addition of fumed silica.
This is a common anti-caking agent also used in cosmetics, paints, and as an abrasive in toothpaste. In batteries, it immobilizes the electrolyte providing additional support to the lead plates.
Manufacturers seal these types of marine batteries since topping up the electrolyte would be impractical. Hence, the rate of charging is slightly lower and needs careful moderating with different set points. The electrolyte cannot leak through a crack or breach following accidental damage.
Absorbed Glass Mat Batteries
AGM batteries use ultra-fine fiberglass separators infused with sulfuric acid electrolyte. This makes them impact and vibration resistant, and to all intents and purposes spill-proof.
Thus they ship as non-hazardous materials. Moreover, they are drop-in replacements for flooded cells having the same charging set points.
These types of marine batteries have other advantages over gel and wet cell designs. With low internal resistance, they are able to deliver high current on demand. They are virtually maintenance free and can sit in storage for months before requiring a top-up recharge. This makes them good candidates for energy storage.
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