There are 3 main types of battery to choose from. These types will perform two general functions on board a boat- as starting
batteries and as house batteries. This first article will look at the different types of batteries, while next week’s article will
look at the differences required in a house or starting battery.

The most familiar type of battery is the flooded cell type. These use an electrolyte in the form of acid and lead plates. A chemical
reaction produces electricity. They are a tried and true technology.

One result of their method is that they produce both hydrogen and oxygen which escape. Therefore they need to be watched and topped
off with water.

Generally these are the lowest cost option for batteries. They also accept over charging better than other types. On the other hand the corrosive battery acid can spill and cause damage, and they need to be maintained and charged when not in use.

Gel batteries are properly known as seal-value regulated batteries. They are a recombinant battery. This means that the hydrogen and oxygen produced by the battery stay in the battery.

The gel part of the battery is a chemical mixture that is put into the battery and then vacuum sealed in place. This prevents the spilling of acid.

Gel batteries are more expensive and not as tolerant to overcharging.

The third type of battery is AGM (Absorbed Glass Mat). AGM are also a sealed case, maintenance free battery. In these batteries
a glass mat sits between plates and absorbs the proper amount of electrolyte. This means there is not excess acid to spill.

AGM batteries can be installed at an angle, are more expensive and heavier than other types.

Typically both AGM and gel batteries charge quicker than flooded cells.

Each type has it’s pro’s and cons. You should pick one type and use it exclusively. Don’t mix types. Each type has a way that
it charges best so types should not be mixed.

The next article will consider how to chose appropriate starting and house batteries.

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