Most marine batteries onboard boats today are of the lead-acid type. This type of battery has been used for many decades. The major reason that the popularity of this type battery has continued is relatively low cost to purchase and maintain. The disadvantages of lead-acid batteries are the weight, the short useful life (2-5 years), the lead ingredient that is poisonous and the fact that it creates a potentially explosive mixture of hydrogen gas.

Although most recreational vessels will generally use a combination lead-acid battery, there really are two types. You could have a starting battery that delivers a short burst of power to start your engine and then is almost immediately recharged by your alternator. You could also have a deep cycle battery that would operate your trolling motor, DC lights, instruments, VHF radio, etc. These are designed specifically to be drained to a low level of charge and then are recharged as necessary. The only difference in the two batteries is how much power is delivered and how long it needs to be delivered.