Well, yes and no. There are actually several different types. A true deep-cycle has relatively few, yet stout, grids . These batteries resist the damage caused by repeated draining, but don't produce as much cranking power as an automobile battery, which has numerous thin plates. To understand how to maintain a battery, you must know the enemies of long life.
Batteries stay healthiest when fully charged.
Their biggest killer is being drained to zero percent. While deep-cycles are designed to resist draining, charging this type of battery after a complete drain decreases the unit's life. When a battery discharges, the active material on both the negative and positive plates converts to lead sulfate. The plates become more a like in terms of their electrical charge, and the battery's acid, which conducts electricity between the two poles, grow weaker. This results in a voltage drop because the battery depends on the polarity difference between the two plates, as well as the acid's strength.