If you look at the top of a plain old flooded-cell, 12-volt marine battery, you see two widely separated metal posts and plastic caps lined up to cover six holes. The six holes let you replace water lost from each of the battery’s six cells during normal discharging and recharging.
A 12-volt battery is really just a box containing six two-volt cells that are wired in series to produce 12 volts. The positive side of one cell is connected to the negative side of the next in a sort of daisy chain that adds the voltages of all the cells together.Click here to read more on Parallel, serial battery wiring basics
