A battery is a container for chemical reaction that produces electrical energy measured in volts. Sealed lead acid batteries (SLAs) are made of cells. Each cell produces about two volts. A six-volt battery has three cells and a 12-volt battery has six.
Sealed lead acid batteries are used when high power is needed and weight and cost are lesser factors.
What an SLA can power and how long it will last depends on voltage and amp-hours. Voltage is a measurement of electrical strength. An amp-hour (Ah) measures stored usable energy. A six-volt battery has a lower Ah capacity than a 12-volt battery.
Two six-volt batteries can be wired to equal a 12-volt battery. Batteries wired in series can be charged to the capacity of the weakest battery. Batteries wired in parallel will equalize the charge, with higher charges flowing to lesser charges until equalized. SLAs generally take six to 18 hours to charge.
The heavier plate structures within each cell of the six-volt battery compared to the cells in the 12-volt battery contribute to longer life in deep charge and discharge cycles. Batteries used in deep-cycle service average four to eight years of life.
Six-volt batteries weigh less than 12-volt batteries and can be handled more easily by one person. This is often a significant decision-making element when considering a six-volt vs.12-volt battery.