A battery is an electric storage device, which can be found in any number of shapes, sizes, voltages and capacities. When two conducting materials (often-dissimilar metals) are immersed in a solution, an electrical potential will exist between them. If connected together through a closed circuit, a current will flow.

The value of this potential (or voltage) is dependent on the materials used, giving rise to a whole family or battery types each having benefits and restrictions in use. Examples are: lead acid, nickel-cadmium, lithium, silver alkaline. A battery is simply an arrangement where a number of cells are connected together with a given voltage and capacity. The more the number of cells higher is the voltage, and larger the plates the larger is the capacity. Purely for convenience, batteries are made in 12 volt blocks with 6 cells, but are also available in 6 volt, 4 volt and even 2 volt single cell blocks.

Batteries can be connected in series to achieve whatever voltage is required (add the number of 2 volt cells), and in parallel to achieve the capacity required (add the capacities of each parallel battery or string of batteries).

For larger systems, a number of series of strings may be connected in parallel with each other. This achieves both a higher voltage and capacity.

The Lead acid battery

There are two concepts in lead acid batteries: 1. Sealed Maintenance Free (SMF) or Valve Regulated Lead Acid (VRLA) 2. Open - vented.

There are three basic applications:

1. Industrial 2. Automotive 3. Traction