To begin with, we will need battery holders and clips. The standard battery that we will be working with is AA and the standard size battery holders will hold two, three and four AA batteries.
The way the AA battery holders work is that they connect the batteries in series. When connected in series, the battery voltage adds up. So, two 1.5V batteries in series adds up to a 3V power supply. It goes to follow that three batteries add up to a 4.5V power supply and four batteries add up to a 6V power supply.
On occasion, we will also use 9V batteries and connectors.