The voltage is based upon the chemistry of the battery. The base unit of a battery is called a cell. When you combine 2 or more cells, you have a battery. A single cell will have what is called a nominal voltage based upon what chemicals are used to make up the battery. For alkaline, the chemistry is generally a magnesium dioxide mix, which has a nominal voltage of 1.5V per cell, regardless of the size. Rechargeable chemistry types like Nickel Metal Hydride (NiMH) and Nickel Cadmium (NiCd) have a nominal voltage of 1.2V per cell (even though some people list it as 1.25). The chemical reactions inside the cell will determine the output voltage. The capacity or run time can definitely be impacted by the size. Compare an alkaline AAA to a D cell. Even though they have the same voltage based upon the chemistry, the D has a much greater capacity based upon the volume of chemicals in the can. If you want to change the voltage, the only way you can go is up by connecting the cells or batteries in a series connection (positive of one cell to negative of the other). To increase capacity, but keeping the same voltage, connect the cells or batteries in a parallel connection (positive of one cell to positive of the other cell).
Tuesday, January 22, 2008
Why batteries of different sizes have the same voltage?
The voltage is based upon the chemistry of the battery. The base unit of a battery is called a cell. When you combine 2 or more cells, you have a battery. A single cell will have what is called a nominal voltage based upon what chemicals are used to make up the battery. For alkaline, the chemistry is generally a magnesium dioxide mix, which has a nominal voltage of 1.5V per cell, regardless of the size. Rechargeable chemistry types like Nickel Metal Hydride (NiMH) and Nickel Cadmium (NiCd) have a nominal voltage of 1.2V per cell (even though some people list it as 1.25). The chemical reactions inside the cell will determine the output voltage. The capacity or run time can definitely be impacted by the size. Compare an alkaline AAA to a D cell. Even though they have the same voltage based upon the chemistry, the D has a much greater capacity based upon the volume of chemicals in the can. If you want to change the voltage, the only way you can go is up by connecting the cells or batteries in a series connection (positive of one cell to negative of the other). To increase capacity, but keeping the same voltage, connect the cells or batteries in a parallel connection (positive of one cell to positive of the other cell).
