Series Aiding, Series Opposing, Parallel, and Series-parallel Battery Connection
Series aiding, series opposing, parallel, and series-parallel Battery Connection
Cells can be connected together to increase the voltage or current rating. There are four different ways that cells or batteries can be connected. These are series aiding, series opposing, parallel, and series-parallel.
Series Aiding Connection
The cells are connected so that the positive terminal of the first connects to the negative terminal of the second; the positive terminal of the second connects to the negative terminal of the third etc.
This is a series connection because the same current flows through all three cells. It is an aiding connection because the voltage adds together. Since the individual emf of each cell is 1.5 volts, the overall emf is 4.5 volts.
Notice that the voltages add together because between cells the opposite polarity terminals are connected. That is, the negative terminal of the first cell connects to the positive terminal of the next and so on. Thus, the three 1.5 volts cells provide a total emf of 4.5 volts.
With the series aiding connection, the total voltage across the battery is equal to the sum of the individual values of each cell. However, the current capacity of the battery does not increase. Since the total circuit current flows through each cell, the current capacity is the same as for one cell.
Series Opposing Connections
The series aiding connection just discussed is extremely important and is widely used. The series opposing connection of cells is just the opposite. It has no practical use and is usually avoided. It is mentioned here because an inexperienced person may inadvertently connect cells in this way.
The two cells are connected in series, but like terminals of the cells are connected together. Here the two voltages cancel each other so that the overall emf is 0 volts. Because the two voltages cancel, this arrangement cannot produce current flow.
Three cells are connected in series but cell number 2 is connected backwards. Consequently, its voltage is subtracted from the voltage of the two cells connected in series aiding. The total voltage for cells 1 and 2 is 0 volts. This leaves the output voltage of cell 3. Therefore, the total output of the three cells is only 1.5 volts.
We have seen that the series aiding connection of cells increases the output voltage but not the current capabilities of the cells.
However, there is a way to connect two cells so that their current capabilities add together. This is termed as a parallel connection. Here, like terminals are connected. That is, all the positive terminals are connected together as are all the negative terminals.
When both a higher voltage and an increased current capacity are required, the cells are connected in series-parallel.
For example, suppose we have four 1.5-volt cells and we wish to connect them so that the emf is 3 volts and the current capacity is twice that of any one cell. To achieve 3 volts, cells 1 and 2 are connected in series. However, this does not increase the current capacity.
To double the current capacity we must connect a second string (cells 3 and 4) in parallel with the first. The result is the series-parallel arrangement.