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Cells and batteries
Cells are a voltage source that generate a difference of potential via a positive and negative electrode separated by an electrolytic solution. The electrolytes pull free electrons from one of the materials which creates a positive charge. The other material gains the free electrons creating a negative charge.
A battery is a combination of two or more cells.
Cells which cannot be recharged are called primary cells. Cells which can be recharged are called secondary cells.
Connecting batteries
Cells and batteries can be connected to each other in electrical ciruits to increase the overall voltage that is produced. There are three main connection types:
- series
- parallel
- series-parallel
The key thing to remember: cells configured in series increases the overall voltage available and cells configured in parallel increases the overall current available
Series connections
With series connections we distinguish series aiding and series opposing configurations.
In the case of series aiding, cells are connected one in front of another with the positive terminal connecting to the negative terminal of the other in a line.
In this configuration the same current flows through all the cells, it is not accumulative. We represent this as follows:
I_{T} = I_{1} + I_{2} + I_{3}
However the voltage is accumulative: it is the sum of the individual cell voltages, represented below as electrical field:
E_{T} = E_{1} + E_{2} + E_{3} \
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In the case of series opposing, negative terminals are connected to each other and positive terminals are connected to each other in a series. This doesn't have many applications.
Parallel connections
Parallel connections follow the series opposing (negative to negative, positive to positive) configuration but they are not connected in sequence.
The same current flows through all cells. This is represented mathematically as follows (T stands for time):