Cells are a [voltage source](/Electronics/Physics_of_electricity/Voltage.md#chemicals-cells-and-batteries) 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:
> The key thing to remember: **cells configured in series increases the overall voltage available** and **cells configured in parallel increases the overall current available**
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.
However the voltage is accumulative: it is the _sum_ of the individual cell voltages, represented below as [electrical field](/Electronics/Physics_of_electricity/Voltage.md#distinguishing-voltage-from-electric-field):
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)_:
