Cells and Battery

Energy storage is an important component of every solar powered system, and one of the most commonly used storage for this purpose is an energy cell.  

Eventually, for most people, the term cell and battery are mixed up unintentionally that most of the time, while one person is talking about a battery, most likely that person is also talking about a cell. 

So, what's the difference between the two?  It's practically as simple as this, a battery is a combination of two or more cells, connected either in series or in parallel.

Series and Parallel Connected Cells

Similar to other electrical or electronic components, a storage cell, when combined with other cells can be connected in either series or parallel connection or a combination of both, and when they are, different rules apply. 

Series Connected Cells

Fig 1. Cells in series connection

Figure 1 is a good example of cells connected in series.  As one can see, along with the drawing is a formula that explains the relationship between the Voltage (V) and the Current (I).

The formula can be simply explained as this, if each cell has a rating V of 1.5v and an I of 30mA, then the Total voltage will be 4.5v and the total I will be 30mA.

As one can notice, George Simon Ohm's Law formula applies in cells and battery as well.

Parallel Connected Cells

Fig 2. Cells in parallel connection

Figure 2 is another example of cell connection; this time these cells are connected in parallel. 

Similar to figure 1, the figure all shows the formula that explains the relationship of V and I in this type of connection, which simply shows that cells in parallel connection have the same Voltage throughout the circuit, and Current I adds up as the number of cells increases. 

For this, IT = I1 + I2 + I3, thus if each cell has a capacity of 30mA. the total capacity is equal to 90mA. 

Series and Parallel Connected Cells

Fig 3. Series - Parallel Connected Cells

Figure 3 is a typical example of how cells can be connected in a combined series - parallel connection.  Aside from this, it also shows how to compute for the Total V and I. 

There is no secret in solving for the Total V ang I of figure 3.  Infact one can easily deduce how it was computed by simply following the color that I have used to perform the computation.  

This method of computing applies to all types of cells, one only needs to get the cell parameters to make the necessary computation.

In conclusion

Learning to compute for the value of combined cells in a Solar based DIY system is a necessity since most of the time the battery pack can be assembled too.  

For my own system, my battery pack was cells that I bought online that I simply put together to produce the desired capacity that I require.  

It starts at very low capacity that I can expand later, should my time and budget permits, this I can simply do by using the method that I have just recently shown above. 

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