Solar Energy Water and Power — 24 July 2013

Solar cells are the individual pieces that make up a solar panel.  Although the pieces or cells are manufactured into different sizes, a common size is 3-inch x 6-inch.  If you are considering building a solar panel yourself, that it is important to know how to wire the cells together.  the objective of this post is to give the basic outline of what is needed to accomplish the task.

Each solar cells has a positive and negative side.  The side that faces the sun (usually has a blue color) is the positive side.  The back side (usually grey) is the negative side.

A stack of solar cells

A stack of solar cells

Each 3-inch x 6-inch solar cell is rated to produce 0.5 volts and 3.5 amps (0.5 x 3.5 = 1.7 Watts).  The individual cells are connected with wire to form a solar panel.  The connection is made by applying rosin flux and tabbing wire with a soldering iron.

It is common to connect the cells in series to increase the total voltage of the solar panel.  Connecting the cells in series (connecting the positive side of one cell to the negative side of the next cell) the voltage of each cell is additive.  So, connecting 36 cells in series should produce 18 volts (36 x 0.5 = 18).  This is commonly done to connect the solar cells to a 12 volt battery.

Here is an illustration on how the cells are connected in series.

Top view of 4 cells

Top view of 4 cells wired in series

The cells have two white strips on the face.  These are called the “bus bars”.  If the solar cells do not already have wiring tabs attached, then they will need to be soldered onto the bus bars.

Side view of 4 solar cells

Side view of 4 cells wired in series

The side view shows how the tabbing wires are connected from the top (positive) side to the bottom (negative) side.  Assuming that each cell produces 0.5 volts, and 3.5 amps, using basic electrical formulas, the panel connected in series should produce 2 Volts (0.5 x 4) and 7 watts (2 x 3.5).

If the cells were connected in parallel instead of in series, the amperage would be additive and the voltage would remain the same.  So the 4 cells connected in parallel should produce 14 Amperes (3.5 x 4) and 7 watts (0.5 x 14).  Connecting in parallel usually isn’t done since the higher voltage is needed to connect to a battery.

Using parallel connections does come in handy when connecting two or more solar panels or battery banks.  More on this can be read at the post solar panel wiring.

 

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