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Mixing and Matching Solar Panels

A common question among solar DIYers and folks looking to expand their solar system revolves around mixing and matching solar panels. The question typically involves panels of different watts and voltage and those made by separate manufacturers.

Mixing and matching solar panels can most certainly be done, so long as some electrical considerations are taken into account. And as it goes with any electrical issue, what you'll mainly be concerned with is volts, watts, and amps (current).

Voltage

Voltage will be your main concern and will be the driving force behind the success or failure of a mix-matched array. Only solar panels of exact or similar voltage should be wired together. A 16.5-volt panel wired with a 24-volt panel will drag the higher voltage panel down to its level. The voltage of all panels in the circuit will conform to that of the smallest rating, possibly resulting in significant loss of power output.

Watts

Wattage is not a big issue. A 60W panel wired correctly to an 85W panel will yield 145W at peak performance. Provided that voltage is uniform and connected in parallel (see below), the total output of the array in watts will be the sum of the wattage for all panels in the circuit.

Amps

Current comes into play with wiring and is especially important when adding on to existing arrays. Amperes represent a sort of bottleneck -- only so much current can fit through that opening. So make sure that wires connecting the solar panel circuit are rated to carry the necessary amount of current. In a parallel circuit, which is how panels of different brands should be wired, the total current of the circuit will be the sum of all its components. So five 3-amp rated solar panels will produce 15 amps of current in total.

Parallel vs. Series Circuits

A good rule of thumb when mixing and matching solar panels, in addition to ensuring that they are the same voltage, is to use only series-connect panels of the same brand. When mixing manufacturers, use parallel circuitry to minimize losses.

In a series circuit all components are wired on a single path, so the same current flows through every resistor along that path. In a parallel circuit each component, or in this case solar panel, is wired to the source in its own loop. In this case all components will have the same voltage (very important) but the current will accumulate along the way.

So, as a random example, if you put an 12 volt/5 amp solar panel in a parallel circuit with a 9 volt/ 3 amp panel, what you'll end up with is 8 amps of current at 9 volts. In series you end up with 21 volts but only 3 amps of current. Here is a good example of how one creative self-installer managed to successfully wire eight panels from three different manufacturers together, using both series and parallel circuitry. Please note that he series-connected only like models and parallel-connected one panel brand to another.

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