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Is the junction box at the back of the panel important?

An important feature in the construction of solar panels is the junction box. Attached to the rear of the solar panel, it serves several important functions.

Firstly, it seals the rear of the solar panel where the inter-connectors exit. As such, it is vital that the junction box is well sealed so that moisture cannot enter the panel. Some are permanently sealed, like LG's junction box which are rated IP67, which means that it is completely sealed.

Secondly, the junction box it houses connection points for the cables which exit to allow you to connect each solar panel together. These connections need to handle different types of weather conditions over the years and need to handle quite high currents so quality connections are very important. The solar panel junction box also houses small electronic devices called diodes which protect the solar cells in the case some are partially shaded. Some diodes exhibit higher losses and create higher temperatures than others, leading to potential stress for the solar cells.

Lastly, many solar panel junction boxes are filled or partially filled with a sealant to protect the entry of moisture to the solar panel and are sometimes filled to the brim to fully encapsulate the diodes, connections and cables. The quality of this sealant is an important factor too.

When you are assessing a solar panel, look very closely and observe the type and integrity of the junction box to ensure it fits well, is perfectly sealed and if operable, that it seals up perfectly when re-closed. In the case of LG’s solar panel junction box, they are permanently sealed to prevent moisture entering the panels (IP67 rated).