The solar panel junction box is the output interface of the solar module. It wires the four solar connectors together.

Each solar junction box has two wires. One wire is the DC positive (+), and the other is the DC negative (-).

These can be connected to the solar PV panels either serially (series connection is when solar PV panels are wired together by connecting the positive lead on one PV panel to the negative lead on another PV panel to increase the voltage of the string).

The second is in parallel (Parallel wiring requires the positive leads to be connected and the negative leads to be connected).

The cables from a solar panel junction box transport the electricity from the solar PV module to the string. Modern PV solar panels tend to use the MC4 connectors because they make wiring the PV array much simpler and faster.

Besides, the PV junction box encapsulates solar bypass diodes that keep solar power flowing in one direction and prevent it from feeding back to the solar PV panels.

How to check the quality of a solar panel junction box?

A quality solar panel junction box minimizes corrosion at the terminals; as it will exclude that moisture enters the PV panel. The majority of solar junction boxes have at least an IP65 rating.

A quality solar panel junction box has an IP67 or IP68 rating.

So, what do IP65, IP67, and IP68 protection ratings mean?

IP67 and IP68 mean:

• IP refers to Ingress Protection,
• 6 stands for Dust-proof and
• 7 for Temporary immersion, 15 cm to 1m, and
• 8 for Permanent Immersion, under pressure

A solar panel junction box with an IP65 rating will provide complete protection against dust and cannot be damaged by low-pressure water jets. There may be limited ingress inside, but it stops the component from properly functioning.

A solar junction box with an IP67 rating is completely protected from dust and will properly functional after Temporary immersion in water (up to 1m deep).

A PV junction box with an IP68 is completely protected from dust and cannot be damaged by immersion in water deeper than 1m.

A quality solar panel junction box is certified (IEC61250, IEC61730, and UL1703).