Integrated PV Junction Box and Split Junction Box

  • 2021-07-16

        PV junction box is a connecting device between the solar cell array formed by solar cell modules and the solar charging control device. Its main function is to connect and protect the solar photovoltaic module, and connect the power generated by the solar cell to the external circuit. Conduct the current generated by the photovoltaic module. The junction box is glued to the back plate of the component through silica gel, the lead wires in the component are connected together through the internal wiring in the junction box, and the internal wiring is connected with the external cable to make the component and the external cable conduction. It is a cross-domain comprehensive design integrating electrical design, mechanical design and material science.

        The PV module junction box includes a box body, which is characterized in that a printed circuit board is arranged in the box body, and N bus bar connection ends and two cable connection ends are printed on the printed circuit board, and each bus bar connection end passes through a bus bar. Connected to the solar battery string, the adjacent bus bar connection ends are also connected by diodes; among them, there is an electronic switch in series between the bus bar connection end and the cable connection end, and the electronic switch is controlled by the received control signal. The Nth bus bar connection end is connected to the second cable connection end; the two cable connection ends are respectively connected to the outside through the cable line; a bypass capacitor is also provided between the two cable connection ends.


junction box of solar panel


Composition of Solar Junction Box

        The junction box is composed of a box body, a cable and a connector.

The box body includes: the bottom of the box (including copper terminal or plastic terminal), box cover, diode;
The cables are divided into: 1.5MM2, 2.5MM2, 4MM2 and 6MM2, these commonly used cables;
There are two types of connectors: MC3 and MC4 connector;
Diode model: 10A10, 10SQ050, 12SQ045, PV1545, PV1645, SR20200, etc.
There are two types of diode packages: R-6 SR 263


Main Technical Specifications

        Maximum working current 16A Maximum withstand voltage 1000V Operating temperature -40~90℃ Maximum working humidity 5%~95% (non-condensing) Waterproof grade IP68 connection cable specification 4mm.



The power of the photovoltaic junction box is tested under standard conditions: temperature 25 degrees, AM1.5, 1000W/M2. Generally expressed by WP, can also be expressed by W. The power tested under this standard is called the nominal power.

1. The shell is made of imported high-grade raw materials, which has extremely high anti-aging and ultraviolet resistance;

2. It is suitable for use under harsh environmental conditions with a long outdoor production time, and the use time is more than 25 years;

3. It has an excellent heat dissipation mode and a reasonable internal cavity volume to effectively reduce the internal temperature to meet electrical safety requirements;

4. Good waterproof and dustproof functions;

5. 2-6 terminals can be built-in arbitrarily according to needs;

6. All connection methods adopt quick-connect plug-in connection.


Junction Box Routine Inspection Items

        ▲Tightness test ▲Weather resistance test ▲Fire performance test ▲End pin fastening performance test ▲Connector plugging reliability test ▲Diode junction temperature test ▲Contact resistance test

For the above test items, we recommend PPO materials for junction box body/cover parts


1) Performance requirements of junction box body/cover

        It has good anti-aging and UV resistance; low electrical resistance; excellent flame retardant properties; good chemical resistance; resistance to various impacts, such as impacts from mechanical tools.

2) Several factors in recommending PPO materials

▲ PPO has the smallest proportion among the five major engineering plastics, is non-toxic, and meets FDA standards;
▲Excellent heat resistance, higher than PC in amorphous materials;
▲The electrical properties of PPO are the best among general engineering plastics, and temperature, humidity and frequency have little effect on its electrical properties;
▲PPO/PS has low shrinkage and good dimensional stability;
▲PPO and PPO/PS series alloys have the best heat resistance and the lowest water absorption rate among general engineering plastics, and their size changes are small when used in water;
▲PPO/PA series alloys have good toughness, high strength, solvent resistance and sprayability;
▲The flame retardant MPPO generally uses phosphorus and nitrogen flame retardants, which have the characteristics of halogen-free flame-retardant and meet the development direction of green materials.


pv module junction box

Slocable pv junction box (PPO material)


Selection of PV Junction Box

        The main information to be considered in the selection of photovoltaic junction box should be the current of the module. One is the maximum working current and the other is the short-circuit current. Of course, the short-circuit current is the maximum current that the module can output. According to the short-circuit current, the rated current of the junction box should have a larger safety factor. If the junction box is calculated according to the maximum working current, the safety factor is smaller.
        The most scientific basis for selection should be based on the change law of the current and voltage of the battery that should be taken out with the intensity of the light. You must understand the area where the module you produce is used, and how big the light is in this area, and then compare the battery The change curve of the current of the chip with the intensity of light, investigate the possible maximum current, and then select the rated current of the junction box.

1. According to the power of the photovoltaic module, 150w, 180w, 230w, or 310w?
2. Other specifications of the components.
3. The parameters of the diode, 10amp, 12amp, 15amp or 25amp?
4. The most important point, how big is the short-circuit current? For this test, the selection of the diode depends on the following quantities:
Current (larger is better), maximum junction temperature (smaller is better), thermal resistance (smaller is better), voltage drop (smaller is better), reverse breakdown voltage (generally 40V is far enough).


Split Junction Box

        As of June 2018, the photovoltaic junction box has gradually derived a branch from the original integrated junction box in 2015: split junction box, and formed a scale effect at the Shanghai Photovoltaic Exhibition, which represents the possibility of photovoltaic junction boxes in the future Enter the trend of diversification and parallel development.
        One-piece junction boxes are mainly used for traditional frame components, and split-type junction boxes are mainly used for new double-glass double-sided components. Compared with the former, the latter may be more needed by the market and customers now. After all, it is imminent to fully realize that the cost of photovoltaic power generation is less than the electricity charge, which means that the cost of photovoltaic industry will be further reduced, and the profit margin of photovoltaic junction box will be further squeezed. The split junction box is born with the mission of “cost reduction” and is constantly improved.


Advantages of Three-Split Junction Box

1. Greatly reduce the amount of filling and potting. The single box body is only 3.7ml, which greatly reduces the manufacturing cost, and the advantage of this small size makes the bonding area on the module smaller, increasing the light area of the photovoltaic panel, so that the user’s photovoltaic power station can get greater benefits.

2. Optimize the shell structure, and the anti-aging effect is significantly increased. This new type of split junction box adopts the latest research and development technology, and its shell (junction box, connector) has superior anti-aging and waterproof capabilities, and can be used normally under harsh environmental conditions.

3. The center distance of the improved bus bar is only 6mm, and the diode adopts resistance welding, the connection becomes safer and more reliable.

4. Better heat dissipation effect. Compared with a junction box, the split junction box generates less heat and has a better heat dissipation effect.

5. Save the length of the cable, and truly reduce the cost and increase the efficiency. The three-part design also changes the installation and outlet method, so that the positive and negative junction boxes can be installed on the left and right sides of the photovoltaic panel, which greatly shortens the distance between the battery panel and the circuit connection of the battery panel during engineering installation. This straight-out method not only reduces the cable loss, but also reduces the loss of power generation caused by the line length, and increases the power of the module.

        On the whole, the new three-split junction box can be described as a model of “high-quality and low-cost”, and has passed the latest TUV standard (IEC62790). The successful development of the split junction box represents that China has a more favorable position in the competitive trend of photovoltaic grid parity.


split junction box

Slocable three split junction box

Dongguan Slocable Photovoltaic Technology Co.,LTD.

Add:Huawei Scientific Valley, Xiangshan Road, Dalinshan Town, Dongguan City, Guangdong Province, China


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