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PV Junction Box: purpose and connection

A photovoltaic (PV)  junction box is an important part of the solar panels. The junction box is an enclosure on the module where the PV strings are electrically connected.
Solar panel PV junction box

Solar panel (PV) junction box

The majority of junction box manufacturers are nowadays based in China.

PV junction box, manufacturer Sunlont (one of the early and experienced junction box suppliers in Shanghai)

 

How is the junction box connected to the solar panel?

A PV junction box is attached to the back of the solar panel (TPT) with silicon adhesive. It wires the (usually) 4 connectors together and is the output interface of the solar panel.
Ugly looking silicon around PV junction box

Ugly looking silicon around solar junction box

How to connect the solar panel junction box to the solar array?

With the use of a junction box, it becomes easy to connect the solar panel to array. Usually cables with MC4 / MC5 connectors at the end are used.

PV junction box connector - Sunlont

A good junction box keeps corrosion at the terminals to a minimum, as it will exclude water coming in.
PV junction box with MC4 compliant connectors

PV junction box with MC4 compliant connectors

When purchasing solar modules, always have a look at the IP rating of the PV junction box. A completely water tight junction box carries IP 67.
IP65 rated PV junction box

IP65 rated PV junction box

How does the PV junction box protect the solar panel?

Most photovoltaic junction boxes have diodes. The function of the diodes is to keep the power flow going in one direction, and prevent power from feeding back into the panels when there's no sunshine.
Inside and opened PV junction box

Diodes inside and opened junction box

A quality PV junction box is certified (e.g. via TÜV) and regulates the heat and offers reliable long-term safety. PV-junction-box-packed-solar-panels
rob scrab
By

rob scrab

on 01 Mar 2019

If a solar panel is purchased with a junction box attached, and clips to attach to the 12 volt battery, mean that a charge controller is unrequired?

DISHANK SHETH
By

DISHANK SHETH

on 18 Dec 2017

what material is used in the junction box used for solar panel

Troy
By

Troy

on 09 Dec 2017

Are junction boxes "universal/interchangeable" as far as 4 tab or 2 tab boxes?

Joe Rathinam
By

Joe Rathinam

on 09 Oct 2017

If a PV Junction damaged by lightning can be replaced? Please let me know how damaged pv jb boxes can be replaced in modules.

sudhakar veerasamy
By

sudhakar veerasamy

on 14 Jul 2017

Hai...what kind of diodes are used in junction box?bypass diode or blocking diode?

Dricus
By

Dricus

on 14 Jul 2017

Solar junction boxes have bypass diodes. Blocking diodes are typically used to prevent batteries from discharging backwards through your solar panels at night.

amrendra
By

amrendra

on 29 Nov 2016

Can we connected new pv junction box after burning old junction box

Rick A Moore
By

Rick A Moore

on 07 Sep 2016

The PV Junction Box I am using is similar to this one, but is manufactured by Amphenol. When I connect my solar panel to it using the first (negative) and fourth (positive) bars, it shorts out the panel. What is the correct way to connect it to my panel? My panel is 36 cells with single negative and positive leads. Panel is generating 23 to 23.5 volts when testing the bare leads (not connected to the JBox. First bar (negative) is the one on the left when the Jbox cables are going downward. Please advise.

tushar vasani
By

tushar vasani

on 31 Aug 2016

any buddy tell me which type certification required for solar pv junction box like tuv but coddind please

Dricus
By

Dricus

on 02 Oct 2015

For the IP rating of junction boxes, IP65 is still a common standard. I'd say: why not require the highest (IP67) standard? Pricing is similar.. You can explore the difference between IP65 and IP67 junction boxes here: https://sinovoltaics.com/learning-center/components/iec-529-ip-65-ip-67-solar-junction-boxes/ Leading brand examples are for example Tyco and Shoals. They're known to be of high quality. However there are dozens of Chinese brands that now offer fully certified and reliable PV junction boxes as well. Junction boxes aren't rocket science, basically they're a couple of diodes in a plastic box ;)

Ncraju
By

Ncraju

on 21 Feb 2016

Can you help me understand (project report/web link) on the manufacturing process of the junction box Or a DPR on manufacturing junction boxes

Neil
By

Neil

on 29 Sep 2015

Can you recommend any reliable junction box brands? And is nowadays an IP67 rating a must? Thanks, Neil.

Stella
By

Stella

on 08 Jun 2016

Hey, Neil, if you are interested in junction box, please have a look at our website; we are a leading enterprise specially engaged in PV junction box, connector and cable used for solar PV module. Or you can contact me @ suncheng@renhesolar.com.

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