Why are flexible solar panels catching fire?

[Sailmonkey]

Originally Posted by tjandoverguy

What kind of material is that star board

Polyethylene sheet material.

https://www.kingplastic.com/products/king-starboard/

[donradcliffe]

We had just returned to the boat last week when this 100 watt flexible panel on the bimini melted down. It caught the bimini on fire, and would have done a lot of damage to the boat if we weren't there to turn a hose on it. It had an aluminum sheet backing, and appears to have shorted along a crack on the upper surface. The panel was part of a 400 watt array, but the controller was not connected to the battery.

He is now planning a hard bimini with rigid panels.

[OceanPlanet]

Originally Posted by donradcliffe

We had just returned to the boat last week when this 100 watt flexible panel on the bimini melted down. It caught the bimini on fire, and would have done a lot of damage to the boat if we weren't there to turn a hose on it. It had an aluminum sheet backing, and appears to have shorted along a crack on the upper surface. The panel was part of a 400 watt array, but the controller was not connected to the battery.

He is now planning a hard bimini with rigid panels.

With those cheap 100W panels, there are no built-in bypass diodes to limit the flow of current into bad and/or cracked cells. However in defense of the panel it's obvious that the cells were cracked. The amount of bend these panels can take is quite limited, even with (or especially with) the aluminum backing.

Which is why we refer to canvas-installable panels as merely "semi-flexible"

[thinwater]

Originally Posted by donradcliffe

We had just returned to the boat last week when this 100 watt flexible panel on the bimini melted down. It caught the bimini on fire, and would have done a lot of damage to the boat if we weren't there to turn a hose on it. It had an aluminum sheet backing, and appears to have shorted along a crack on the upper surface. The panel was part of a 400 watt array, but the controller was not connected to the battery.

He is now planning a hard bimini with rigid panels.

So how in the heck did the panel get that crack? was it over something, like a bimini bow? Did something land on the bimini?


I'm not a fan of bimini mountings of cheap panels. they just aren't built for the abuse they can see. They belong on rigid surfaces.

[Cadence]

Without quoting thinwater. He hit the nail on the head. Flexible means being able to match a contour not continually flex.

[Sailmonkey]

Originally Posted by donradcliffe

We had just returned to the boat last week when this 100 watt flexible panel on the bimini melted down. It caught the bimini on fire, and would have done a lot of damage to the boat if we weren't there to turn a hose on it. It had an aluminum sheet backing, and appears to have shorted along a crack on the upper surface. The panel was part of a 400 watt array, but the controller was not connected to the battery.



He is now planning a hard bimini with rigid panels.

Was that crack overlaying a bow?

[noelex 77]

One factor that has not been mentioned is that while almost everyone installs a fuse between the batteries and the solar controller, as they should do, many do not realise that in some installations fuse protection is also needed on the solar panel side of the wiring. Fortunately, this additional protection is only needed where you have a string of three or more panels so it is not required in many installations, but especially with flexible solar panels mounted on a flammable surface it is vital the wiring is correctly done.

[noelex 77]

Faults in solar panels can only produce a reasonably limited amount of energy and while this is enough to ignite flammable materials (as many boat fires have shown), I suspect this energy is small enough that it could be contained, preventing the underlying structures reaching their ignition point relatively easily. I wonder if there is a practical benefit to adding a non flammable layer underneath the solar panels?

Fire blankets are readily available and cheap. This material could be sewn on top of the bimini or as a replacement for the Sunbrella in the area where the solar panels are fitted. There are many other options such as a thin sheet of aluminium, which would also have the advantage of reducing the stress points. Some experimentation would be needed to see if these ideas have any practical benefit.

[OceanPlanet]

Originally Posted by noelex 77

One factor that has not been mentioned is that while almost everyone installs a fuse between the batteries and the solar controller, as they should do, many do not realise that in some installations fuse protection is also needed on the solar panel side of the wiring. Fortunately, this additional protection is only needed where you have a string of three or more panels so it is not required in many installations, but especially with flexible solar panels mounted on a flammable surface it is vital the wiring is correctly done.

The fuse will never blow. The only power source on the panel side of the controller is the panel. The most current it will ever produce is when it's functioning properly.

Really shouldn't install semi-flexible panels over the Bimini support bars.

[noelex 77]

Originally Posted by OceanPlanet

The fuse will never blow. The only power source on the panel side of the controller is the panel. The most current it will ever produce is when it's functioning properly.

This is a common misunderstanding, but it is not correct in an installation with a string of three or more panels.

Marine solar arrays are becoming larger and it is important to understand how to wire these more sophisticated systems correctly.

[OceanPlanet]

Originally Posted by noelex 77

This is a common misunderstanding, but it is not correct in an installation with a string of three or more panels.

Marine solar arrays are becoming larger and it is important to understand how to wire these more sophisticated systems correctly.

Interesting. Can you provide an explanation of how the fuse will blow?

[goboatingnow]

Originally Posted by noelex 77

This is a common misunderstanding, but it is not correct in an installation with a string of three or more panels.



Marine solar arrays are becoming larger and it is important to understand how to wire these more sophisticated systems correctly.

Given the fuse has to rated above the Isc value of the panels. How will it ever blow

[noelex 77]

Originally Posted by OceanPlanet

Interesting. Can you provide an explanation of how the fuse will blow?

The internal solar panel wiring is kept as thin as possible to avoid shading the cells. If a fault, such as short circuit, occurs in one panel the total current produced by the other two panels can exceed the rating of this wiring, creating the risk of a fire.

This risk only occurs with a string of three or more panels

A more detailed discussion of this problem is available on many solar panel manufacturers’ and installers’ websites. This is one example that is simple but reasonably easy to understand:

https://www.cedgreentech.com/article...-when-not-fuse

[OceanPlanet]

Originally Posted by noelex 77

The internal solar panel wiring is kept as thin as possible to avoid shading the cells. If a fault, such as short circuit, occurs in one panel the total current produced by the other two panels can exceed the rating of this wiring, creating the risk of a fire.

This risk only occurs with a string of three or more panels

A more detailed discussion of this problem is available on many solar panel manufacturers’ and installers’ websites. This is one example that is simple but reasonably easy to understand:

https://www.cedgreentech.com/article...-when-not-fuse

You're talking about internal panel wiring, not about external fusing. And this is why higher grade panels have several built in bypass diodes to prevent back feeding not only from additional panels in series but from the rest of the panel itself.

[noelex 77]

Originally Posted by OceanPlanet

You're talking about internal panel wiring, not about external fusing.

No, the article I quoted is specifically about explaining the need (in some circumstances) for external fusing. It is correct that this fusing is designed to protect the internal wirng of the solar panel from overheating and potentially starting a fire in some fault conditions.

Originally Posted by OceanPlanet

And this is why higher grade panels have several built in bypass diodes to prevent back feeding not only from additional panels in series but from the rest of the panel itself.

Bypass diodes are incorporated into most solar panels, but these do not eliminate the requirement for these fuses.

Below is another slightly more technical article describing the necessity to fit these fuses that may make things clearer. In some electrical standards it is a legal necessity. Note there is no exception for (the majority) of panels fitted with bypass diodes.

https://ep-us.mersen.com/sites/merse...Tech-Topic.pdf