Fact or Fiction: Bad idea to leave unconnected panels in sun

2twisty · September 2014

There are LOTS of rumors out there.

One I've heard recently is that you can't leave solar panels in the sun without them connected to a CC or some load. The rumor is that it will damage the panels since the power "has nowhere to go." I have a neighbor out here that is just terrified of having sun on their panels while disconnected from the CC.

Is there any truth to this? It doesn't seem sensible to me. I believe that if I disconnect the panels from the CC that I could leave them in the sun for as long as I like.

Please advise.

vtmaps · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

It is true that some CdTe (cadmium-telluride) panels can be damaged if left without a load in the sun.

As a practical matter, it is not an issue for your silicon based panels.

btw, an unloaded panel runs hotter than a loaded pane, so to whatever extent it is heat shortens the life of a silicon based panel, it is better to have a load.

--vtMaps

2twisty · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

OK. Long term, it's a bad idea. These neighbors were worried about leaving the panel unloaded for a few hours/days. From what you're saying, that's not really a problem.

ILFE · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

Typically, other than installing or modifying the array, there would be no need to have them disconnected, right?

I mean, every morning I'm like a kid on Christmas Day, impatiently waiting for the sun to come up. I'm waiting for those panels to soak up every ray that hits them, then mustering every bit of energy possible, and sending it to my controllers. (Okay, so I lead a pretty boring life. Obviously, I don't have a lot to do, being retired.) Perish the thought of me losing even one watt of that energy because of a wire not being properly connected somewhere along the way!!

2twisty · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

Oh, absolutely. This neighbor has a stack of panels that they are (slowly) installing. I suggested mounting all the panels and then doing the wiring. They were worried about damage to the panels if they were left unloaded. If they didn't take too long to hook them up, it will not be a big deal.

To me, unused panels (either unmounted or just disconnected) is silly. They've been relying on their generator too much....and since it's easier to pour gasoline into the genny than to install the panels, laziness took hold. I've been trying to get them to USE the panels that they paid a lot of money for.

ILFE · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

2twisty wrote: »

I've been trying to get them to USE the panels that they paid a lot of money for.

If your negotiation skills are sharp, I can see an expanded array in your future.

waynefromnscanada · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

Does your neighbour realize that (if it's an 0ff grid system) once the batteries are fully charged, the controller basically unloads the panels anyway?
Explain that to him, make him afraid, make him very afraid. Hahahaha

BB. · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

For standard Silicon Panel--Don't worry about it.

For an off grid system--Hopefully they get everything installed quickly (days, few weeks)--The battery bank is who will be "unhappy" if they don't get enough charging current (and/or over discharged).

Especially if they start realizing how much money they are pouring into the genset every week (they will have to do some of that in winter anyway--Don't want to do that in summer too when the panels are just begging for use).

Do they know how to monitor the charge/health of their battery bank--Killing the battery bank in a couple of years is a good possibility here (as much, or more than the cost of the solar panels).

-Bill

niel · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

and your neighbors are doing this themselves? it seems to me they should hire somebody if they are so unknowledgeable to believe such nonsense. i can imagine just how many other wrong things they believe and it could degrade or destroy it from being a good pv setup. they can go ahead, as you wanted them to, and install all of the pvs without connecting them. i might be worried the battery bank isn't getting properly charged if they are taking their time and are doing this off grid. light a fire under their hind ends in that case as batteries don't like to be kept undercharged or allowed to self discharge for a long time.

SolarPowered · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

Under no load, for protection, you should connect the MC4 pin and socket pigtails together, when left out in the weather.

The only concern really is in humid/moist conditions, the pin and socket should be interconnected when there is no load present during disconnection. DC current (IF) the connections are close enough can make a floating circuit. I had a client that voided a warranty with me because he decided to do work on his own, turned the panel upside down, and through the rain and moisture blew out the diodes within the IP65 between the negative and positive terminals. After voiding his solar warranty I fixed the problem for $300.

waynefromnscanada · September 2014

Re: Fact or Fiction: Bad idea to leave unconnected panels in sun

niel wrote: »

and your neighbors are doing this themselves? It seems to me they should hire somebody if they are so unknowledgeable as to believe such nonsense. I can imagine just how many other wrong things they believe and it could degrade or destroy it from being a good pv setup.

Well said Niel. Have to agree with you, they need someone to help and guide them, someone who knows and understands such solar projects. Unfortunately depending on location, finding such help can be difficult. Even some "professionals" don't fully understand what's going on. And where I live, when I can no longer look after my system, it will have to be shut down.
I have you and several other members of this forum to thank for helping me out early on when I still had so much to learn. Still learning, but building and maintaining a successful off grid system that's now over a dozen years old, has been an awesome education.

Fact or Fiction: Bad idea to leave unconnected panels in sun

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