Connect, Disconnect, where does the solar energy go?

[anewbiewannabe]

So, a response on the battery not charging from solar thread reminded me of a question or more that I have. I thought it would be better to ask in a separate thread.

1. So when disassembling a solar set-up, the panels get disconnected first? That's the way I read it.
2. At the point they are disconnected do they need to be out of the sun?
3. When assembling a solar set-up do solar panels get connected last or first?
4. When assembling the solar set-up at what point do the panels get exposed to the sun? The only solar build I remember reading didn't take off the protective covering until the entire system was hooked up.
5. Is it safe to have solar panels in sun when not hooked up to anything or is a protective covering needed? If it's safe then what happens to the solar energy that the panels are exposed to/soaking up?

Along another line but related:
6. If the batteries are fully charged what happens to the energy coming into the solar panels?
7. Is there a risk of overheating or something---either batteries or panels?( I saw something the other day about batteries being overcharged.)

I thought I had finally understood this but then something I read on here the other day made me question it.

Thank you in advance for humoring me wth answers to these questions. I have read so much about solar but it just hasn't sunk in if I've already read the answers to these questions.

 

[Optimistic Paranoid]

A basic general electrical principle is that no electricity flows unless there is a complete circuit.

Based on that, I would say that even though light is falling on the photovoltaic cells, no electrons move if the panel isn't plugged into anything.  Nor is the panel damaged if sunlight falls on it and there is no place for the electricity to go.

 

[anewbiewannabe]

Thanks OP, that would answer #s 2 & 5 and maybe part of 7?!?!

 

[MrNoodly]

A basic general electrical principle is that no electricity flows unless there is a complete circuit.

Based on that, I would say that even though light is falling on the photovoltaic cells, no electrons move if the panel isn't plugged into anything.  Nor is the panel damaged if sunlight falls on it and there is no place for the electricity to go.

However, the instructions for my TriStar MPPT controller say the panel(s) should be out of sunlight or covered up when connecting to or disconnecting from the controller.

 

[anewbiewannabe]

Okay. So, at least, if I'm understanding right, solar panels can hang out and catch some rays by themselves with or without protective covering. Making progress. Now whether or not they need protective covering when meeting up with the electrical system is on the fence but leaning towards better safe than sorry. ROFLMAO

I'm amending question 7.
7. Is there a risk of overheating or something---either batteries or panels *or controllers?

 

[Reducto]

Think of the panel as a battery. It's trying to push electrons, but it can only do so if something is hooked up to it.

Older simple controllers used to be prone to burning out if hooked up in the wrong sequence and could potentially over-charge a battery if left hooked up to an already charged battery. With a modern NPPT controller none of this should really be an issue. If you let us know what specific panel and controller you have we might be able to offer further guidance.

The only time a panel is really dangerous is if it's in sun and the wires are exposed. If you were to touch the ends together it would short out and could damage the panel or start a fire just like touching the ends of battery leads together are dangerous. That's probably why those instructions say to leave it covered when hooking it up. If your panel has MC4 connectors on it already and you plan to leave them intact you shouldn't have an issue. The connector keeps the ends separate so they won't short. Just connect everything and make sure all wires are secure before plugging in the panel.

 

[blars]

When connecting or disconnecting an electrical circuit, it's best to have it deentergized to avoid sparks. Switches and circuit breakers are designed to minimize sparking. So cover the panels when connecting or disconnecting, and do that last (connecting) or first (disconnecting). The controller should prevent your batteries from overcharging. (It needs to be designed and set for the batteries you are using.) The solar panels don't have a problem with being in the sun disconnected.

 

[Spaceman Spiff]

So, a response on the battery not charging from solar thread reminded me of a question or more that I have. I thought it would be better to ask in a separate thread.

1. So when disassembling a solar set-up, the panels get disconnected first? That's the way I read it.
 -    YES
2. At the point they are disconnected do they need to be out of the sun?
 -    NO
3. When assembling a solar set-up do solar panels get connected last or first?
 -   Last is safe.  You must connect the solar panels to the charge controller AFTER connecting a load (usually the batteries) to the charge controller.
4. When assembling the solar set-up at what point do the panels get exposed to the sun? The only solar build I remember reading didn't take off the protective covering until the entire system was hooked up.
 -   Any time.  As OP said, current doesn't flow until there is a complete circuit.  So long as the panels are not connected to anything no current flows.
5. Is it safe to have solar panels in sun when not hooked up to anything or is a protective covering needed? 
 -   Yes.  In fact one test of solar panels is to measure the open circuit voltage when the panel is in the sun and not connected to anything.
If it's safe then what happens to the solar energy that the panels are exposed to/soaking up?
 -   It is converted to heat.
Along another line but related:
6. If the batteries are fully charged what happens to the energy coming into the solar panels?
 -    Depends on charge controller type: when batteries are full PWM stays in the open circuit part of its cycle, MPPT charge controllers increase the input voltage, driving the current to 0 (I think, not as clear on working of MPPT controllers).  Some controllers have a third circuit that shunts excess solar output to a secondary load (like heating water).  
7. Is there a risk of overheating or something---either batteries or panels?( I saw something the other day about batteries being overcharged.)
 -    For batteries: Yes but probably not with solar.  This usually happens when using a large external battery charger on 120V or when equalizing.  For panels, you would not want to be in an environment that would damage the panels.
I thought I had finally understood this but then something I read on here the other day made me question it.

 -- Spiff

 

[anewbiewannabe]

Thanks.

I don't have any panels or controllers in mind and it's going to be a while before I put anything together. I'm just trying to understand the concept of how they hook up in general and the safe way to do it. Just like learning how to hook up jumper cables---best to know before you need to know. No touching wires just like you don't touch the positive and negative together on jumper cables if they are attached on one end. It seems like there would be a basic protocol with solar like there is with jumper cables.

I'm just looking for the answers to the specific questions. I'm thinking perhaps I'm not the only one that would benefit from the answers considering how many of us end up hearing Charlie Brown's teacher voice when we start reading the solar stuff. I have short-term memory issues so I have to write stuff down in ways that will make sense to me later when I can't remember.

 

[MrNoodly]

7. Is there a risk of overheating or something---either batteries or panels *or controllers?

Panels should be mounted so that they get airflow on both top and bottom, otherwise, yes, they can overheat. Two to three inches under the panel(s) should be enough.

 

[highdesertranger]

good advice given so far. I want to add, you might get an arc when plugging the panels in live(exposed to the sun). this arc has the potential to damage the connection. my panels are mobile at the moment so I plug and unplug a lot. I installed a switch on the hot feed(+) from the panels. like this one. https://www.amazon.com/Volt-Battery..._3?s=automotive&ie=UTF8&qid=1473038634&sr=1-3 . when the key is in the on position it cannot be removed. when it's off you can remove the key. highdesertranger

 

[anewbiewannabe]

Spiff, thank you. Your response was what I was looking for. I swear your response wasn't there when I made my last one---oh duh, we cross-posted at the same time I just checked. Makes more sense now as I couldn'f figure how I missed it and the one from blars.

It does sound like it would better to cover the panels if possible when connecting or disconnecting if I'm reading everyone right. I hope to rarely need to do that as they will be mounted on rack on top of a high top that I will get one way or another depending on if I manage to buy a high top or have to have one installed.

MrNoodly, I know some people mount solar closer to the van top than that but I do plan to mount on a rack so I will have decent air flow.

6&7 tie together. I just wanted to make sure I couldn't fry anything with too much solar.

HDR, that switch looks like a good thing for people like me with memory issues---having to turn the key.

Thanks everyone. I think I've got this part now.

 

[ZoNiE]

Heaven. The unused energy goes to heaven.

 

[anewbiewannabe]

Heaven. The unused energy goes to heaven.

LOL I don't even think I asked where it went, just what happened to it. Didn't want it burning anything up cause then it would be hell insteada heaven.

Thanks for the giggle!