And Yet Another Question.

[Gunny]

I have found the first and possibly only panel to buy. There is a chance of mounting a second panel. I plan on using an MPPT large enough to handle two panels. 

The question; Since money is involved and I have very little, if I buy just one now and another later do the panels have to be exact matches? Or should I buy two now and wait on the MPPT controller and if two don't fit just use the other for a frizbee?

Rob

 

[John61CT]

The only thing that really should match is voltage output.

Good MPPT can adapt OK, just might be a bit inefficient.

Maybe get both panels now for a matching pair, but a super-cheap PWM controller for temporary use.

Then upgrade just the controller later, whenever you can afford it.

That way, you get the much more significant (double) power increase now, and the much smaller one from MPPT efficiency later.

Plus labor efficiency, getting the roof mounting project done in one go.

 

[jimindenver]

Rob

If you want to do two panels, get two panels and sell the one that isn't going to fit. Matching panels is the only way to get the most out of the controller even though I have heard varying degrees of mismatched is ok. Two panels that are rated the same yet act differently under different conditions are mismatched panels, I have seen it. Watching the controllers MPPT program scan the voltages looking for the sweet spot shows you right off it doesn't like it and with out the sweet spot, you are not getting as much as you possibly can.

You can avoid all of the indecision by believing someone that has measured your roof, getting up there and remeasuring or cutting a piece of cardboard to size and seeing if two will fit visually.

 

[Gunny]

Jim, I watched the video last night and she never mentioned the name of the panels she bought. I've looked on their website and can't find them. If you are still close to her ask her what the name or brand is, Please...


Rob

 

[jimindenver]

I can ask her on you tube.

 

[Gunny]

I am just looking for the most 'Bang' for my buck. Poly as per you or whatever gives me a shot at keeping things charged. Az. Wind is having some items on sale at very good prices if you pay by check or cash.

I don't know if it would work, but the front window cover raises when stopped and in my deluded mind might be a spot for number 2.

Rob

 

[jimindenver]

There is also your truck.

 

[Zizzer_Zazzer_Zuz]

If you are using just one panel a PWM is probably the way to go.

Sent from my SM-G920V using Tapatalk

 

[Optimistic Paranoid]

If you are using just one panel a PWM is probably the way to go.

That sort of depends on how many watts the panel produces, and what voltage it runs at.

PWM would certainly be the way to go if the panels are running at less than 20 volts, and you only have a few hundred watts.  MPPT wouldn't really pay for itself under those circumstances.

 

[jimindenver]

Possibly but Rob has room for a 270w poly, I know since I was the one on the roof of his trailer. We might be able to squeeze more out by trying to fit as many smaller panels up there but the cost difference would make a MPPT controller look cheap in comparison with little to show with what 12v panels run compared to 24v panels. A second panel could be on a rack in his truck running parallel on the proper sized controller, giving him the extra watts and flexibility of a portable.

There are always multiple options that we can work out until he gets the trailer back. I know he will be at ease once one is picked, I relish working the different scenarios out until then.

 

[DannyB1954]

If one of the panels doesn't fit on the roof, you could make that panel portable. Maybe even mount it on the tow vehicle.
Then have an extension cord that can be plugged in between the tow and trailer. Just run wires from the controller to the outside of the trailer with a jack on the end.

 

[Gunny]

My hope is I can learn by doing. I have read and watched so many articles and videos that they seem to blend together. As with so many things in life, I may have to 'poor boy' it and do one item at a time.

It'll get done, and I think when I see what things do I will understand better. JiminDenver and many others have patiently answered my questions and while it's a small thing to you perhaps, it means a lot to me.

There are things I am quite good at but none of you have asked about calling in artillery, setting up basic security at an Embassy or Consulate Office or any of the other useless crap I know I can just say thanks. But if anyone gets their own artillery battery, I'm your man for questions..

Rob

 

[DannyB1954]

There are things I am quite good at but none of you have asked about calling in artillery, setting up basic security at an Embassy or Consulate Office or any of the other useless crap I know I can just say thanks. But if anyone gets their own artillery battery, I'm your man for questions..

Rob

If I ever get married and divorced again, I will give you her address. lol, Or should I say grid coordinates ? this book was written for boats, but most all of it applies to RV's as well. for $4, it might be worth a read. http://www.ebay.com/itm/The-12-Volt...728041?hash=item2115447269:g:oHkAAOSw6n5XtuxX