Panels, Volts and MPPT's

[Gunny]

I have room for one 60 cell panel for certain, might be room for two. 

JiminDenver has tried to guide me and has been a great help but how does someone who does not quite grasp all of the things going into a system compute the size or type of MPPT?

Az Wind is having a sale on a panel I covet, here are the specs on it, 295 watt panel. I want to install one for sure and possibly two.

 

• SolarWorld part number: 82000430
• Maximum power (Pmax): 295 Watts
• Open circuit voltage (Voc): 40.0 Volts DC
• Maximum power point voltage (Vmpp): 31.5 Volts DC
• Short circuit current (Isc): 10.10 Amps
• Maximum power point current (Impp): 9.45 Amps
• Module efficiency: 17.59%
• Power sorting: -0Wp / +5Wp
• Maximum system voltage: 1000 Volts DC
• Maximum design loads (two rail system): 113 pounds per square foot (psf) downward, 64 psf upward
• Maximum design loads (three rail system): 178 psf downward, 64 psf upward
• Cells per module: 60
  
• Rob
  
  

 

[Travelmonkey]

I'm not an expert, but is that panel typically run as 24V? Is that the goal? I think it might be much less complicated to configure a 12V system as that is typical of a travel trailer.

 

[jimindenver]

20 amp MPPT for one, 40 amp MPPT for two.

 

[Gunny]

Thanks Jim, could you tell me how to determine that? It's no big thing, I am just curious.

Rob

 

[highdesertranger]

Impp = 9.45 amps, so a 20 amp MPPT would give you plenty of cushion for power spikes. a 10 amp would leave very little cushion. highdesertranger

 

[jimindenver]

Rob

Look at controller specs and you will see a 20a is rated for 300w. A Morningstar TS-MPPT-45 is a nice match to 600w. I would like to see more of a buffer but since most can be over paneled AND you will not actually see 295w per panel flat mounted, it is fine.

On the other hand, I have been using 20a controllers to handle my single 60 cell panels for 5 years. It would be a bit under spec at 10,000 ft, tilted and tracking where a 245w mono produces 17.5a and a 250w poly does 18.5a. Even more with some cloud effect but I don't see you up there often, dragging huge panels out and adjusting them all day for maximum output.

 

[rvpopeye]

Figure about 6amps per 100watts @ 12v

Controller??
Get a controller that will handle the total amount of panels you might ever get (plus maybe 40-50% for a peak cushion)and you will only have to buy it ONCE.
The Morningstar 45 is a great choice^jim^, the 60 if you think you might ever go bigger

Wire ??
The size is dependent on how many panels and the distance from the controller and battery(ies)
Get as heavy as you can afford.(again buy it once)

AW&S will give you minimums.
And there is a little help available here too ;>)

 

[Gunny]

Thanks for the answers. It is humbling to look at something you need and not have a clue what else is needed.

Rob

 

[jimindenver]

I use 10 gauge MC4 cables for my three 250w panels in series and my 435w panel on it's own. It works because the three in series push low amps at 105 Voc, the 435w was pushing just over 100 Voc even though it is rated for just 79.9. Soon I will switch the three on the roof to parallel tripling the amps while cutting the Voc down to 38. I will use 1/0 to carry the combined output down then as the amps at that point would melt 10 gauge MC4 gear. It's overkill but I need to use up the spool of 1/0 somehow.

 

[rvpopeye]

YW Gunny
Just post about anything you're doing.
By now , you know who's got your 6

 

[Gunny]

I can't get around Jim's attack dog or I would take him with me but Max is fierce. And Faaaaast.

Rob

 

[jimindenver]

Ya know Rob, a big enough bag of Jerky treats could be deployed as a diversionary tactic. Better said, bribe the little....

 

[Gunny]

Popeye said;

YW Gunny
Just post about anything you're doing.
By now , you know who's got your 6
Stay Tuned
popeye

Yes I do and I thank the powers that be for you and friends like Jim and others.

Could just be my two sleeping pills kicking in but I read this forum to be uplifted. Works every time.

Rob