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Old 10-03-2015, 10:05 AM   #1
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Sizing system Panels vs Charge Controller

I have a Blue Sky solar boost 2512ix-hv with panels on the roof of my 22' Sport. I am considering setup up a 2nd set of fixed panels for use while closed in the shop for winter and want to understand the math of how to maximize the panels for this controller.

Specs:
50VDC absolute maximum (Recommend maximum VOC at STC ≤ 40VDC)*
Recommended maximum, 340W with 36 cell modules / 270W with 60 cell modules

340 watt max doesn't seem to correlate to a 25amp max. In looking at several panels, it seems like I am able to size 4x panels with a spec of 225 watts, 5.21 amps, 43.4 volts. Subtract out the losses in wiring, sun angles, etc.

Where am I going wrong here?

Thanks,
-Dwight
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Old 10-03-2015, 05:36 PM   #2
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600 watts of good panels would probably put out more than 25amps. With 640 on my last trailer (panels from AMSolar) is usually saw mid 30 amp inputs.

Also the panels should match very closely in voltages between you new and old panels. I think it is the Voc voltage that should be less than .5 volts difference between them. Maybe Lew if he sees this can confirm.

Also you linked panels are 43v panels, perhaps not matching what you already have.
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Old 10-03-2015, 06:47 PM   #3
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Matching the existing panels shouldn't be a problem, my plan is to unplug the roof panels, and just plug in the new ones when closed in the shop. When I go mobile, switch back to roof mounted.
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Old 10-03-2015, 08:29 PM   #4
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Matching the existing panels shouldn't be a problem, my plan is to unplug the roof panels, and just plug in the new ones when closed in the shop. When I go mobile, switch back to roof mounted.
I use a 2-position marine battery switch with an Anderson Power Pole plug set for the remote array. Wired correctly, you just flick the switch from position 1 (roof array) to position 2 (ground array), plug in the auxiliary array and you're done.

This allows for one permanent connection to the charge controller and saves a huge amount of hassle when changing arrays. Your Blue Sky 2512iX-HV will clip the battery charge amperage at 25 amps, but doesn't like to be severely overloaded with excess incoming array amperage. 400 watts is recommended, but it will work well with up to 500 watts.

For a ground-based array, look at AM Solar's GO-160 panels. 3 of these will easily do the trick for your use.
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Old 10-03-2015, 08:43 PM   #5
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Hows the math work out? AM Solar is out of the 160's right now.
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Old 10-03-2015, 09:38 PM   #6
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Ok, I figured out my confusion.... the limit is 25amps out, so it depends on your output charging voltage as to what the amps is going to be based on the wattage incoming.

Thanks.
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Old 10-03-2015, 10:53 PM   #7
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The GO-160s have a I(MPPT) of 8.65 amps while the SF-100s have an I(MPPT) of 5.55 amps. During solar noon with the panels perpendicular to the sun, you should see about 27 amps from 3 GO-160s and 30 amps from 5 SF-100s. Either arrangement will probably max out your controller at 25 amps to the batteries.
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Old 10-04-2015, 06:10 AM   #8
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Is there a spec listed that tells you how many watts you can have hooked up without damaging the controller, or just experience that you have with it specifically?

-Dwight
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Old 10-04-2015, 10:56 AM   #9
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Is there a spec listed that tells you how many watts you can have hooked up without damaging the controller, or just experience that you have with it specifically?

-Dwight
Should be listed in the Blue Sky manual. I'll check one tomorrow when I'm back at the shop.
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Old 10-04-2015, 11:58 AM   #10
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You'll get better performance with a Morningstar Tristar MPPT...
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Old 10-04-2015, 02:41 PM   #11
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You'll get better performance with a Morningstar Tristar MPPT...

Not really! Can you quote your source for that statement?

If you look at the hard technical specs, the Blue Sky controllers do their MPPT sampling at much quicker intervals, yielding more MPPT charge boost.

That reason, and the quick and easy process of adding more charge controllers in parallel are two of the main reasons that we (AM Solar) stopped offering Morningstar MPPT controllers.


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Old 10-04-2015, 03:17 PM   #12
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I have used both brands. I prefer Morningstar. Just let everyone do their own research and have their own opinion. I'm not going to argue with you.....and I don't have to substantiate my choice.
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Old 10-04-2015, 03:41 PM   #13
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X2^ on the Morningstar, Morningstar anything!
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Old 10-04-2015, 06:54 PM   #14
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I have used both brands. I prefer Morningstar. Just let everyone do their own research and have their own opinion. I'm not going to argue with you.....and I don't have to substantiate my choice.

That's very true......YOU DONT!!! Folks can do as they please, but when you state that one product is better than another, it is always appreciated to give the specifics or some hard data behind your statement....... or it becomes a thread about which oil to use.




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Old 10-04-2015, 07:09 PM   #15
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I agree Lew. My system is about 10 years old.....I tried Blue Sky and didn't like the performance....then I tried the other and liked it.

Anyone can do a simple Google search on "blue sky or morning star mppt" and read all the threads out there. I'm not going to requote what anyone can read. I think folks should do there own fact finding and choose from what they want or can afford.
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Old 10-04-2015, 07:13 PM   #16
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I had a string of disappointing Blue Sky failures.... Jumped ship after being stranded.
Been using morningstar for a while with 0 issues or failures. Much happier with performance and zero failures!
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Old 10-05-2015, 09:57 AM   #17
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Thanks

Thanks,
At this point I have the controller, and am looking for understanding so in the future I can appropriately size both panels and controllers.

-Dwight
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Old 10-05-2015, 09:45 PM   #18
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Lew, did you find that spec?
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Old 10-05-2015, 10:38 PM   #19
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Lew, did you find that spec?
The manual says a maximum of 340 watts of 36 cell panels at STC. IIRC, you have 32 cell panels (AM Solar's GS-100) and their recommendation is 400 watts max. I have used 480 watts (3-GO-160 watt panels) into the 2512iX-HV with no issues.

The manual also states that you should calculate a derating factor of 1.25 for NOC (normal operating conditions) which would bring a 425 watt array right to the recommended 340 watts.

Also remember that while Blue Sky doesn't like over capacity at the input of the controllers, they WILL accept it and simply clip the output amperage to the batteries at 25 amps. A typical solar array will only be producing maximum output for a short period as the sun's azimuth changes with regard to the panels' surface........... unless you employ an automatic solar tracking device that always points your array towards the sun at the optimum angle for maximum solar radiance.
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Old 10-06-2015, 05:32 AM   #20
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Thanks. Part of me says that I want to know what is max safe watts while "clipping", the other part of me says why....controllers are not expensive, size it right and use every ray of sun on a limited footprint install.

Thanks for the input as always, and I am still loving my crazy over done solar install. Nothing like being able to run my microwave off solar whenever I want. Now if my batteries would quit living forever so I can get some lithiums. Of course, at only 3 years on the AGM batteries I expect quite a few more years, and I am not looking forward to getting them out from under that dinette seat on my sport.

-Dwight
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