System Configuration Question

[joeedens]

Here are the components that I'm planning for my off-grid system:

HUP Solar One 48V 950 AH Battery Bank
2 each Midnite Solar Classic 250 Charge Controllers
24 Evergreen ES-A-215-fa3 215W Panels. 3 Strings of 8
1 Outback Flex power Two FP2-10 VFX 3648 (Dual Inverters)
1 MNPV 6 Midnite Solar Combiner Box

My Questions:
1. Is the Classic 250 a real viable product which can be used in a production environment now?
2. Can I connect 3 strings of 8 of the Evergreen panels above, to the two Classic 250?  I can't find a string size calculator for the Classic so I'm just trying to verify that this will work.
3.  Is the Graphics Panel included with the Classic 250 or is it an option that must be purchased separately?

[boB]

Here are the components that I'm planning for my off-grid system:

HUP Solar One 48V 950 AH Battery Bank
2 each Midnite Solar Classic 250 Charge Controllers
24 Evergreen ES-A-215-fa3 215W Panels. 3 Strings of 8
1 Outback Flex power Two FP2-10 VFX 3648 (Dual Inverters)
1 MNPV 6 Midnite Solar Combiner Box

My Questions:
1. Is the Classic 250 a real viable product which can be used in a production environment now?
2. Can I connect 3 strings of 8 of the Evergreen panels above, to the two Classic 250?  I can't find a string size calculator for the Classic so I'm just trying to verify that this will work.
3.  Is the Graphics Panel included with the Classic 250 or is it an option that must be purchased separately?

The Classic 250 is available.  It can handle strings of 8 of those modules easily (Voc = 183.2 Volts at 25 C), but 24 * 215 Watts = 5160 Watts
which could be 100 Amps into a 48V battery bank.  100 Amps is too much for one 250V Classic and 48 Volt battery though.

For a  950 Amp-Hour bank, a C/20 charging rate (around the minimum you would probably want to use) would be
around 50 Amps which the Classic 250 can do, but you may still want that 100 Amps for a C/10 charge rate possibility.

You could divide the array up into two arrays and two Classics instead of one, but then you wouldn't  need 8 modules in
series so you could get along with a 200V Classic if the array was divided up evenly.

Or, you could compromise and use one Classic 150 with something like 1/4 to 1/3 less modules if the wire run from PV
to batteries isn't too far.

boB

[Halfcrazy]

Here are the components that I'm planning for my off-grid system:

HUP Solar One 48V 950 AH Battery Bank
2 each Midnite Solar Classic 250 Charge Controllers
24 Evergreen ES-A-215-fa3 215W Panels. 3 Strings of 8
1 Outback Flex power Two FP2-10 VFX 3648 (Dual Inverters)
1 MNPV 6 Midnite Solar Combiner Box

My Questions:
1. Is the Classic 250 a real viable product which can be used in a production environment now?
2. Can I connect 3 strings of 8 of the Evergreen panels above, to the two Classic 250?  I can't find a string size calculator for the Classic so I'm just trying to verify that this will work.
3.  Is the Graphics Panel included with the Classic 250 or is it an option that must be purchased separately?

The Graphics panel is included.

With 24 panels you would need to break them into two groups for the 2 controllers we do not have true Parrnell operation done just yet. I would look at strings of 6 and run 2 strings each into a Classic 150. You could also run 2 strings of 8 into one Classic 250 and 1 string of 8 in the other. The first Classic may spend some time current limiting at the height of a cold bright day.  Another option would be to do 28 panels and run strings of 7 then you could run 2 Classic 200's with 2 strings each but this would require more panels.

[joeedens]

Bob and Halfcrazy, thank you both for responding.  You've pointed out an issue that I didn't understand.  I thought that 2 classics could be tied together and run as if they were a single 500v charge controller.  So If I use 2 of them each with their separate array input, would I just connect them both to the battery bank in parallel?
If I run 2 strings of 7 modules each into 2 classic 200 for a total of 4 strings of 7 divided between 2 classic 200s, which combiner box would I use?  Is there one that could handle the two seperate arrays or will I need 2 combiner boxes?

[Halfcrazy]

you are correct the 2 would hook to the same battery bank no problems there. A MNPV12 with 300 volt breakers would be perfect and it is made for a single feed to the charger or 2 separate feeds. It would come with everything needed just make sure to get the 300 volt version and 300 volt breakers

[boB]

I thought that 2 classics could be tied together and run as if they were a single 500v charge controller. 

The Voltages ratings would stay the same...   250 Volts.  I think that's what you meant.
It would sure be nice if one could run the inputs in series though.

Is there one that could handle the two seperate arrays or will I need 2 combiner boxes?

Each separate "array" of strings would go to its own Classic.

Each Classic would go to the one shared battery bank of course.

boB

[joeedens]

boB and Halfcrazy,

I've been playing with the numbers a little and it looks like I could go with 2 Classic 200s with 4 strings of 6 modules which would result in Vmp to the controller of about 110V, or I could go with 2 Classic 150s with 5 strings of 5 modules. This would result in result in Vmp to the controller of about 92V. I think that I've heard that it is best to try to minimize the number of parallel strings if all else is equal.  Would there be any significant reason to go with the classic 150s because of the lower Vmp?  Are there significant enough efficiency reasons to go with one configuration or the other? 
Thanks for all your help on this.