Midnight Classic 250 Xantrex freedom 3000 inverter charger????? 2.8 kw array

[tony]

I putting together an off grid system.  So far I have the panels and have decided on the Midnight Classic 250.  Still shopping for inverter and so far the Xantrex Freedom 3000 seems to be the best choice.   Are there any problems with the ClaSSIC 250 controller and that specific inverter charger?      Thank you

[niel]

I putting together an off grid system.  So far I have the panels and have decided on the Midnight Classic 250.  Still shopping for inverter and so far the Xantrex Freedom 3000 seems to be the best choice.   Are there any problems with the ClaSSIC 250 controller and that specific inverter charger?      Thank you

i think i have a problem with the inverter choice for i think you would be far better off with a 48v battery bank, but no less than a 24v battery bank and an inverter to run off of the higher and more efficient battery voltages. i will not point you to any particular inverter as there are many and you must sift through the features, but with a 12v battery bank you would need to send hundreds of amps from the battery to the inverter and wiring that without high losses is difficult.

i'm sure everyone is wondering too why you have elected to go with a high voltage classic as opposed to one that goes up to 150v like the classic 150. unless the pvs need to be wired due to an extra long distance necessitating the greater than 200v to overcome voltage drops you should go with the 150. the number of pvs in series will be reduced meaning that more strings will need to be put in parallel to obtain the same wattage. this will be closer to the battery voltage outputted and will give a slight increase in efficiency that way. yes, efficiencies are increased when using higher voltage in the wires, but the controllers lose a bit of efficiency the farther appart the input to output voltage is.

[Robin]

Tony, Niel is correct. You do not want to use the Classic 250 if your PV array is 100 feet or less to the batteries.
The Freedom Series is an RV modified sinewave inverter built in China. You will be better off getting a pure sinewave made by any of the US manufacturers like OutBack or Magnum. These inverters will cost more than the Freedom series, but they are designed for off-grid living. The Freedom series was designed to be installed in an RV that might get used two weeks out of the year. Even then, it cannot run the loads presented by a house. You do not have table saws and deep well pumps in an RV. The Freedom Series was designed back in the early to mid 90's. The inverter manufacturers have all learned a lot since those days. Stay away from a 12V inverter. The controller will run out of power with only a few panels attached, but at 24V, you can double the quantity of panels and at 48V, you can quadruple the quantity of panels all with just one controller.
Good luck

[tony]

Thanks Niel and Robin

I'm new to this and am just finding my way.  The Xantrex Freedom inverter was listed as "pure Sine wave" and had the capability of 240v etc... that's why I picked it.    I'll look into the classic 150 and re-think my stuff.  I was planning on wiring the panels to 24v ( so I would have 14 sets of 2 in parallel).  If you have a sensible choice for the inverter such as the magnasine magnum models I'd love to hear about it.  The array will be right next to the little bunker housing the batteries and electronics.  From the building to the house wil be a 95 foot run of #2 awg for the AC panel in the basement.     

One other thing I'm getting conflicted info on.  Should the inverter have a charger if I  desire to add a generator in the future?

Suggestions and hints gladly accepted.

Thank you
Tony

[Halfcrazy]

Tony
First off welcome to the forum and congratulations on the leap into renewables. When choosing a Classic you only want to use the 200 or 250 when you are forced to as Niel and Robin pointed out. With any manufacturers MPPT controller the efficiency is always the greatest when the pv voltage is closest to battery voltage. We prefer one nominal voltage above the battery voltage so we have a little room to work with the array on real hot days. The efficiency does not drop that much as you go up but if there is no reason to go high voltage than I would not recommend it. The Classic 150 is our most powerful controller in output terms and is the least expensive so it is the logical choice here.

For inverters I would without a doubt get a good sine wave inverter/charger. If you require 120/240 60hz AC than you can not go wrong with the Magnum stuff they have a MS4024PAE and a MS4448PAE these both have a split phase 120/240 output the first is a 4000 watt 24 volt battery and the second is 4400 watts and a 48 volt battery. I would recommend no less than 24vdc battery in your case. Take a look at magnums stuff I have used a lot of it and been very happy. I have used my Share of Outback inverters as well and they are very nice.

                                                                                 

http://www.midnitesolar.com/productPhoto.php?product_ID=241&productCatName=FACTORY%20PRE-WIRED%20SYSTEMS&productCat_ID=20

[tony]

Thank you for the solid advice.    I will get the Classis 150 and the Magnum 24v inverter charger.   EXCITING!!!!!!

[niel]

tony,
can i ask you what kind of current is involved here as you did not say the make and model of the pvs you had in mind? the length of 95ft to travel for 1 positive and 1 negative wire is quite far in terms of voltage dtrop. it may be easier to just give the vmp, voc, and imp of the pvs you are thinking of using and i can roughly figure for your voltage drop and percentage. long distances for wire runs is a reason to up the pv voltage to overcome losses that become too much. if you did not buy the wire already is it possible for you to go to larger wire gauges to make that run? like #0 or #00? if so i can calculate the voltage drop % for those wire gauges as well. i will not be including the voltage drop % from the pvs to the combiner and keep in mind all voltage drops are additive and means that losses there will add to the losses as a whole so keeping this low is important.

added: i am assuming that you already have the pvs and numbers 28, but have you bought anything yet as far as batteries or is everything just still in the works here. i am going to assume you know to what degree you'll need in watthours for your loads and is why you have chosen certain pvs and the number of them. there will of course be times when the weather just does not allow us enough sunshine so a good generator and charger may be good to use in such cases. now using the magnum inverter you could feed the generator's power into it and it could allow for the running of your loads while charging the battery bank with its built-in charger if the generator is rated high enough to do both.

[Halfcrazy]

I was planning on wiring the panels to 24v ( so I would have 14 sets of 2 in parallel).  If you have a sensible choice for the inverter such as the magnasine magnum models I'd love to hear about it.  The array will be right next to the little bunker housing the batteries and electronics.  From the building to the house wil be a 95 foot run of #2 awg for the AC panel in the basement.     

Niel I took it as the pv and charge controller where within feet of each other the 95ft run is ac from the inverter to subpanel

[tony]

Halfcrazy you are correct the 95  foot ( a little less now)  wire run is the AC power to the house.  I ordered a pallet of a-si panels from Amplesun in China,  the price was great and I just liked them aesthetically.  At one point and time everything gelled and I had a moment of clarity on most things solar .  I did figure out the wire size and voltage drop, the reason I have it configured the way it is.   I like the Classic 150 controller so I'll be ordering that one.  I read the installation manual on the Magnasine MS4024PAE inverter / charger today and you are right, that is the best choice.  As I recall with the panels wired in a series to 24v the amps ended up being 116.


I'll be picking up my panels probably at the end of the week.....I'm sure I'll be writing to your forum a few more times.

Tony

[Westbranch]

Tony, are these the panels you ordered?

http://www.ample-sun.com/html/item/9.html

  the numbers you show above do not correspond to the data sheets from what I see..

Eric

[tony]

You're right!!!   For some reason I was thinking 12v panels.  How on earth did that happen?  Wired in parallel there shouldn't be any issues right?

[Westbranch]

I forget, how many panels do you have?

Eric

[tony]

Hello,
There are 28 panels.   

[Westbranch]

Assuming you have the 100W panels: you will have 2800W from 77 V (nominal) and 36.12A. the 90w panels are just a bit lower but the following applies as well

If you were to run 2 panels in series you can not use the 150 Classic as you would be over the limit of the CC before temp compensation is factored in (below the 25 * C they are rated at) however they do not give that number.  A 200 would work though for 2 in series.

Niel is the expert on line loss over large distances but you do want to keep total loss from PV to Charge Controller to less than 3% if possible.  Here is the link to the line loss tool, It will help you determine if you need to go the 2 in series or all in parallel.  http://www.wind-sun.com/ForumVB/showthread.php?t=29.

Eric

[tony]

Hi Eric,

You know I just placed an order for the Midnite classic 150 last night.  I'm going to call first thing this morning and change that to the Classic 200.   I think I'll want to run two panels in a series and then go to parallel just  to keep the wire to a minimum.  There will be two strings of PV panels 10 panels across with a row of 8 panels centered behind that with the concrete building at the edge of that.  I think I can run the heavy cable from string to string and then into the controller. 

How would you recommend placing the combiner boxes?    I was thinking...... I don't know yet what I was thinking.