upsizing questions

gruntgrunt Solar Expert Posts: 37 ✭✭
Me and my wife would like to double our current solar system as of now are system consist of the following.
xw6048
Midnight solar E panel
Out back flex maxx 60 MMPT
15- Canadian solar 180 watt panels
8 Sun extender AGM's 224ah 48 volt
Back up Kohler gen
and a outback combiner box
So as of now it is a 2.7K system we would like to and 15 more Canadian solar 180watt panels to a total of 5.4k.
My question is I am assuming I will have to get another combiner box and another Flex Maxx 60. Am I to assume that after the combiner boxes can I still use the same E panel and if so, will there be two combiner boxes (one for each array) or one for both arrays? Also how would two MPPT wire in to the E-panel. Now mind you I am not doing the wiring myself, I am just trying to get a feel for how much more is it going to cost. So what are my options and what do you think?
Thanks in advance.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: upsizing questions

    Welcome to the forum.

    First question: is this an off-grid or grid-tie system?
    If off-grid, you're already past the maximum array size for that battery bank.
    If grid-tie, you have room to add more panels to the FM60 (although not doubling capacity).

    Just to start things off. :D
  • gruntgrunt Solar Expert Posts: 37 ✭✭
    Re: upsizing questions

    It is a grid tied system. I was curious about what you ment about battery bank being too small for more solar capacity. Durring the setup of this system I ran a few days with out putting power back on the grid and all that happens is the FM60 runs a charge cycle and then just stop at float and runs float all day. We do plan to inlarge our battery capacity but not in till we have to replace them.
    We have also ran a week our so off grid durring power outages.
    Our bank was sized to run the critical loads and seems to work fine but at 50% dischare we only get about 12 hours of power intill we have to run the gen.
  • gruntgrunt Solar Expert Posts: 37 ✭✭
    Re: upsizing questions

    Cariboocoot, I punched around the board and I see what you mean by having more solar capacity then I need for my current battery setup but since we are grid tied we are not wasting the extra capcity.
    The main reason I would like to increas my arrary sizes is because when the well pump kicks on it runs around 2.5-3.KW. Granted it is does not run for a long time. Also our REC gives us one for one trade on the solar power we send back to them on the grid, so I can off set the times where I am not making much energy. It also looks like I would have to add another out back MPPT or go with Midnight's larger MPPT and sale off the 60 I have now.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: upsizing questions

    Since it's grid-tie and all the power "has someplace to go" ...

    Your existing controller could take another 1 kW (approximately - depends on the exact install).
    With an FM80 you could have an array of about 4.5 kW (again, depending on the details).
    The Midnight Classic is only just now becoming available. The 150 will handle 96 Amps, so that's an array in the neighborhood of 5.4 kW.
    That would be about the largest you could go on a single controller. Depending on what derating is necessary for your area, power loss through lines et cetera - possibly a total array size of 7 kW.

    Note: if you increase the controller and array size you may have to rewire to accommodate the increased current.

    I don't know what your water pumping situation is, but your quoited power usage for the pump is pretty high. Perhaps look in to a more efficient pump?

    As for the batteries ... only getting 12 hours power 'til the gen is needed isn't nice. With your existing array you could increase your battery bank. In fact it could be doubled or even tripled. Since it's grid-tied, all power is available for charging until batteries are charged. You could go with the "5% current" target:

    2700 Watts @ 77% efficiency (typical) = 2079 / 57 Volts charging = 36 Amps
    That's 5% of a 720 Amp hour bank. That should give you more than 12 hours running time!
    Just remember; you may have to buy all new batteries, as mixing old and new is a formula for losing lifespan on the new batteries.
  • gruntgrunt Solar Expert Posts: 37 ✭✭
    Re: upsizing questions

    When my bank was sized I asked for 24hours worth of back up for critical loads and they gave it to me..if I want to run my AGM all the way down:confused: so at 50% DOD I get 12 give or take. Since the power outages only last about a day that seem to be the way to go.

    My well is in excess of 300+ feet but I think you are right there is room to increase efficiency. In all honesty 1k more would do the trick for most of my needs. I need to get some books and read up on Panel wiring and configuration to see what my choices are.
    I am also curious on how two charger controllers would tie in to each other for a single battery bank.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: upsizing questions
    grunt wrote: »
    When my bank was sized I asked for 24hours worth of back up for critical loads and they gave it to me..if I want to run my AGM all the way down:confused: so at 50% DOD I get 12 give or take. Since the power outages only last about a day that seem to be the way to go.

    It's surprising the number of "professionals" who don't understand you can't use 100% of the Amp hours. :roll:
    My well is in excess of 300+ feet but I think you are right there is room to increase efficiency. In all honesty 1k more would do the trick for most of my needs. I need to get some books and read up on Panel wiring and configuration to see what my choices are.
    I am also curious on how two charger controllers would tie in to each other for a single battery bank.

    There are some "direct PV" powered water pumps, but they are pricey. At 300 feet you are probably running a 2 HP 240 VAC deep-well submersible. Pretty big power user. :cry:

    There's no problem with paralleling charge controllers.
  • BB.BB. Super Moderators, Administrators Posts: 29,698 admin
    Re: upsizing questions

    Properly wired and programmed, two charge controllers in parallel with a single battery bank is fine... Unless they are controllers with digital com links--they will not be "in sync" as they charge... One will hit Absorb and Float before the the other--but it is not an issue.

    What you do want is a properly wired battery bank (if two or more parallel strings) and that the two controllers each have their own run of wiring to the battery bank (heavy gauge wire and don't parallel charge controllers on one wire run--The two controllers sharing and undersized wire run could confuse each other).

    While I am a big believer in not drawing a battery bank down too deeply--If you are using the system for occasional power outages and get the bank recharged above ~75% state of charge relatively quickly--Taking a deep cycle battery bank a few times a year below 50% state of charge is not going to hurt the batteries--They will probably die of "old age" vs deep cycling first.

    You should have a backup genset anyway to recharge the bank when needed (longer blackouts/poor sun) especially if your outages are because of stormy weather. The AC battery charger would just be parallel connected with the other charge controller(s).

    -Bill

    PS: Sizing your battery bank for surge loads (like water pumps) may drive your ultimate bank size (larger bank to handle surge current).

    AGMs are supposed to be great for heavy current loading--It would be interesting to know how well your bank performs with your pump setup.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gruntgrunt Solar Expert Posts: 37 ✭✭
    Re: upsizing questions
    BB. wrote: »
    Properly wired and programmed, two charge controllers in parallel with a single battery bank is fine... Unless they are controllers with digital com links--they will not be "in sync" as they charge... One will hit Absorb and Float before the the other--but it is not an issue.

    So It looks like wiring them in Parallel and using an out back Mate would be the way to go for dual Fm60's
    What you do want is a properly wired battery bank (if two or more parallel strings) and that the two controllers each have their own run of wiring to the battery bank (heavy gauge wire and don't parallel charge controllers on one wire run--The two controllers sharing and undersized wire run could confuse each other).


    While I am a big believer in not drawing a battery bank down too deeply--If you are using the system for occasional power outages and get the bank recharged above ~75% state of charge relatively quickly--Taking a deep cycle battery bank a few times a year below 50% state of charge is not going to hurt the batteries--They will probably die of "old age" vs deep cycling first.

    Your right this is just my first bank and I want to make sure I dont mess it up.
    You should have a backup genset anyway to recharge the bank when needed (longer blackouts/poor sun) especially if your outages are because of stormy weather. The AC battery charger would just be parallel connected with the other charge controller(s).

    If you look in my first thread you will see I do have a back up generator.
  • gruntgrunt Solar Expert Posts: 37 ✭✭
    Re: upsizing questions

    If I am running a second charger controller in parallel, can I get away with running a different make of panel on the second charger controller? I know when you run one array it is important to use panels that are mainly alike but if I am using two charger controllers am I stuck with having to use more Canadian Solar 185 watt panels? I ask because I can get the power increase I want with fewer panels if I go with 220 or greater. Plus save money on a rack and installation.
    Thanks
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: upsizing questions
    grunt wrote: »
    If I am running a second charger controller in parallel, can I get away with running a different make of panel on the second charger controller? I know when you run one array it is important to use panels that are mainly alike but if I am using two charger controllers am I stuck with having to use more Canadian Solar 185 watt panels? I ask because I can get the power increase I want with fewer panels if I go with 220 or greater. Plus save money on a rack and installation.
    Thanks

    Yes; like panels to any given controller, but two different controllers can have two quite different arrays. As long as the output of the controller is within the right Voltage specs. Id est:

    Any Voltage array to MPPT controller = correct charging output.
    and
    "12 Volt" array to PWM controller = "12 Volt" charging output.

    But not:

    "24 Volt" array to PWM controller = "24 Volt" charging output.
    and
    "12 Volt" array to PWM controller = "12 Volt" charging output.
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