Maximum Array Size

ColoradoSolar
ColoradoSolar Registered Users Posts: 63 ✭✭
On my current system I have a Flexmax80 charge controller with 12 120w panels. I am going to be installing a new (much bigger) system soon and reusing the mount for some new 270w panels. So I wanted to go ahead and mount the new panels and use them on the current system. But I have a question about the specs of the Flexmax80. It says for a 24v system that the max array is 2000w. I do understand that 2000w is a bit more than the CC could output at 24v (2000w/24v=83A) but technically the CC can handle a much bigger array at it's maximums (80Ax140v=11,200w). I understand that anything over the 2000w would be "unused" and the CC may not be as efficient with a larger voltage difference but can I use my 12 270w panels (3240w array) without hurting anything?

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    MPPT charge controllers are rated at their max Output Amps.  In your case, 80A.  80A @ 30V is 2400 watts, so maybe they are derating somewhat, and as batteries charge up, their voltage changes from 23V to 29V, that subtly changes the wattage.

    But anyway, the more robust, name brand controllers will limit their output to their safe, rated amps, so some days when the batteries are way way low, the controller may be in limit mode @ 80A.  Within some reasonable limit, you can overpanel a controller, and it will still operate in a safe region.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    The wattage shouldn't be an issue, but you will want to be conservative in wiring panels so voltage doesn't get too high on a clear cold morning.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited February 2017 #4

    As a technicality,  the OB FM CCs DO also have a specified limit on the PV array total Isc,   but it is difficult to exceed this limit on 12 V and even 24 V systems.  From the manual for the OB FM80   ...

     "The largest PV array must have a rated short-circuit current of 64 amps or less under STC (Standard"   ...

    The 64 A figure is just the rated maximum output current divided by 1.25.

    Some have said that the OB FM CCs,   and perhaps the MX as well can be a bit slow in limiting output current,  so one might want to be a bit cautious in over-PVing arrays feeding FM CCs  ...   this was from some conversation on the OB Forum,  some years ago.

    FWIW,     Vic


    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • ColoradoSolar
    ColoradoSolar Registered Users Posts: 63 ✭✭
    The Isc of the array I am going to connect is 47.2A so I am way under the max of 64A.