Mixing Panels

fireflyfirefly Solar Expert Posts: 66 ✭✭
Hi All...I have the opportunity to get 4 BP 85 watt panels, 18 Vmp, 22.1 Voc, 4.72 Imp, 5.0 Isc.
I am looking to add them to my already mix of 4, 51 watt Kyocera, 12 volt Vmp 16.9, Imp 3.02 and 2 Solar World 165 watt, 24 volt, Vmp 35.3, Voc 44, Imp 4.68, Isc 5.1.
I know this combination will exceed the MX60 wattage limit by 60 watts, what I don't know is what I also might loose with this combination. Can someone please advise the pit falls?

Firefly/Steven m

Comments

  • mike95490mike95490 Solar Expert Posts: 9,571 ✭✭✭✭✭
    Re: Mixing Panels

    How will they (panels) be configured ? All in parallel for 17V, to charge 12V batteries?
    This would need pretty heavy wires to the PV's


    If you can make up some series strings for higher voltage, and still keeping matching pretty close, you could run thinner wires, and allow the controller to downconvert to 12V, and you would still be able to charge on a hot day. 17V panels won't do much charging thru a controller on a hot day.

    While you *may* aproach the limits, usually by the time you get a day of dust, imperfect aim, and wire losses, you only harvest 80% of nameplate wattage. If you do reach the limit, the controller will just throttle back till it is happy.

    DO NOT EXCEED it's high voltage input limitsm if you string up some series panels.
    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
    gen: http://tinyurl.com/LMR-Lister ,

  • fireflyfirefly Solar Expert Posts: 66 ✭✭
    Re: Mixing Panels

    The panels that I have right now are wired at 48 volt, 4 x 12v, 2 x 24v. Each are own their own breaker. The MX60 was reading Voc 88.2, with a Hi Voc of 114.4. Can I still wire the 4 BP 85 watt in series, and put them on a separate breaker?
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Mixing Panels

    Steven,

    Your system is configured as "48/12". You could add the other four modules wired as a series string in parallel with your existing array.

    The combined array size would technically violate the MX60’s 800 W rating for 12 V systems. However, the output of the MX60 can be user set to as high as 70 A. As long as the MX60 is kept cool, it should work OK with the “larger” array.

    From an operational perspective, the array really wont be quite as large as the raw specs suggest. The Kyocera modules set the array voltage since they have the lowest voltage specs (67.6 Vmp in series). Installing the BP’s will add 67.6 V x 4.72 Vmp = 319 W, not 340 W. Additionally, the SolarWorld modules’ string adjusted specs are 67.6 V x 4.68 A = 316 W, not 330 W.

    Accordingly, the “low voltage” adjusted array rating is 204 W (Kyoceras) + 319 W (BPs) + 316 W (Solar Worlds) = 839 W.

    All in all, this should work OK, especially in the summer, when hot array voltage and power are reduced. You may need to keep on eye on winter operation in Canada, when cold array voltage and power may approach the STC specs if the array is well aligned (tilted).

    Some risk mitigation strategies to consider:

    1)[FONT=&quot] [/FONT]Order a replacement cooling fan or two for the MX60.
    2)[FONT=&quot] [/FONT]Consider rewiring the array for 24 V. The MX60 will operate more efficiently (cooler).

    HTH,
    Jim / crewzer
  • fireflyfirefly Solar Expert Posts: 66 ✭✭
    Re: Mixing Panels

    mike90045 and Jim/ crewzer, thanks for the quick response, that is what I was hoping for, the BP panels are free. I guess I should replace the 60 amp breaker with a 70 amp and get an additional fan, how could the fan be placed in the system and what would trigger it to come one when needed? As far as winter goes, I close down in late November and just leave the MX60 on for maintenance, so I could turn off one breaker to reduce the wattage. As far as changing to a 24 volt system, not an option, due to the high cost of the batteries. Thanks Again, Cheers
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Mixing Panels

    Steven,

    My suggestion was to change the array to 24 V, not the batteries. They would stay at 12 V, for a "24 V / 12 V" system configuration.

    The extra fan(s) would be an on-hand replacement for the MX60's internal fan should it fail. The replacement instructions are available from OutBack's website.

    HTH,
    Jim / crewzer
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