Panel Configuration With Outback Flex 80

ktersius
ktersius Registered Users Posts: 4
in Solar Beginners Corner #1
I'm will be installing a solar array soon and I just wanted to find out the opinion on how to configure the panels.

Some information on the setup.

48V Battery Bank
12x300W Panels, 48.8Voc, 36.6 Vmp , 8.2 Imp 8.69 Isc. Vtc -0.3%/°C
VToc = 48.8/100 * 0.3 = 0.1464 ?
Vtmp = 36.6/100 *0.3 = 0.1098 ?
Outback Flexmax 80
6 mm2 solar cable.
Temperature range 5°C to 70°C.

I've spoken two several people and I cannot seem to get a consensus on whether I should install 3 panels in series or 2. With 3 in series you will be looking at voltage ranges of 83.4-140.4V and with 2 panels 54.4V-93.6V.

One's argument is the voltage drop and therefore you should go for the higher voltage configuration while the other says the system will perform better with the lower voltage.

What would you recommend 2 panels in series or 3?
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Comments

  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #2
    Re: Panel Configuration With Outback Flex 80

    Depends on how far you have to run the lines.
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  • ktersius
    ktersius Registered Users Posts: 4
    #3
    Re: Panel Configuration With Outback Flex 80
    solar_dave wrote: »
    Depends on how far you have to run the lines.

    I don't think it will be more than 30 meters.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Panel Configuration With Outback Flex 80
    ktersius wrote: »
    I don't think it will be more than 30 meters.

    That's a pretty far distance, actually. 100 feet for our American friends.

    Plug some numbers in for a 48 Volt system. We're missing the total number of panels, though. Is it just six? That would be three parallel strings of two in series for current of 24.6 Amps. You'd need 6 AWG minimum to keep the V-drop low enough.

    Two parallel strings of three in series: Voltage of 108 current of 16.4 Amps. Now you're looking at 10 AWG wire. The problem is that the Voc goes up to 146.4 and that will shut down the FM80; even though it says max V In is 150 it will turn off before that level to protect itself. Cold temps will push it even higher. In other words it just won't work. Voc is not affected significantly by wire length as there is no current draw.

    So either do the two panels in series with larger wire, or buy a Classic 200 charge controller instead of the FM80.

    BTW Outback does have an array sizing tool on their website that you can use to double check my off-the-top-of-my-head calculations.
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