Suggest a differnt approach.

Chris11Chris11 Registered Users Posts: 126 ✭✭
Please remind me as I tend to forget what I've learned ...

I have 10 100 watt panels.  An Outback 80 CC.  4 Costco GC batteries.  A midnight solar combiner with 2 10 amp breakers. 

I was going to have two arrays of 5 panels series.  Voltage would be 90 to 105 in the winter.

I'm ready to put it all together but am now aware you guys don't recommend such high voltage through the controller into a 24 volt battery bank. 

Can I put some of the panels into parallel, then series in the combiner with more breakers?  Please suggest the most efficient method.  Oh, one more thing...I was planning on much higher loads but have now decided to just run lights in multiple buildings.

Thank you.  Chris


  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    To get the most efficient method, you also need to consider voltage drop in the wire from pv to cc.

    If panels are far away, you can use reasonable sized wire for acceptable voltage drop by going with higher voltage strings, but with some loss in cc efficiency.

    If panels are close (and/or you have heavy cable lying around) you can run lower voltage strings.

    I think Midnite Solar has graphs with efficiency curves for their controllers on their site. Outback is likely similar. Using curve values along with voltage loss table with your distance and wire size you could play around with the trade-off to get optimal for your application.
    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
  • bsolarbsolar Solar Expert Posts: 103 ✭✭✭
    a different approach - i wouldnt sweat it, and theres no reason to run such a high voltage .. voltage drop unless your running 100 yards across the lawn is really negligible .. yes you want to be efficient where you can be, but the truth is you can simply add another panel and offset any loss you can come up with ... so .. in my humble opinion simplicity of the design trumps getting an ulcer worrying about efficiency, if its not putting out enough for your needs keep adding panels .. battery looks like no problem in your case, if you want the ability to push loads better during the day i guarantee you that you can jerk off for a week playing around trying to make what you have more efficient and it wont be as good as simply adding another panel or two ..
  • Chris11Chris11 Registered Users Posts: 126 ✭✭

    The array is just a few feet away from the electronics.  I built a housing box on the 4 by 4's holding the array.  So distance isn't a problem.

    Perhaps the word efficient was the wrong choice.  I was more concerned that the array voltage was so much higher than the battery bank voltage.  I'd read here that it's hard on the controller to have such high voltage, stepping down to 30 or so.  

    I'm still going to mount all 10 panels but may just use 5 of them.  But that still leave me wondering..... would putting 90 to 105 volts into the controller cause any problems? 

  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    I don't think running the controller at 90v is going to be particularly hard on it, but it isn't necessary if you're close to the array.

    What is hard on controllers is running them at full current, especially if the box you have them in isn't well ventilated. They get hot at full current and electronics don't do well in heat.
    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
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    Hi Chris,
    The most efficient configuration using this panel with flooded lead acid batteries at 24 volts would be three per string. However, four or five will work just fine also. A few watts of power will be lost to heat in the controller converting to battery voltage for each additional panel beyond three. The FM80 is a large controller so it's not going to be hard on it. If it were me and I had already purchased the panels, I wouldn't change the configuration.  

    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • Chris11Chris11 Registered Users Posts: 126 ✭✭
    I'm very thankful you said's makes it easier.  And the housing for all the electronics and bats is very well ventilated.  I even separated via a panel, the bats from the electronics.

    I really appreciate you guys taking the time to help me.

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