series or parallel

System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
I have (2) 110w solar panels (16.40 volts 6.7amps) charging (3) Group 31 Lifeline AGM batteries and controlled by a Solar Boost 2000 with temperature monitoring. Should my panels be wired in series or parallel? If I wire them in series how will shade affect effieciency?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: series or parallel

    the sb2000 is a 12v controller only so parallel them. series pvs would exceed the maximum input voltage. see the specs in this pdf or read your manual.
    http://www.blueskyenergyinc.com/pdf/SB2000Edatasheet.pdf
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: series or parallel

    Thanks for the reply Niel. Would I be better off with another controller and wiring the panels in series? These panels are charging (3) Group 31 Lifeline AGM batteries.
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  • Moe
    Moe Solar Expert Posts: 60 ✭✭
    #4
    Re: series or parallel

    The SB-2000 float voltage is also higher than that recommended by Lifeline.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: series or parallel

    Bmats,

    Watts are watts are watts. Series, parallel, series/parallel,,, the battery doesn't care in the end. What matters is the length of wire run from the panels to the batteries, the longer the run, the more advantageous it is to run higher voltages. That said, with only two panels, ~220 watts of pv it probably wouldn't be cost effective at this point to change out the cc. If memory serves the sb 2000 is a mppt controller that does a pretty good job of converting as much sun into power into the batteries (net) as most anything else. The advantage of parallel is that shading of one panel ill not affect the output of the other like it would if you were to wire them in series. If you went with a bigger mppt controller and ran the panels at 24vdc I think the size of the panels would cause the controller to operate in a quite inefficient range.

    I second the notion of reading the battery and cc manuals.

    Tony
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: series or parallel

    that would depend on some things. seriesed pvs are nearly always utilized in very large arrays of pvs to reduce the size of the wires used or in the case of long distances between the pvs and controller. if you wish to check if your wiring is too small or long for your system that would benefit from placing the pvs in series or larger wire you can check here, http://forum.solar-electric.com/showthread.php?t=29
    another factor may be if you plan to expand in the future and by how much. otherwise there isn't any difference to series/parallel for your 2 pvs. remember that the 25a rating is output and not input and should not exceed 20a input. i think there was a discussion not too long ago on this controller and its ratings that may be good to search the forum for.
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  • System2
    System2 Posts: 6,290 admin
    #7
    Re: series or parallel

    Niel, thanks again. Moe, Icarus thanks for your input.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
    Re: series or parallel

    one more point brought up by moe is that the sb2000 does not have a float charge to it and will continue to charge based on the absorb charge setpoint being it is a 2 stage charger. this is a case of diminishing current as it is charged at that voltage setpoint, but you may want to check with concorde (they make lifeline batteries) if that will hurt the batteries or not. this is the case for a few other pwm controllers out there like the sunsaver series (not the sunsaver mppt though) as they are also 2 stage chargers. the 14.0v factory absorb setting is too low for lifeline batteries too as a range between 14.2v and 14.4v should be used and it is recommended for a battery temperature sensor to be used no matter the controller. (assumes controller can accomodate one)
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  • System2
    System2 Posts: 6,290 admin
    #9
    Re: series or parallel
    niel wrote: »
    one more point brought up by moe is that the sb2000 does not have a float charge to it and will continue to charge based on the absorb charge setpoint being it is a 2 stage charger. this is a case of diminishing current as it is charged at that voltage setpoint, but you may want to check with concorde (they make lifeline batteries) if that will hurt the batteries or not. this is the case for a few other pwm controllers out there like the sunsaver series (not the sunsaver mppt though) as they are also 2 stage chargers. the 14.0v factory absorb setting is too low for lifeline batteries too as a range between 14.2v and 14.4v should be used and it is recommended for a battery temperature sensor to be used no matter the controller. (assumes controller can accomodate one)
    Niel, the camper that this sytem is on stays in storage most of the time. I keep the batteries charged with the PD45 converter and I dont leave it plugged in all the time; just enough to charge the batteries. When we are using the camper the 12 volt refrigerator provides a good load for the battery bank so it generally keeps the batteries from overcharging. I just wanted to find out about panels wired in series because I was under the opinion that parallel was better becuase your increasing amps instead of volts. I understand now some of the reasons for wiring panels in series and the importance of controller specifications when determining how to wire your panels.

    Thanks you for your help,

    Ben
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