panels in series

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ws9876
ws9876 Solar Expert Posts: 440 ✭✭✭
I'm thinking of mixing 2 205s and 2 smaller square 100s watt panels on my house. Starter system.
Just to be sure.... I can get a cheap combiner box and join the voltages in series for about 70-120 volts dc
and feed an Outback flexmax. yes..??? after that...it seems that the inverters that take any voltage m/l
are better right?? since they can be used later with diiferent battery voltages..???yes??
off grid battery no grid tie wind assist

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: panels in series

    Well, not quite.
    You've got a terminology problem for one thing:
    An Outback FM60/80 is a charge controller, not an inverter. It can take an array Voltage up to 150, and "down convert" it to a usable system Voltage (12, 24, 48v).
    Inverters run from a battery bank with a nominal system Voltage (as above).

    As for connecting the panels in series, this is probably not a good idea. One of your panel sets is 205 Watts and the other set is 100 Watts? In such a case the Imp and Vmp are likely going to be far, far apart so the panels are probably not compatible for either series or parallel connection. A bit more detail on the panel specs would tell for sure.
  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
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    Re: panels in series

    many people have a mix of many panels...how do they do it..???

    and inverters like the SMA take an input of about 100-400v input this is not 24 or 48

    do you not use a controller with the SMA units???
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: panels in series
    ws9876 wrote: »
    many people have a mix of many panels...how do they do it..???

    and inverters like the SMA take an input of about 100-400v input this is not 24 or 48

    do you not use a controller with the SMA units???

    More confusion.

    The SMA inverters you refer to are grid-tie inverters; they do not use batteries or charge controllers. They have their own built-in MPPT function, and take the high Voltage DC array and convert it to 240 VAC 60Hz - but only with utility power available.

    You can mix different panels if the specs on the panels are close. Chances are pretty good that the 100 Watt panels you refer to are a "12 Volt nominal" panel whereas the 200 Watt ones are "24 Volt nominal". That alone makes them unlikely to work together. The further apart the specifications on mis-matched panels, the less efficient the array becomes. It will work to some degree, but sometimes the loss is so great that the lower powered panels actually become a detriment rather than an asset.

    Maybe you should start over with the design. Step One: define your loads. It is very important to know how much power you're trying to supply, and a far better way of designing a system than coming up with panels & other equipment and seeing how much power you get and deciding what you can do with it.
  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
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    Re: panels in series

    about the people with many random panels( like the home of the guy who started Homepower)
    i saw it on one of there covers..

    you can wire in parallel the similar pairs and then combine the voltages ,series, at the combiner box...yes??
    if not why not??
  • BB.
    BB. Super Moderators, Administrators Posts: 33,491 admin
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    Re: panels in series

    A good place to start--panels that are within ~10% on Vmp--you can parallel those panels. Panels within ~10% on Imp--you can string those in series.

    If you have a "24 volt" Vmp=35v panel, you can parallel that one with two series ~17.5 Vmp "12 volt" panels.

    You can also series parallel panels too... Take 1x 200 watt Vmp=35v/Imp=5.7amp panel and put it in series with 100 watt Vmp=17.5v/Imp=5.71amp panel for a Vmp=52.5v/Imp=5.71amp 300 watt string--etc.

    Using an MPPT type controller sometimes make it easier to configure a mixed array... You may have different Vmp/Imp panels and find it impossible to build a "12 volt" (Vmp=17.5v) array (you may have other panels with 35/38/etc. volt Vmp's)--but You could build out a ~70v+/- 5% array with your mix and match components.

    Also, many of the smaller solar panels are not designed for use with "High Voltage" DC as used in most Grid Tied systems... Many older/smaller panels are rated at 70 volts (or other voltages) maximum... For GT in the US, the panels/wiring/etc. all needs to be rated at 600 VAC minimum.

    Also, when you start paralleling strings (or single panels) together--In theory, each parallel connected string is going to need its own, properly rated, series fuse (roughly 2xImp or 2xIsc)... The good panels could feed a short in a bad panel and cause the wiring/panel to overheat and set off a fire. (the combiner box is typically where the series fuses/breakers are installed)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
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    Re: panels in series

    i guess I am going to stick to new identical panels, but please someone make a decent litle wind turbine..
    I beg you........
  • Chuck46
    Chuck46 Solar Expert Posts: 95
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    Re: panels in series

    Well one thing you need to do is let folks know if you are talking about off grid or grid tie systems that may be some of the confusion.

    Chuck
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: panels in series

    Before you invest any money in any type of wind turbine, even home-made, invest in an anemometer and find out if you really have enough sustainable wind to make it viable. That's the #1 fault with wind turbines; the sites really don't have the needed wind to make any significant power.

    The #2 fault is that most of them are poorly-made junk that couldn't generate a Watt of power if you towed them behind a 747 at 600 mph. (Of course they'd fly to bits long before that.) :p