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Newbie here, What MPPT would you recommend?

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  • #16
    Originally posted by SunEagle View Post

    Yes. Series wiring reduces the wire size between the panels and CC and works better for a MPPT type..
    The first problem is not to exceed the maximum DC input voltage.
    The second problem is if you can't wire all of the panels in one series string then you need to be able to have a second string with an equal number of panels.
    That is why having a odd number of panels works against you.
    So with 5x 100 watt panels you wouldn't be able to wire 2 in series then the other 3 in series then wire the two groups in parallel?

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    • #17
      Originally posted by Skwidward View Post

      So with 5x 100 watt panels you wouldn't be able to wire 2 in series then the other 3 in series then wire the two groups in parallel?
      No. The 3 panel string would generate a higher voltage then the 2 panel string. Since the voltage will be more than 5% higher on the 3 panel string there will be very unequal voltage paths. That won't work for most CC's since they are looking for a single voltage or at least multiple voltage strings within that 5% deviation. The end result may be a CC that can't work properly or a reduction in panel wattage which would be the same as throwing a panel away. Balance is critical to a solar / battery system.

      I could be wrong with my statement so I would hope others drop in and confirm my post.

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      • #18
        5 panels paralleled 2-3 will put out only slightly more than a pair of each 2 panels
        in series. That needed editing. Bruce Roe
        Last edited by bcroe; 04-20-2019, 09:30 PM.

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        • #19
          If Renogy still sells a comparable panel you may want to consider buying a sixth panel. That would give you the ability to run 2S3P or 3S2P.

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          • #20
            With a mobile application you should think about where/when you'll actually be travelling. Most principles of solar design are built around homes, which don't move much. Some people only travel in fair weather. Some never leave the desert. Others spend a lot of time in big cities with tall buildings, signs, powerlines to shade. Some travel in rainy, dismal places. Some stay in RV parks most of the time and only boondock a day at a time; others have never paid for an RV hookup in their lives. These factors all come into play when you set up your array. So how are you using your van? Are you chasing work in cities? Chasing waves at beaches? Chasing good weather in the desert? Or any of a hundred other possible ways to travel?

            Since you don't already have the MPPT but do own the 5 panels, your cheapest option would probably be paralleling them into a 40A PWM. You do need to fuse them in the combiner box as SunEagle mentioned in his initial response. This would be tolerant of partial shade on some of the panels, but you'll also be "throwing away" some power during high production periods, and performance in overcast or low-angle (winter) light will be dismal.

            Going MPPT will cost more for the controller, and you have to reckon with your odd number of panels (since they should be wired in series), but you'll see better performance on overcast or winter days vs. the PWM arrangement, and in super strong sun conditions you can expect to get better output than PWM. If you wanted to go MPPT you could simply leave off the 5th panel, or (as PNW_Steve suggests) acquire a 6th one and find a place for it. Since you have limited roof space, something interesting you could do is permanently mount one 3s string of panels on the roof, and use a second string of 3 panels as "ground deploy" units, connected in parallel to the roof string with a convenient connector. Since they're in parallel you can add or remove the ground panels at will. No configuration or settings to change in your charge controller. When parked in the city you can remain "stealth" and still get charge from the 3 on the roof -- presumably in town you will be using most of your power inside houses, coffee shops, businesses anyway. Most vandwellers i know spend all their time in town doing laundry and scavenging free wifi. When in the woods you can put out the extra panels to support greater energy use. Another advantage of ground-deploy panels is you can leave them in the sun and park in the shade (although this generally requires a pretty long cable to do it really well). A 3s string of ground panels will be a little heavy to handle, though, and you'll need to rig up a simple stand to hold them tilted.

            - Jerud
            ------------------------------------------------------------
            1220W array / 1000Ah LFP house bank
            MidniteSolar Classic 150, Magnum MS2812
            ME-RC, Trimetric, and JLD404
            Full-time 100% electric boondocking (no propane, no genny) since 2015
            2001 Fleetwood Prowler 5th wheel 25 foot, self-rebuilt
            www.livesmallridefree.com

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            • #21
              Screenshot_20190430-203646.png renogys 500 watt kit all in series 40 amp 150 volt renogy commander charge controller.

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              • #22
                Originally posted by Ho jo View Post
                Screenshot_20190430-203646.png renogys 500 watt kit all in series 40 amp 150 volt renogy commander charge controller.
                Did not realize the Renogy controller is 150V - kinda surprised. Totally solves the problem.

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                • #23
                  Originally posted by zamboni View Post

                  Did not realize the Renogy controller is 150V - kinda surprised. Totally solves the problem.
                  Some of their controllers are 100 voc. This is a higher end product.
                  2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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