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Per-Panel Optimizers & Charge Controller for Off-Grid +48VDC system w/AC Generator

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  • Per-Panel Optimizers & Charge Controller for Off-Grid +48VDC system w/AC Generator

    Hi,

    I'm taking over a remote off-grid site (no grid anywhere near) that has an existing +48 VDC battery bank, and ancient charge controller, and some older panels that are in pretty good shape. There's also an AC generator that charges through a separate AC-to-+48VDC charger. As part of upgrading a few things, I may need to replace a few panels, add some new panels, replace the +48 VDC charge controller, and possibly the generator 48 charger as well. I'd LOVE to update existing and new panels using per-panel MPPT optimizers, but to do so I need to find a great non-MPPT-but-optimizer-compatible charge controller. Any ideas or recommendations for such a charge controller? I'd love a system that perhaps combined AC-from-a-generator charging of the +48V batteries as well as solar panel charging--but if not, no big deal. What cannot and will not change is the battery system. They're quite new, and the equipment is all set up on the +48v (negative ground) power system. That's non-negotiable.

    Benefits of going with per-panel optimizers to me are partially shaded panels in winter (from snow), varying outputs due to the panels being older, and mismatched panels (new ones likely will be higher wattage).

    I do NOT want any systems that require "cloud" or network connectivity. All functionality must not require connections. And I'd love stuff I can monitor myself (likely via ethernet/IP talking to a Raspberry Pi system, etc.--but MODBUS over IP works too...)

    Suggestions?

  • #2
    Originally posted by astounding View Post
    Hi,

    I'm taking over a remote off-grid site (no grid anywhere near) that has an existing +48 VDC battery bank, and ancient charge controller, and some older panels that are in pretty good shape. There's also an AC generator that charges through a separate AC-to-+48VDC charger. As part of upgrading a few things, I may need to replace a few panels, add some new panels, replace the +48 VDC charge controller, and possibly the generator 48 charger as well. I'd LOVE to update existing and new panels using per-panel MPPT optimizers, but to do so I need to find a great non-MPPT-but-optimizer-compatible charge controller. Any ideas or recommendations for such a charge controller? I'd love a system that perhaps combined AC-from-a-generator charging of the +48V batteries as well as solar panel charging--but if not, no big deal. What cannot and will not change is the battery system. They're quite new, and the equipment is all set up on the +48v (negative ground) power system. That's non-negotiable.

    Benefits of going with per-panel optimizers to me are partially shaded panels in winter (from snow), varying outputs due to the panels being older, and mismatched panels (new ones likely will be higher wattage).

    I do NOT want any systems that require "cloud" or network connectivity. All functionality must not require connections. And I'd love stuff I can monitor myself (likely via ethernet/IP talking to a Raspberry Pi system, etc.--but MODBUS over IP works too...)

    Suggestions?
    What's your exposure like? From what I've seen optimizers are rarely worth the cost and effort. I recently installed my first solar edge optimized system and it's performance is roughly the same as similar non-optimized systems in the area. If you have a lot of shading issues, you're space limited and/or panels facing different directions it may be worth it. If not just take the $$$ you would have spent on optimizers and overbuild your array.... Optimizers are going to cost at least $50/panel. These days that will buy you at least 100w of additional PV plus the racking to support it. No optimizer will increase output that much.

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    • #3
      How big are your batteries, and how big will your loads be? I'm assuming with a 48V battery bank, you're loads are likely to be large? Are they golf-cart size, or L-16 size? To charge a golf-cart sized bank at 48V I'd say you need about 1200 watts of panels. For an L-16 sized bank at 48V, about 2100 watts. Those are the low values.

      The big advantage of using an MPPT controller is that you can wire panels in series to mix and match, then let the controller transform the voltage to what the battery wants. Let's say for example that your old panels are putting out 5 amps at 18 volts. You could wire 4 of those in series to get 72VDC. Then you buy some new grid-tie panels putting out 8 amps at 36V. If you put 2 of those in series you'd get the same voltage, 72 as your first string. So, string #1 would put out about 5 amps at 72 volts, and string #2 would put out 8 amps at 72V. Run them into a combiner box that has breakers, and that feeds your charge controller. You controller will take those 13 amps at 72 volts, and transform them into about 17amps at 54V (more or less). When you have multiple strings you can position them separately to optimize their insolation, and can be positioned further away from the cabin because voltage drop is lesser.

      Something like this Midnight MPPT would work well. https://ressupply.com/charge-control...rge-controller. Keep in mind your batteries should guide you into how many strings you need. For golf-carts you'll need at least 18 amps of charge current, and L-16's >31 amps.

      Newer sine-wave inverters can be designed to take generator input and use that for charging the batteries, eliminating the need for a separate charger. Something like this Schneider would work for you. https://ressupply.com/inverters/schn...nvertercharger. The Schneider can be upgraded with various accessories that allow remote monitoring via a display box, or even hooking up a laptop.

      Comment


      • #4
        Optimizers are not used with off grid systems (that I know of) If you have no shade issues, they won't help. Snow would coat them all evenly till you clean them off.

        Schenider makes 150V and 600V PV MPPT string chargers. Also a solid line of house sized inverters - the XW series, 4kw & 6kw in 48V. They have done the Generator support properly too, so you can use any size 240V generator for charging and loads.
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          Tigo optimizers are Off Grid compatible. I was never clear though as to how they optimize for off gird.

          https://support.tigoenergy.com/hc/en...ge-controller-
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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