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840 watt 12 volt solar system.

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  • 840 watt 12 volt solar system.

    I am setting up a 12 volt solar system for my shed. I have 3 *315 watt Suntech Poly Panels, a Victron 150 / 100 mppt controller, Victron BMV 700 battery monitor, and a 12/24 v 65 amp battery protector, connected to 4 * 6v 520 amp batteries. (Total 1040 amp storage) The regulator will allow me to upgrade to 24 v and then 48 v as time goes by, and we live on the property full time.

    We estimate that we will use approx 120 amps a day. (Between 1500 - 1800 watts day) This gives me 4 days back up from the batteries with a 50% capacity. (I will assume the panels will produce 20 amps a day in inclement weather.) I know we normally speak in wattage for total power draw, but amps for myself, works better when comparing battery storage.

    According to our calcs, the 3 panels wired in series will produce around 70amps to the MPPT regulator per sun hour... Our area has an average of 4.8 sun hours a day.

    I understand the nuances between float charge and full charge etc...My questions are 3 fold. Perhaps 4.

    1.) Does 70amps going into the regulator equate to 70 amps hour going into the battery system?

    2.) What size fuse would you recommend I use for the system between the batteries and the load. I have a 12/24v Powertech 6 way illuminated switch panel to wire the various lights and equipment to. Which totals in 35 amps total for the unit. Each switch varies in its breaker switch between 5 to 10 amps.

    3.) What size invertor would you recommend I use on a 12 volt system. I have a small 350 watt power tech, which I use off a 120 watt panel system to recharge my power tool batteries. We also have a 3000 watt invertor on our caravan, which we don't use, and I can salvage from it. But, our intention is mostly to use 12 volt appliances. ( I know 24 volt, and 48 volt is a much better system, but for now, 12 volt is what our budget allows for.)

    4.) Do I have to ground the system somewhere between the batteries and the panels.

    Thanks in advance... P.s the panels will be ground mounted and not roof mounted.

  • #2
    I have no idea what the "Battery Protector" is. A fuse? A BMS ? A plastic cover for the terminals ?

    MPPT controllers work by "wattage in = wattage out". If you have 70A in, it's very possible you could get 100A out. What voltage have you wired the panels for ? If you are charging 12V batteries, your panels should be wired for at least 35V to take advantage of the magic of MPPT so you don't have to rely on 70A input cables

    840W @ 12V is 60A output
    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

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    • #3
      A battery protector is a programmable cut off switch, to stop the batteries from draining. Ours is the 12 / 24 volt 65amp one. The guy who advised me on the equipment is very switched on. (Pun intended.) And yes, I like your terminology about the mppt being magic.

      https://www.victronenergy.com/blog/2...says-and-more/
      Last edited by craig bennett; 08-27-2018, 09:16 AM.

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      • #4
        What other company has as much cool, and important stuff as Victron?

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        • #5
          Originally posted by Brian53713 View Post
          What other company has as much cool, and important stuff as Victron?
          Brian. I was impressed with the reviews I found when I researched them. I read through these forum for over a year before joining. The guy I bought it from (Bassam, Snap Tech, Kings Park Sydney, ) is extremely knowledgeable, and honest. He could have sold me stuff that I needed, but he told me to go to the local hardware and get some stuff, that was cheaper than he could sell it for.

          When I explained I needed a12 v system initially, and the tight budget we were on, but had plans to expand over the next 2, and then, again 2 or 3 years, he went through all the options with me. Basically, all we need when we upgrade will be the charger inverter (and batteries and panels of course.

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