Need a little help getting started.

Hi, I am new to this forum and could use a little help. I am building an off grid system for an underground root cellar/storm shelter. I have tried the "Solutions from Science" piece of junk and the DIY Harbor freight kits. I am now ready to put everything that I have acquired together but am unsure about a few things.

I have Twelve 15 watt Harbor freight panels wired together into an array. I also have a 95 watt Solution in Science panel. All the panels are 12 volt. The panels are all going to be wired to a Tracer MPPT 30 A charge controller (with the remote LCD meter). I have 6 six volt Duracell golf cart batteries 215 AH (3 pairs wired in series and the sets wired in parallel to produce 12 volts). The inverter is a Harbor Freight 12 volt 2000 watt (4000 peak) unit. The system is to be installed in an undisclosed location in NE Texas, so plenty of sunshine (and I have my monthly angle chart)

The batteries will be vented (and I have a generator to equalize them as needed) Mostly this system will run lights and a few small 12 volt fans (maybe recharge cell phones, etc). I have a proper grounding rod installed prior to pouring the slab so everything with be grounded.

Does anyone see any problems? Mis-matches, over-kill, missing anything...etc?

My two main questions are...

Is it safe to combine the two different brands/wattage panels in parallel?

How many fuses, breakers, switches do I need? Where do I put them and what size do they need to be?

(I have ordered several ANL 30 amp fuses with holders to start me off.) I will work on a schematic if anyone needs to see that.

Suggest away. Thanks in advance.

KK

Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Need a little help getting started.

    I see a bunch of problems.
    Given that you will use an MPPT CC, there was not reason to pay too many $ per watt to get all of those Harbor Fright (sic) panels.
    If you put them in series (say three strings of 4 each) you will get a good match to the Tracer CC and minimize the wiring costs.
    Any time you have more than 2 strings of panels, you need to put a separate fuse on each string. The 95W 12V panel will unfortunately be odd man out in that scheme.

    Putting batteries in parallel is always a bad idea if there is any way to avoid it. You would have been better off getting 4 volt batteries to get the same capacity and putting three in series instead of two. But that is battery acid under the bridge now.
    A 2000W inverter is really too big for a 12V system. The 400A surge will require 400A from your batteries and that is really big wire and lots of problems.
    If you have, say, 600AH worth of batteries (three strings of 200AH batteries) then you would need at least 600W of panel for proper charging. You have either 180W or 270W if you can squeeze the other panel in.
    Grid tie type panels (~30V, 200-300W) can be had for less than $1 per watt if you shop around and know what is good and what is trash.

    If you want to put all 13 panels in parallel, that will work, but you will need 13 fuses to comply with NEC, and the fuse size for the 95W panel will be different. Each panel label should show the maximum series fuse size and you need to follow that.
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need a little help getting started.

    Welcome to the forum.
    Does anyone see any problems?
    I have Twelve 15 watt Harbor freight panels wired together into an array.

    Well right there. First off those panels aren't very good, and second you need twelve fuses or breakers if that's an all-in-parallel array. That's only 180 Watts, and you could buy a good, single panel that size for about $220. The 95 Watt panel is probably the same Vmp range and about 5 Amps.

    You sure don't need a 30 Amp charge controller, because even at 12 Volts that much PV is only going to put out about 15 Amps even with the other panel added in.

    You've got three parallel battery strings, which is known to leave a system open to potential problems. Plus this totals 645 Amp hours @ 12 Volts, which that little array is not going to charge. At 15 Amps peak you would be at maintenance level from that array (around 2%).

    My advice would be to do yourself a big favour and start over. Sell off the experimenter's stuff, figure out a power need (max Watts and daily Watt hours), and begin a design from that point so that it isn't a bunch of mis-matched equipment not really suited to the need.

    The Duracell batteries aren't bad, but if you don't keep them charged they soon will be. If you could get two more of those and shift up to a 24 Volt system it will work better. Then you would have 430 Amp hours @ 24 Volts: up to about 4kW hours AC. You'll need about 1340 Watts of PV and an MPPT controller capable of >50 Amps to recharge it.

    You may find that low Voltage (12 VDC) equipment is not worth the investment compared to running off-the-shelf 120 VAC equipment through an inverter which you might have anyway.
  • KKRoadie
    KKRoadie Registered Users Posts: 4
    Re: Need a little help getting started.

    So assuming I don't start over...I need more (and larger) panels? Re-wire everything for 24 volt (and add two batteries)? Hypothetically I add the two batteries so I now have a 24 volt system and I scrap the odd panel but wire the others for 24 volt...how much wattage would I need? (and I thought I knew what I was doing....I feel so "new")
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need a little help getting started.
    KKRoadie wrote: »
    So assuming I don't start over...I need more (and larger) panels? Re-wire everything for 24 volt (and add two batteries)? Hypothetically I add the two batteries so I now have a 24 volt system and I scrap the odd panel but wire the others for 24 volt...how much wattage would I need? (and I thought I knew what I was doing....I feel so "new")

    What you really need is a power target: how much power you need/want to supply. Even if you stay with 12 Volts.

    But yes that array is too small to keep that much battery charged.

    Lots of panels = lots of connections = lots of potential failure points.
  • KKRoadie
    KKRoadie Registered Users Posts: 4
    Re: Need a little help getting started.

    so drop back 20 and punt....got it.
  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Need a little help getting started.

    I'd imagine the loads for a root cellar would be pretty low. That's the first thing you need to do, measure your expected loads. Get a Kill-A-Watt.

    Ditch anything Harbor Freight. You might be able to salvage the charge controller and some of the batteries once you figure out what your loads are.

    Cariboocoot showed how you can expand your system. But you might need to reduce it. All depends on your loads. Just a few lights and small electronics? A chest freezer and refrigerator? Big difference between those.

    If all you want is a small 12V system, you might consider selling the HF panels and buying a couple larger panels, possibly keeping the charge controller, and reducing the size of your battery bank to match the capacity of the panels. A different (not HF) inverter is also a good idea.
  • KKRoadie
    KKRoadie Registered Users Posts: 4
    Re: Need a little help getting started.

    Thanks for the help all...
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Need a little help getting started.

    Does anyone see any problems -

    HF sells things that look like PV panels, but are just shade structures.
    Powerfab top of pole PV mount | 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 ,

  • ZoNiE
    ZoNiE Solar Expert Posts: 100 ✭✭
    Re: Need a little help getting started.

    Did you keep the boxes? They take returns...

    For all the money you spent on HF panel kits, ($150 x 5= $750) you could buy three or four of good "real" panels (300-500W) and a charge controller that will not die in a few months. I paid less then half what you probably did for three NEW 130W Kyocera panels from Craigslist. I'm getting a Kid MPPT controller, but I could also easily buy a $50 PWM controller.

    HF panels are good to play with to light a shed or path or something, but not to rely on for regular power usage.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Need a little help getting started.
    ZoNiE wrote: »
    Did you keep the boxes? ....
    The boxes are the best thing about stuff from HF.
    Powerfab top of pole PV mount | 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 ,

  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Need a little help getting started.
    mike95490 wrote: »
    The boxes are the best thing about stuff from HF.

    I find Harbor Freight an interesting place, If you search you can find a "free coupon" for many somewhat useful things there!

    I've been picking up small 5x7 tarps free with my tiny purchases this summer, I grocery shop next door once a week so go in and pick up a tarp and a 75 cent paint brush, or box of SS screws, or some other small item that I'll use at some point in time. There's a coupon for 'throw away' LCD multi meter free, as well. I think some consumables are just fine there, sand paper, utility knife(often freebe also) razor blades and utility knife blades. I typically would stay away from any tempered steel tools... While their solar panels send multitudes of people to this forum, they have had their solar flood lights cheap enough for me to disassemble and use just the light for one use and the panel for another...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.