Real Basic Newbie Questions

I want to put a tiny (searched archives and don't think it will even qualfy as "small") solar set up in my barn (in sunny Arizona) - mainly for lights for night time chores, feeding and vet emergencies, radio would be nice as would a small cooler/fridge. (If I could also run a small angle grinder for hoof trimming, it would be like going to heaven.)

I'm uneducated but teachable and fairly handy. I haven't a clue if I want to use just DC or even consider an inverter (which I realize would be needed for any tools). Looking at the NAWS site has given me some ideas, but I really need help with a "shopping list" and - like many, I'm on a tight budget. So I'd like to start very basic/small but not shut out optios for future expansion.  My most important need is for good lighting for a 24x36' area (4 stalls and a center aisle) and a 12x12 work room. It's a semi-protected area (roof and partial walls) but gets wet in storms. Metal roof, 4" per foot slope, ridge runs north/south. Would also like to light the outside areas at each end as I hate it when I trip over a rattle snake. Would like to be able to switch barn lights, work room light and outside lights separately.

What I have:
Uni-Solar Module US-64:  64 Watts, 16.5V, 3.88 amps. I used this on my 5th wheel when I was living there while having house built.


Battery charge regulator (is this same thing as a controller? Or does a controller go between the battery and the lights/appliances?) And it seems I also need some kind of disconnect between the panel and the battery?
Battery (more than one? 6v/12v? acid/gel/AGM? golf cart/marine deep cycle?) Temps range from 10F in winter to 110 in summer. How many batteries could I expect to charge off this one panel (for intermittent use)?
Then do I need to have some kind of fuse box between the battery/s and switches?
Wire gauge? Most runs (except to one outside light) should be less than 25 feet)

Panel mount - given the amount of sunlight here, can I just mount it flat on the metal barn roof (would be on a westerly facing slope) or should I use a tilt mount that will face the panel more south? I'm getting too old to do much ladder climbing to make adjustments. We also get some really high winds. The RV mounts I see on the website look like what I might need.

Grounding - the panel frame has grounding wire holes. The barn is metal pipe construction, so I presume the roof is actually grounded (as long as I attach to bare metal). Is this really necessary?

Lights - someone suggested 12v LED lighting to me, I only see "fluorescent" on the NAWS site. The outdoor 16watt lights look like what I'd need but I'd probably have to start with only two or three and add more when I could afford them. Or would I do better to use an inverter and AC lights?

My grinders says 5amps, 580watts - would I be able to add an inverter and run this?

I'm sure these questions are below simple for you - but it's totally new for me, and I appreciate any help/ideas you have.

Patti K
Vail AZ


  • System2System2 Posts: 6,290 admin
    Re: Real Basic Newbie Questions

    Been doing some reading and got my questions on mounting and roof angle answered (found Solar John's blog - thanks! - and the "budget system" schematic is exactly what I needed). So hopefully I'll have the panel ready to mount by the end of the week, will decide where the battery/s will go.

    I may have a controller stashed in the barn - is there a way I can check it to make sure it works?

    Also looks like I should stick with DC, at least for now.  But still need help on wire gauges, best lights to use, etc.

    Thanks - even though a lot of the info here is above me, I've been able to figure out a lot just reading through some of the posts.

    Patti K
    Vail AZ
  • BB.BB. Super Moderators, Administrators Posts: 30,520 admin
    Re: Real Basic Newbie Questions


    First you would want to identify how much power you will need--that will drive the size of solar panel(s) and the amount of storage you will need.

    Continous loads (like a refrigerator--even a small one) is on the order of 1,000 Watt Hours per day--that would suggest you would need about 300-500 watts of solar panels just to drive that one item.

    For small loads, LED lights, small 12 volt fan, a little 12 volt radio, etc. all will work just fine on 12 VDC with reasonable sized wiring. For example, your standard 14 gauge house wiring can supply 15 amps--which is about 150 watts of load. With your 64 watt panel, you could run a 150 watt continuous load for about 1-1.5 hours (of course, winter/summer, solar panel temperatures, type of batteries selected, tilt of the panel, weather where you live, will all affect the actual amount of power you can generate--but 150-200 watt*hours is a good starting estimate).

    Compact florescent or even standard Energy Star fluorescents with electronic ballasts are very efficient (for your use, you would probably like the fluorescents more than the LED lighting at this point). But to light a large area (12x12 workshop and four stalls) you would have to decide how much light you will need. Would one 40 watt fixture for whole light area work, or are you looking for 4x40 watt fixtures in each area:

    4 * 40 watt * 2 = 320 watts

    If you run all 8 fixtures for 1 hour that is 320watts * 1 hour = 320 watt*hours. That would run down your daily charge in less than 1 hour (example 150 watt*hours / 320 watts = 0.47 hours or about 28 minutes).

    Notice that 320 watts is about twice the amount of power that a single 14 gauge +/- wire set can carry current for... When you start using more power (or need speciallized 120 VAC tools), then using a 120 VAC inverter (highly recommend a true sine wave inverter--yes more expensive--but much better for a whole lot of reasons) makes sense.

    If three 16 watt lights is a good start for you--they will run for:

    150 Watt*Hours / (3*16 watts) = 3.125 hours per day with your 64 watt solar panel.

    The 580 watt grinder you can run about (60 min per hour * 150wh/580w) = 15.5 minutes per day (assuming no lights).

    Of course, if you don't need the grinder and lights every day, but say, on average every three days, you would use larger batteries to store three days of charge or 3*150wh=450watt*hours.

    There is lots of ways to play the numbers--but you have to define what it is you will want to do.

    The Battery charge controller--you can just hook it up and watch the battery voltage and make sure that it charges to the specified voltage (for the temperature of your barn) and no higher.

    By the way, the temperature range will be pretty hard on the batteries (you can freeze and ruin a battery if it is not fully charged and you get low temperatures). Also, if you want the batteries to last a long time (5-10 years vs a couple years) you will want a temperature compensated charge controller (the good ones will have a little electronic thermometer that can be bolted to the battery to accurately measure its temperature).

    There are lots of other decisions to be made--but starting with your electrical usage plan (and expected $$$ budget) is the place to start before getting buried in the details.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SolarJohnSolarJohn Solar Expert Posts: 202 ✭✭✭✭✭
    Re: Real Basic Newbie Questions


    I'm glad you found my blog helpful.  Since it's past my bedtime, I'll just give you a short answers.  I'm sure others will provide advice as well.  

    First of all, how much are you willing to spend on this project?

    Since you want to run a frige, grinder, lights, and a radio, consider a good inverter.  I like the 1100 watt Exeltech Pure Sine Wave inverter.  Having that will eliminate the need to buy expensive dc lights and a dc refrigerator.  You can use compact fluorescent lights, and don't get a refrigerator bigger than you actually need.  Since it may be on 24/7, the energy needs are significant.  

    How many hours per day/week will you be using the grinder?  The lights?  And how many lights will you need?

    With answers to these questions, I'm sure someone on this forum will give you a pretty good estimate of how many watts of PV you'll need, and suggest an appropriate battery bank.  Since you said you want to build a "Tiny" system, mabey you'll want to opt for a Modified Sine Wave inverter $30 instead of $600, but you'll have to forget about running the grinder.  And, it might produce a buzzing sound in the radio, and it could burn out the refrigerator's compressor.  But the compact fluroescent lights will work, and you'll get by with less panels and batteries.

    Since a typical panel produces a peak current of 5 to 7 amps, 10 guage wire will work.  If you want to stay within the electrical code, use the appropriate type of wire.  Battery inerconnections and battery-to-inverter wire passes more current, and therefore should be heaver.  

  • mike95490mike95490 Solar Expert Posts: 8,764 ✭✭✭✭✭
    Re: Real Basic Newbie Questions

    only 64 watt panel. You are asking a lot, but if you don't use much, it would work.

    You say you want enough light to not trip over a rattlesnake - so how good is your night vision? How cold does it get there? CF bulbs take a couple of minutes to warm up to put out full light, so maybe LED lights are your answer.
    A store I've bought from before has 12 Volt compact fluorescent bulbs and 12 V LEDs, but they ain't cheap. I haven't found 12V CF bulbs anywhere else.

    I'd try getting another panel to add, then you could leave a CFL light on all night.

    All the 12V lights are pretty low power, 16 or 18 ga speaker wire would likely be fine, except for the longest runs.

    I have concerns about 120VAC CFL working of a $30 mod sine inverter, they may not last long, but they are cheaper than the 12V CFL bulbs

    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

    gen: ,

  • rplarryrplarry Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Real Basic Newbie Questions

    I think if I wanted to do the same thing you wanted to do I would get a Honda eu1000i generator, it will fill all your lighting needs and power tool needs, but it would not be a good choice for the refer. It has enough power to run the refer but you would have to refuel it a couple time a day to keep it running. Not worth the hassel. Is your barn so far from the house that running an elec line from the house is not practical? If you go with solar I think that you will find that your small system will get real expensive very fast. Good luck with your project, it will be fun put together.
  • mike95490mike95490 Solar Expert Posts: 8,764 ✭✭✭✭✭
    Re: Real Basic Newbie Questions

    I have built a very tiny system - using a uni-64 panel too. The panel can charge 2 Costco Deep Cycle batteries, if adjusted several times a day
    Look at the first item here listed as TRAVEL and click on the photo on the left, next to travel.
    Now linked to my facebook page, which is open access to this album:

    You will likely want to expand beyond what my C-12 controller handles, but it would work fine, up till 12 Amps of solar (2 more uni-64 panels)

    I run a 300 watt mod sine inverter all night, powering several strings of LED Christmas lights (maybe 20 watts), and can be recharged by noon the next day. I have to move the panel angle several times to track to sun for the most charge, the easiest way was to just adjust for the least shadow I would just plug in a 300W car inverter to run power tool chargers, they ran really hot, but lasted. 4 or 5 charging hours of 64 watts, is not a lot of power. Even a small fridge is out.

    You could run a couple 12V CFL's switched on only as needed. I also retract my suggestion about 16 ga speaker wire, in my monolith, I used some nice Malibu Light wire, made for outdoor use, and good and heavy. You may be able to find some LED yard / path lights that you could use too. For the lights, using ordinary light switches should work ok, as the DC load is pretty small. (for larger loads, you need switches rated for DC)
    You can use a small LED light that would run 24/7, to illuminate your bank of switches, or even rig one up that would light the plastic switchplate up from inside the box, the translucent Nylon plates (called unbreakable - great for barns) should work OK
    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

    gen: ,

  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Real Basic Newbie Questions


    As discussed above, there are basically two ways to approach your situation. One is to estimate what you’d be able to do with the single 64 W PV module. The other would be to determine your typical energy requirement by adding up all of the loads you’ve specified and then specifying a system to meet that requirement in your location (Vail = SE of Tuscon). We can continue to pursue these approaches if you’d like.

    There are also some spot solutions to consider. For example, Malibu makes simple and cost effective solar floodlight kits. Something like this might work for illuminating the outside area around the barn door(s). Another solution is a solar floodlight with proximity sensor. Both are usually available at Home Depot and/or Lowes.

    See: and:

    Jim / crewzer
  • System2System2 Posts: 6,290 admin
    Re: Real Basic Newbie Questions

    Hey everybody ~

    Thank you for all the replies and ideas - lots of food for thought. Especially as you've taken the trouble to break it down in terms I can understand w/o making me feed stupid - greatly appreciated.

    (BTW -running electric from the house is out - just ditching and running wire would cost more than a couple of solar panels and batteries - besides, it's the principle, especially after reading Solar John's blog.)

    I'm going to start with what I have and see what it does - any light will be an improvement and I'm seeing that it will not be too difficult to expand as I learn.  I bought the angle aluminum to build a roof mount today - life and my day job (I'm supposed to be retired but my patients don't seem to realize that) have slowed down my schedule. Will get one or two batteries this week and order a light

    I do have a couple of six volt light kits I've been using and once this project is on its way, I can tweak and move the 6v lights to better locations (they're useful but good for only 60-90 minutes) but might help with the "outside" needs.

    Vail AZ
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