Portahut PV Solar Install

Post by WildSnow.com blogger | December 16, 2011      

Now the fun begins. Or is it? Yet another acronym for the challenged do-it-yourselfer: IANAE, I Am Not an Electrician. But, are not risk and challenge the spice of the alpine life, even if it means smoking wires and 300 volts where you wanted 12?

Honestly, I’m not that bad. But it’s amazing how complicated for the amateur a “simple” PV install can get when you try to do it right. Got started over the last few weeks, progress below:

Solar system batteries.

Our pair of Trojan L16H lead acid batteries, in temporary hookup for maintenance charging. These guys weigh 125 pounds each, they're not exactly easy on the back! Rated at 420 amp hours each, when new.

Solar PV electricity for small cabin hut.

The trick seems to be integrating the controller and digital display correctly with an exterior breaker box and the panels, along with solid and safe residential style wiring. When I fired things up yesterday, the readout showed my battery voltage, but I wasn't getting any juice from the control to the interior lights and such. Turns out the batteries are under the threshold for the controller's automatic shutoff. Time to hook something up to give them a boost. Perhaps we can get the panels going sooner than later. We'll see.

Solar electricity for small  backcountry skiing cabin.

We don't have much sun in our location, so I bought two used (still with 7 year life) 6 volt larger sized Trojan batteries (connected in series for 12v) and opted to double up on our panel install. Pricey, but necessary. Instead of sealed batteries, these archaic units (probably invented by Egyptians a few thousand years ago) produce inflammable hydrogen when charging, so venting the battery box correctly is essential. Luckily, hydrogen floats so a vent at the top of the box tends to capture the evil photon farts -- though you have to be careful of back-drafting in a tight structure such as this. Experimentation and evaluation will take care of refining the vent issue.

Credit goes to Steve and Sunsense Solar here in Carbondale, Colorado for helping me though this process and making sure I had the parts and pieces. Shew, let’s hope the next report has some glowing light bulbs!


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28 Responses to “Portahut PV Solar Install”

  1. Tom Gos December 16th, 2011 9:40 am

    Lou, just curious, are you able to drive up to the portahut now or are you having to haul everything up there on a sled or ATV?

  2. Lou December 16th, 2011 10:38 am

    Tom, just a short walk from parking down the hill to the place. We sled things down in a pulk, or just load up a big pack. Snowmobile access would be ok as well, as a lot of our friends around here have. Lou

  3. Toby December 16th, 2011 11:56 am

    Any exterior pics of the panels? What are you going to run on the electricity? Got cell coverage and internet with your range extender? Where’s the 60″ LED LCD going to go? Gotta have a blu ray player right?

  4. Mark December 16th, 2011 12:27 pm

    He’ll be powering his blogging cockpit, I suspect.

  5. Derek Weiss December 16th, 2011 1:16 pm

    How many total amp hours in your battery set up? How many watts in your panel array.

    I had a Solar Boost 2000E MPPT charge controller that is great for small solar systems that does balance charging, etc, etc.

  6. Lou December 16th, 2011 3:01 pm

    Spec later, gotta get that whole thing hooked together! The purpose is just to run some lights, a small music unit, netbook once in a while, and perhaps turn the range hood fan occasionally. We’ve been running the music with a small car booster battery charged at home.

  7. Michael Pike December 16th, 2011 11:40 pm

    Those Trogan T-105’s will give you 220 amp hrs @ 70 degree temps with low discharge rates, less with colder temps (as much as 50% less) and less with higher discharge rates. That’s a pretty common setup for rv campers and one I used for several months in winter traveling around Colorado, N Mex and Utah.
    With Colorado’s sunny days you should do ok, but a small Honda EU 1000 or 2000 generator would be a good backup for extended storm periods. Also trying not to discharge the batterys below 50% will keep them healthy.
    I had 220 watts of solar on my roof, but got most of my charging from my135 amp alternator as I drove from trailhead to trailhead.. Adding some insulation to the battery box will help keep them warmer.

  8. Lou December 17th, 2011 6:01 am

    Thanks Michael, you saved me from looking up the specs. Main mistake I made so far was not already having the small generator. I’ve got a big generator stored at home, but the thing is tough to move around once we can’t drive to the location, and it eats fuel. Consultant told me I’ll damage the batteries if they get much more discharged and freeze, so I’m headed up there today to hook up my small folding panels as a trickle charge till I get the big ones on the rack and connected. Am planning on everything being done in a few days. Good time for a project like this, since we don’t really have much in the way of decent and safe backcountry skiing right now, due to lack of snow.

  9. Mark W December 17th, 2011 7:31 am

    Neat project, Lou. Yeah, you want to keep on top of those batteries. I had frozen a car battery before–definitely a bad deal.

  10. Derek December 17th, 2011 7:36 am


    We had the same batteries, but four of them in our motorhome with 170w of solar. We always made sure to keep our batteries above 12.0v, fully charged is 12.72. Batteries don’t like being discharged much below 12.0v, and it’s good to pay attention to protect your investment. Also good to check the water levels periodically.

    In winter, your panels won’t produce nearly the same amount of amp hours that they do in summer, so pay attention to them and try to position them for optimal sun exposure.

    I would also run low watt lights.

    Our motorhome had a furnace with a blower that pulled 6-7amps, then all the 12v lights. In winter, we had plenty of power to run the furnace all night at a temp setting of 50 degrees F, and use a light or two. By the end of a sunny day in February, our batteries would be fully recharged. Our panels were mounted flat on the roof (not ideal), but it worked for us. Our water pump was also running on 12v.

    Doesn’t look like you’ll have much amp draw, just lights? So that set up should be fine for you if you just pay attention to your usage.

  11. George December 17th, 2011 8:33 am

    Lou, I put LED lights in my camper and it made a big difference in battery life. My used 55 watt solar panel keeps the battery charged. I picked up the 12v LEDs from superbrightleds.com and then used bluestick from DAP to secure the LEDs inside the light fixture.

    Device Drain Time:
    Propane sensor 0.05 A 1700 Hr
    Type 1156 incandescent bulb (supplied with Casita) 1.47 A 58 Hr
    Cooking hood fan 1.15 A 74 Hr
    Cooking hood light 1.37 A 62 Hr
    Fantastic roof fan (medium speed) 1.32 A 64 Hr
    Bathroom fan 1.49 A 57 Hr
    Furnace fan 2.97 A 29 Hr
    Evening lighting (4 ceiling lamps) 5.88 A 14 Hr – replaced with LEDs
    Type 1156 incandescent bulb 1.47 A 58 Hr (replace most commonly used)
    Type 1156 Cool White LED 0.19 A 447 Hr
    Type 1156 Warm White LED 0.17 A 500 Hr
    Evening lighting (4 Warm White LEDs) 0.68 A 125 Hr

  12. Michael Pike December 17th, 2011 11:03 am

    Lots of good info at http://www.rv.net.
    If you’re using one of those small generators to charge your battery bank, its better to use a smart charger on the 110v output circuit rather than the 12v output line. The 12v line takes forever to charge the batteries.
    One last point: don’t add distilled water to batteries until they are fully charged
    (unless the level is below the plates), as the water level will rise as the batteries become more charged, and might overflow the top.

  13. Feldy December 17th, 2011 7:48 pm

    Lou, FWIW, “PV Solar” is redundant. Like “The La Brea Tar Pits.”

    Probably being too nitpicky here, but it’s my day job. (PV, not grammar) 🙂

  14. Lou December 18th, 2011 12:11 am

    Hey! Just keeping all the keywords in there… also, PV could be a panel running under your kitchen lights or a lab experiment running under a spotlight, so actually, PV solar is not redundant, only 100% accurate, meaning sun powered photovoltaic instead of kitchen light powered photovoltaic. There, now you know how much my editors like me (grin).

  15. Doc Smiley December 18th, 2011 2:45 pm

    Love the porta hut!! I have that same battery set up in my Sportsmobile with a solar PV system flat on the roof and it works great. With the Colorado sun you will have power to burn. I travel for work from Leadville to Winter Park to the Eastern Plains and live in it at least 3 days a week. Mine powers a Directv satellite box, microwave, LCD flat screen, propane furnace, fridge & lights. I have never ran out of juice and this thing has been in some COLD weather!! My only caveat is make sure the batteries are super secure when moving it. That straight inline cable is like a rod, and it pulled the post off one of my batteries from small movements. I have a very tight fitting box for mine and with the cables holding things down and the close fitting lid I didn’t think they were moving, but I was wrong…….. Oops…..$350 wasted:(

  16. Feldy December 18th, 2011 8:31 pm

    Crap, you totally out literal-ed me, Lou! And wait, you have editors? 😆 (All meant in good fun)

  17. Lou December 19th, 2011 7:29 am

    Just added another photo of the batteries, in temporary location. They’re used Trojan L16H model, 125 lbs each, rated at 420 amp hours each when new. This much capacity is a bit of overkill for running our music and a few lights, but the idea is since we usually only use the place one night at a time, with days in between for charging, we can can store power from the limited sun in our location so the batteries have plenty of power for when we visit.

  18. Ralph December 19th, 2011 7:58 am

    is that picture showing batteries charging next to a cranking wood stove? Looks like potential for overheating to me. Yikes.

  19. Lou December 19th, 2011 8:28 am

    Ralph, yep. Just a small maintenance panel providing electricity and cold room with ventilation. Nothing got hot. In fact, it was too cold which is why the batteries are near the stove getting some heat. No need for you to get scared (grin).

  20. chris blatter aka silvertonslim December 19th, 2011 9:47 am

    Lou- I’ve installed similar setups at my cabin, in my snowcat, and at my brothers yurt in Idaho.. Add the temperature sensor to the charge controller so batteries are charged adequately in cold temps….and if you add an inverter to the system be sure to add a switch on the input side (12 or 24v dc) ..when not in use turn the input power off because the inverter will draw a small ammount of power even when no AC load is connected…..this will help keep batteries charged in winter when sunlight is at lowest.

  21. Lou December 19th, 2011 9:53 am

    Great tips Chris! I made that mistake with the inverter in our camper, wired it in real nice and a couple days later the camper battery was drained even though the inverter was turned off. Bogus, but once you know you can put in the switch. Do have the temperature sensor for the controller. From your experience, how concerned do I need to be about hydrogen? The battery enclosure has a vent at the top, but it tends to draft in rather than out sometimes due to the dynamics of the building…

  22. Scott Nelson December 19th, 2011 10:19 am

    Yikes, those batteries are huge. Did you install a block and tackle to maneouver those things around?

  23. chris blatter aka silvertonslim December 19th, 2011 10:29 am

    I would certainly pay attention to the battery off gas. If the batteries are mounted in the portahut I would build a box (or use one of the plastic tubs with a snap on lid) and run a 1/4″ vent line to the outside. It is not likely but if the batteries ever got overcharged and or damaged (like heating them uo next to a wood stove…grin) they just might discharge hydrogen gas. Colorado state electrical inspector would make you vent outside if you were trying to get a permit in a cabin or such. Jeez I wish I’d known you needed batteries……I just traded (6) 2vdc Solar Star sealed batteries for some shitty welding work…cheers

  24. Lou December 19th, 2011 10:35 am

    Hi Chris, they’re in a sealed box with a 1 1/2 inch ABS plumbing pipe vent to daylight. Probably overkill? Problem is, I get cold air from the vent… tricky.

    Thing about those batteries is they are very cost effective, and worth the tiny bit of hassle with venting, at least that’s my theory. I got the pair for $250.00, which if they have the claimed 7 years of life left was a good deal.

    The whole project cost us more than I expected, due to building materials being so dear — saving a bit of coin here and there is important so long as it’s not a penny wise and a pound foolish…

  25. chris blatter aka silvertonslim December 19th, 2011 11:02 am

    Reduce the 1 1/2″ to 1/2″ at the box…then run 1/2″ pipe outside…that will help with the cold air…if the batteries “burp” it will be with some positive pressure (maybe up to 1 psig = 27″ water column)… and this pressure will get the bad gas out the vent.


  26. Lou December 19th, 2011 6:51 pm

    Chris, do you mean run _another_ 1/2″ vent in addition to what I’ve got?

  27. chris blatter aka silvertonslim December 20th, 2011 10:28 am

    Lou- No, add a reducing bushing to neck the 1 1/2 down to 1/2″ or even 3/8″. This would reduce the cold air flow coming from outside back into the portahut.

  28. Michael Pike December 20th, 2011 8:41 pm

    My appologies for the battery missinformation. From the top those Trojans look similar and I tend to think in terms of truck camper sizing. Should of known you’d be going big! Looks like a great setup.

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