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  • Off grid cottage questions ..

    Done some reading, done lots of research in the last 6 months, I don't consider myself a newbie, but I have some basic requirements, nothing extreme, so I'm hoping you can give me a kick in the right direction

    Last May, I got a cottage that is off grid. The owner had a primitive, and hastily wired system, using extension cords and some other electrical wire, connected to light socket, with 12V incandescent bulbs. He brought in his battery booster pack, and plugged in the cigarette lighter plug, and that was his light for a weekend. all cooking is propane, fridge was propane, even propane lanterns are still hooked up on the wall. No tv, or fancy electronics for him.

    - I ripped all this out, keeping the sockets, and bought a bunch more.
    - I looked for a good deal on stranded wire, and really couldn't find much affordable at the time, so I went with 14 gauge speaker wire, with the intent of hooking it up, figuring out what lights and plugs I wanted where, and eventually replace the cable with proper in-wall cabling when the time came
    - I got 2 deep cycle batteries from Costco, 120ah each, connected in parallel. (12V @ 240ah)
    - installed a single 100 W coleman solar panel
    - I used standard household light switches, which I plan to replace
    - a 12 V battery disconnect switch from princess auto
    - an 8 way fuse block holder with the red LED to indicate a blown fuse
    - coleman 30A charge controller
    - 1100 Watt KRUIGER inverter .... never had to use it, but will be for popcorn, or make a fast coffee with microwave

    I also purchased a Honda Companion 2000 watt generator, which I didn't have to use once last summer. I used it more to charge my Milwaukee batteries for lanterns and power tools.

    I visit my cottage on weekends, sometimes only every other week.

    LOADS: I have a total of eight (8) X 9 watt 12 V LED light bulbs. They are never all left on, but have done so a couple of times just to try it out...We run 2 CPAP's at night. I have a couple of USB charge stations. I may add another 2 bulbs this year. No TV, no satellite. The outhouse has it's own independent system, with a single 12V battery I pulled out of a DSL high speed modem, which is 9ah, and a single 9W LED bulb, the battery has a 2.5W panel on it, and lasted all summer no issues.

    I have never ran out of power in the cottage. The voltage is around 12.5 by end of sunny day, sometimes as low as 12.3 and holds all night with the CPAP on. (using the 12V cable) My stays last 3 nights on average. I do expect to be there a week maybe this summer. My biggest hurdle last year was refrigeration. I have a propane fridge, and a propane cooler, They have to be lit when I arrive,and turned off when I go, food has to be brought and taken... And propane isn't cheap.

    I found "in-wall" speaker wire, which has a CSA approval, at Canadian Tire for $40. I'm considering replacing the original speaker wire with this, if I stay with a DC system....

    I'd like to get a DC fridge - they are $1300. Was going to upgrade to a 335W panel, with an MPPT controller ($500 more) so with taxes that's about $2,000 more.

    Alternatively buy 2 more 100 Watt Colemans, for a total of 300W of panels - Total $400 with taxes for 2 moe panels. I also expect to buy 2 more batteries identical to the ones I have now, so I'd have 4 X 12V 120ah batteries Then I still need the fridge, but avoid having to replace the charge controller.

    And of course I toyed with the idea of putting 2 of those batteries in series, and run the fridge off the 24V setup and leave the original setup as is.

    Until I realized maybe, maybe I should think outside the box, and buy 2 X 335 watt panels, with the MPPT controller, an inverter and a household style fridge. The fridge is only $600 that way., and spend the money on the panels...or just go the whole 9 yards, rewire it with solid core, and invert all my power and go AC.

    The math tells me I should go AC setup.....

    So I'm really struggling with the best way to attack this. just to have a fridge. my requirements should not exceed anything more than basic lights, charging, and cpaps.... I simply want to add a fridge and not have it kill the system when I'm not there.

    Sorry this was long, but want to get all the details out... Hope it made sense and hope you guys can offer some input!.

  • #2
    Figure out exactly what your loads are. I don't mean "about this and about that much" I mean figure out what you're running and how many hours a day.

    Fridges are pigs. Straight up. You're probably looking at 700 Watt hours a day for one (but pick a model and try to figure out exactly what it'll need, then add 20%)

    If you go the AC route, then you are looking at leaving your inverter on 24 hours a day, so there are significant losses from leaving it on. Inverters have specs listed to tell you their losses, usually in the 15-25 Watts an hour x24 hours means 360-600 watt hours per day.

    So for the fridge you're looking at

    1.2kWh/day (ish) for the fridge. Now, if you go that route, switching your lights to AC isn't a bad idea. Just add your lighting loads to the running total, along with CPAP machines


    Now, take your total number of watt hours and DIVIDE by 0.8 to account for inverter efficiency.

    Starting to get to a fairly big number.

    So now figure out how much solar power you can harvest. Where are you located? Can you mount panels facing the sun?

    Am MPPT charge controller will definitely be the way to go, along with 300+W panels.

    Once you get the loads figured then we can talk batteries.
    Last edited by Xplode; 03-30-2019, 04:52 PM. Reason: Said multiply but meant to say divide

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    • #3
      Why not use #12 house wiring, that is cheap enough. I use a chest freezer converted to a fridge. Never get anything less than 7cf. Condensation is a real problem. You need at least double the panels. Buy more panels not batteries. I can run my fridge even on a rainy day. I don't believe in storing your way out of a problem. With any excess power I make hot water, hot showers are nice. Just to show what can be done, I even have a dishwasher with heated dry with only a car battery. Don't try this at home.

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      • #4
        Originally posted by Xplode View Post
        Now, take your total number of watt hours and multiply by 0.8 to account for inverter efficiency.
        You sure you want to multiply by 0.8 and not divide by 0.8 ?

        Taking a 0.8 inverter efficiency into account would require dividing the load by 0.8. Makes a big difference.

        Multiplying by the load by 0.8 makes the load 20 % smaller. Dividing by 0.8 makes the load 25 % larger.

        Comment


        • #5
          Originally posted by J.P.M. View Post

          You sure you want to multiply by 0.8 and not divide by 0.8 ?

          Taking a 0.8 inverter efficiency into account would require dividing the load by 0.8. Makes a big difference.

          Multiplying by the load by 0.8 makes the load 20 % smaller. Dividing by 0.8 makes the load 25 % larger.
          Yes. Posting before morning coffee was applied. I will edit the original post. Thank you.

          Comment


          • #6
            Originally posted by Xplode View Post

            Yes. Posting before morning coffee was applied. I will edit the original post. Thank you.
            You're welcome. My post was motivated more by empathy than criticism.

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            • #7
              Thanks for the replies....

              My cottage faces due east, and is on the water, the second the sun comes up across the lake it's pounding on my cottage. the panel I currently have is on the roof, and is pointed south east with an approximate 35 degree incline. From about 9:30 till 1:30 she is putting 5-6 amps into the batteries, and another 2 amps an hour for several hours before and after that peak time... I'd have to guess I get ~40 amps of charging a day.

              The bulbs are .75 amps each. Ran from 8PM till 11/12PM upon arrival in the evening. I would say 5 run at any given time. Let's just say 5 amps of LED's per hour, 4 hours = 20AMPS of lighting per night max.
              2 X Phone charger 2.1AMP for 3 hours per day. 12 Amps.
              I have a 12V ceiling fan, and it's .5A draw, and it runs maybe 12 hours a day. Another 6A/
              No heaters on the cpap. Last summer only ran one of them, this summer there will be 2 going. 2.5A X 7, round up to 20A. X 2 = 40A.

              This is a maximum scenario. I don't use 5 bulbs at a time, it's often just 2. I often use a portable USB charger for the phones, and I don't always have the fan on either.

              So in total, 20 + 12 + 5 + 20 (57 amp hours, and was an average last summer, and I'll need 75 amp hours this year.

              With one cpap going, I'm short 20 amp hours a day as is. So 2 nights here, I've used 40 more amp hours than I can create. And if the wife is there, it will be short 40am hours per day. The system can handle that as is, but probably not for more than 4 days. Then I go home, and it gets fully recharged a day later.

              Regardless what I do about the fridge, I definitely need to add at least 100 watts more as my current system stands.

              Now to add a DC fridge,which is available at my local Solar reseller, and also at Costco, brand name is Unique...

              Regardless what I do about the fridge, I definitely need to add at least 100 watts more as my current system stands.

              Now to add a DC fridge,which is available at my local Solar reseller, and also at Costco, brand name is Unique...

              Size: total: 9.0 cu./ft.
              DC Power: 12V/24V
              Total Watt HR. draw (24V DC): 572 Wh/24 hrs
              Total Amp. HR Draw (24V DC)24 Ah/24 hrs
              Power consumption: 56 W on 12V/24V
              Avg. run current: 4.5 A on 12V - 2.5 A on 24V
              Fridge temp. range: -4C to +10C

              To PNPmacnab - wouldn't #12 house wire be solid core? I need stranded if I stick with the DC scenario??

              I've read reviews and testaments about this fridge and it seems 200 watts and 2 batteries should run it 24/7.

              so my dilemma is back down to adding another 200 watts to my current system 2 batteries, and a DC fridge, or switch to a 335 (or 2) watt panel with mppt, extra batteries, or spend the money on extra panels, an inverter, and a small household fridge (7-9 cubic, I haven't looked at any single one in particular)

              Hope somebody has a suggestion now.
              Last edited by bglassford; 03-31-2019, 12:09 AM.

              Comment


              • #8
                Stranded wire is flexible and resists vibration. Solid wire is stiffer and will break with vibration. Both are usable for AC or DC, staying within the insulation voltage limits.

                For DC wiring, I don't like speaker wire, it's not rated for it, and the insulation often goes bad over time (sticky or brittle). DC garden lighting cable is rated for outdoor use and usually burial in ground and is heavy enough to work OK. And it's often zip cord type.
                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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                • #9
                  Originally posted by Mike90250 View Post
                  Stranded wire is flexible and resists vibration. Solid wire is stiffer and will break with vibration. Both are usable for AC or DC, staying within the insulation voltage limits.

                  For DC wiring, I don't like speaker wire, it's not rated for it, and the insulation often goes bad over time (sticky or brittle). DC garden lighting cable is rated for outdoor use and usually burial in ground and is heavy enough to work OK. And it's often zip cord type.
                  Good suggestion on the garden wire. I was looking at 12 gauge extension cords at costco, 100 feet for $39.99. Was thinking this would be a good solution, the in-wall speaker wire I had mentioned is CSA rated for "in wall" use, so it should have proper insulating value.. The speaker wire I used thus far was proof of concept, and learning, allowing me to cut, and waste without caring too much, but definitely plan to replace ASAP. IT was my understanding the DC voltage travels in the outer strands of the stranded wire much more efficiently than it does with solid wire.


                  One MAJOR consideration I forgot to mention guys, and it's not my expertise at all...

                  I have, within about 100 feet of my cottage, a natural spring that runs year round.... it has ran since my dad was a kid, so it's no risk of drying up soon. I've estimated the head to be about 100 feet higher. I have looked at a few hydro turbine solutions, but haven't found one affordable enough.... I do not know the flow yet, never considered using the spring until the middle of winter. The local solar place told me $2,000 just for a turbine. This put me off immediately for the complexities involved... If there are cheaper options to use the spring, I'd be seriously considering this instead, and my fathers cottage is only 50 feet from the spring. Could possibly power both cottages *IF* we took this option.

                  Comment


                  • #10
                    Originally posted by bglassford View Post

                    Good suggestion on the garden wire. I was looking at 12 gauge extension cords at costco, 100 feet for $39.99. Was thinking this would be a good solution, the in-wall speaker wire I had mentioned is CSA rated for "in wall" use, so it should have proper insulating value.. The speaker wire I used thus far was proof of concept, and learning, allowing me to cut, and waste without caring too much, but definitely plan to replace ASAP. IT was my understanding the DC voltage travels in the outer strands of the stranded wire much more efficiently than it does with solid wire.


                    One MAJOR consideration I forgot to mention guys, and it's not my expertise at all...

                    I have, within about 100 feet of my cottage, a natural spring that runs year round.... it has ran since my dad was a kid, so it's no risk of drying up soon. I've estimated the head to be about 100 feet higher. I have looked at a few hydro turbine solutions, but haven't found one affordable enough.... I do not know the flow yet, never considered using the spring until the middle of winter. The local solar place told me $2,000 just for a turbine. This put me off immediately for the complexities involved... If there are cheaper options to use the spring, I'd be seriously considering this instead, and my fathers cottage is only 50 feet from the spring. Could possibly power both cottages *IF* we took this option.
                    You'll also need some idea of the flowrate of the water source. Potential turbine output = f(mass flow rate * head). One without the other doesn't work.

                    Some other possible considerations: Construction cost of getting the flow down to the level of the turbine - pipe, penstocks, trash screens, any necessary site modifications, permitting/Environment Canada compliance/concerns, controls, energy storage either by ponding or batteries, etc. The cost of the turbine will not be the only/largest expense. Big energy needs and a lot of potential might make a turbine and associated equipment worth it. Small loads and low potential turbine output usually makes it hard to get something worth the trouble and cost effective.

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