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  • Upgrading a small system in phases to avoid huge lump sum costs...

    Was curious to see if the 'phased upgrade' process below seems OK to some of you who have done it all.

    This is for an existing small system for an off grid cabin, which has been working fine for 6-7 years and is basically powering tiny loads for weekends - laptop, lights, LCD TV, a couple other small odds and ends.

    I'd like to get the span of power coverage up a bit - enough to cover 3 or 4 days without needing to fire up the generator, and also expanded such that I can also run a few larger appliances for longer...but to buy my 'dream system' for this is just too much cash at once. To avoid having bits and pieces appear and languish in the shed until everything is acquired I thought I might upgrade in phases.

    Anyone see any egregious issues? Or tips a mostly-noob like me might benefit from?



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    Current system: 2 x 140w Kyocera panels, 12v Morningstar 30amp PWM charge controller, Xantrex 12v 2000w inverter, Xantrex 12v battery charger, 4 x huge Dyno 12v deep cycle lead/acid batts (wired 12v - but almost end-of-life), and a Honda EU 2000 genset.

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    The Plan:
    ---

    Phase 1: Get 4 x 300w new solar panels, using 24v wiring, w/good quality/expandable MPPT charge controller to hook into existing system, charging existing batteries along with the PWM and old panels. System remains 12v for now.

    Phase 2: Get 4 x 6v new AGM batteries, wired in 12v to begin with, to take over for the existing old 12v battery bank. Other 12v hardware remains in service. Also, get a battery desulphator, and a bogart battery monitor/shunt, so the new battery bank will have monitoring capabilities from the start.

    Phase 2A: After new AGM batts installed, use desulphator and TLC to determine if any of the existing 12v Dyno batts still have an effective life in them, then wire up a separate 12v system using the old 2 x 140w Kyocera panels, Morningstar PWM charge controller, and surviving Dynos for a dedicated 12v system for treehouse lights/radio/laptop.

    Phase 3: Purchase a new 24v/3000w Inverter/charger, rewire the 6v/AGM batts from 12v to 24v.

    Phase 3A: 1 or 2 paychecks after the above, acquire another 4 6v batts soon so as to have better storage capacity.

    Phase 4: Purchase a new Honda EU3000w genset. (EU2000 relegated to emergency backup and/or for occasional portable use)

  • #2
    Issues I see:

    "Get 4 x 6v new AGM batteries" - why AGM? More expensive per kwhr. Flooded cells are a lot more robust (and cheaper.)

    "After new AGM batts installed, use desulphator and TLC to determine if any of the existing 12v Dyno batts still have an effective life in them" - this almost never works but if it's going into a "treehouse" that doesn't matter too much, I guess it's not a big concern.

    "acquire another 4 6v batts soon so as to have better storage capacity." - also worrisome. Again, I'd consider flooded cells - and take the money you save to purchase everything at once.

    Comment


    • #3
      You cannot do it in increments at least not with batteries. AGM long term cost are 400% more than FLA. AGM's cost twice as much and only last half as long as FLA. With each upgrade requires total battery replacement.

      Now if you are informed you can buy say a 80-Amp MPPT Controller. and use strictly 200 or 250 watt panels to grow with. If you start at 12 volt battery your limit is 1000 watts. Once your go above 1000 watts you must make the move to 24 volts which allow you to grow to 2000 watts. Once you cross 2000 watts requires 48 volt. Each time you grow is new batteries and possibly a new Inverter.
      MSEE, PE

      Comment


      • #4
        You mention running "a few larger appliances" , like always the exact load(s) will dictate what your system needs to be, and if it is summer only, or any winter usage and the solar isolation for that location.
        It is possible to do it in stages as long as it is very well thought out, and probably want to be careful with new batteries until you are ready for that phase that they can stay in and be matched properly to the charging rate and load draws.
        Last edited by LETitROLL; 03-14-2017, 09:17 PM.

        Comment


        • #5
          The 3Kw inverter troubles me. You have a generator to use for the big loads. The large inverter has a large standby loss, just sitting there keeping the FET's warm, A smaller inverter has lower losses.

          Your Loads determine the size of the system. Or else you over /under build the setup.
          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

          Comment


          • #6
            Thanks for the responses!

            I had been thinking AGM mainly because of the maint-free aspect. I knew they were more expensive then lead/acid, but didn't realize the premium was 400% over the life of the batteries, so I'll dig in some more on that side of the research and possibly reevaluate. Maint free is nice, unfortunately when i am at the cabin I tend to want to recreate and relax rather then check distilled water fill level, check specific gravity, decide if its time for an equalization charge, or things of that nature...so a lot of the wear and tear on the existing batteries is because of the 'abuse of neglect'. But 400%....hmmm...

            I have read that batteries generally should be installed/replaced in one large lot at once, but had been thinking if the period between when a new/replacement lot of 6Vs was put in and wired 12v to maintain compatibility with the old 12v inverter, and when a new 24v inverter was acquired such that the new 6Vs could be rewired to 24v (likely supplemented by a second set of 4 at or near the same time) was kept to a minimum - say just a few months - then the impact wouldn't be as bad.

            Other then the existing load of laptop/monitor/lights, I do have an upright-style freezer using an external thermostat to keep it at refrigerator temps instead of deep freeze, so thats the main additional load I would like to have running constantly during a 3 or 4 day visit.

            Regarding a 3000w inverter - I don't really run anything at the moment that goes any where near that, occasionally some corded AC power tools such as a circular saw, but you are right...99/100 when I do that I have them plugged directly in to the generator AC outlets anyway. That being the case, do i really need 3000w? hmmm.

            Just the kind of posts that get me to research a bit more on the key topics.

            Comment


            • #7
              Research the option of a Propane refrigerator or DC refrigerator, the up front cost is usually still less then the cost of additional upgrades to make sure a solar off grid setup is large enough to handle the AC appliance, and the long term cost savings are usually quite large due to a much smaller battery bank (where most of the money goes long term) . Also in your case it may make it easier to stomach the higher cost of AGM or Lithium to get the low maint. you desire from your battery bank. The smaller the battery bank the smaller the premium in real dollars for that benefit. In other words, even though it may be near 400% higher, with a small inexpensive battery bank that may only be 100-200 per year over time additional, with a large battery bank you will have to choose between much higher monetary losses, or staying with the burden of maintenance.

              Comment


              • #8
                Originally posted by rainyweather View Post
                I had been thinking AGM mainly because of the maint-free aspect.
                Well, you can treat flooded batteries as maintenance-free too; just throw them out when the water gets low. (That's what you have to do with AGM's.) Or add water and extend their life - something you can't do with AGM's.

                I have read that batteries generally should be installed/replaced in one large lot at once, but had been thinking if the period between when a new/replacement lot of 6Vs was put in and wired 12v to maintain compatibility with the old 12v inverter, and when a new 24v inverter was acquired such that the new 6Vs could be rewired to 24v (likely supplemented by a second set of 4 at or near the same time) was kept to a minimum - say just a few months - then the impact wouldn't be as bad.
                The problem is that the "good" string will take most of the load, and the "old" string won't see full charges, thus aging it faster. The one exception to this is long floats - so if you can float your batteries for days at a time (i.e. zero load at a cabin) you may avoid some of that, since a long float will tend to charge even older batteries if you give them long enough. But you'll still have the "good string taking most of the load" problem.

                Regarding a 3000w inverter - I don't really run anything at the moment that goes any where near that, occasionally some corded AC power tools such as a circular saw, but you are right...99/100 when I do that I have them plugged directly in to the generator AC outlets anyway. That being the case, do i really need 3000w?
                Consider something like a 1000 watt Prosine or even a 300 watt Suresine. Both will surge to far more than that to start motors.

                Comment


                • #9
                  There are many reports of the 300w suresine being unable to handle the starting surge of a fridge motor. It likely can do other motors in small steps, but not a compressor
                  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

                  Comment

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