X
  • Filter
  • Time
  • Show
Clear All
new posts

  • In search of Best BAng for the Buck...

    Hi, I'm Lance from the Ozark Hills of Southwest Missouri, where we average 4.73 hours of solar insolation a day...

    I'm going to slowly build a home and live on-site in a mobile for the next several years, and can't/don't want to hook to the grid just yet. Right now I have a 2000w generator & two(2) GLC115 230ah 6v in service @12v. I don't yet have appliances other than LED TV, Blu-Ray, & laptop; and plan to use a propane stove, propane hot water, and wood heat. Refrigeration is undecided but probably a converted chest-type freezer. I'm going to have to start small on the solar system and upgrade along the way, so my goal is to get as much solar electricity as I can for my money. Rather than build to a certain watts/day goal, my thought is that I can add more creature comforts as the electricity to run them become available. I also think it's probably more economical to just fire up the generator during periods of lots of electrical use, like power tools, etc, rather than buying a large enough solar system to run them.

    Because it's a bad idea to mix new and old batteries and I already have 2 in service at 12v, I'm going to stick with 12v until these need replaced and then upgrade to 24v. If I understand correctly, it's best to charge batteries at 10-13% current, so my 230ah batt should be charged with 23-30a, which means I need 331-432w to charge these batteries with enough current to keep them mixed and not require charging off the generator (23ax14.4v=331w, 30ax14.4v=432w). I'm not entirely clear if this means I need a 30a charge controller to avoid sending too many amps to the battery, or if it means I need at least a 40a charge controller to handle the watts required before losses and have some overhead for usage while charging? If the 40a, do I need to limit amperage to the battery somehow, or will the battery simply not pull more than 30a?

    The best values in charge controllers seems to be at the 40a point, costing only $20 more than 30a controllers and hundreds less than 60a controllers (looking at EPever/EPsolar, which seems to be a decent brand of genuine mppt at a value price). Now I want to get the most out of every piece of equipment I buy, but this is a balance between maximum output and long life. The EPever Tracer4210 is rated 520w@12v, 1040w@24v and claims to be able to handle 300% more PV than that, but will clip production to no more than the rated watts. This means it can handle over-dimensioning, but only charges the battery at mpp if the panels are producing less than 520w. If the panels actually produce more than that, the excess is clipped to maintain the rated watts. And because STC rarely if ever occur in the real world, this means I need more than the rated watts of pv to full utilize the capabilities of the controller. But how much more? I see 75% thrown around as a downrating for real world conditions, so perhaps 690w STC generates about an actual 520w? If so, that would be the max pv to avoid any clipping, but when designing for maximum value it seems like some clipping would be desireable. But how can I determine how much? Perhaps I can maximize my power produced per dollar spent by going with 800 or 900w (rated STC) of panels into this controller? Anybody know where I can find more info on over-dimensioning calculations?

    Sanity check. If I produce an actual 520w with about 4hrs solar insolation/day, that is 2080wh/day actual production. That might work for most days, but seems likely I will need more with refrigeration. So my longer term plan would be to double this by eventually going 24v on the same controller and doubling the number of panels, if my actual usage on the 12v system indicates I need to. Thoughts?

  • #2
    How much do you want to spend, before you hook to the grid ? Why build a large comfortable system, and then connect to the grid making it obsolete ?
    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


    • #3
      I wonder if the OP knows what the cost in toil and treasure of off grid electricity. If it was me, I'd take my best shot at electrical service requirements at buildout, add 20-30% to it for goofs/giggles/feel good and run power now. Might make the build easier as well.

      Comment


      • #4
        Any plans to eventually hook to the grid will be due to growing electrical requirements. Right now I live alone and don't require much electricity. If down the road I have a larger house, pool, and entertain there, then hooking to the grid to use as a battery may make more sense. There seems to be a point below which off-grid solar is actually cheaper and above which grid-tie is cheaper. But at no point will the solar panels be unused.

        I don't want to spend more than $1000 on solar equipment right now, and another $1000 when I upgrade to 24v. I think it can be done with a controller under $200 and about $500 in panels from SEP that I will pickup and install myself, but I won't be surprised if I go a little over budget. I'll run better numbers once I determine if I have to stick with a 30a controller to limit current to the battery and how much pv I can most efficiently run through a single controller.... Any thoughts on the over-dimensioning or whether a 40a controller will be ok when I don't want to charge the battery at more than 30a?

        Comment


        • #5
          Originally posted by SupraLance View Post
          Any plans to eventually hook to the grid will be due to growing electrical requirements. Right now I live alone and don't require much electricity. If down the road I have a larger house, pool, and entertain there, then hooking to the grid to use as a battery may make more sense. There seems to be a point below which off-grid solar is actually cheaper and above which grid-tie is cheaper. But at no point will the solar panels be unused.

          I don't want to spend more than $1000 on solar equipment right now, and another $1000 when I upgrade to 24v. I think it can be done with a controller under $200 and about $500 in panels from SEP that I will pickup and install myself, but I won't be surprised if I go a little over budget. I'll run better numbers once I determine if I have to stick with a 30a controller to limit current to the battery and how much pv I can most efficiently run through a single controller.... Any thoughts on the over-dimensioning or whether a 40a controller will be ok when I don't want to charge the battery at more than 30a?
          Before I did any of that, and before I started ordering equipment, I'd get a realistic load size and use profile and PV generation potential, and see/estimate how much of the est. load can be met with an expenditure of $1K (including batteries ?). Not trying to rain on your parade, but consider that you may be underestimating costs, and maybe a bit light on design and understanding solar potential.

          Comment


          • #6
            If you even think you may need to grow into 24V system, just do it now, and not wait till you have to sell off the old 12V inverter to buy a new 24v inverter.
            Wire is cheaper (half the size), and thinner wire pulls easier too. Plan your solar rack and combiner box for future growth, you don't have to stuff them full now, but again,
            to pull the 3 ch Combiner Box, to install a 6ch Box, is a pain. If your loads this year are really light, a pair of 12V 100ah deep cycle batteries from a big box store will only set you back $200 for flooded lead acid batteries that are good for at least 2, maybe 4 years (if you did your sizing math right)
            I'd say get a decent controller that can grow with your system. Most of the better ones, allow you to set a amps limit in software, so you can overpanel a bit for cloudy weather harvesting.
            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


            • #7
              To the OP, do you have an inverter in mind? I did not see that in the opening list, and between a good inverter and batteries would seem you would be very close to your 1k budget long before you got to the panels and Charge controller. I also second the comments above to go 24v (if not 48v) right out of the gate.
              285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

              Comment


              • #8
                New member here
                So new I can't figure out how to post a new topic.
                Looking forward to designing and installing a new solar power system.

                Comment


                • #9
                  Ok, I appreciate the concern. Here are a few numbers that answer those questions, and you guys can point out if I'm missing something. The amount of estimated load I can meet with $1000 is exactly what I'm trying to figure out with the over-dimensioning questions. Is the controller to battery to inverter wiring the only wiring that can be smaller at 24v then 12v? And how much actual cost difference are we talking if those are all close together? I really don't know how to estimate wiring costs just yet.

                  My estimated costs to get producing at 12v:
                  $0 ................230ah@12v (2xglc115) batteries, already have
                  $140-$190 ....Epever 4210a or 4215bn 40a controller ($190 4215bn has 150w Voc limit)
                  $300-$450 ....600-900w of pv from SEP
                  ....................(depends how much the controller can optimally be over-dimensioned, with actual production limited to 520w by controller)
                  $110-160.......Wagan Elite 2601 400w OR 2602 700w psw inverter (refrigeration will be 12v cooler in car, not ran off solar, until I go 24v)
                  $300 ............wiring, mounting hardware, fuses, etc (boxes would be sized for twice the pv being installed now)
                  =$850-$1100

                  Costs when upgrading to 24v later:
                  $450 ............4x 230ah 6v (I have 2 now, but not good to mix old/new)
                  $0 ...............same controller
                  $300-$450 ....600-900w of pv
                  $300 ............1000w psw inverter
                  $200 ............wiring/mounting hardware for 2-4 additional panels into existing boxes
                  =$1250-1400
                  total invested after upgrade to 24v = $2100-$2500

                  Cost to go 24v now:
                  $450 ...........4x 230ah 6v (I have 2 now, but not good to mix old/new)
                  $140-$190 ...Epever 4210a or 4215bn 40a controller ($189 4215bn has 150w Voc limit)
                  $600-$900 ...1200-1800w of pv from SEP (for 1040w actual production over-dimensioned)
                  $300 ...........1000w psw inverter
                  $450 ...........wiring, mounting hardware, fuses, etc
                  =$1950-$2300
                  So it looks like I only save about $150-$200 by jumping straight to 24v (and this is mostly the inverter, which I will keep for car-camping), and I waste the batteries already in use @12v. There might be stuff I'm not seeing, like more $$ in wiring savings? How much?

                  Of course my biggest question is still just how much pv to buy to get the most out of my $1000 system with over-dimensioning of the controller... I'd like to buy pv right away because I'm concerned the tariff is going to raise the prices here in the USA, but I'm not sure how much I should overpanel the controller.
                  Last edited by SupraLance; 02-11-2018, 11:59 PM.

                  Comment


                  • #10
                    To be able really take a shot at your needs, we need to see projected load calculations in Watt Hours per day. That is how many Watts total from all devices you anticipate to need to power And also how many days of autonomy you plan to build into the system. You need either 1.) 2-3 days of autonomy (so that would be daily Watt Hours x the number of days = total need) Or a generator to off set those days when you have no sun or grid power or charging. Batteries do not like to sit around under charged for very long.
                    285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

                    Comment


                    • #11
                      Matrix, just assume my load predictions are over the amount of solar I can afford right now, and I'm trying to run the generator less by charging the 230ah@12v battery bank I already have with solar, and won't have trouble using any extra but can only spend about $1000.

                      As of right now, the following options are the best I've found and I would appreciate opinions and/or better options:

                      620w (clipped at 520w at controller when pv actual production exceeds that):
                      $140 ....EPever 4210a 40a mppt (can only run pv in parallel or exceed mpp range)
                      $440 ....two(2) Trina 310w 72cell 61lb panels including $150 shipping from SEP batteries
                      $110 ....Wagan Elite 2601 400w inverter
                      $60 ......wiring/breakers
                      =$750 plus mounting costs for 620w

                      OR 690w (clipped at 520w at controller when pv actual production exceeds that):
                      $190 ....EPever 4215bn 40a mppt
                      $456 ....three(3) EcoSolargy 230w 60cell 42lb panels including $150 shipping from SEP batteries
                      $110 ....Wagan Elite 2601 400w inverter
                      $72 ......wiring/breakers
                      =$828 plus mounting costs for 690w ($28 for 70w, $50 for more robust controller)

                      The EcoSolargy panels are cheaper per watt, but I'm concerned that they are likely to be older stock, and perhaps not as good as Trina panels. Do pv warranties go from date of manufacture? For instance, if I buy panels that have sat in a warehouse unused for 8 years, with a 25 year warranty, do they only actually have 18 years left on warranty?
                      Last edited by SupraLance; 02-16-2018, 02:11 PM.

                      Comment


                      • #12
                        Hey all - new here and I am embarrassed to hijack the thread but I cannot create a new post! I seem to be only able to reply to existing posts. Anyone know how to create a new post? (yes, I feel stupid but I can't figure this out!)

                        Cheers,
                        Dan

                        Comment


                        • #13
                          Originally posted by dstroot View Post
                          Hey all - new here and I am embarrassed to hijack the thread but I cannot create a new post! I seem to be only able to reply to existing posts. Anyone know how to create a new post? (yes, I feel stupid but I can't figure this out!)

                          Cheers,
                          Dan
                          I'm a low level mod, and cannot upgrade you, split a thread, but I can approve your posts
                          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


                          • #14
                            Originally posted by Mike90250 View Post

                            I'm a low level mod, and cannot upgrade you, split a thread, but I can approve your posts
                            Thanks Mike! So reading between the lines I am hearing that I can't create posts because I lack privileges and I need an upgrade?

                            Cheers!

                            Comment


                            • #15
                              Originally posted by dstroot View Post

                              Thanks Mike! So reading between the lines I am hearing that I can't create posts because I lack privileges and I need an upgrade?

                              Cheers!
                              Unless things have changed, you can post a new topic or start a thread.

                              --->>>Solar Panel Talk --->>>Forums --->>> pick a forum that covers the area that seems to cover what you want to discuss click on it --->>> click on button that says "new topic" --->>> start typing.

                              Not an immediately apparent path, and as a computer Luddite, I take the admin. to task for that. But on the user side, some user input and daring to try new stuff and root around is probably reasonable to expect.

                              Comment

                              Working...
                              X