Need advice on small system

machineman
machineman Solar Expert Posts: 129 ✭✭✭
I'm looking to build a small starter system for my off-grid cabin to run a few light lights at night. Maybe 0.3Kwh/day. I also want to use a single 190w 24V solar panel (possibly an evergreen) so I can add more later when upgrading to a larger system. I also plan to get a couple 12V AGM batterys in series to make 24V and approx 34ah. 1 Day of autonomy is fine.

What cheap but quailty charge controller do you recommend for a 24V system?
Xantrex C35 controller ($100) or get more efficient morningstar MPPT 15A MPPT ($235)
When they spec the charge cortollers at 24V does that mean 24V in and 24V out?

How about a quite inverter that is about 300W+ for 24V system? The AC will be hardwired to it.

Thanks.

Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Need advice on small system

    A couple of thoughts,

    First, don't scrimp on the controller. You WILL want to expand the system, because once you get used to 24/7 power you will find all kinds of uses for it.

    Second, Why 24vdc? With a good mppt controller you can run your panels at 24vdc (or 48vdc for that matter) and still charge into 12vdc. There are of course advantages to 24vdc systems, mostly due to wire sizes and controller efficiency, but the advantage of 12vdc is the availabitly of 12vdc hardware, including lights, radios, phone charges, pumps, fridge controllers etc.

    Third try to think as much of this all through as much as you can. Try to define your loads, and then come up with a battery bank that will run those loads, along with a generator charging system to keep the battery up when there is no sun. (A generator is much cheaper net/net for topping up and eq charging if your panels can't quite keep up. My guess is you will have a generator on site for tools anyway). You can always add panels to a system, but it is much harder to add batteries to an existing string.

    I am very happy with my morningstar ts300 inverter. 300 watts, pure sine wave, very efficient. As for controllers, (most but not all) MPPT controllers will accept higher voltage inputs, and give you 12 or 24 or 48 vdc outputs. As I said above, I strongly suggest that you spend some time reading about controllers, and spend the extra money now, because you WILL spend it later. (I have 3 charge controllers that have been retired,,,I still haven't learned the lesson,,,I would like to get a mx 60 and then add to my panels).

    Good luck,

    Tony
  • machineman
    machineman Solar Expert Posts: 129 ✭✭✭
    Re: Need advice on small system
    icarus wrote: »
    A couple of thoughts,

    First, don't scrimp on the controller. You WILL want to expand the system, because once you get used to 24/7 power you will find all kinds of uses for it.

    Second, Why 24vdc? With a good mppt controller you can run your panels at 24vdc (or 48vdc for that matter) and still charge into 12vdc. There are of course advantages to 24vdc systems, mostly due to wire sizes and controller efficiency, but the advantage of 12vdc is the availabitly of 12vdc hardware, including lights, radios, phone charges, pumps, fridge controllers etc.

    Tony

    I can only afford one panel for now and the 24V panel will still work with my larger system down the road. My plan was to get something simple and then later upgrade the charge controller, inverter, batteries to someing much larger, perhaps a XW system. I do have a back up generator if needed. Just need a few lights for night time and maybe oocasionaly charge a cordless drill battery. The inverter will be wired to my AC panel so I can use the existing wall switches.

    If I get a high dollar XW60 MPPT controller will it work with such a low wattage system?

    Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Need advice on small system

    A couple more ideas,

    When you plug the inverter into your breaker system, you will need a transfer switch to prevent back feeding a generator or the inverter. See the IOTA on the NWAS site, works great, never have to think about it.

    You are right, that controller efficiency will drop somewhat with a small system with a bigger controller, but IMHO the money spent now, plus some extra generator fuel until you upgrade will more than be offset by not needing a bigger controller later on. That, and being able to run the system with a 24 vdc panel with a 12vdc battery bank.


    I'm sure others will chime in with their opinions of 12vdc vs 24 vdc.

    As I said in the previous post, the availabilty of 12vdc hardware makes using 12vdc good sense in your case, IMO.

    Also as I stated before, your loads will grow with time. We live off grid with 210 watts of panel, using ~4-500watt/hr/day for lighting, water pumping radio, modem, misc charging. Before we added the water pumping it was 350-400.

    Good luck,

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on small system

    just an observation here. you are starting with a small system and later expanding to a system with the xw so go with the cheap batteries like at walmart or costco and make your mistakes if any on the cheap ones. the ah on them will be higher than you initially planned, but thats ok. you can still get a small sinewave inverter and have it as a spare if you get a larger capacity inverter down the road
  • machineman
    machineman Solar Expert Posts: 129 ✭✭✭
    Re: Need advice on small system
    icarus wrote: »
    A couple more ideas,

    When you plug the inverter into your breaker system, you will need a transfer switch to prevent back feeding a generator or the inverter. See the IOTA on the NWAS site, works great, never have to think about it.

    Tony

    Good point on the transfer switch. Maybe an even cheaper route would be a manual transfer switch.

    Does walmart or Costco have AGM batteries (Safe to keep in a closet)? Would an Optima gel marine deep cycle blue top do the trick?

    All good info. Thanks.

    Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Need advice on small system

    Suggest the following links for battery info: http://www.batteryfaq.org/ http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries http://www.rpc.com.au/products/batteries/car-deepcycle/carfaq4.htm#charge

    You'll learn more than you can imagine about batteries

    T
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Need advice on small system

    > Does walmart or Costco have AGM batteries (Safe to keep in a closet)?
    No

    > Would an Optima gel marine deep cycle blue top do the trick
    Possibly. I've never looked into them. Likely much better than 34AH though. I dont think a 34AH bank could power much of an inverter, for more than a minute or two. The little sealed cells for UPS and power fail lights (common sources of small gell cells) will not last very long at all.

    Mike
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • quid_non
    quid_non Solar Expert Posts: 48
    Re: Need advice on small system

    Good advice on the previous responses...
    Spend the time to better learn what you need, but realize as said above - it will expand, guaranteed!

    I also have a small off-grid system powering my small mountain shack. We make do (now) with ~110W of assorted panels an inexpensive 110AH deep cycle batt and a good charge controller. System is 12V for all the reasons stated above - stuff is easier to find and readily available. We power 2-3 12V CFL's, sat radio, boom box, multiple fans for moving air. No fridge---yet! Do have a Honda EU1000 genset for occasional batt charge and less than often AC needs. Spend the $ on a good battery monitor.

    I intitally bought an inexpensive shunt type controller - after 1 year, I replaced it with the Morningstar SS20L. What a difference it made. Now I wish I would have applied the $ towards a MPPT controller due to the long distance from the panels to the batt.

    Got most of my initial stuff from Northern or Harbor Frieght. After "the need for more power" set in, stores like the sponsor site were very cost effective and very helpful.

    Best
    Wayne
  • machineman
    machineman Solar Expert Posts: 129 ✭✭✭
    Re: Need advice on small system

    Nice. So in summary here's where were at.

    Known
    --Single 24V ~200w panel <$900
    --Charge controller (oversized for later expansion) $250 - $600 Maybe get XW MPPT 60
    --IOTA Transfer switch to prevent generator AC backfeed <$60

    Still researching
    --Inverter, Can be low end to start, replace later for higher capacity. Maybe get cheap invert/charger for when the generator is on?
    --Battery's, Can be low end, Need batterys safe to keep in house. Still looking.

    Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Need advice on small system

    Another note on Inverters,

    Most small inverters cannot wire directly to the building panel. The MorningStar TS 300 is (one) exception. You can wire this inverter to the panel including the proper ground. Most small SW inverters, and all (that I know of) small MSW inverter use a floating neutral. If you wire one into a grounded neutral panel, you will burn it up right now! I speak from experience on this subject, burning up two MSW inverters before I figured out why the first went up in smoke.

    As stated before, I have had very good luck with the Morningstar, wired through the transfer switch. You could conceivably wire two into an ac panel, using each to energize one bus, the other energizing the other bus. That way you could start out with one, energizing both busses, and if the demand required it you could then add the second. (I would have to think about how the transfer switch would work however).

    As for a transfer switch, you can buy a double pole, double pole switch of with proper amperage rating and do it manually. I know over the years I have built systems with multiple generators feeding a line, some 240vac and others 120vac. I was able to get a rotary 3 pole switch rated at ~50amps, that I could wire so that in each position,, whatever generator that was on line would feed both busses in a 240 panel, even though only 120vac was available.

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on small system
    machineman wrote: »
    Does walmart or Costco have AGM batteries (Safe to keep in a closet)? Would an Optima gel marine deep cycle blue top do the trick?

    All good info. Thanks.

    you won't find agms to be cheap compared to other types and gels can be used, but they can still be expensive. you will only be running 2 batteries for 24v (unless you are going 12v and i misunderstood) and 2 standard batteries won't hurt anything. the batteries i had in mind are just over 100ah each and i'm not sure what the prices of them are up to now, but they most likely have smaller capacity as well. when putting 2 of these in series the current will stay the same, but the voltage will double.
  • machineman
    machineman Solar Expert Posts: 129 ✭✭✭
    Re: Need advice on small system
    niel wrote: »
    you won't find agms to be cheap compared to other types and gels can be used, but they can still be expensive. you will only be running 2 batteries for 24v (unless you are going 12v and i misunderstood) and 2 standard batteries won't hurt anything. the batteries i had in mind are just over 100ah each and i'm not sure what the prices of them are up to now, but they most likely have smaller capacity as well. when putting 2 of these in series the current will stay the same, but the voltage will double.

    Which batterys do you have in mind and are they safe for indoor chargeing, possibly <15feet from the pilot light on my water heater.

    Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on small system

    i tried to go to the websites, but they don't list batteries. try checking around your local area and ask for leads on where you can get either the gels or deep cycle batteries and then you can go there and look things over for capacity, type, price, etc. interstate makes some as do many others. many times rv, marina, or automotive businesses will either carry these or possibly know where you can go for them besides the usual walmarts or cosco type stores. of course you can still go with an agm if you want to and both agms and gels are sealed so not acid spillages too. here is the battery page for naws and if you can't find anyplace near you know that the agm and i think the gels too can be ups'ed up to a certain weight. http://store.solar-electric.com/batteries.html explore the batteries there and note the prices so you know somebody local isn't taking you for a ride. i believe naws does not sell gels and both gels and agms must be carefully charged in that the voltage is kept within specs set by the manufacturer.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Need advice on small system

    You can also use a couple of Marine type battery boxes, and use some duct work to vent conventional flooded cells to an exterior wall.

    I think someone built a window bench seat, vented it outdoors, and used that for battery box.

    AGM's are nice, but pretty expensive compared to flooded cell. They do have an edge in efficiency, up from 80% to about 95% when recharging. You do need to be aware the charge voltage is critical to not boiling them dry, no way to replace any lost water.

    Thread about some other battery boxes: http://forum.solar-electric.com/showthread.php?t=3387
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • machineman
    machineman Solar Expert Posts: 129 ✭✭✭
    Re: Need advice on small system

    Here's some AGM battery's

    --Tempest wheelchair battery 12V 75ah for $136. http://www.batteryspec.com/cgi-bin/cart.cgi?action=link&product=140

    --Optima Marin Blue top 12V 75ah for $216 (I can proabbly find this one locally) http://bigtimebattery.com/store/d31m23.html

    I will do some more looking locally. Is 75ah enough?

    I think I need to go AGM so I don't blow up my cabin with hydrogen reaching my pilot light.

    Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Need advice on small system

    Consider a battery box vent fan: http://www.zephyrvent.com/
    coupled with a voltage controller they only draw a couple of watts, and only run at voltages that create hydrogen gas.

    75 amp/hours translates (sorry Bill, rough numbers) as such

    To draw down to 50% soc/dod would be ~37.5 ahs which would be ~ 450 watt hours, figuring no inverter loses etc would run a 15 watt cfl bulb for ~ 30 hours, or some combination of loads.

    To draw only to 80% soc (20 dod) (my preferred maximum discharge) would translate to 15 ah or 180 wh or the same 15 watt cfl for ~12 hours. (Assuming 12vdc) double all of this for 24vdc.

    In toto ballpark 50% decrease in these numbers to average in charging efficiencies and inverter efficiencies.

    If you "do the math", especially on the load side it will give you a pretty good idea of what you need.

    Tony
  • machineman
    machineman Solar Expert Posts: 129 ✭✭✭
    Re: Need advice on small system

    Update: So I checked out that MorningStar SI-300 inverter on NAWS and it says I can select it to be 115VAC 60Hz or 20VAC at 50Hz. Would my assumption be correct in that the 220VAC version at 50Hz is for Europe and would not work for me? Spec also say other voltages offered upon request. Not sure what that details but a 230VAC version at 60Hz would be great and I could just wire it up directly (through transfer switch) to the L1 and L2 in my cabins main box. And as Icarus said the nuetral won't be an issue with Morningstar.

    Off Grid Cabin, 24V 440ah 6V GC battery bank, Xantrex MPPT60-150 CC, Magnum MS4024 inverter-charger, >1200w Solar bank

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Need advice on small system

    I would not be sure about the "neutral" issue and using a 220 VAC European inverter for a 120/240 single phase North American distribution box...

    For 220/240 VAC US, you need the equivalent of a center tapped transformer (which is the neutral grounded lead).

    For Europe, 220 VAC, they do not have the concept of the Center Tap 120/240 VAC Transformer (just a "two lead" transformer).... So my guess is that the Morning Star running at 220 VAC would have only two wires (plus safety ground), and you would not be able to hook up 120 and 240 loads (or a pair of common neutral 120 VAC branch circuits) as you would in North America.

    If I understand your thoughts correctly.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset