380watt 24V System.. does these components sound correct??

ywhic
ywhic Solar Expert Posts: 621 ✭✭
I am looking at:

2- AstroEnergy 190watt panels (24v panels, 5.47 amps, 34.74 volts @ max)
1- Morningstar MPPT 15 Amp Controller (seems like all the Specs are met with the 2 panels above)..
(thought the Morningstar Pro 30Amp non-MPPT may work also?? :confused: )
100 ft of M4 cable
#10 terminal lugs..
2- 12V deep cycle batterys, or 4 Trojan 210AH T105's 2 sets of parallel to maintain a 12v DC output..
??-Inverter TBD.. (thinking heavily on a SAMTRAX 1000W Modified Sine-Wave 12V)

I know I want a fuse on the panel end.. and a fuse on the battery side..

I'd prefer a 12V DC output to charge the batteries and give me flexibilty on just grabbing a 12v inverter..

$50 for the fuse/holder seems a little much.. anyone got suggestions for that??
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Welcome to the forum.

    If you want to run a 12 Volt system with those panels you've got problems. First, you need an MPPT controller to down-convert the Voltage. Second, the MS 15 Amp won't work there. Fine for 24 Volt system, not for 12. Here's why: 15 Amps (output current limit of the controller) * 12 Volts = 180 Watts. So putting more than 200 Watts of panel on the input side is just wasting panel.

    Realistically, for a 12 Volt system you'd be looking at about 24 Amps peak current from those panels through an MPPT controller. Which is good, but it means having to buy a bigger controller such as the Rogue http://www.roguepowertech.com/products/mpt3024.htm

    Now the other thing is the amount of power that would be available. The panels would be capable of "harvesting" about 760 Watt hours AC per day, and would work well with a couple of golf cart batteries (6 Volt, 220 Amp hours wired for 12 Volt) and only 25% depth of discharge. You could go up to four but ... 24 Amps is only just 5% of 440 Amp hours and it would be very marginal for recharging, especially with loads drawing at the same time.

    That 100 feet of M4 cable: is that 50 feet from the array to the controller? If so you are going to have problems with Voltage drop and will want to be able to wire the panels for higher Voltage to overcome this. Again that means MPPT controller, but it may also mean the Rogue is out if you have to put them all in series (exceeds the controller's input maximum). You may want to plan for bigger wire.

    Fusing. If all panels are in series or there are only two parallel connections the array does not require fusing. The charge controller's output should be fused, as should the inverter's input. Can't say I'm keen on MSW inverters of any brand. Consider carefully what you plan to run on it before buying one. It could be a false economy. Samlex makes some fairly inexpensive sine wave inverters and Morningstar's 300W one is well loved by all its owners.

    Once you get those details worked out and have the wire sized right you can pick the fuses. They really do have to be able to handle both the expected current and Voltage. 12 Volt systems have something of an advantage there, as many automotive/RV parts can be had for reasonable amounts of money.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    I read the specs for the MS 15 MPPT.. it said upto 400 watts of input with 24v panels.. unless I read that wrong and 200 watts with 12v panels..

    It will more than likely end up being 30 feet from the 'cabin'.. I just figured buy 100 ft..

    I'd prefer to PARALLEL the two 24v panels to have 24V coming in at 11 amps (est).. (this would = 264 watts used of the panels?)

    So your suggesting just 2 T105 220ah batterie for this setup in series to get 12v correct??

    The other option would be 2 - Kyocera 140W 12V panels.. and then I COULD use the MS Pro 30amp unit.. no MPPT needed.. correct??


    Al
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Would the 280w Kit below be better and get the most out of the panels?? (I'd be using the 2 Trojan T105's in series..)

    http://www.solar-electric.com/rvmakitwi280.html

    I'd like to maximize output and storage..
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    I read the specs for the MS 15 MPPT.. it said upto 400 watts of input with 24v panels.. unless I read that wrong and 200 watts with 12v panels..

    Nope. It's 400 Watts of panels with a 24 Volt system.
    It will more than likely end up being 30 feet from the 'cabin'.. I just figured buy 100 ft..

    There's a big difference in V-drop between 30 feet and 50 feet for the same Voltage/current/wire gauge. Example:
    10 AWG wire with 48 Volts & 12 Amps; 30 feet, 1.54% drop; 50 feet, 2.57% drop. That's a whole 'nother percent. That's a difference of "this will work" vs. "uh-oh, running out of Voltage".
    I'd prefer to PARALLEL the two 24v panels to have 24V coming in at 11 amps (est).. (this would = 264 watts used of the panels?)

    Effectively the Watts of the panels will be the same regardless of the configuration (serial, parallel, or a combination). What it changes is the Voltage to current ration. Higher Voltage and lower current is better for long wire runs because there is less power loss. If we rework the example above:
    10 AWG with 12 Volts & 48 Amps over 30 feet you get almost 25% V-drop, so you end up losing 1/4 of your power. To compensate you have to increase the wire size to 2/0 or more, and that's ridiculously expensive and difficult to work with.
    So your suggesting just 2 T105 220ah batteries for this setup in series to get 12v correct??

    That is a good match for that much panel, yes.
    The other option would be 2 - Kyocera 140W 12V panels.. and then I COULD use the MS Pro 30amp unit.. no MPPT needed.. correct??

    Yes, but 280 Watts is less than 380 by 100 Watts. You could expect about 18 Amps peak current from that. But you would still have a serious V-drop problem over 30 feet.

    So why don't we start back at what you're trying to power and see what sort of options are available?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 380watt 24V System.. does these components sound correct??

    I am a little confused--You are talking about a 12 volt or 24 volt battery bank?

    And specifically what brand/model of solar panels:

    AstroEnergy 190watt panels (24v panels, 5.47 amps, 34.74 volts @ max)

    I don't know if that 34.74 volts is Vmp or Voc...

    It is very rare these days to find high wattage panels that match the Vmp~17.5-18.5 volts (for 12 volt bank, 2x for 24 volt bank) for proper and efficient use with a PWM controller.

    The Kyocera 130-140 watt panels are one of the exceptions...

    Controllers are usually rated based on output current and voltage (i.e., 15 amps at 12 OR 24 volt battery bank). Still limited to 15 amps in either case... Roughly, the maximum "cost effective" input power for a MS 15 amp MPPT controller:
    • 15 amps * 14.5 volt charging * 1/0.77 panel+controller derating = 282 watts "maximum" for 12 volt battery bank
    • 15 amps * 14.5 volt charging * 1/0.77 panel+controller derating = 565 watts "maximum" for 24 volt battery bank

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    Would the 280w Kit below be better and get the most out of the panels?? (I'd be using the 2 Trojan T105's in series..)

    http://www.solar-electric.com/rvmakitwi280.html

    I'd like to maximize output and storage..

    One good thing (among many) about NAWS is that they don't bundle crappy components into kits like some retailers do. They don't even sell crappy components. That is a good, small 12 Volt system for moderate power needs. But the wire is 30 feet total, meaning 15 feet from array to controller.

    And remember that 15 Amps on Trojan T-105's is just 6% charge current. Trojan specifically recommends 10%, so you would have to expect shorter life from the batteries (or use slightly smaller batteries).
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    What size/type of battery would you recommend?? Would you say a 100AH battery in 12v flavor??

    Like a Trojan AGM31 ($250)?? or the SCS150 Group 24 ($160)??

    I appreciate all the help.. for the over $1K this is going to cost I want to be correct/right..


    Al

    One good thing (among many) about NAWS is that they don't bundle crappy components into kits like some retailers do. They don't even sell crappy components. That is a good, small 12 Volt system for moderate power needs. But the wire is 30 feet total, meaning 15 feet from array to controller.

    And remember that 15 Amps on Trojan T-105's is just 6% charge current. Trojan specifically recommends 10%, so you would have to expect shorter life from the batteries (or use slightly smaller batteries).
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    What size/type of battery would you recommend?? Would you say a 100AH battery in 12v flavor??

    Like a Trojan AGM31 ($250)?? or the SCS150 Group 24 ($160)??

    I appreciate all the help.. for the over $1K this is going to cost I want to be correct/right..


    Al

    See, here's the thing: we can't even hint at what size battery to get without knowing what your power needs are.
    It's much, much simpler to design a system around the maximum Watts and Watt hours needed than to try to piece-meal components together and hope they can supply the required power.

    For example, a 220 Amp hour 12 Volt bank can supply a maximum of 1320 Watt hours DC not including losses. Normally you'd only take it to 25% discharged, which would be about 660 Watt hours DC (without losses).
    Such a battery bank should have about 342 Watts of panel for recharging, and you could expect perhaps 385 Watt hours AC "out the door".

    A Watt hour is one Watt used for one hour. A 100 Watt bulb left on for 1 hour is 100 Watt hours. For fifteen minutes it's 25 Watt hours.

    Some loads have their own special requirements that affect system design, such as start-up current demands or need for sine wave over "MSW".

    So without knowing what you're trying to run we're shooting in the dark here.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Lets say a 5 cu ft. dorm refrigerator. 1 20" box fan (from walmart @ 12watt est.). 2 - 25 watt light fixtures @ night as I have 2 skylights for the daytime :D . and laptop which is 12Volt DC and 3amp on the AC adaptor (so I can run that straight off the 12v DC outlet on the invertor I suppose with correct 12v adaptor)..
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 380watt 24V System.. does these components sound correct??

    A small dorm fridge uses almost as much power as a full sized fridge (~300 WH or so vs 360-400 WH for a full sized efficient fridge/freezer).

    Since this is for your own education/fun... Get a Kill-a-Watt meter from our host or from the local Home Depot.

    You will be shocked when you see how much power a few appliances use vs how much (or how little) power an off-grid solar power system can supply.

    You are looking at a 1-2 kWH per day system... To run a full, energy efficient home off grid is probably in the 2-3 kWH per day range. And that is a $5-$10,000 system. Yours would be a 1/2 or or a 1/3rd that price (just really rough/round numbers).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    So forgoing the 5 cu ft refrig.. and just say the 2 25w lights and 1 fan (12watts)..

    What battery would be ideal with the 2 panel setup I outlined??

    Would a single 12v battery be better than 2 6V batteries??
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    Lets say a 5 cu ft. dorm refrigerator. 1 20" box fan (from walmart @ 12watt est.). 2 - 25 watt light fixtures @ night as I have 2 skylights for the daytime :D . and laptop which is 12Volt DC and 3amp on the AC adaptor (so I can run that straight off the 12v DC outlet on the invertor I suppose with correct 12v adaptor)..

    Here's a thread about refrigerators and their abysmal power usage: http://forum.solar-electric.com/showthread.php?12272-Just-how-bad-a-small-frige-is

    As for other things ...
    50 Watts of light bulbs * how many hours? Two hours and you've got 100 Watt hours right there.
    Laptops are usually pretty good on power consumption, especially compared to their desktop counterparts! It probably uses a max of 3 Amps @ 12 VDC = 36 Watts. That's what my wife's Gateway chews through. My netbook uses 1/3 of that.
    But still, its like running another light bulb and you'll probably run it a lot longer. Even at 25 Watts over 8 hours you hit 200 Watt hours.

    But those are nothing compared to a refrigerator.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    So forgoing the 5 cu ft refrig.. and just say the 2 25w lights and 1 fan (12watts)..

    What battery would be ideal with the 2 panel setup I outlined??

    Would a single 12v battery be better than 2 6V batteries??

    If you want to work it backwards ...
    280 Watts of panel would support 180 Amp hours of 12 Volt battery. Possibly more if you use no daytime loads.
    At a maximum that would be roughly 900 Watt hours AC, and that would be pushing things to the limit.

    So two 25 Watt lights plus one 12 Watt fan is 62 Watts. Divide 900 by 62 and you get 14 hours of run time. And that's good because it means six hours of use per day is not an unreasonable expectation, provided you are willing to run your batteries close to 50% discharged.

    If you have no more than 180 Amp hours of battery with the 280 Watts of panel you could probably run the laptop during the day without much loss of charging (based on 3 Amps @ 12 VDC).

    It's all rather complicated and interconnected, isn't it?
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    So running the 12v DC bulbs (that fit into normal household bases) would be a MUCH better thought then also..

    I am going to try to keep everything 12v DC as much as I can.. I found a few 12v DC RV type water pumps that use pressure sensors to run.. and I'd be pumping water up from say 4 feet with them.. but again they are already 12v DC and low amp draw when only used..

    Thank you for all the help.

    I concluded 2 140 Watt 12V Panels (wired in parallel), the 30 Amp MS Pro Controller would be the 1st order.. (this would allow me to add a 3rd panel without upgrading the controller)

    Then a modified wave 115 inverter in the $200 price range should work for my needs..

    But again, the ? is which battery should I get??
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    I found a 6000BTU AC that says 900 watts.. I'm guessing thats per hour..??

    I also have an 800 watt microwave.. so would I be safe to run that for 45-60 mins??

    So IF I had a 2500 watt invertor (continuous) I could run the A/C for about 45 minutes.. if I ran nothing else??

    I'm trying to get my head wrapped around this, but I was not good at math.. hence the help/direction needed..

    Al
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Staying with all 12 VDC has the advantage of not having to buy and run an inverter (they use power themselves) but it has the disadvantage of limiting distances between the power source and destination due to the Voltage drop problem. Obviously many RV applications are all 12 Volt, but they are usually small enough that the V-drop isn't a significant issue.

    As for the which battery question ... Is this something that will be at a fixed location or mobile? Will the batteries have to be located in living space? AGM's offer some advantages over FLA's, but at a significant increase in price per Amp hours @ Voltage.

    A couple of examples around 180 Amp hours @ 12 Volts:
    Universal 200 Amp hour 12 Volt AGM, size 4D 115 lbs. $343
    Two Crown 95 Amp hour 12 Volt FLA, size 24 50 lbs each. $124 * 2 = $248

    Most batteries will be over 200 Amp hours or under 150; it's hard to find batteries that meet needs exactly. Usually you round the battery capacity up to the nearest available size and increase the panel size accordingly. It's better to have power to spare than run short.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 380watt 24V System.. does these components sound correct??

    Also, a 50 watt 12 VDC bulb uses exactly the same amount of power as a 50 Watt 120 VAC bulb (plus the extra ~15% losses from the inverter).

    So--What you want to look for is not a 50 watt filemant bulb, but a 10 watt CFL or LED bulb that outputs as much light as a 50 Watt filament bulb (conservation).

    Yes, DC will save to the 12 DC to 120 VAC conversion--But if you have to send the power more than 10 feet or so (say a 100 foot extension cord), then an AC inverter is usually the better deal...

    You can send 10 amps @ 12 VDC with ~1.0 volt maximum drop, or you can send 1 amp @ 120 VAC with a ~5 volt drop--The AC distribution needing much less copper wire and having less wiring losses.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    I found a 6000BTU AC that says 900 watts.. I'm guessing thats per hour..??

    What that means is that it draws 900 Watts while running (not including a nasty shock on start-up because it takes a lot of current to get a compressor going). If it runs for one hour, that's 900 Watt hours. A/C units are murder on off-grid systems. That's why there's a great long thread on "minisplit" units: http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-%28inverter-variable-speed%29
    I also have an 800 watt microwave.. so would I be safe to run that for 45-60 mins??

    800 Watts cooking power isn't 800 Watts used, unfortunately. I have a "700 Watt" unit that actually uses slightly more than 1,000 Watts running. See why the K-A-W meter is so much better than relying on supplied Volts & Amps or Watts?
    So IF I had a 2500 watt invertor (continuous) I could run the A/C for about 45 minutes.. if I ran nothing else??

    Chances are a standard window A/C unit would smoke that inverter, especially if it were MSW type. What's more, if the inverter could take it the battery bank wouldn't: trying to supply 900 Watts on 12 Volts requires roughly 75 Amps of current. If you had a 750 Amp hour battery bank it could take it. For a battery around 200 Amp hours it would be about 50% of the capacity being demanded all at once. Funny thing about batteries: the higher the current draw the lower the capacity for the same battery. When we give the ratings it is for the "20 hour rate", meaning a steady current discharge that will drain the battery in 20 hours. When the discharge rate goes up, the actual capacity goes down exponentially.
    I'm trying to get my head wrapped around this, but I was not good at math.. hence the help/direction needed..

    Al

    That's what we're here for; to try to make a very complex subject understandable or at least "do-able". :D
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??
    As for the which battery question ... Is this something that will be at a fixed location or mobile? Will the batteries have to be located in living space? AGM's offer some advantages over FLA's, but at a significant increase in price per Amp hours @ Voltage.

    This would be for a FIXED 12' x 24' cabin/shack..

    The panels may just endup on the roof.. so the distances will end up being less than 20' from panel to control unit and 'baby box' with breakers...

    And the wiring at most would be up 1 length of wall.. (24')

    I was entertaining running 115v AC outlets in the stickwork (per norm) and just supply the feed with the 110-120V produced by this setup.. (aka down-n-dirty)..

    Later if I went ON-GRID I would just swap the junction panel for a regular 'house' one and not have to re-wire the entire builing..

    The building has basically an open floor plan.. so I agree on using the LESS wattage CFL/LED lights like Bill stated..

    Sample pic of 'cabin'

    lengthpic.JPG
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Good. With a fixed location you don't have to worry about how heavy batteries are because you don't have to move them about. You also should have better insolation on the panels, because you can determine the best angle for your use there and it isn't going to change (season adjustments notwithstanding). If you're putting panels on the roof be sure you build the cabin so it has proper orientation. This is where running a few simulations with PV Watts http://www.nrel.gov/rredc/pvwatts/ can give you some idea of what to expect.

    For small-scale 120 VAC you can't beat the 300 Watt Morningstar inverter: http://www.solar-electric.com/mosu300wasiw.html
    No, it's not going to run A/C or a refrigerator or a microwave. But if you really need that stuff you really need a lot more battery & panel capacity. Here's a hint: I run a full-size electric 'frige (1200 Watt hours) plus water pumps, microwave, computer, lights, et cetera. The whole household scenario. That's the system in my sig. That's $8,000 or so.

    Now, are you likely to go on grid? Sometimes the cost of the hook-up is much less than the price of solar power equipment and on a per Watt hour basis it is always cheaper than battery power.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    They want $450 to come out and tell me if I am eligible (co-op electric co.).. I'm like 60' from the pole..

    They would install an RV 6x6 post and put an outdoor meter and breaker box on that.. or directly on the side of the 'cabin'.

    Thats a $450 gamble.. as they can just say NO..

    I'd rather spend the $1300 (or so) and not have any bills if necessary..

    I was leaning toward the SAMLEX 1000 Modfied Sine Inverter. http://www.solarhome.org/1000wattmodifiedsinewaveinverter12v.aspx

    Or the Whistler Pro 2000 Watt.. http://www.amazon.com/Whistler-Pro-2000W-Watt-Power-Inverter/dp/B003R7M6CS/ref=wl_it_dp_o_pC_nS?ie=UTF8&coliid=I3ETJNYS64VB3C&colid=1Z1T1QE4RJUZ9 which I am sure you guys will beat up..

    I'm trying to stay below $200 for the inverter.. got any other suggested ones??
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??

    $450 just to say yea/nay? That's quite a rip-off.

    We could evaluate it this way:
    Two lights @ 25 Watts each = 50 Watts
    One fan @ 12 Watts = 12 Watts
    One laptop @ 35 Watts (probably less than) = 35 Watts
    Total = 97 Watts

    So if those are all your loads you would run less than 100 Watts. The Morningstar 300 Watt would handle these things easily and only draws 6 Watts running. In standby mode it uses far less.

    If you pick up a couple of golf cart batteries cheaply at a warehouse store you get 220 Amp hours @ 12 Volts. Keep the discharge rate to 25% maximum, and that's 55 Amp hours @ 12 Volts or 660 Watt hours DC. Roughly 600 Watt hours AC. That's about full load for six hours, not including inverter power and some fudging of system efficiency.

    Those batteries would work with your proposed two 140 Watt panels, with about an 8% charge rate. You would still have to either minimize the wiring distance and maximize its gauge (looks like 6 AWG for 24 feet) or go with the Rogue controller.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Would 2 of these 85-90 AH Marine Deep Charge Batteries work??

    and for the price should I just buy 3-4 and run parallel?? this would be equal or less than the 2 Crown 90AH you mentioned earlier..
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??
    ywhic wrote: »
    Would 2 of these 85-90 AH Marine Deep Charge Batteries work??

    and for the price should I just buy 3-4 and run parallel?? this would be equal or less than the 2 Crown 90AH you mentioned earlier..

    Marine/RV "deep cycle" batteries aren't true deep cycles; they're a hybrid. Like automotive batteries with extra thick plates. They aren't really suitable for RE and won't last. And no I don't sell batteries. But last year I scrapped about 20 from defective systems around here. Four of those were Marine/RV types that were only 2 years old.

    If you've got a nearby Sam's club or Costco see if they offer the golf cart batteries. Several people on the forum have had good luck with these bargains.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    I found this.. says for sweeper.. US Battery 185XC.. 12v.. 200AH.. $210..

    No Costco or SAM's nearby unfortunatly..

    I'll keep jamming away on the battery goal of 180-220 AH..

    I found the MS 300 inverter for $220.. so I may go that route just be safe..

    Thank you all for the help..
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    If I added 1 more panel for another 140 watt and 7.7 amp (max) and 12V..

    I figured the raw numbers would be 23.4 AMPS (total), 12v, 420 watts..

    The Morningstar Pro 30 controller is rated at 30 amps..

    How much GAIN would I have in usable powe with the added panel over the 2 panels??

    (I noticed you said 900watts (max) and 180 watts from the panel..)



    Al
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??

    Basically a 50% increase in array capacity is a 50% increase in power.

    420 Watts would potentially yield:
    420 * 77% efficiency / 12 Volts = 27 Amps, enough to support 270 Amp hours of 12 Volt battery. 810 Watt hours DC @ 25% DOD.
    420 Watts * 4 hours equivalent good sun * 50% over-all system efficiency = 840 Watt hours AC per day. This is a pretty good balance.

    Here's the problem, and it's a big one: if you keep adding panels in parallel to the array the amount of current the wire has to carry from the array to the controller goes up. So you run into this: 27 Amps @ 12 VDC over 30 feet requires 2 AWG wire to keep Voltage drop below 3%. If you price out that much 2 AWG wire you may instantly see the advantage in putting the money in an MPPT controller. I don't know how bad it is where you are, but around here it's very pricey.

    I think you may have confused the 900 Watts running of the A/C and the 180 Amp hours of one of the battery choices with some of the power production figures. We've been tossing around a lot of numbers and configurations; it's pretty easy to get lost in them.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    So I should grab a MPPT controller than I can use my normal 10ga wire??

    How bout bringing all 2 (or 3) panels down that same 25' feet using the 10ga wire.. and tying them off in a CV combiner box??

    And if not the above, which MPPT controller (for low $) would work for me.??

    I see a 15amp Morning Star.. and the Blysky SB2512i...


    Al
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 380watt 24V System.. does these components sound correct??

    When using an MPPT controller you wire panels in series so that the Voltage goes up and the current goes down.
    If we take the example of 18 Amps @ 12 Volts over 30 feet needing 4 AWG wire and up the Voltage to 24 thus lowering the current to 9 Amps the wire size changes to 10 AWG (both sizes chosen to keep V-drop under 3%).

    You join them at the array, and send the higher Voltage down to the charge controller. That will lower the Voltage and increase the current. This is where you need to have the right controller, because their numbers are based on output current @ system Voltage. This means the 15 Amp Morningstar is not a good choice here, as you should be seeing current over its maximum output.

    The Rogue 3024 is the probably the best in the low-power MPPT controllers. $325
    The least expensive choice would be the Blue Sky SB2512i at $198, but naturally it has fewer features than the Rogue. You may find those features desirable. Blue Sky offers some add-ons and more advanced models, which of course increases the price.

    Keep in mind that these have a maximum input Voltage around 60, which limits the total Voc of the array; you'd only be able to run two panels in series before you run the risk of exceeding the input maximum. But as noted above just going up to "24 Volts" (two in series, actual Vmp around 35) makes a big difference in the V-drop.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: 380watt 24V System.. does these components sound correct??

    This must be why NA Wind & Sun includes the combiner box and 10ga wire on there 280watt RV kit they have for $945..

    They bring 10ga wire down for 15' (or so) to the combiner and then to the charge controller.. the SunSaver 20amp..

    My build is almost the same.. except it maybe 3 panels instead of 2 like theirs..

    Figure my roof is 12 x 24.. If I put 3 panels up there.. and run the 3 separate 10ga leads down from each panel to the combiner box (about the same 15' away), the loss SHOULD be under 3%.. I'll center the setup on the wall 1/2 way.. so 15' of wire should be it for each panel..

    **using a calulator (online) I came up with 26 feet of 10ga wire for 12VDC@8Amp as acceptable.. 8)

    I will then run 8ga wire from the combiner over to the controller (Morningstar Pro 30amp).. which will be less than 2' away on the same wall section.. the battery wires will be 4ga and going about 4-5 feet down to the floor to the 200AH battery (or batteries)..

    Does this sound like a do-able plan??