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Thread: solar panel out puts

  1. #1

    Default solar panel out puts

    Im just finishing 1 small 36 cell panel 3x6 poly .5volt 3.6 amp. My question is after i make a few of these sizes[ i have alot of glass that size] I plan to run a bus bar to connect the panels to. I know that some will put out different voltages and amps. In between Each panel and buss bar I will be putting a blocking diode. Then go to a controller MPPT or a PWM, I don't know which one yet. I hope to end up with about 1000 system atleast. Useing 12volt batteries. Guess my question is. will all the panels be putting voltage or amps into the batteries if they are calling for it?Like if one panel is putting out 18 vdc and another is putting out 15 vdc, will it Draw amps from the 15 volt panel and 18.
    tks
    in this exp. each panel will be tied in to the buss bar.
    John

  2. #2
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    Default Re: solar panel out puts

    If you are using a PWM controller or attaching the panels (through a diode) directly to the battery bank, they will each supply current based on their I*V Curve...

    The 18 Volt panel charging a battery bank to 14.4 volts will be near maximum current.

    The 15 volt panel as it gets warmed up, will probably not supply its maximum current to the battery bank once the battery is much over 13 volts or so (as solar panels heat up, their Vmp drops--that is why a "12 volt" panel has Vmp=~17.6 volt or so and to support ~1-2 volts of controller/wiring voltage drops too).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  3. #3

    Default Re: solar panel out puts

    B.B. thanks for the reply,thats what i though, that each panel would produce something. The way made the panels I will be able to add more cells in series to bump up the voltage for each and not waste any cells. Like add just 4 more cells to get 2 more volts to to that one panel.
    I don't know what type of controler to pick up yet.I know that I want to ATleast build up to 500watts ,and then more.
    Tks
    John

  4. #4

    Default Re: solar panel out puts

    BB. my other question is ,Will the 15 volt panel be supplying ANY amps to the buss bar,like i said, I will be hooking all these panels to a buss bar.I know if the battery is above the voltage of the panel that panel will do nothing in supplying voltage,so I guess it will not supply any amps either.Where voltage carries the amps.
    Johnny
    .....PS....
    Which one of these would be the better of the two.I think the 1st one is because it is a mppt
    .
    Wellsee charge controler Ebay Item number: 280608149734 and cost $70.00
    ws-c2430 20A
    .
    p fangpusun PR3030 Ebya ITEM NUMBER IS 110625631643 and cost $69.00
    Last edited by conntaxman; December 31st, 2010 at 17:36 PST. Reason: add another question

  5. #5
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    Default Re: solar panel out puts

    Quote Originally Posted by conntaxman View Post
    BB. my other question is ,Will the 15 volt panel be supplying ANY amps to the buss bar,like i said, I will be hooking all these panels to a buss bar.I know if the battery is above the voltage of the panel that panel will do nothing in supplying voltage,so I guess it will not supply any amps either.Where voltage carries the amps.
    Yep--The old water analogy is helpful... Water needs to flow down hill... Electricity needs to push current from a high(er) voltage to a low(er) voltage point. If the voltages are equal--no current flow.

    Which one of these would be the better of the two.I think the 1st one is because it is a mppt
    .
    Wellsee charge controller Ebay Item number: 280608149734 and cost $70.00
    ws-c2430 20A
    .
    p fangpusun PR3030 Ebya ITEM NUMBER IS 110625631643 and cost $69.00
    So far, I have not heard of a cheap/successful MPPT type charge controller... And if you are planning on Vmp~17.5 volts (not connecting in series for 2x17.5=35volts for example)--I would choose the PWM as it is probably more likely to work correctly.

    Realize, that you are paying about 1/3rd to 1/4th the going rate for a low end MPPT charge controller. There is a lot that can "go wrong" with MPPT and you don't want to have to hunt down issues and figure out what is going wrong (controller or elsewhere).

    And if you are Vmp=18 volts + 15 volts or so, an MPPT is not going to do anything better for you (and may be worse) when compared to a simple PWM type charge controller.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  6. #6

    Default Re: solar panel out puts

    BB. Thank you very much for the info about the controllers. It was /is very helpfull.So now I will get the PWM. Later if I put them series then I'll think about the other .But it is very nice to get info from you.
    I still have a few more of these 60 watt panels to make and then I will try them on the office with a computer which draws 1 amp per hr with monitor. I bought a watt meter that everyone was talking about on the site,It is very help full and Fun to use/see.
    Have a nice day/night.
    tks
    Johnny

  7. #7
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    Default Re: solar panel out puts

    Remember that 1 amp at 120 VAC is 10 amp draw at 12 VDC (unless that is a very low power monitor running off 12 VDC)...

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  8. #8

    Default Re: solar panel out puts

    oh, didn't know that 1 amp 120vac = 10 amps dc. Thats a lot. I'll have to remember that.But i was amazed when I saw only .90 amps draw for the computer and monitor, and that is while it was working, like surfing the net.It's amd.
    tks
    Johnny

  9. #9
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    Default Re: solar panel out puts

    I am guessing the amps... Remember Power = Volts * Amps

    • Power = 1 amp * 120 VAC = 120 Watts
    • Power = 10 amps * 12 VDC = 120 Watts

    The AC vs DC is not the issue here--It is that (typically) we talk about 120 VAC and for DC on small systems, 12 VDC.

    For larger off-grid Solar PV systems, there are 24 and 48 VDC systems too:

    • Power = 5 amps * 24 VDC = 120 Watts
    • Power = 2.5 amps * 48 VDC = 120 Watts

    AC Amps actually does get more complex (lots of math)... But basically for AC:

    • Power = Volts * Amps * Power Factor

    Power Factor for Resistive loads (like heaters and filament light bulbs) is PF=1.0

    For CFL bulbs, many electronics, electric motors and such, PF typically is ~0.6 to ~0.7 -- So the Amps measured * Volts measured do not always equal power (Watts).

    AC quickly becomes not like DC when measuring power... There is another unit called VA (Volt Amps) to represent how much current and voltage an AC device is using.

    And VA*PF = Watts (Power)

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  10. #10

    Default Re: solar panel out puts

    hello BB. What would you think of this solar controller for a starter.
    -----------
    http://sunelec.com/index.php?main_pa...products_id=39
    .
    Morningstar Solar Charge Controller 45A TriStar TS-45
    $159.12
    ------------
    Ive been reading a few days and looking at many.This morn/ts45. seems that it would do good .I would like a dig/meter on it ,but I could buy an amp and volt meter and hook those up myself, I want to build up to atleast 1,000 watts of panels. I think this will only take up to about 500 watts, not sure on that one. But another thing about it is that it has Knock out steel plugs and takes a large wire size. I think it is made in the USA also. So what would you say, good/s and bad/s.
    tks
    John
    Going to go work on more cells.[tab em] also metal frams and uv epoxy /vacum out air also.

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