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solar charging regulators

Discussion in 'Renewable Energy' started by Thunderchild, Mar 15, 2009.

  1. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Sunshine hours is simple, The year round standard is 12 hours of sun followed by 12 hours of dark. But the seasonal variance depends on how far you are away from the Equator.
    Prove me wrong!

    Actual intensity is almost never a realistic number I have found. Its only an average.

    If your solar panels are in a location that gets even a little shade durring some part of the day they will be less efficient. OR if you dont have a full range of tracking from morning until night you wont get anywhere near what the maximum capability of the solar panel is.

    And like its been posted on countless threads here. Most solar panel manufatures rate there panel output at bright sunlight while pointing directly at the sun. The real life values are often far less than the manufactures values.
     
  2. Thunderchild

    Thunderchild New Member

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    ebay, I got 20 W panels for £ 55 (yea some nutcases want as much as 200 but their crroks)
     
  3. wombweller

    wombweller Member

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    My house is situated front east and rear west so at best I get sunlight on my shed 11.00am ish onwards.
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi tcm.
    You are talking daylight hours, not sunshine intensity at ground level.

    Actual sunshine intensity does vary from one annual season to another.

    Tree rings are a good indicator of warmth/sunshine for summers in years gone by.

    Are you convinced.?:)
     
  6. wombweller

    wombweller Member

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    Cheers Eric

    Did look at the regional met site and couldn't find what you found:D

    Yes I did see that about no blocking diode ect. required for my said battery but this being a GEL battery is this the same? If not I can always buy another.

    Just need a supply of empty jam jars, maybe search the bottle bins;)

    Like I said hook up maybe 4 sper bright LED's in each jar and stick them round the garden.Hooked up to a daylight sensor should do the trick.

    Cheers Mark
     
  7. Thunderchild

    Thunderchild New Member

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    find your local freecycle group (The Freecycle Network) and you will find someone that can give you some jars
     
  8. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    you could have just copied and pasted from my own post. :confused:
    I said...
    You said:
    Your statement is no different than mine. You are using a year to year comparison, I was just using a more generalized comparison. ;)

    The actual statement by me was:
    Intending that you need to prove that you do not have a 12 hour day and 12 hour night when averaged over a one year time scale. And that being farther away from the equator creates a greater difference in the day to night ratio from season to season! :p

    your trying to make a point about a differerent topic made after the "Prove me wrong" statement. Not before it! :D
    I never asked to be proven wrong about intensity levels. I know they are variable given any reasonable time scale! :):D

    Hense the being referenced to an average number not an actual number. :)
     
  9. bryan1

    bryan1 Well-Known Member

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    Well Thunderchild,
    Do keep ya eye out for secondhand gelcell batteries and I can't complain as those 30 6 volt 110ah gelcells are still going strong 4 years after I got them from the junkyard. My 350 watts of pv keep them nicely charged even with a full size fridge going and the inverter on 24/7 I'm still dumping around 18 amps into my heating element and the ali backing plate is starting to warp after so much heat everyday. My other bank of 24 2 volt 275ah have only about a 140 watt PV array and they keep em topped up and once a month I change the bank over just to cycle the batteries. Even after 2 solid days machining the bank is still above 26 volts.

    If your going 24 volts checkout Kipoint for inverters, my 3kw pure sinewave works perfect and you wont go wrong with one of them. A tip dont buy em off ebay email em direct and you'll get it cheaper.

    Cheers Bryan
     
  10. Thunderchild

    Thunderchild New Member

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    well at present I'm on my old car battery and I'll look for something better in the mean time. do I assume correctly that a SMPS between the panels and battery will increase the efficiency as the panels are 17.5 volts nominal and i need around 13/14 volts or will voltage/current sort of self regulate making it redundant ?

    I'm not sure how a SMPS will react to not having enough input amps to put out the amps it would want to though.
     
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    The voltage will self regulate at the battery voltage.

    If your panel can provide considerably more current than the battery can woithstand once fully charged, then use a solar panel regulator to dump the excess energy - this is how it's normally done.

    Using an SMPS to try and keep peak efficiency will help to a certain extent, but the complexity probably isn't worth it - it's probably more cost effectvie just to buy a bigger panel in the first place.
     
  12. Thunderchild

    Thunderchild New Member

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    But does that mean that at higher battery voltage less current will be available and at lower voltages more current will be available ?



    well I suppose depends on how much gain, a SMPS is much cheaper than a solar panel and the more panels you have the more you are gaining.

    Would I gain more overall efficiency by putting the 2 12 V (well 17.5) panels in series and uning a SMPS to bring the resulting 24-35 volts down to 14 volts ?
     
  13. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You need to measure the peak power under differing circumstances, under bright sunlight you will get the maximum power, and a direct connection to the battery is probably all that's required. Under poor light a peak tracking SMPS should be able to provide more current to the battery than a direct connection, it really depend how much more it manages, and if it's cost effective.

    A while back someone posted here a link to a micro-controller based system for doing just that, perhaps you can find it?.

    Bigger panels may cost more, but they provide more power, and it makes the job simple and reliable, as there's pretty well nothing to go wrong.
     
  14. Thunderchild

    Thunderchild New Member

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    right so really I'm not acheiving much with a SMPS then
     
  15. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You need to test first and find out - but probably not a lot.
     
  16. smanches

    smanches New Member

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    You specifically a MPPT controller. It's basically just a buck circuit that tracks the current/voltage curve of the panel.

    Solar panels are constant current devices, so it wouldn't matter if you were charging a 6v cell or a 12v cell, it's still charging at the same current. MPPT controllers pull the power at the current panel voltage, then buck it down to the correct charging voltage, thereby increasing current.

    On average it's about a 30% boost in full sunlight.
     
  17. Thunderchild

    Thunderchild New Member

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    well a smps does that takes in a range of voltages and outputs a voltage we want in this case13.5-14.5 I beleive the difference between Vin and Vout should be converted into extra amperage (minus losses due to no device being 100 % efficient) so whats all the fuss about ? another mystical "black box" which nothing more than something we already know about.

    the only difference my be that the output should vary with the battery charge so as to be more efficient at lower battery voltage but also rise to keep charging when the battery voltage rises
     
    Last edited: Mar 31, 2009
  18. Elecholic

    Elecholic New Member

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    Is there anybody help me find a concept of MPPT with ATmega Cointroller? :)

    Thanks for the suggestion :D
     
  19. rotorgoat

    rotorgoat New Member

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    It depends on what your battery usage is. From a practical standpoint I've been using on my camper in the mountains a 30 watt panel powering two 6V golf cart batteries in series = 12V with no controller. My typical daily loads (all 12V) are two lights for about 3 hours in the evening, a water pump for about 30 minutes total, an inverter to run a computer and charge various cell/drill/etc. batteries (1 hour) and when it gets cold it powers the blower on the propane heater for about and hour. The battery doesn't boil out and at noon the voltage is usually back to about 13.5V. Once or twice a month we leave for about a week and always come back to a fully charged battery = no issues. I think if you are just charging with no load that eventually you will overcharge and boil out your batteries but what is the purpose in that?
     
  20. Thunderchild

    Thunderchild New Member

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    you do all that on a 30 w panel ?
     
  21. rotorgoat

    rotorgoat New Member

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    I'm a little suprised myself, but yes, 2 x 15 watt panels and my batts are always topped off. In May and late Sept if night time temps are low (< 30*F/0*C) I run a generator in the eves for about 45 minutes to warm up the bed and camper-- of course it tops off the batts I expect.
     
    Last edited: Oct 1, 2009

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