Author Topic: My small portable solar station  (Read 1696 times)

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AbyssUnderground

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My small portable solar station
« on: June 28, 2006, 06:17:42 PM »
Ive recently set up a web page to show my small portable solar station. Its only 6watts but its getting me into the flow and works well for low current devices.


http://m3ezw.no-ip.com/stuff/index.htm is the url.


Please let me know what you think of the setup.


Andy.



Editors Note;


I think this trend towards linking offsite stories for discussion here is a bad idea. It eventually will lead to confusion when the remote site changes or goes away. I believe we should discourage this practice by not allowing them.

« Last Edit: June 28, 2006, 06:17:42 PM by (unknown) »

AbyssUnderground

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Re: My small portable solar station
« Reply #1 on: June 28, 2006, 01:47:55 PM »
Because of the editors comment, Ive posted everything here instead, a duplicate of the webpage...


The camping project:


Started April 2006:


I needed a suitable power supply for camping for when we go every year. So I decided to make my own. It consists of:


 

  • A 12v powerpack (£18 - Macro)

     
  • 2x Cold cathode tubes (£6 a pair - ebuyer.com)

     
  • 2x 1.5w Solar Panels (£20 + £10 - maplin.co.uk (one was on offer at half price))

     
  • A 600w power inverter (£20 - maplin.co.uk (on offer at half price))


    Total: £84




    The powerpack is a 17.2Ah lead acid battery capable of 400 cranking amps to start a car with a flat battery.




    The cold cathode tubes are two 8 inch tubes. They draw about 0.5Amps each and Ive only ever used 1 at a time.




    The two 1.5watt solar panels are identical and each gives out a maximum voltage of 21v open circuit and 125mA at full capacity. I can connect them in series or parallel, depending on light conditions.


    Low light - Series for more voltage


    High light - Parallel for more current




    The inverter is 600watts. It draws about 50A at full load. It will be used sparingly because of the amount of current it draws.



    Power Pack:


    17.2Ah isnt a lot but for its price of £18 it was worth it. It has enough power to start up to a 2.0L petrol car and up to a 1.8L diesel car. It has 2 cigarette lighter sockets on the front hidden behind a sliding panel, and a charge state display in the form of 4 LED lights. You can connect things to the jump leads too. I have to do this for the solar panels as they use crocodile clips.


    Solar Panels:


    Because the solar panels give out so little current they have to be positioned for optimal use. Generally this is at a 45degree angle to the sun. Most light is collected at this angle. The maximum current I can get from each is 125mA, meaning a top current of 250mA. This is half the current of its original mains charger.


    Cathodes:


    I tested that the lights it will last roughly 20 hours continuous use on 1 cold cathode tube. This should be plenty for camping in May as it gets dark at around 10pm. Meaning we use the light for about 4 hours per night.


    Inverter:


    The inverter is a different matter. At full load (600w/50A) it will last less than 20 minutes! Using it sparingly is a necessity. Because the powerpack is a lead acid battery, letting it go flat will damage it to the point where its useless. Also, the solarpanels will not charge the powerpack very fast, especially in low light.


    Lead acid battery charge level chart:


    State of charge | Specific gravity | Voltage (12v | 6v)



    1. % | 1.265 | 12.7v | 6.3v
    2. % | 1.225 | 12.4v | 6.2v
    3. %* | 1.190* | 12.2v* | 6.1v*
    4. % | 1.155 | 12.0v | 6.0v
    5. % | 1.120 | 11.9v | 5.9v



    * Once at this point, the battery will start to sulphate, damaging it and preventing its ability to hold a charge.


    Here are some pictures to show you how bright just one of these cathode tubes is. The room was completely dark before I turned the cathode on.





    June 2006:


    I have recently purchased 2 additional panels to go with the original two. They are the same type but a different colour. These ones are grey. I also got a charge controller.


    Camping:


    I have been camping but without the additional panels (I had the controller) and the system held up for the week while I was there, approaching a critical 12.5v (12.3v under load) during the week, but this was topped up with sun as every day I managed at least 10 hours of bright sun (every day was pure sun, so I was made up). I turned the panels as each day progressed to make the best of the sun. I managed to run the cathode tube most nights but the backup LED light came into play when the voltage fell to the critical level. I also used the system to charge up my mobile phone and PDA through their "car" chargers on the ciggy lighter sockets.


    More pictures:


    Multimeter showing a fully charged voltage of 13.25v.



    The charge controller I am now using. It is rated at 0-25v at 5A.



    This is the battery and connections setup. Not exactly neat but its a portable setup. Im going to make this neater as time progresses.



    These are the specs shown on the box of each solar panel, just as a bit of proof!



    These are the panels set up against the window. I would put them outside but I need to build some sort of protection from the elements for them first.



    Any comments? :-)

  • « Last Edit: June 28, 2006, 01:47:55 PM by AbyssUnderground »

    asheets

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    Re: My small portable solar station
    « Reply #2 on: June 28, 2006, 02:25:49 PM »
    I'm trying much the same thing, except that I'm using CFLs and that my battery pack is one that is designed as one of those external laptop batteries (like this http://www.batterygeek.net/ whose external supply can be replaced by the solar panels).  


    The problem I'm having is that the battery pack I'm using is old and not all the cells are conditioned the same, so I'm getting erratic performance because a couple of cells drain out the rest prematurely.

    « Last Edit: June 28, 2006, 02:25:49 PM by asheets »

    Ungrounded Lightning Rod

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    Re: My small portable solar station
    « Reply #3 on: June 28, 2006, 02:32:05 PM »
    You should not series the 21v panels.  Low light does not drop voltage, just current.


    Voltage is set by a parameter of the quantum-mechanical structure of the semiconductor (the "bandgap").  It won't drop (except for lead resistance I*R voltage drop and a slight drop from panel temperature rise) until load overcomes the current or the light goes away completely.  Parallel, not series, is the solution for the former, more light for the latter.  B-)

    « Last Edit: June 28, 2006, 02:32:05 PM by Ungrounded Lightning Rod »

    AbyssUnderground

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    Re: My small portable solar station
    « Reply #4 on: June 28, 2006, 02:37:53 PM »
    Thats probably true, but I have made it open circuit in low light and measured it with a multimeter, and it is well below 12v, usually 8-10v in lower light conditions. So what you are saying may be correct on paper, but in reality it isnt ;-)


    They reach their peak of 21v though in bright sun, Ive measured the voltage the same was as above, open circuit.

    « Last Edit: June 28, 2006, 02:37:53 PM by AbyssUnderground »

    Ungrounded Lightning Rod

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    Re: My small portable solar station
    « Reply #5 on: June 28, 2006, 06:44:42 PM »
    Remember that your multimeter is a load, too.


    Try it in low light first with one panel, then with two in parallel.

    « Last Edit: June 28, 2006, 06:44:42 PM by Ungrounded Lightning Rod »