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  1. #1
    Join Date
    Jul 2008
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    Default Very Small Solar setup

    I have a couple of questions about a solar electric project I'm working on.

    I wasn't sure if I should post this in the "Electrical" or "Green" section but this made the most sense. Sorry if it's a lot of questions. I mostly understand what I'm doing except for some of the finer details below.

    Setup:
    To light my shed I use a small solar panel that produces 6 Watts at about 18V in full sun. This is wired to an inexpensive charge controller (from eBay) which charges a 12V deep cycle battery (SLA) and cuts off the load if battery voltage drops below a certain point. I wired 2 12V receptacles to the "load" screws. One has a 12V hand held spotlight (rarely used) and the other has an AC power inverter. This feeds a string of LED xmas bulbs for a total of 25 Watts.

    My questions:

    - Everything worked fine until I added the charge controller into the mix and also added a new inverter into the mix. The old one was... well OLD and I killed it on a road trip, unrelated to the solar stuff (and it's not just the fuse... it's dead and it eats fuses now). But as soon as I plug in the new inverter (by itself with nothing plugged in) the battery voltage drops significantly and the controller kills the load. I think it's because the new inverter has a cooling fan and the old one did not. I assume I need to get an inverter without a fan. Does this sound right?

    - Does it matter that the Inverter is rated for 20Amps but the controller is only rated for 12Amps?

    - My multimeter reads 18V +/- in full sun at the panel, but only 12-14V on the charge controller's solar panel connection screws. It seems like it increases slowly as the battery charges but I've never seen it above 13.6V even though the panel reading is consistently over 18V. Is that a normal aspect of "controlling" the charge?

    - I put my battery in an old metal toolbox with the lid ajar. Is this safer than no container? Do I need to worry about fire on a system like this? The panel is obviously outside but everything else is protected inside.

    - Is there anything I overlooked in this setup? It was mostly an experiment but I like having free light in my shed at night.

  2. #2
    Join Date
    Jul 2008
    Posts
    4

    Default Re: Very Small Solar setup

    No offense taken and I appreciate what you are saying.
    I tried a couple of those all-in-one setups including the one you mentioned and the light it provides is barely enough to see your hand in front of your face.

    I love Harbor Freight but in this case you get what you pay for.
    Most of the ones in this price range are junk.

    The LED xmas lights were only about $25 Bucks, produce amazing light (3 LEDs per bulb), will last for years, and only use 1 Watt per bulb. And they go all around the ceiling of my shed allowing me to see in most every corner. The charge controller was also only about $25 and I'm not sure I even needed it. I got the solar panel at a garage sale for $5. Battery cost was $15. And the rest I had on hand until the old inverter died. So my total investment is still under $100 and gives me the light I actually need with no utility cost.

    And I should also mention that my main purpose was to learn something for the day when I add solar panels to my house. It's been a fun and educational DIY project.

  3. #3
    Join Date
    Aug 2007
    Location
    Maryland
    Posts
    1,587

    Default Re: Very Small Solar setup

    I don't know why the charge controller would effect the system other than limiting the voltage into the battery. While high charging voltage will kill a battery with a regular charging system putting out a lot of amps, I don't know that a 5 watt charger at 18 volts will. I used a similar sized panel to charge & maintain a battery on a sailboat without a controller & I never had any problems with the battery.

    It seems the inverter draws a lot of power. Maybe you can compare the specs to the old one. The fan of course will keep the inverter cool, especially at full output. It seems a string of LEDs could get by with a very small inverter. Do you need the 110v power for tools or equipment? Even if you do you might go to a 12 v lighting system. There is always an inefficiency added with more components.

    I would suggest boating stores, books & articles as a reference. Sailboaters have been dealing with this for a long time given the power requirements for running & mooring lights as well as equipment & general lighting. There is a lot of info out there.

    In general small boats have the batteries in boxes and secured so they can't tip over. I think a ventilated box or enclosure is a good idea. A non-conductive box might be better in case the terminals get shorted by the lid. It may be 12 v, but they can put out a lot of amps when shorted. Enough to cause a fire.

    One more thought about your voltage drop is that maybe your battery is dying. Even when recharged properly they have a useful life that sometimes just declines or goes all at once. A battery may indicate a full charge with a volt meter, but have an excessive voltage drop when a load is applied. That indicates the battery has lost its usefulness.

    Also be sure to check the electrolite & add distilled water if needed even if it's a maintenence proof battery. Be carefull not to let any crud fall into the cells.

    So do you have enough room for a nice tv, refrigerator and loungers. You may need to upgrade to a wind turbine come football season so you can "work" on some important projects.

  4. #4
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,798

    Default Re: Very Small Solar setup

    Quote Originally Posted by MickeyBoo View Post
    I have a couple of questions about a solar electric project I'm working on.

    I wasn't sure if I should post this in the "Electrical" or "Green" section but this made the most sense. Sorry if it's a lot of questions. I mostly understand what I'm doing except for some of the finer details below.

    Setup:
    To light my shed I use a small solar panel that produces 6 Watts at about 18V in full sun. This is wired to an inexpensive charge controller (from eBay) which charges a 12V deep cycle battery (SLA) and cuts off the load if battery voltage drops below a certain point. I wired 2 12V receptacles to the "load" screws. One has a 12V hand held spotlight (rarely used) and the other has an AC power inverter. This feeds a string of LED xmas bulbs for a total of 25 Watts.

    My questions:

    - Everything worked fine until I added the charge controller into the mix and also added a new inverter into the mix. The old one was... well OLD and I killed it on a road trip, unrelated to the solar stuff (and it's not just the fuse... it's dead and it eats fuses now). But as soon as I plug in the new inverter (by itself with nothing plugged in) the battery voltage drops significantly and the controller kills the load. I think it's because the new inverter has a cooling fan and the old one did not. I assume I need to get an inverter without a fan. Does this sound right?
    If the batteries have exceeded their useful life, when charging they will build a surface charge which is quickly drained under load. Without specs on the inverter it is hard to say what the no load draw is. but it's possible that it is to high.

    - Does it matter that the Inverter is rated for 20Amps but the controller is only rated for 12Amps?
    The rating is for maximum output, if you try to run the inverter at full load you will blow the controller or it will shut down if it has current limiting circuitry.

    - My multimeter reads 18V +/- in full sun at the panel, but only 12-14V on the charge controller's solar panel connection screws. It seems like it increases slowly as the battery charges but I've never seen it above 13.6V even though the panel reading is consistently over 18V. Is that a normal aspect of "controlling" the charge?
    The charge controller is probably limiting the voltage to the batteries.

    - I put my battery in an old metal toolbox with the lid ajar. Is this safer than no container? Do I need to worry about fire on a system like this? The panel is obviously outside but everything else is protected inside.
    Charging batteries give off hydrogen gas. Sparks can ignite the gas. It is better to have the box vented.

    - Is there anything I overlooked in this setup? It was mostly an experiment but I like having free light in my shed at night.
    One thing you might consider is installing 12 volt lights rather than using an inverter. Inverter are pretty inefficient with about a 30% lose of power compared to input. Keep an inverter but put it on a switch so it can be used if necessary.
    If you buy LEDs rather than Christmas lights you can build your own lights. LEDs are low voltage DC . You are converting 12 VDC to 120 VAC to feed a light string that has circuitry to convert 120 VAC to low voltage DC, not terribly efficient.
    Each year more and more 12 VDC equipment and appliances become available, you might want to check some of them out. You can usually find them At RV dealers or on the net at such sights as 12volt accessories.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,798

    Default Re: Very Small Solar setup

    Quote Originally Posted by YukYuk View Post
    Not all 12V LEDs are designed to work on DC, some are designed to work on 12V AC, some are sold dually rated.

    Contacts are different on 12VDC and 12VAC sockets, bulbs, etc. You can find a lot of cordless chargers that have car socket adapters.

    http://www.ledlight.com/
    I have never seen a 12 VAC diode, I have seen 12VAC "led bulbs". Generally LEDs operate on 9 VDC or less and is installed inseries with a risistor or multiple LEDs. At any rate a loss occures whenever you convert. That looks liike a great source for LED bulbs.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Jun 2007
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    Fayette County, Ohio
    Posts
    5,798

    Default Re: Very Small Solar setup

    Do you have any idea how long it's been since I worked with tubes. I should have said LED rather than diode. And of couse diodes are routinly used to convert AC to DC.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  7. #7
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Very Small Solar setup

    Quote Originally Posted by YukYuk View Post
    I was tinkering with an old short wave just yesterday.

    Point being, individual LEDs are made to specific design tolerances, voltage, current, cycled or not, etc. for that useful life rating, safety, etc.
    Huh ???
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,798

    Default Re: Very Small Solar setup

    Quote Originally Posted by YukYuk View Post

    Point being, individual LEDs are made to specific design tolerances, voltage, current, cycled or not, etc. for that useful life rating, safety, etc.
    As i said, Ive seen diodes and diode bulbs made to specific design tolerances, voltage, current, cycled or not, etc. for that useful life rating, safety, etc but have not seen LEDS with such diversity.
    You turned any screrw drivers into welding rods yet?
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  9. #9
    Join Date
    Jun 2007
    Location
    Shamokin, Pa.
    Posts
    645

    Default Re: Very Small Solar setup

    Quote Originally Posted by JLMCDANIEL View Post
    Do you have any idea how long it's been since I worked with tubes. I should have said LED rather than diode. And of couse diodes are routinly used to convert AC to DC.
    Jack
    Learned a few things about tubes back in the day.
    It was a big deal when miniature tubes hit the market.
    Guess that makes me old......

  10. #10
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,798

    Default Re: Very Small Solar setup

    Yes, I guess we did diverge a little.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

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