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Thread: Anyone do a successful solar panel install (5W+)? Thin strip across windsheild?

  1. #11
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    Quote Originally Posted by wywywywy View Post
    I saw that some of these say "17v while charging". Is it not going to potentially damage electronic components?
    It's not a good idea to install a panel without a charge regulator. This is for the protection of the panel and your electronics ex. If your panel is producing 3 volts but you system is charged to 13 you will feed current into the panel and possibly damage it. This could be avoided with a diode, but the regulator serves another purpose. Its a dc/dc converter so if the panel makes over 13 volts it will step the voltage down and provide more current vice versa if the panel produces 9 volts it cant charge the system the regulator will step up the voltage while reducing current allowing your batters to charge.

  2. #12
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    All solar panels should have a blocking diode to prevent batteries/supplies discharging in to them.
    They also need a regulator or limiter to ensure they do NOT boil batteries (above ~14.4V) and loads - typically above 16V.
    Most 12V loads operate or tolerate 8V-16V; few exceed 16V reliably. Some may not operate below 12.3 or 12 or 11V etc, but they should not be damaged from 0-15V etc.

    And an AGM will accept charge at a greater rate than wet cells.

  3. #13
    FLAC
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    Ok so I ended up buying this 12V 6W panel:
    http://cgi.ebay.ca/ws/eBayISAPI.dll?...=STRK:MEWNX:IT

    It claims up to 0.36 amps and 17.5v max, anyone know how those numbers will change under average conditions? There will be tons of sunlight in the summer, but as for how it will change during the winter Im unsure. I just measured my video surveillance system to consume 0.25 amps at 12v, so having a bit of "excess" current from the panels should be beneficial to keep my battery trickle charged.

  4. #14
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    The voltage doesn't matter much other than meaning it's for a 12V system. That will drop under load and be limited to whatever the regulator allows (max ~14.4V max for most batteries). (That assumes common linear regulators.)

    So that gives you 0.36mA for a 0.25A load.
    In my experience, it will be rare that you get 0.36A....

    A rule I use for solar panels with batteries is - for a load of whatever Amps....
    - double the load (for 12 hours of sun in a 24 hour day)
    - double the Amps again (assuming 50% output for a panel with good sun)

    And that's for Australia (say 35 degrees latitude), though I am still somewhat novice in the reality of panel behaviour.

    So, for a .25A load, I'd be looking at a 1A panel - ie, 20W. (A 0.25A load is 3W@12V, [email protected] etc) That assumes 0.25A 24 hours a day.
    But that may still not be enough - especially a higher latitudes, colder temps and during winter etc.
    It also hugely depends if you are tracking the sun...
    You'd best seek info relevant to your area....

    No matter what, there should be some low-voltage cutout to preserve the battery. At least then WHEN the battery depletes, it isn't damaged.

  5. #15
    FLAC
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    Quick calculation here, based on this article:
    http://www.eionwireless.com/library/...VIP_app146.pdf

    Assuming my system draws 3W regardless of voltage (Im using a high efficiency switching regulator to go from the car's voltage to 5V and 12V for the security system) and typical 12hrs of operation per day, then I need about 12hr*3W = 36Whr or 3 amps per day. Use a factor of 1.5 to take into account inefficiencies, then 3*1.5 = 4.5 amps per day.

    Calgary isnt very sunny, so estimate a Peak Sun Hour of 3, which will give 4.5amp/3 = 1.5 solar amps required. Divide this by the peak current output of the panel, so 1.5/0.34 = 4.4 panels.

    The solar panel definitely wont be able to provide 100% of the power and Id still be relying a bit on my alternator as well as weekend driving to keep the battery topped =(

  6. #16
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    Good getting the map from that pdf, but OMG what a complicated method....

    Notice how the calcs and up with Amps, so why the Watts, Watt-hours, Amp-Hours etc? But that just my opinion.... whatever is easiest for people to work with.

    I use Amps throughout.
    But I think of it more as a duty factor or 24-hour demand/capacity (I don't like Amp-Hours per se - nor do I like Watts when considering what is effectively a current delivery device, and often linear/resistive "current" loads - not constant power etc).

    As to what you really need depends on desire & availability. With an alternator, you merely determine the minimum reserve time required and get a battery to suit (assuming say 80% capacity etc).
    Any solar panel is then at least a trickle charger that will pay itself of after 10-20 years.

    And low voltage cutouts cost a mere $20 (eg the MW-728)....

    It's only when wanting self sufficiency that the design gets tricky - you need higher peak power generation than the average you intend to use. (The joys of mere humans becoming power engineers... solar Erlangs and all that....)

    But 4.4 x 6W panels is 26W compared to my suggested 20W (for my ~3.5 to 4 sun-factor region) so we concur....
    My PolyCrystaline 20W panels were AUD$140 some years ago. Now I'd consider a MonoCrystaline 34W panel for $190; or 3 for $140 each. (Larger panels are near $5 per Watt; they were $10/W say 5 years ago.)

    BTW - make sure your panels have a series diode unless that's part of the regulator etc.

  7. #17
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    HMMMMM, let me ask, since you mentioned cut out panels. Do you think these can be applied to a cars roof? A lot of vehicles now a days have the top black to match the windows or what not, so image a whole roof with solor cells, that should be a good deal of power. Maybe enough to power the Car PC when the engine isnt running?
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  8. #18
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    Who mentioned cut out panels?

    Roof is fine - better than inside of windows. But they aren't protected and probably aren't tracking.

    And it depends what the PC takes.
    A bigger battery is probably still the most economic solution - and that's why many use the simple twin battery where the batteries are joined only whilst charging (that's a mere $5 relay for this 30A system).

  9. #19
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    i don't see how a bigger battery solves the issue if he doesn't drive the car long enough to replenish the charge. In which case you have a bigger, but still dead, battery.

    A solar panel at least prolongs this a bit.

    I'm anxious to see how this works out for you. I may do the same thing if it does work.
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  10. #20
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    Whenever I install anything in my car whether it's a subwoofer, carpc screen, or solar panels, I keep in mind that in the future Im probably going to replace the car so I always think about if the mods Im doing are reversible. Solar panels on the roof (if properly integrated) sounds like a great idea, but it's practically irreversible since I would imagine you having to glue the panels on or something. I wouldnt trust $100 worth of panels installed in any sort of non-permanent manner on the roof.

    Anyways, ill give an update on how this goes.

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