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

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

    I have a video surveillance system in my car that draws about 4-5W when running. I usually leave it running during the day for 8-15hrs when I am at school/work. I have an isolated deep cycle battery in the back that runs this system, and I usually drive for about 1 hr a day which is enough to keep the system charged up.

    However, due to my new downtown job, I will be parking at a local park n ride and then taking the bus to work, so each day I might only drive the car for about 20 mins. Not enough to keep the system charged up. Im looking to offset some of this power consumed maybe via solar panels but I would need atleast 5W. Im thinking perhaps a thin strip across the top of the windshield. Most cheap solar cells Ive come across arent very efficient, so I was wondering if you guys know of some higher efficiency stuff that could realistically generate 5W or more using just a thin strip across the windsheild. Some of the 5W panels Ive seen are huge and expensive. Unfortunately my rear has 5% limo tint so I cant install panels in the rear windows.

  • #2
    i havent seen anything, but have been pondering a camera system in my car for a while-- this being the biggest thing to overcome, so i am also interested to see what can be done.

    here is what i came up with:

    either, 4 of these across the top of the windshield(claimed 1.5 watt output, per unit but no specs)
    http://www.harborfreight.com/cpi/cta...emnumber=44768

    or this 5 watt unit, maybe just keep it on the dash?
    http://www.harborfreight.com/cpi/cta...emnumber=41144


    also, what about a second battery with a isolator?
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    • #3
      Keep in mind that a 5W panel often means 5W max with sun perpendicular to it (and vertical - ie, less atmosphere & refraction) without glass or dirt or cloud.....

      The usually method is a second battery that connects to the main battery when charging (that's just a $5-$10 relay powered from the charge light circuit else a voltage sensing circuit) and usually a low voltage cutout to protect the 2nd battery (~$20).)


      PS - The problem with small panels is their price.
      Normal prices were $10 per Watt but now often $5/W.
      One "minimum" rule I sometimes use is panel size = 4x demand - eg, 20W for a 5W load. But that's based on 50% daylight & 50% of required solar energy (which is max 1kW per square meter (bit more than a sq-yd).
      FYI - efficiency with the sun 3-degrees off normal (off perpendicular) can be down by 5%; 5-degrees can be down by 20%. (Hence why trackers are so profitable.)

      But any solar augmentation will extend the reserve time - though a 2nd battery may be cheaper....

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      • #4
        I already have a 2nd battery with isolator. The problem is that I dont drive for long enough every day to keep it charged if Im going to run the surveillance system for 8-15 hrs a day, that's why I was hoping for a solar supplement.

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        • #5
          Get a Larger/more efficient/second Altenator

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          • #6
            A 2nd or bigger alternator will not have any effect unless the existing alternator is supplying the power or the volts.

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            • #7
              I saw that some of these say "17v while charging". Is it not going to potentially damage electronic components?

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              • #8
                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?
                No, usually stuff that is made specifically for the car has a range of 12V-18V. Especially on Cameras. As for the Car PC, the PSU can usually except 11V-24V.
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                • #9
                  Over voltage isnt a problem so I would be comfortable with piecing together my own solar array. My camera/DVR is regulated, and that is the only thing that will be on while the car is off.

                  A bigger alternator isnt an option because the limitation is not the alternator, but the fact that no modern lead acid battery today can charge itself up quickly enough in a short 15 min drive.

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                  • #10
                    Originally posted by soundman98 View Post
                    i havent seen anything, but have been pondering a camera system in my car for a while-- this being the biggest thing to overcome, so i am also interested to see what can be done.

                    here is what i came up with:

                    either, 4 of these across the top of the windshield(claimed 1.5 watt output, per unit but no specs)
                    http://www.harborfreight.com/cpi/cta...emnumber=44768
                    I use a unit alot like this one in my car because I have a constant draw of about 2 watts in my setup, but the panel normally puts out just about 1-1.1 watts in normal sunlight sitting in my back window.

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                    • #11
                      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.

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                      • #12
                        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.

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                        • #13
                          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.

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                          • #14
                            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 [email protected], [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.

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                            • #15
                              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 =(

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