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Solar powered LED project questions

Hi all

I'm pretty "green" when it comes to electronics so i'll appologise in
advance for my ignorance. =)

I'm interested in building a Solar Panel -> Battery -> LED light system
to put on/In a Geodesic dome i've built. The idea being that the panels
charge the Battery during the day and then i flip a switch (or
something) at night and the LEDs come on (lighting the inside of the
dome), being powered by the battery.

so my questions are as such:

1) i was thinking of using 3-LED bundles - perhaps 3 of them (so 9 LEDs
total) since i don't need TONS of light, just enough to not be tripping
over stuff. Is a rechargable 12V battery (like this one >
http://www.cabelas.com/cabelas/en/t...&cm_ven=srchdx&cm_ite=srchdx&_requestid=24926)
large enough.. or TOO large to power the LEDs for the entire night?

2) if a get a 12V solar panel (like this one >
http://store.sundancesolar.com/20wasopa.html), do i need any circuitry
between the panel and the battery for it to charge correctly/safely
(assuming the battery and solar panel are the same/similar voltage)?

3) do i need any circuitry between the Battery and the LEDs?

i searched High and Low on google, but couldn't find much DIY project
info on this kind of thing.. which surprised me as i figured lots of
people would be into it?!?

any help, suggestions etc are apprecited.

thanks!
Chris Lev
chrislev at gmail dot com
 
B

Ban

Jan 1, 1970
0
Hi all

I'm pretty "green" when it comes to electronics so i'll appologise in
advance for my ignorance. =)

I'm interested in building a Solar Panel -> Battery -> LED light
system to put on/In a Geodesic dome i've built. The idea being that
the panels charge the Battery during the day and then i flip a switch
(or something) at night and the LEDs come on (lighting the inside of
the dome), being powered by the battery.

so my questions are as such:

1) i was thinking of using 3-LED bundles - perhaps 3 of them (so 9
LEDs total) since i don't need TONS of light, just enough to not be
tripping over stuff. Is a rechargable 12V battery (like this one >
http://www.cabelas.com/cabelas/en/t...&cm_ven=srchdx&cm_ite=srchdx&_requestid=24926)
large enough.. or TOO large to power the LEDs for the entire night?

2) if a get a 12V solar panel (like this one >
http://store.sundancesolar.com/20wasopa.html), do i need any circuitry
between the panel and the battery for it to charge correctly/safely
(assuming the battery and solar panel are the same/similar voltage)?

The panel is a good choice.
you will need a charge controller like the one on the bottom of the page to
not overcharge the battery. If your panel puts out 1.2A max., you might
receive around 6-8Ah every day. Your battery is a bit small for this, that
means it will not be able to absorb all of the charge, but after half day
the panel is switched off by the controller and the capacity is wasted.
A good rule of thump is to use a battery with 3-4 times the dayly output, so
a 24Ah would be better. If you use the lighting every day, your consumation
should be a little less, lets say 5Ah. This avoids a run-down battery, which
shortens its life a lot. also the battery should never be discharged to less
than 50% to keep it alive for a couple of years.
white LEDs are very expensive and do not give much light either, I would go
for the depicted flourescent light with 11W/12V, at least as a main light,
which outputs the equivalent of a 40-60W incandescent bulb. It will consume
about 1A, meaning that you can run it for 5 to 6 hours every night without
stressing the battery. If you want to run the lights a lot longer, there are
2.5W LED-arrays(18 or so) in a 50mm halogen fixture that will last 3times as
long, so you can run them the whole night.
 
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