Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Building Solar Cell Battery Light

  1. Mar 20, 2010 #1
    Hello. As a memorial I am trying to build a light-sensitive unit that will make an LED continuously glow at night. I want to put this in an extremely remote place and be reasonable confident that it will continue to operate indefinitely. The idea is that once it becomes dark, a photodiode will permit current to flow through the LED until dawn. Once the sun rises, a solar cell will recharge the battery. I want the circuit to be able to continue doing this without any component replacement or repairs for as long as possible (greater than five years would be ideal).

    Is this a feasible idea? What parts would you recommend? I need a rechargeable battery that can last an extremely long time (is there a way to substitute a capacitor?). I also need a somewhat reliable LED and solar panel. The longer the circuit can last, the better- it will be exposed to the elements, but I plan on encasing as much of the circuit as possible in resin. I am not concerned with cost.

    Also, if anyone has a decent circuit schematic for this sort of setup, I would appreciate it. I have a few, but options are always nice.

    Thank you for any advice.
  2. jcsd
  3. Mar 20, 2010 #2


    User Avatar
    Science Advisor

    There is a circuit in this thread that may be useful:


    It is a redrawing of a commercial circuit, but looks very clever.

    You could have simpler circuitry, but you would then need at least 3 NiMH batteries and 6 solar cells to operate a white LED.

    A common application for this is the solar garden light, although these are often poor quality and only light for a few hours after a sunny day.

    Your application would really need a serious solar panel and a long-life lead-acid battery such as the ones that are used in electric wheelchairs.

    A possible source of parts for this (although not a good as the above) would be this:
    http://www.northerntool.com/shop/tools/product_200306871_200306871 [Broken]
    However that is intended to be switched on as required, not run continuously when it is dark. So, some expertise would be required to convert it.
    or this one:
    which doesn't include the battery.

    Is this a feasible idea?
    Probably not, unless you have somone who can help you.
    Last edited by a moderator: May 4, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook