Building Solar Cell Battery Light

[wil3]

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.

 

[vk6kro]

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

https://www.physicsforums.com/showthread.php?t=365810

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
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:
http://www.northerntool.com/shop/tools/product_200396364_200396364
which doesn't include the battery.

Is this a feasible idea?
Probably not, unless you have someone who can help you.