Solar light for a little free library

June 21, 2023 2:09 PM

I am building a little free library that I want to be lit :) I am able to find lights with detached solar panels like this one, but not something that fits all the points on my wishlist, more inside.

The specifics:
* To be installed under a tree, so the panel needs to be detached so I can mount that nearby where the sun shines

* Low profile light so it does not take up a lot of room inside the little library

* Want to have it lit dimly after dusk (so people can be aware), and then light up brighter when someone comes nearby (to save power)

* Due to the above, I'd like the motion sensor to be separate from the light if possible so I can mount the sensor under the library facing outward to detect passersby

* As reliable / long lasting as possible because this is going to be installed near a community dog park


I know that's a lot on my wishlist, but does such a unicorn exist or do I have to build something custom using parts?

posted by thewildgreen to Home & Garden (5 answers total)

Solar string lights often come with panel that mounts separately from the lights. I have not heard of a solar light that can do different light settings or has a motion sensor attached.
posted by amanda at 3:52 PM on June 21, 2023

You may have to divide the project into two parts, one that lit up dimly after dark, then a separate system that lights up brightly once someone comes near. They can share the power source, but it may be easier to configure them separately.
posted by kschang at 6:26 PM on June 21, 2023 [2 favorites]

I don't know any off the shelf kit to do all that. As mentioned 2 systems, would be what I would do if keeping it to online off the shelf. However even if you had a motion detector step light you would likely have to separate the sensor from the housing to have the light inside and sensor under. I generally expect a couple of years from these products, batteries and water intrusion mostly.

Custom using parts will take more space but will do it all. If you have a old but still holds some charge 12v battery and appropriate container for the battery and controller you save $ as battery boxes are $$. There are some great lighting/solar charge controllers out there.
posted by blink_left at 7:15 PM on June 21, 2023

(Please post a picture on Projects once it's built!)
posted by cnidaria at 8:06 PM on June 21, 2023 [3 favorites]

The LEDs on solar fairy lights generally use so little power, that it will usually be inefficient to have a motion sensor, as that will use more power than it is worth if that is really the only motivation (on higher wattage devices the tradeoff is worth it).

Detachable solar panel in a public place is also at more risk of going walk about, and the considerable amount of faff of moving a solar panel around say a campsite to get sun is a lot of effort for not alot of charge. A backup battery charged at home lasts a really long time in comparison, and is, in my experience, less hassle for similar tasks.


The lowest hassle budget work around mvp might be:
Get a long enough string of solar fairy lights that the panel can be installed (possibly on a branch) on the south side of the tree, and then the fairy lights on a long enough cord to just wind through the tree and around the library box.
The fairy lights switching on at night only.

Even the seed lights on copper wire are enough to illuminate a little library.

If I was upgrading that set up, it would be for replaceable batteries rather than a removable solar panel, so that spare batteries can be charged at home and then swapped out, which will get you through cloudy days better than moving the panel around.
posted by Elysum at 3:18 AM on June 22, 2023