Need design for motion sensor battery operated LED light.

That would be a real prize for the little vandals.

You would certainly want a PIR based sensor, but they require a detection in the change of heat (i.e. person enters the can) and that takes detection circuitry. [At one time switch cap, but today just sample data system).

I'm more inclined to go for a high efficiency green LED and just run it all night from a battery that is charged during the day. Look at those cheap outdoor LED garden lights for inspiration. Green is where you eye peaks, and for some reason it also is a wavelength that is efficient for LEDs. [There are papers that go into the wavelength where your night vision is most efficient, and this differs from where your eye peaks in daylight.]

I've seen these lights with white LEDS for as cheap as $2. In the past, I used to plop down these cheap lights on remote mountaintops on BLM land. Eventually somebody would climb where I planted a light and remove it. I guess the BLM thought I was destroying the night time scenery. These are non-trivial climbs, so somebody must have really been POd to go through such effort and remove the light.

If you roll one yourself, I assume you just trickle charge a NiMH with the solar cell, and high side current sense when the solar cell is no longer producing current, which is your clue to power the LEDs. Probably an over-voltage detect on the NiMH, though if you size the solar cell properly, I bet just trickling would be fine. I doubt these cheap Chinese lights are very sophisticated.

While you are at it, an electric fan in the outhouse would be appreciated!

Google or look from Amazon 'pir battery led'.

Or get a panasonic PIR sensor from Mouser and connect it with a LED. To prevent LED from using the battery during day, add LDR. The PIR sensors consume about 1uA, so they can run on battery for quite long time.