Solar lights too

power managent in a simple application

While the firefly jars were nice they lacked the utility of a simple solar light. The way I had to use epoxy to fix the panels inside the jar was also a bit of an annoyance. A light would also need some diffusion to work well. I decided to trade a some of longevity for convenience and lower BOM and start using simple glass jars with metal screw tops. The glass should be milky and thus scatter the light of a few warm white LED to give the light a nice glow.

I also experimented with higher voltage panels to improve runtime in December / January and try to use cheaper LiPo cells instead of NiMH batteries.

Turns out that pre-made small milk-glass jars are almost impossible to find and the only good way to make them yourself is using acid that get regularly taken off the market because they are kinda dangerous. There are alternatives that are based on acrylic paint but they are sadly not long lasting. Sandblasting glass at home is right out as well.

The main takeaways for me are as follows:

  • NiMH is superior to LiPo cells in this application
  • jars with metal caps work well and can keep out moisture
  • the limiting factor for lifetime of these is that the damn things fall down and shatter :P
  • the epoxy the cells are made with goes blind in a year or 2 but can be “regenerated” with a gas burner

I will probably do a third version and plan for a larger series that time.


Lights in snow :)