Boing Boing

Boing Boing

What are those blue dots on coin cell batteries?

Mark Frauenfelder
Nov 26, 2024
∙ Paid
2
5
Share

Energizer coin cell battery with Color Alert coating

Yesterday a redditor named joshcam posted a photo of a coin cell battery with purple colored dots arranged in three concentric semicircles. They posted:

To the naked eye, these dots are an iridescent, deep purple, the kind of purple you see when you look at a black light.

There are three rows of dots run…

Keep reading with a 7-day free trial

Subscribe to Boing Boing to keep reading this post and get 7 days of free access to the full post archives.

Already a paid subscriber? Sign in
© 2025 Happy Mutants LLC
Privacy ∙ Terms ∙ Collection notice
Start writingGet the app
Substack is the home for great culture