It’s the big paradox of emergency-use flashlights … by the time you eventually need to use them, their batteries have died. Eton’s new Blackout Buddy H2O, however, will reportedly still work after sitting for up to 10 years. And to turn it on, you just add water.
This latest member of the Blackout Buddy line has a magnesium-oxide battery, which starts delivering power to the light’s three LEDs when exposed to H2O. To initially fire it up, you dip it into a small cup of water, or pour water into its battery compartment.
For more detail: Blackout Buddy H2O runs on water to provide emergency lighting