A Flashlight that runs on Water

"Batteries are bulky, expensive, and risk polluting the environment with harmful chemicals when improperly disposed of. This DIY water-powered flashlight, however, uses an energy source that’s safe and free."

http://www.mentalfloss.com/article/73805/how-make-flashlight-runs-water

Surprise, surprise, it's the old "lemon battery" again. Yes, it also works with ordinary water, though even less well than with lemon juice.

Zinc and copper are not free. They're cheap, but so are AAs, and AAs are a lot more effective.

Actually, this battery runs on zinc and copper. Water is just part of the electrolyte. (Pure water is a poor electrolyte--more likely there is a dry chemical waiting to be dissolved in the water to form the electrolyte.)

IMO, most likely just a novelty.

BTW, there are "real" water activated batteries for applications with long storage until short usage. They would have a dry chemical waiting to be wetted by the water or might require sea water (ie sodium chloride dissolved in water). https://en.wikipedia.org/wiki/Water-activated_battery

Doug

how many lumens does it have? )