You’re unlikely to be going through batteries at the same rate you did even as recently as a decade ago, but those icons of yore are piled up en masse around the world. It turns out many used batteries still have a little juice in them – an average of 400 milliamps, to be exact. A promotional campaign called “Dead Batteries For Dead Batteries” takes advantage of that fact.

In a bid to promote a brand of soy milk, an ad agency set up a cell phone charging station in Thailand that was powered entirely by the energy left over in discarded batteries. The campaign used the residual energy stored in 1,500 batteries to charge 140 smartphones, amounting to an extra 830 hours of talk time.

Dead batteries might not be the solution to our growing energy problem, but this approach is certainly a lot more sophisticated than putting a couple of them in the fridge in hopes of powering your Walkman for a few extra hours.

[via Gizmodo]