Tough economic times? Take 1.2 volt, 2.5 Amp/hr NiMH batteries (technically “cells”). Call it 3 W/hrs of energy each. The going electricity rate here is about $0.15/KW-hr. Thus fully charging four batteries with a 50% efficient charger costs approximately $0.0036.
More collected Geek Thoughts at http://geekthoughts.info.