http://www.newton.dep.anl.gov/askasci/gen01/gen01159.htm
Hey Einstein, where in this link you provided is the mention of ordinary batteries obeying the E = mc^2 equation?
Apparently, my substandard education in the English language came of no help in this regard.
Sorry. I assumed you could make the leap from 'burning' is a chemical reaction obeying E=MC^2 to batteries being a chemical reaction obeying E=MC^2. That would be about a 7th grade level chemistry topic.