I'm creating a voltaic cell project for my high school chemistry students. This is a design challenge for them to use electronegativity differences to produce enough voltage and current to power a small DIY motor and fan. So far, I have been able to generate about 1.7V but only 0.4mA using lots of spirals of Mg ribbon along with a Cu electrode using porous cups (and not a salt bridge). I've increased the concentration of Copper nitrate. What methods might increase the current? We're have enough voltage to run 1.5V DIY motors but they won't run due to lack of current.
We're doing this: http://static.nsta.org/files/tst1409_30.pdf