That's good! If you learn something from it, I'd call that a successful project.
Two things you should play around with and see what you can get are concentration and electrode surface area.
I've already explained concentration in a nutshell, but to play around with it, take some vinegar, for example, and boil off some of the water. You should have concentrated it. Try a battery with the concentrate versus the normal stuff right out of the bottle and see what you get.
Electrode surface area - a battery works by the reaction between the electrolyte and the metal. This means that in the middle of the battery, nothing is "happening" aside from electron transfer - no reaction occurs there. It occurs on the outside of the electrode.
Larger electrode = larger reaction = more energy yield
That being said, try finding various metal objects of different sizes and wiring the leads to them, and test them all with a common electrolyte (acid or base). You should get better performance out of the one with the larger plates!
Just some food for thought.
solidus
