What fruit/vegaetable has the most power to give (voltage)?

Question

http://en.wikipedia.org/wiki/Lemon_battery
well according to that link "lemons are preferred because of their higher acidity"

im doing this experiment for a science project and im gonna be powering my psp (3.6 volts) so what fruit/vegeatble would give me the most voltage
and how would i put this together a link would be nice too

Answer 1

The open-circuit voltage in a battery is determined by the metals used for electrodes. The electrolyte affects how much current you can draw and how much the voltage drops when you draw current.

Answer 2

for a cooler project, you should test several fruits/veggies of varying acidity to test your hypothesis if acidity is linked to higher voltage. try also pineapples and grapefruits