Nickel-penny composition for voltaic cell

[BuddyPal]

I was organizing pennies into categories based on what they were composed of; before 1982 (I believe) pennies were made out of 95% Cu, and after they were made primarily out of zinc. I thought that the ideal penny for a voltaic cell would use a Copper penny, and a Nickel. However, I found that the composition of Nickels is 55% Cu. I care a lot more for this specific project because my physics class has turned it into a competition for highest voltage. I would test these metals myself but I do not own a voltmeter. =(

Specifically my question is; should I use 95% Copper pennies along with 55% Copper Nickels, or should I use 97.5% Zinc pennies along with 55% Copper Nickels for the highest voltage? Or better yet, are there other cheap and easily found metals that work better than these?

P.S. What kind of liquid (preferably non-odorous) should I use as an electrolyte?

P.S.S. My impression is to use zinc pennies and copper nickels, mostly because they are the most different, if this is the case, should I strip the covering off of the Zinc pennies? -unless that's illegal of course-

 

[anorlunda]

Your question is unclear. It sounds like you are using electroplating. But weight or resistance are much simpler ways to sort pennies.

What is your procedure? What do you mean by max voltage?