Expert: Mike Fulcher - 9/20/2008

Question
Mike,
You asked :
Now for more questions.
Which side of the paper do you paint on?  My guess would be the paper side, not the foil side right?

After painting on the non-foil side you've got a manganese dioxide - aluminum cell with paper as the separator.  Sounds straightforward enough.

When you stack the cells, how do you stack them?  Do you stack aluminum to aluminum and then MnO2 to MnO2?  Or do you stack aluminum to MnO2?  This would be the preferred way, but it's important to separate each cell a piece of metal foil if you do this.  Otherwise no matter how many cells you stack you'll still get the voltage of only one cell.  This would also give you a rapidly decaying voltage as the cells react.  The foil is intended to prevent electrolyte leakage via diffusion but still allow the cells to be electrically connected.  If you haven't already, give this a try and let me know how it goes

Q1 I did paint on the paper side.
   
Q2 I stack AL,P,MNO2, Al,Paper,MNO2, Al,Paper,MNO2 Etc.

Suggestion 1:
I redid my stack to be AL,Paper,MNO2, AL, AL,Paper,MNO2, AL,AL,Paper, MNO2 Or looked at another way. Cell1+AL+Cell2+AL+Cell3+AL+Cell4...
I think that is what you had in mind.
Result: There was a slight voltage increase. But the quickly decaying voltage problem was the same.

I am truly confused. ;-) Any thoughts as to what (undoubtedly silly) thing I am doing wrong?

Thank You,
Paul Prado

Answer
Well, from what you're telling me it seems as if there may be an current leakage path in the battery.  This is a common problem in bi-polar cells, where what typically happens is that ionic transfer occurs around the edges of the electrode plates, bypassing the non-permeable current collector (extra Al foil).  As a way to check this, try making your MnO2  electrodes smaller while keeping the separator paper and Al foil pieces the same size.  1/4" smaller per side should give you a suitable cell.  Let me know how that works out.