Custom Batteries --- Cheap!

The 12 volt "remote control" battery shown at right is available from WalMart at a cost of 2 for $1.77.

These batteries each contain 8 individual cells.  Peel off the casing and they fall right out.

Next, find some washers that are just slightly larger than the individual cells.  Solder  wires to two of these as shown above.  I used black for the negative end and yellow for the positive.

Now clamp one lead to a holder and slip an approriate size heat shring tubing over the bottom washer.  Stack the cells (at 1.5 volts each) with the negative end down to get your desired voltage.

Put the other washer/wire assembly into the top and seat it against the stack of cells.

Using a lighter or other heat sorce, shrink the whole thing as much as possible.  The tubing also shrinks along its linear dimension which pulls the whole stack firmly together.

The one shown here has 4 cells and produces 6 volts suitable for directly powering PIC's.  Other choices for the PIC are 3, and 4.5 volts.