How to home make a battery for HP25/c/21

1. Obtain radio shack part numbers 23-149 1000mAh Nicad Batteries (2), 270-382A 2 cell AA battery holder. 2. Snip off the snap end, the plastic is a little brittle, so I used Diagonal Cutters to cut it off right where the flat plastic that holds the snaps 3 Snip off the spring from the snap part and place it in the bottom of the cell holder. 4 Install the two NiCad batteries one with positive showing, one with negative showing 5 Insert the assembly into the back of the calculator, you will have to compress the springs to get it to fit. The positive battery should touch the left terminal in the calculator as you are holding the calculator with the terminals up (upside-down), viewing the back. I use a slip of cardboard to close the back cut into a rectangle with one tab on one side and 2 tabs that fit into the slots on the calculator. An X-Creditcard or somthing of that same thickness would work better.