"Make My Day" is powered by two of these customized battery packages.
They are made from battery packs that came with Black & Decker 9.6 V cordless drills. Each
"stick" contains eight 1.2 V cells formed into a star shape of 5 cells per layer.
The capacity of each cell is approximately 1500 mAh.
How To Make "5 Up On A Stick"
WARNING: It is important to not put too much heat
into the batteries when you are soldering them together. If you do,
they can explode just as they do when overcharged. The cells contain a solution of
potassium hydroxide which is very caustic. Not nice to have flying around your
shop or on you hands and face. Put a heat
gun on the terminals for 10 or 15 seconds. If you don't get the solder joint right, stop
and wait until the terminals cool down. Then try again. Always wear proper protection when doing this.
A full face guard is recommended. You have been warned!
The following calculations can be used to find the diameter needed for a stick to
properly fit a designated number of batteries around it.
Calculations:
A=360/# circles
B=(180-A)/2
C=r/cos B
D=(C-r)*2
The Steps: (select an image to see a larger version)
Individual battery cells.
Cells connected and fitted around central holding stick.
Taped battery cells.
Internal cell connection.
External wiring.
Finished product: 5 Up On A Stick!
Some tips
To connect the cells side by side, use a bit of copper or brass flat stock cut into the correct rectangular shape. Or you can buy Deans connectors available from hobby stores.
To connect them end to end, put them in a V block to maintain alignment. Tin the terminals you want to solder. Wait for them to cool somewhat. Then push both cells against the solder gun. When the solder on both terminals has heated up sufficiently, quickly remove the gun and slide the two cells together.