In many projects you need a power that is capable of producing 5 volts DC, and AA battery holders just don't have the right cell count in most cases.
I know many people just go ahead and use 9-volt batteries, but they cost more than AA's and rechargeable 9Vs and chargers are harder to get a great deal on. So my portal power sources consist of rechargeable AAs and 12v SLAs
If you primarily use 1.2 volt rechargeable batteries like I do then getting the right voltage to your projects can get annoying. In a 4 cell, there is not enough voltage to even get to 5 volts since it tops out at 4.8V. A 5 cell pack is would produce 6V which will source a 5V regulator like the common 7805, but the cell packs are hard to find and they carry an inflated price tag too.
This forces you to move up to a 6 cell pack which will produce 7.2V and to add a power switch to your project which takes up space.
Replace the extra battery in a 6 cell battery holder with "Battery Switch".
Difficulty: 2 of 5
Time: 10-15 minutes
Cost: <$3 USD
Step 1: Materials
1 - 1/2 dowel the length of a AA battery
3.5 inches 18 gauge solid copper wire (a bit more if using higher gauge, a bit less if smaller gauge)
1 - SPST switch (SPDT could also be used)
Solid core wire (I used 18 gauge)
Drill bit the size of your wire or slightly larger
Saw (to cut a slot in the dowel - a coping saw would work well)
Soldering iron and solder (gas torch would be a fire hazard on this project)
Hot glue (I used hot glue, read my not later on)
Step 2: Cut, Drill, Cut
Cut a battery size chunk off the dowel. Make it the length of the body of the battery not including the positive(+) nipple.
Draw a line along the length of the dowel chunk. This will help you align the holes to be drilled.
Drill 2 holes in each end of the dowel chunk. Drill one hole about 1 inch in along the line you drew and the second hole about a 1/2 inch deep opposite the first hole.
Carve out a slot big enough to fit your switch in and to expose the 2 deep holes that you drilled. The slot you cut should remove the center of the line you drew earlier.
Step 3: Insert the Wire
Cut a 3-4 inch chunk of wire and strip off the insulation. I recommend using a wire stripper and cutting the insulation in 1/2 inch pieces for easy removal. Then cut the wire slightly off center so you have 2 wires.
Coil the end of each wire so that one end will reach the switch contact and the other end will fit into the shallow holes.
Step 4: Attach the Switch
Stick the switch in the slot, solder the 2 wires to the switch contacts.
Glue the switch into the slot. This returns some of the strength to the dowel, makes the switch stable, and insulates the contacts.
Note: When you glue in the switch be sure to not fill in the open ends of the switch. If you get hot glue inside the switch it will prevent the switch for closing. I learned this the hard way so you don't have to.