This Instructable will show you how to make a 18650 Li-Ion cell holder for FREE. Use it to recharge your cells or add it as the power supply to any project you see fit.
Step 1: Gather the Components and Tools
1) Prescription pill bottle
2) 2x Metal Screws
3) Bits of Foam
4) Connector wire of Choice
1) Drill and small drill bit
2) Rubber cement (adhesive depends on type of foam you choose)
3) Soldering Iron
Step 2: Add the Battery Terminals
Drill a hole in the bottom of the bottle and in the cap just a bit smaller than the screw size. Add a screw into the cap to act as your positive terminal and a screw inside the bottle to act as the negative one. Most pill bottles will allow for the top to be turned over so it doesn't lock when closed. This is for people without children in the home or for people who have difficulty opening and closing things. We will turn our cap over to make it easy to open and reduce wear and tear when adding and removing the battery. Test fit your battery a few times to get the proper screw depth.
Step 3: Add the Foam Spacer
Cut and shape your bits of foam to act as a spacer inside the bottle. We do this so the battery can maintain a braced position and keep good contact with the terminals. Ultimately will use adhesive to hold the foam in place, but not yet.
Step 4: Test Your Connection and Add Connector Wire
Place your battery inside the bottle and use a multi-meter to make sure your battery is in a good position and maintains contact with the terminals. Now solder on a positive and negative lead wire. I recommend using heat shrink on the remainder of the exposed screw. Or you could wrap it in electrical tape. Remember, when soldering and heat shrinking that the pill bottle is made of thin plastic. It doesn't take much heat to deform your bottle.
Step 5: Finish It Off
Now that all the soldering and heating is done, you can use the adhesive to hold your foam in place. Apply liberally to the outside of your foam spacer and place it back into the bottle. Then place a battery inside with it to help hold the desired shape while it dries. I added red tape to the bottle cap to remind me it was the positive terminal and covered the rest in black tape. Totally unnecessary but it makes it look a little better. I use my battery holder to recharge cells salvaged from old laptops. These cells can go for upwards of $10 each from a reputable dealer. New battery holders are actually pretty cheap themselves, but this one is FREE.