In this instructable I'll show you how to make a battery holder for Lithium 18650 batteries so you can use unprotected cells in your DIY projects without worrying about over discharge, overcharge, or short circuit.

What we need:

- 18650 Holder (http://ebay.to/1K3CY55) Edit: http://ebay.to/1K9HbyP These are cheaper. Thanks Elac.

- 18650 Battery protection boards (http://bit.ly/1fGCJi6 buy 5 sets and it's cheaper)

- Soldering equipment

- Hot glue

If you find cheaper alternatives for the Holder and protection boards please let me know in the comments. With these items every protected holder costs 0.97$. Edit: With the Battery holders suggested by Elac. it is only 0,83$.

Step 1: Preparing the Battery Holder.

Start off with the removal of the negative side of the battery holder. To do this bend the retention brackets to the center. From experience the easiest way to bend them is to use a small flat-blade screwdriver. Then you should be able to pull the spring and the wire out. The Wire is connected to the spring with the metal post you just pulled out of the battery holder. Separate the wire, the metal post and the spring. We won't need the post but keep the black wire and the spring.

Now push the red wire through the hole to the inside of the battery holder. The red wire will be the wire from the battery to the protection circuit. Measure the length of the battery holder and cut the red wire to a length that it reaches the negative end of the battery holder.

Step 2: Preparing the Protection Circuit

Strip the end of the positive wire inside of the battery holder. Make sure not to remove too much of the insulation. Just enough to later attach the wire to the B+ pad of the protection circuit.

Take a wire (preferably a black one as it will be the negative side). The one previously attached to the battery holder is perfect for this. Cut the wire into two pieces. One short one which reaches from the B- pad to the other side of the protection circuit. This wire will connect the spring to the B- pad. The rest of the wire will be used for the P- pad and act as your negative output. So don't make it too short.

We will need a red wire too. The leftover of the previously cut wire is probably not long enough but if you think it's long enough to fit your use go with it.

Step 3: Connecting Everything to the Protection Board

Now it's time to attach everything to the protection board.

Start with soldering the long black wire to the P- pad, the short one to the B- pad and a red wire to P+ pad.

After you've done this solder the red from the battery holder to the B+ pad.

We're almost finished. Just solder the spring to the short black wire. Make sure you solder it in oriented correctly as it'll make life easier later on.

Now glue the spring to the underside of the Protection circuit.

Step 4: Final Assembly

Before putting everything into the battery holder make sure everything is soldered in the correct way and please ensure that you haven't created any short circuits.

Finally put the red and black wire from the P+ and P- Terminal through the hole of the battery holder and put the protection circuit into the battery holder. You may wan't to glue the Protection circuit into the battery holder but from my experience I can tell you that it isn't necessary. Just insert a Battery once and it should stay in place.

Now you have a protected 18650 battery holder for your projects so you don't have to worry about your unprotected 18650 battery.

Disclaimer: I'm not responsible for any damage. Please be extremely careful when dealing with Lithium batteries. They can be dangerous if they are mistreated. If you have no experience with Lithium batteries whatsoever please inform yourself about the dangers of Lithium batteries and how to treat them correctly.