I have a couple of protected 18650 battery cells. So I decided to put them to use as battery packs for other project. - If you don't have protected cells, do not discharge them too much!

Most of the time the 3.7V a LiMH cell puts out, does not fit the requirements of circuits. Therefore, I constructed a battery pack around a MT3608 DC to DC booster converter board. IC Station sells a MT3608 based booster that can turn 2-24V input into 5-28V output voltage regulated with a potentiometer.

To connect the board to the cell, I use generic AA battery contacts. To fit the design they should be 13x11mm in dimension with a lip at the bottom to solder to. 

To get the boosted voltage out, you can use any lead that suits your need. There are additional holes for a cable tie acting as a strain relief. Most people (I think) will opt for a Molex style connector like the KF2510. You could also use a lead with a barrel jack.

When the contacts, booster board and output lead are connection, place the separation plate in for the battery to rest on. The plate comes in two flavors, with raised and with embossed letters.

Edit: Made the text on the separation plate a parameter for easier handling. You can change the “18650” to anything suitable, like “5V” for an according booster module…

A word of Warning If you want to buy 18650 for this project, or any LiMH in general, do not fall for shiny pictures or nice wording. Insist on seeing the manufacturers marks that state voltage (3.7V), capacity (~3000mAh) and peak currency (10C). Well established brands are Samsung and Panasonic. Part numbers like NCR18650B that can be traced to 3.7V/3400mAh by Panasonic are a good indicator, too. - As always, if you trust the seller, you can trust the product.