18650 2x2 Battery Holder

thingiverse

This is a 18650 LiPo battery holder that can hold four 18650 batteries in various configurations. You can connect the four batteries either all in series, 4S1P, or all in parallel, 1S4P, or two sets of two in series, 2S2P. It uses eight M5 x 20mm hex head bolts as contacts to the battery terminals. I recommend filing or sanding the heads of the bolts smooth for best contact because the heads often have numbers or letters stamped on them for identification purposes. The main screw that runs through the middle of the holder is a 1/4" x 3.5" Phillips head bolt with a matching 1/4" nut on the opposite side to thread into. For connecting the M5 bolts to each other, I used 1/16" thick by 1/2" wide aluminum flat stock that I cut down to pieces that were 1.25" long. A hacksaw or diagonal cutters can be used to easily cut the aluminum pieces. This type of aluminum bar is commonly found at most hardware stores for about $3. Ring terminal wire connectors can then be used to connect wires to the M5 bolts and back to whatever device you are trying to connect the batteries to. I wanted this holder to provide a quick and reliable way to make 18650 battery packs without having to solder or spot weld tabs on them. So far, my testing has shown it works very well! Note that when tightening the center 1/4" bolt, be careful not to screw it too tight together because you can potentially squeeze the M5 bolts too tight against the batteries and slightly dent them. The batteries in the picture are all connected in series with one another, 4S1P.