rbx battery 18650 assembled

There are 2 versions of the Battery Brick, This version is powered by a single 18650 Li-on battery. The other version uses 4 x AA batteries (alkaline or rechargeable), which are more commonly found in most households, but is heavier and bigger.

Both versions make use of 11mm conical springs (0.5x8-11x14x7mm) as the negative terminal contact:

part conical spring

These can be quite easily harvested from old toys and remote controls if you are always on the look out for these things.

Brass plated round head fasteners function as the positive terminal contact:

round head fasteners

A small 3-pin toggle switch functions as a central on/off switch to the power supply:

part toggle switch

Parts list

11mm conical springs 1
Brass plated round head fastener 2
3-pin toggle switch 1
M2 self-tapping screw 6
Prototype board  1
2-pin JST RCY connector (female) 2


Prepare a piece of prototype board that has 7 holes across and 5 holes down. Its dimension should be approximately 20mm across and 15mm down.

rbx battery aa circuit 01

Insert the 3-pin toggle switch in the middle of the prototype board.

rbx battery aa circuit 02

Cut off the legs from a brass plated round head fastener. Solder the brass legs and the 2-pin JST RCY connectors to the toggle switch as follows:

rbx battery aa schematic

The brass strips are connected to the left and right pins of the toggle switch, and they will evenutally make contact with the positive and negative battery terminals. The red wire of the RCY connector is connected to the middle pin. When the switch is toggled in the direction of the positive pin, the middle pin will become positive, hence powering the RCY connector.

This is how it looks when done:

rbx battery 18650 circuit 01 rbx battery 18650 circuit 02

 Pay attention to how the positive (right) and negative (left) sides are oriented. This is important because of how the strips will make contact with the battery terminals later.


Print out the enclosure parts on a 3D printer.


rbx battery 18650 3dview

Secure the prototype board to the switch holder using 2 x M2 screws. 

rbx battery 18650 assembly 01 rbx battery 18650 assembly 02

Push the switch holder into the switch cover from below.

rbx battery 18650 assembly 03 rbx battery 18650 assembly 04

At the positive terminal of the cell holder, insert a brass plated round head fastener. Bend the legs to one side, and trim excess with a cutter.

rbx battery 18650 assembly 05

Cut off the legs of the other fastener, and connect them with a short piece of wire (length about 1cm less than the length of the cell holder).

rbx battery 18650 assembly 06

Insert the brass legs into the respective slots at the positve and negative ends of the cell holder. 

rbx battery 18650 assembly 07 

For the brass strip at the negative end, push with a thin blade so that it is sitting against the wall as shown in the diagram below. This is to ensure better contact with the end loop of the conical spring when we insert it later.

rbx battery aa terminals 03

Insert the conical spring into the negative terminal. The end loop of the spring goes into the slot and touches the brass leg inserted previously from the adjacent battery compartment. Then the spring is pushed down with a flat blade screwdriver so that it catches in the horizontal retainer slot and stays in place.

rbx battery 18650 assembly 08

Then insert the cell holder into the bottom body:

rbx battery 18650 assembly 09

Align and secure the switch cover in place with 2 x M2 screws The brass strips from the switch circuit should make contact with the brass strips on the cell holding body as indicated in the diagram below.

rbx battery 18650 assembly 10 rbx battery 18650 assembly 11

Assemble and secure the top cover in place with 2 x M2 screws.

rbx battery 18650 assembly 12

Line up four 3x1 brickbases on a faceplate, one row apart. Surround the brickbases with a few other bricks to assist in alignment.

rbx battery 18650 assembly 13

Add two drops of superglue on each brickbase and mount the module. Press and hold for 60s.

rbx battery 18650 assembly 14

The finished module:

rbx battery 18650 assembled