6V 4.5AH Size Lithium Rechargeable Battery

This is a three-part shell that houses four 18650 cells that will source 7.2 to 8.4 volts with double capacity being that two sets of the cells are in parallel. Using 1-1/2AH cells yield 3AH battery, 2AH cells yield 4AH. Caution: Since it can put out 8.4 volts make sure your application can except the higher voltage and input charge voltage exceeds the 8.4 volts for proper charging.

Assembly: Mount the white BMS holder to the middle board using two short 4mm countersunk screws. Seat them tightly so the tops are below the surface of the holes. If left up to high, it could short across the board. Set aside. When assembling the batteries it would help to use the bottom case to hold the batteries in the proper configuration otherwise if they are not kept together in a tight group, they will be difficult to install. Cut three wires well longer than you think you will need. I used red for positive, black for negative and green for the bottom section group of cells for the mid connection. Solder them to the cells. Set cells in base and fish the wires up through the white insulator and the middle section. Middle Section: Set middle section onto the base. Solder red and black wires to the BMS board end B+ and B- pads. Solder green wire to the opposite end single pad.  Flip the board over and align in the white BMS holder. Hot glue the board in place. Move excess wires from the mounting holes and hot glue them down. The area around the holes need room for the top section boss to seat onto the middle section. Top Section: Since the battery terminals need to protrude through the top enough to connect to your application, they need to be trimmed to allow them to push through farther (as pictured).  Solder wires to the terminals, 3/16" (5mm) to negative and ¼" (6.3mm) to positive. Once pushed through, bend over the terminal at the soldered wire, hot glue them in place. Use plenty of hot glue to prevent the terminal from being pushed back down but not to exceed the height of the screw boss.  Solder wires to P+ and P-. Place top on middle and add 4mm screws. The threaded holes in the base are about 10mm deep, use 30 to 35mm countersunk or other head that covers the countersink in the top. There will be no measured voltage until the board is activated by putting a small charge across the terminals.

Printing: Base was about an 8-hour print, 0.2 layer, 3 walls, 20% infill. Middle was about 2 - 2-½ hour print 0.2 layer, 3 walls, 20% infill. using support for the rim. Top was about 2 - 2-½ hour print 0.2 layer, 3 walls, 20% infill. Insulator and BMS were about 15-minute print each 0.2 layer, 3 walls, 20% infill. 

BMS Board: Purchased from Amazon. 2S 7.4V 8.4V 8A 18650 Charger PCB BMS Protection Board for Li-ion Lithium Battery Cell