LiIon Battery 21700 4s2p V2

This is a 4-in-series, 2-in-parallel (4s2p) lithium ion battery using 21700 cells. The materials, tools, and build steps, are presented below. The total cost of a single battery minus labor is around $76, while mass is around 644 grams. Nominal voltage is 3.6V X 4 = 14.4V, while fully charged voltage is 4.1 X 3 = 16.4V. Charge capacity is the charge capacity of the chosen li-ion cell times two since the cells are in a two-in-parallel configuration (e.g., for EVE 50PL cell with 5 Ah charge capacity, total battery capacity would be 10 Ah). Build instructions are found in the included PDF. ####Physical Properties Mass: 644 grams (+/- 20 grams depending on the 21700 cell type used) Length: 318 mm Width: 47 mm Depth: 25 mm ####Cost per battery Cells: $8 per cell * 8 cells = $64 Filament: $3 Wire: $3 Connectors: $1 Conductive strip: $5 Labor (2 hr @ 30 $/hr): $60 TOTAL COST: $136 ####Materials carbon fiber rods (diameter = 2mm, length >= 240 mm), quantity: 4 PETG filament spool, quantity: 1 21700 cells, quantity: 6 (I recommend EVE 50PL or Molicel P50B as of November 2025) Red 10 AWG wire, 11 [cm] length Black 10 AWG wire, 35 [cm] length Red 22 AWG wire, 10 [cm] length Black 22 AWG wire, 80 [cm] length 4 pin JST-XH female connector housing, quantity: 1 (this is the balance connector) JST-XH female connector, quantity 4 (these fit into the JST-XH connector housing) XT60 connector, quantity: 1 (this is the power connector) Shrink tube kit, quantity: 1 21700 2P nickel-plated copper busbar, (purchase via AliExpress, Alibaba, or eBay: search 'Copper Nickel Busbar 21700 2P Direct', I've included an image with the dimensions: match the dimensions on the AliExpress listing to those in the image; strip length of 200 mm should be more than enough) Tools Spot welder (I use the Sequre SQ-1) Soldering iron Needle nose pliers Super glue Metal shears ####Build Steps See the 'Li_Ion_Battery_21700_4s2p_Overview_and_Build_Steps' PDF file. I recommend printing it out and following step-by-step.