If you are using LFP (LiFePo4 / Lithium Iron Phosphate) cells:
To build a 12V Battery Pack, it requires 4 cells in Series. Nominal Voltage for every cell is 3.2V X 4 = 12.8V
You can place cells in Parallel within a pack to increase the AH. Cells in Parallel act & appear as "one cell" but there are GOTHA'S!
It is extremely important to have matched cells in parallel otherwise they can imbalance and create issues.
Each Parallel "Set" of cells get's ONE BMS Sense lead, therefore you need a 4S BMS.
Battery Packs in Parallel (meaning identical 12V Packs) divide & share both Load & Charge.
If one fails within a parallel bank the others keep going unless they are all discharged.
Below are some graphics & guides I have written up to help.
Below is a Graphic showing standard LFP Battery Pack layout for 12V.
A Guide on how to assemble your own battery pack(s) with lots of handy ref info:
Luyuan Tech Basic Lifepo4 Guide V1.0A
And a few more reference graphics below that you may want to download.
Note that each 12V Battery Pack will require it's own 4S BMS (Battery Management System) and fused appropriately.
It is best to "Right Size" BMS to the pack. IE: 100AH Cells use a BMS that supports 100A Discharge, if using 280AH Cells use a BMS capable of 200-250A Discharge.
---> LFP CHEMISTRY Voltage Range Chart.
---> VOLTAGE CURVE TO SOC (basic)
---> AN A-TYPICAL COMPONENT BASE SYSTEM