A DIY car jump starter: Li-ion 3S, LiFePO4 4S and supercapacitors
How much current the starter of a 1.3 to 6 L engine draws, and why a start takes seconds, not minutes. A Li-ion 3S jump pack with USB-C charging: cells, "C" rating, contactor, diodes, controller and code. A LiFePO4 4S pack with a 200 A BMS that pre-charges a flat battery and helps start the car. Whether you can do without a lead-acid battery, Li-ion or LiFePO4, supercapacitors.