I’m looking for a Car Jump Starter.
Preferably 4S LiFePO₄ (4 x 3.2V = 12.8V) so i can also use it to recharge the car battery if it drains too low while working on the car.
Bonus would be USB-PD one or two-way (to charge the battery pack and/or to charge laptops).
Put [LiFePO₄ jump starter] in a search engine and go to it.
Most jump starters do not specify the battery so I assume they are some variety of 18650 Lion.
I swapped the lead acid battery from a 1.4L Ford Focus with a 12V battery made from Headway cells, then tried to start the car. Nothing. Did even hear the starter motor.
Only the windshield wipers worked.