I have a DC-DC converter which converts 9-36V to 13.8V with a 20A rating. I would like to use this converter to charge a 100aH LiFePo4 (with BMS, see: https://ca.renogy.com/renogy-smart-lithium-iron-phosphate-battery-12-volt-100ah/) from my car's 12V SLA battery.
From what I understand, the 13.8V output of the DC-DC converter works for charging my LiFePo4, but I don't believe that the converter has any current limiting built in. I assume that this means that when I connect the batteries using the converter, the LiFePo4 will immediately try to draw as much current as possible.
The converter has over-current protection, which I assume means that it will shut off at >20A.
What is the simplest way to add current limiting to my setup? Or... can I use the DC-DC converter as is?