I am using two of the “DROK 600W 12A DC Boost Voltage Converter 12-60V to 12-80V Step-up Power Supply Transformer Module Regulator Controller Constant Volt/Amp Car”
(Amazon link: https://www.amazon.com/gp/product/B00E8D7XYG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1)
I have a heavy wire going from the car battery, through a 30AMP fuse, then to a 30AMP switch and then to these two modules. I have the outputs going to drone batteries to charge them. I’ve set the output voltage to 26 Volts on each and the output current to 6 AMPS each. The problem is that my 10 AWG 5′ long wire is getting hot and my 30AMP fuse is melting and blowing.

Have I calculated it correctly?
Input current = output power / efficiency factor / input voltage
Input current = 2modules*(26V * 6A) / 0.95% / 12V = 27.4 Amps

I’ve even had problems at 5AMP output.

Also, I set the output voltage to 26.0 volts but when I connect the battery it drops to 24 volts.