Are relays considered to be maxi fuses

Hello, No, maxi fuses are just fuses, and relays are internally switched to allow a low amperage circuit (like the ignition switch) to power a high amperage circuit (like the starter). Try cleaning the battery terminals first, then test all of your fuses with a test light. If there was any sparking when the new battery was connected, of if the battery was connected or jumped backwards, grounded, or arching occurred, this will likely lead do electronic component damage. Your testing should start at the battery cables and work towards the power distribution center. Also, check around for rodent droppings. Mice love wires.