Power question

Do I need to do anything special for dual power source?

If I have a mains powered 12v line, and a battery powered 12v line, can I just hook the positive and negative lines together and use that as the input, or do I need to make it disconnect the battery when the power comes on?

The battery is going to be permanently connected, the mains will be sporadic.

Not a good practice to just wire them together as there can be back feed problems in some situations.

A common solution is to wire a series diode from each positive wire source and wire the two diode cathodes leads together to supply the load. The two source ground wires can just be wired together.

This will allow isolation between the two voltage sources at the expense of a .6vdc voltage drop. Be sure the diodes current rating is selected to be able to handle the maximum current draw expected from the load circuit.