No.

-On the headunit, the red power wire goes to the ignition. That way when you turn on your car, the headunit is able to turn on.
-The yellow power wire goes to the battery. This gives a constant feed of power to the headunit. That way, the headunit can retain information like the radio presets, EQ, or clock.

If you connect both of those wires to the battery, the headunit will be on ALL THE TIME. Not good.

Just another reason to get the harness. Itll sort it out for you.