the big powerful 12V power supply is far away from the load using long cables with a small amount of resistance. when the load switches on and current flows, it pulls the voltage down by over 3V. the immense power of the 12V supply does nothing, as the power cannot get to the load and is spent on the power cables making them nice and warm.
the solutions are to use shorter thicker cables with less resistance, and put big capacitors close to the heavy load. the capacitors will store charge and act like a power supply close to the load. the load will pull power stored in the capacitors first.
