How to properly wire a 4.5V LED strip with 12V motors
simulate this circuit &ndash; Schematic created using CircuitLab

You will need to use a 12V LED strip, just using a series resistor with a 4.5V strip will probably not work.  If you use a 12V strip, the resistor can be omitted. 

Here is the problem with putting the resistor in series with the LEDS:







simulate this circuit

The problem is that you need a drop of 8.1V (12.6 - 4.5V) at R1.  In order to calculate the value of the resistor you need to know the current through this resistor.  The current will vary with the temperature and aging of the LEDS, so the value is going to be approximate.  This may work, if you have a way to measure the current for the LED bar at 4.5V, then you can use ohm's law R=V/I where V=8.1 and I = the current of the led bar in amps to calculate the value for the resistor.  The LEDs will tolerate a range of current values so you might get away from this, but if you need whatever you are making to be reliable you might want to just purchase some 12V LED strips or modules and run them directly instead (they are dirt cheap from the usual providers).