There are two types of Charge Controllers, MPPT and PWM. This modification only applies to PWM Controller Solar Systems.
Additionally, you will only want to use this when your battery(ies) are near fully charged and you have a few hours of full sunlight left for the day. Furthermore, this will only work if your PWM Controller has a pair of "Load" terminals available.
I purchased a 12 volt 3-port expansion module to increase the functionality of my Solar System. This allows me to use my Solar system to directly charge my 12 volt and USB devices without using my 12 volt battery.
Here is the 3-port expansion module...
This has a 12v socket, a Volt Meter and a 2 port USB Charge module.
I connected these to the "Load" terminals on my PWM Charge controller with an "on/off" switch for each of the 3 ports ( this eliminates any parasitic drain on my battery from the volt meter or the USB ports ). Additionally, I had to read the PWM controller instructions in order to learn how to turn the "Load" terminals on.
I can now recharge my devices directly from my Solar system without using electrons from my battery.