Sorry for my english and sorry for my drawings, I dont have electricity, just the phone!!!!!!!
Step 1: Materials
-Voltage regulator 0-32 volts to 0-32 volts US$1 www.aliexpress.com
-Solar panel 10 watts (used)
Step 2: Connect
Step 3: Adjust
If the "input voltaje" change (12 volts to 17 volts) the output is fixed 12 volts.
The converter change the voltage from 12 volts to 5 volts in the usb ports.