Just to be clear, a power INVERTER changes DC current to AC current.
A step up CONVERTER is used to change 6V DC to 12V DC.
Here is one example of a STEP DOWN converter to change 6V DC into 5V DC to charge electronic devices through a USB...
https://www.ebay.com/itm/DC-6V-12V-2...oAAOSwywRaQiBZ
