All the usb chargers I’ve tried in my 6v truck work just fine
The modern ones all buck the voltage down
So worst case they need literally like 0.1v more than the regulated output to function
So just try it and see, if it works good, if not try a different one.
-s
A typical regulator requires minimum ~1VDC between the input and output voltages. An LDO is typically in the 0.3VDC range.
I will throw a couple adapters on my bench supply this weekend and see when they drop out. With an operating voltage of 7.5 like HRL mentioned, I would expect any of them to work. With the engine off and just the battery voltage as the source, you could get some weird switching issues and much more parasitic drain than you expect.
I would recommend ignition switching the power if you do go down this route.
