There are strange things happening!
The USB cable should not enter in to the equation as USB is USB and the pins should be wired correctly.
Here is what I have found.
If charging in the car all is ok until the power is cut, then it only charges whilst off until the TYTN is soft reset. This looks to me like there is a software / powercontroller confilct. It is a little confusing but see the scenarios below;
Soft reset TYTN, leave it off. Plug in to cigarette charger, turn TYTN on/off all is fine.
Turn off TYTN and unplug, all is fine, plug back in (TYTN off) will still charge when TYTN on.
Turn TYTN on, unplug, will not charge whilst on anymore until soft reset but will charge whilst off.
This is the same if I turn the ignition to power the lightere socket.
However, another spanner in the works, if I pull out the charger even with the device off and re-insert it it stops charging until soft reset.
What seemd to work best was to do a soft reset whilst the unit is charging and powered on. After that I was able to unplug, plug in even when the unit was on, turn ignition off/on etc... It only reverted back to not charging when I removed the charger from the socket as it was charging.
These are my findings and I presume each charger will be different.
I presume whatever electronics are in the chargers also causes problems. I have tried 2 USB and one fully wired charger and it is the same with all. I know for a fact that at least 2 of them have overcharge circuitry built in but do not think the 3rd has, I also presume the TYTN also has so perhaps there is some conflict here also.
I do know that there are car chargers specifically for the TYTN so will try one of those and see if it solves the problem. (anyone tried one?)
Anyone with more ideas please let us know.