The magnetic pin connector on the TRIPLTEK 9 does work as a direct power supply to the the TRIPLTEK 9 without using the battery.
 
The TRIPLTEK 9 battery will not charge through the magnetic pin port.   
When you connect it the first time , you will hear a sound although the charging indicator will not light up.
 
Used in conjunction with the 9VDC converter it will maintain the battery level all times.
The connector will mantein the battery level even when the T9 is using the power need it to run the GPS navigation APPS at the maximum screen brightness.
 
No suitable for TRIPLTEK 8