This is an old topic, but I have similar questions.
I just fried my tracker trying to use a 9v battery. I had started hooking the 9v to the blue screw terminals on the GPS shield, but that didn’t seem to powerup the Electron. So I tried using VIN/GND and it still didn’t seem to power everything up right.
So… stupid me, I tried VBAT/GND pop (and that unmistakable smell)
Needless to say, that split second completely ruined my day.
SO… What is the recommended connection? If there is a 9v adaptor out there somewhere with the same connector end as the LiPo battery that would be great, but I don’t know what kind of plug to search for?