Exposure light battery extender question

[Bathroom_Security]

Am I right to assume I can take both the extender and the light, fully charged to the trails, plug the extender in and turn on the light and leave it? And it'll just act as a piggy back light?

Had it on setting 2 tonight and just left it and after about 2 hours it started to flash to suggest it was running low.

Generally get 2.5 hours from the Zenith before it starts to flash (switching between high and low on and off the trail)

Cheers