Q. During last Pesach the lights went out for a few hours. Could someone have used then an LED flashlight that was plugged into the electrical outlet to maintain its charge, since there was no electrical power and a turned on flashlight should not be muktze on Yom Tov?

A. Horav Shlomo Miller’s Shlit”a opinion is that indeed it would be permitted to use it on Yom Tov, if it turned itself on automatically when the power was cut. However after its use, it should not be plugged back into the outlet even if the power is still off.
The above applies only for Yom Tov. On Shabbos, he recommends to consider the flashlight muktze.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a