An interior door does not have to withstand extreme weather changes. Interior and exterior doors are not the same product sold under different labels. The construction of each is different, with exterior doors given special treatment to stand up to the elements and frequent use.
The charging of lead-acid batteries can be hazardous. However, many workers may not see it that way since it is such a common activity in many workplaces. The two primary risks are from hydrogen gas formed when the battery is being charged and the sulfuric acid in the battery fluid.
The signals work directly off of the battery's power. If the battery is a tincy bit dis-charged (weak) the signals won't operate properly. Those batteries don't last very long and are inexpensive. First try to charge it, then change it if necessary. The charging system directly powers the headlight.