Emergency lighting system shall be running all the time. The exit-lights and all other emergency lights are powered by on-grid power supply, which includes powering the battery to keep it fully charged. Once the grid power is cut off (by any accidents), GEM battery will turn on to work and to provide continous power supply to the lights and soundings. GEM Battery GS series batterie are compact, hermetically sealed and maintenance-free, with long lifespans and helps your emergency light working all the time.