Only work under the darkness or weak light. It is highly suggested to attach to the wall, fridge or place parallel to human body. not suggest to put them like under the cabinet, not enough space to sense body. but it it is ok to do so if you can guarantee there are enough space to sense human body The usb on left or right side will strengthen the sensitivity when you attach the magnet sticker. No need battery USD Rechargeable for use . More economic and cheaper in a long run Charging mode(if support): USB charging style: Warm white / Cool White Charging time(if support): 2 hours