Alarm control unit batteries are rechargeable sealed lead-acid batteries. Battery manufacturers recommend that these batteries be replaced every for (4) to five (5) years. As these batteries age their ability to provide standby power gradually decreases, hence the 4-5 year recommendation. Many alarm systems use detection equipment such as motion detectors, smoke detectors and door contacts that have small internal batteries. The life of these batteries depends to a large degree on the amount of motion within their range or the number of times a door is opened and closed. However, these devices monitor their batteries and generally will report a low battery condition and still continue to function properly for at least another thirty days.