Under normal circumstances batteries in all devices should last up to two years. However, the battery in the Mk1 Shock Sensor will last for up to one year. Excessive use or poor signal strength may adversely affect battery life. When a battery reaches the end of its life the transmitter will send a ‘Low Battery’ message or a ‘Supervision Fault’ will be indicated at the panel, warning you that the battery requires replacing. We recommend that batteries are replaced routinely after two years (one year in the case of the Mk1 Shock Sensor).