Panasonic Digital Business System - Installation ManualMarch 1997 Issue 531External BatteryAs an alternative to using the internal battery option in the event of a power failure and external battery systemcan be installed to provide a longer period of operation when the power fails. If the external battery option is usedinternal batteries cannot be connected.The external battery consists of the following components; VB24971 Battery Cabinet and VB24973 Battery. Thebattery itself consists of 2 parts of BT2004B rated 12v 24Ah.The batteries will maintain system operation for approximately 3 hours on DBS 38 and 1 hour on DBS 68 and DBS90 cabinets. When using external batteries each CCU in the system will require a cabinet and battery unit. Thepower failure operation time will depend upon prevailing traffic conditions.The maintenance maximum back up time Panasonic recommend replacing the batteries every 3 years. Therecommended replacement is VB24973 but any other battery meeting the specification can be used.ImportantThis apparatus is designed for use when powered by VB24971, external battery unit in the event of a powerfailure. Other usage will invalidate any approval given to this apparatus if as a result it ceases to comply with theedition of BS6301 to which it was approved.Figure 26 - Installing The External Battery