TABLE OF CONTENTS Transmission equipment is usually required to operate off the -48 and/or +24 V power supply. In wireless networks, battery backup shall provide sufficient reserve capacity to allow the uninterrupted operation of equipment for at least four hours for the cell sites and at least eight hours for the switch office. Customers may specify more or less capacity, as local conditions such as travel time (MTTR), standby generation of power, and power reliability may vary with location. The equipment shall be capable of successfully operating within published specifications and satisfy all required operational specifications with power variations that do not exceed -56 VDC or fall below -40 VDC at any given time. In newer and more advanced power systems, alarms will notify the user when the voltages get to within 20 percent of these extreme values. In the case of battery drain, it will signal when the equipment is within one hour of losing backup power.
Both the constant-voltage and the constant-current charge methods are suitable for charging recombinant lead-acid batteries. Of the two, the most common method used is simple constant voltage, which allows the battery to seek its own current level in overcharge (or float charge). For cyclic applications in which batteries undergo regular charge and discharge, the charge voltage per cell can range from 2.4 to 2.5 V. Although a float charge of 2.25 to 2.35 V is advisable for batteries in standby use, it is important to consult...
