Around here they don't bother putting backup power at most cell sites.
> When Nextel put one of their cell sites on the building we're in we
> offered them a tap off our generator but they didn't want it.
The typical power "board" for a cell site consists of an AC-to-DC rectifier system that changes the 240VAC commercial power to +24Vdc needed for the equipment. Almost always, a string of twelve 2V VRLA batteries is provided for backup. A common size for the battery string is 1040 Ah (Amp-hours). The actual back-up time is dependent upon the load being drawn by the cell site equipment, age/condition of the batteries, ambient temp inside the cell site, etc.