Many remote radio repeaters operate from 12, 24, 36, or 48 volts, directly
from float-charged batteries. There is no interruption of service whenever
the AC power fails... and when the AC power is restored, the float charge
continues to keep the battery array at the design voltage level.
Not quite. When the AC power is restored, if it has been off for a while
and the radios have been drawing current from the batteries, the charger
has to supply a high charge current to the battery array, not just a
float current. For this reason the power supply actually has to be
capable of providing significantly higher current (some systems are
designed at 2X) than what the radios need to operate. If it cannot do
so, the battery won't get charged back up in time for the next power
outage. Or when the battery is taking a large charging current, and all
the radios get keyed up drawing full current, the power supply gets
overloaded, pops a breaker or fuse. It is pretty common for radio
traffic to be highest at the same time that power outages and recoverys
are happening.
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