Definitions for "BACK-UP BATTERY"
A battery which is available to maintain memory contents in the event of primary power failure.
A separate battery added to the security system as an alternate power supply to serve as a backup in case the vehicle's main battery should be disabled by a thief.
A battery installed in the alarm panel to supply the power in an electrical shortage
Keywords:  bang, cheap, twice, buck, get
a relatively cheap way to get twice the bang for your buck, though
a sensible (and necessary) accessory for all but the most casual of photographers