Battery capacity is affected by the cold of spring or fall.
A cable extension lets you power your Bear Sentry from inside your tent where you can keep your power supply a bit warmer, safely. You can charge another device meanwhile with a DC splitter cable.
A 3m/10ft extension will reach the energizer in a standard Backcountry fence layout (59g). The Base Camp model already comes with this cable. But you may need another for a larger campsite or when your vehicle is set back aways.
The 1.5m/5ft cable is for those who have to count every gram, and make it work (31g).
DC 5.5mm x 2.1mm barrel plugs, female to male, 20AWG