This weatherproof 12V adaptor cable allows you to connect the Batcorder to existing 12V batteries (as opposed to the 6V/2.7Ah battery pack that comes as standard with the Batcorder). The adaptor has crocodile clips allowing it to be connected to a variety of different batteries.
If the batcorder is connected to a normal 12V battery you should expect to get enough power for at least 2 weeks. If connected to a car battery, you could probably expect 4 to 6 weeks. However, this is very dependent on levels of activity at the site.