i use a car battery and charge it once a week. it powers a 150' fence around my chickens all year round and also a 2000' fence around my garden that keeps the deer out. during the winter the battery is not so good since those kinds of batteries put out less when its cold out but the local predators surely know this fence by now and avoid it. if I had a more critical fencing situation I would probably not rely on the method I use.