We have a Rutland ESB275 unit which is battery powered but needs to be housed in a waterproof box- a spare coop in our case. We bought large leisure batteries which were expensive, but they last a month. Our enclosure consists of two 50m poultry nets which are the earth circuit as it is difficult, if not impossible, to stop them shorting to earth when used as the manufacturer intended. Then we have two lines of electric wire around the outside. Adding to that we have solar lights every 10 metres. So far we've had no problems although all the chickens are locked up at night in secure coops anyway. Not sure this arrangement would work in UK as you have fearless urban foxes rather than the cautious rural ones here.