My horses are too far away from the house to have a plug in electric fence charger, because of that I have a solar charger that requires a battery. If the fence isn’t checked often the battery can be worn down by vegetation on the line.
All it takes is a branch or two to drain a battery and make the electrical system useless. Even in winter the fence row has to be checked regularly. In the summer you can loose a fence all together if it isn’t cleared often.