If you have a TSC, they have everything you need. My guess would be around a couple hundred which would be the charger strong enough to let any predator such as a bear know the hot wire is there. Once they get zapped they don't usually test it again and most predators first explore with their nose. On a bear the nose and tongue getting zapped should be enough to send it packing. Their fur is quite thick so the wire touching the fur isn't as effective as the nose and tongue. The reason for baiting the wire is to get the bear to touch it with either its nose, tongue or lips which are the most sensitive parts.