Just as a point of (humorous) reference, I bought and resold an old style fence charger a few years back.
It was a 6 volt model, with a mechanical balance wheel to time the pulses, each time it zapped the line, it gave a click as the balance wheel kicked.
Anyway, didn't have a six volt battery handy when the fellow that wanted to buy it came by. But I had the twelve volt one off the Horse trailer! We had it hooked up and running, on the kitchen table. I showed the spark that was jumping across about a 1/2 inch gap, using a screwdriver to vary the distance.
But the guy says "but does it have any real authority?", as he reached for it....
BAZAAAAP! He hit the wall pretty hard, when he recoiled off the strike. The laughter, well, let's just say his feelings were pretty hurt, there were three of us (his wife, myself and mine) laughing so hard WE were in pain. Seriously. Could hardly breathe!
Anyway, he thought it had authority enough.
Fencers vary a lot in their output. The old style ones (before the lawyers got involved) have a pretty good jolt to them, esp when you run them over their correct voltage.
A dab of peanut butter or bacon fat on the wire to get their attention, is said to work pretty well, too.
It really becomes a cost-benefit calculation, at the end of the day. How much stuff can you carry with you, vs. how much effort is the bear going to put into getting at your stuff.
Chain link cage for your camp, anyone?
Cheers
Trev