MAJOR PRODUCTS: ELECTRIC FENCE CHARGERS: INTRODUCTION
Choosing a Charger:
CAMPERS: Get a weak (light and compact) battery-powered charger (see below).
If your fence is within easy range (160 feet) or an AC outlet, you should get a strong (3 joule or so) AC-powered charger. Plan on plugging the charger into this outlet. Don't put the charger near the fence for connection to a distant outlet with a household extension cord, because that's dangerous. Instead, put the charger near your AC outlet and carry the charger's output (which is safe despite its high voltage) from the charger's positive terminal to the fence with heavily insulated hookup wire designed to carry high voltage. Be sure you get a long enough length of hookup wire to do the job.
If your fence is over 160 feet away from the nearest AC outlet, consider getting a solar-powered charger. Solar-powered chargers are more expensive than AC-powered ones.
Campers don't need a strong charger, because they have a temporary installation (hopefully with no food smells about), and because a bear approaching a new campsite will typically be wary--so that in most cases even a little shock will send the bear away. This means that the best camper chargers are small battery-powered chargers like the Field Guardian D Cell that weigh little, put out .35 joules or so (enough to do the job), and run for weeks on four flashlight batteries.