Expansion packs are available with 30 meters (100 feet) polywire and 2 posts each. They give you the option of having:
You may consider adding a line, for instance, to protect game or food caches from smaller scavengers as well as predators.
As for a door, you could use 2 of the 6 posts that come with the stock Base Camp fence. But this would sacrifice square footage. Better to use an Expansion Pack, which could also extend the perimeter and add a line.
The Bear Sentry energizer can power up to 20 km (over 12 miles) of wire and remain extremely capable. So there are practically no limits to how you configure your fence for your particular needs.
The Backcountry model can secure up to 25 m2 ( 269 ft² ) with 65 m ( 196’ ) of 2 mm ( 5/64” ) polywire; Expansion Packs are available for larger enclosures. Again, we recommend no more than 5 m (16’) between poles to reduce sag in the 3 lines.
1. Optimal voltage. This is the electrical “pressure” in the fence that enables a connection with a bear. Use your voltage tester to see if dry conditions are lowering that potential (we explain here). You may have to water the ground stake and maybe the area outside where a bear would stand.
2. Current fault. Look for any “short-circuit” where energy is being rerouted from your fence or “leaked” to the ground via grass or a branch touching or too close to a line.
If you hear a crackling fizzle noise or see light arcing off your fence, that’s a short. Disconnect the fence from the energizer before removing the problem.
3. Tension. Check that your lines have some tension, because slack polywire can loop off an insulator clip and touch the pole for a short. (The more tension the better anyway, here’s why). Again, shut down the fence, straighten up the poles and adjust the lines. Guylines make this easier.
Do not test the fence yourself!! That’s the hard way.
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Next, hook the energizer up to the fence: red to the polywire, black to the ground stake. Stab the probe of the voltage tester into the ground as deep as you can and touch the clip to anywhere on the hot line.
If you see much less than 10,000 V, water your ground stake at least.
(Other things to check for optimal performance are reviewed here).
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If a bear tries to enter your camp site, the Bear Sentry energizer is highly capable of delivering the shock to deter it. However, you’ve got to provide the best circumstances for that big shock to happen: make sure the system is operating properly (see the FAQ) and reduce sag in the lines.
Here’s why.
The best and more likely scenario has the bear touching the polywire with its wet nose; the electrical connection will be relatively easy.
Your Bear Sentry does have the high voltage potential or “electrical pressure” to get through long and thick fur to the skin for a shock (see the FAQ). However, it will help if the line penetrates the fur in the first place, physically, and this requires some tension in the line.
So watch for ways to make your Bear Sentry as robust as it can be. This includes tensioning the polywire with guylines.
Bear Sentry guylines are available with More Good Kit.
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When we designed our electric fences we knew they had to be functional and easy to use. We developed our own guylines with this in mind.
They help to reduce sag in the lines for both fences. When it comes to performance, the more tension, the better (see the FAQ ). And, they make it simple to adjust for tension in the lines before bed.
The Basecamp model is inherently more stable because of its step-in posts. But this Bear Sentry can benefit from guylines too, particularly over longer stays when small movements in the fence, for example near a gate, may loosen their footing.
Finally, guylines help to secure both models when the weather turns ugly (and make them visible).
Bear Sentry Guylines can be purchased separately.
Note: the best way to pull the guylines taut is downward, having looped the end with the aluminum tensioner around the top of the pole, and the end with the bowline onto the peg. This way the tensioners are closer to hand during set up.
]]>The flow of electricity is regulated by the energizer (also called a charger). It stores electrons in a “capacitor” and then releases them in a “pulse”; after each pulse the capacitor stores up electrons for the next pulse.
Clicking indicates pulses being released by the second. However, each pulse lasts a tiny fraction of a second.
Pulsing allows a bear to break contact from the fence once it has taken a shock i.e the connection will last but for a split second so the bear’s muscles won’t lock up and make him “stick” to the fence for a continuous shock. The bear will be able to run away, shaken and deterred, not harmed.
This is a good design feature for you too in case you touch a hot wire by accident (or metal while you’re using the voltage tester)!
Then hook the spooler onto a pole.
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You’ve clipped the 3 blue insulators to each pole with the bottom clip 8” to 12” from the ground. The other two should be evenly spaced with the top one at the very top.
Take the yellow ring terminal that is already crimped onto the polywire, and hook it onto the little upright arm of the bottom clip as per set up instructions in the manual.
Then swing the line to the left underneath the clip. In this position, under tension, the ring terminal is less likely to slip off as you move.
String your fence counterclockwise, keeping some tension on the line slightly upward as you go.
You can make a gate or ‘door’ in the Base Camp model. You’ll need to use 2 posts for the door and string the polywire in a zig zag pattern. An Expansion Pack can be used for a door.
Without stepping it in, position a ‘door post’ right up against the ‘start post’. Loop them together with the Velcro tie straps that come with this Bear Sentry. Make a doorway by inserting a ‘pivot post’ about a meter or yard away. Space the rest of the posts evenly around your campsite perimeter.
String this set up starting from the bottom clip of the start post and move away from the door posts. Once you’ve gone all the way round, step up for another line on the door post. Then zig back in the direction you came until you reach the start post again, where you step up for another line, zag back and repeat the pattern for as many as 5 lines.
To exit through the door, be sure to disconnect the fence from the energizer first and then swing the door post out. Once you’re back inside and the fence is hot again, check to see that your Bear Sentry is working properly (see the FAQ) and that your lines haven’t sagged.
For longer stays you may want to use guylines on the posts because small movements can loosen their footing over time. They help keep tension in the lines, which is a good thing (see the FAQ). Bear Sentry Guyline kits are available.
To exit from a Backcountry fence it’s a matter of procedure, not set up, because of the spiral flow of the polywire in one direction (and you wouldn’t want to sacrifice a pole to make a door).
Rather, to exit, disconnect the energizer and follow these steps:
1. Separate the top section of a corner pole.
2. Lightly pull that top section outward and downward, keeping the lines taut.
3. Lower it to the ground and use the bottom section to brace it.
When an electrically conductive body like a bear contacts a “hot line,” it becomes the missing link between the fence (positive) and the ground (black).
The bear completes the circuit between the ( + ) and ( - ) poles of the energizer.
A huge 1.0 Joule pulse of electrical energy flows from nose to paws to ground for a split second. Shocked, the bear runs away. Deterred, it won’t come back.
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You’d be doing a service to the bears by preventing them from associating food with people, in the wilderness or at home. For, bears have excellent memory. If they develop bad habits, it doesn’t work out well for anybody.
Keep the skat on the right side of the line!
However, as with any electric fence, you do have to be careful about children or pets getting too close: the Bear Sentry shock is nasty although not dangerous per se.
]]>Let’s start with the Basics
When an animal touches the hot wire of an electrified fence, it closes what was until then an open circuit. Electrical energy is allowed to travel from the energizer (along the wire), through its body, and back to the energizer (through the ground).
How easily that circuit can be closed is a function of the voltage established by the energizer. How large of a shock the animal feels is a function of how much energy the energizer delivers.
Higher Voltage – Better Connection
Voltage is a measure of the electrical “pressure” created by the energizer from hot wire to ground. The higher the voltage, the easier it is for a predator to close the connection, and the less that dry conditions can affect that connection.
5000V is generally accepted as the ‘bare’ minimum (it takes 5000V - 6000V to make a connection through a Black bear’s fur). The Bear Sentry energizer creates 10,000V - think big, hairy Grizzly.
Energy is Everything
Energizers are rated by how much energy they store and by how much energy they can deliver under load (“stored energy” is theoretical, “delivered energy” represents the real world).
That ‘output’ rating of a bear fence energizer is critical, because size does matter when you’re dealing with an apex predator. Research shows that at least 0.5 Joules of delivered energy is needed to turn away a curious bear. But if a motivated, hungry Griz comes round, you’ll want more than the minimum shock!
Bear Sentries Really Deliver
The Bear Sentry energizer stores 1.8 Joules and delivers at least 1.0 Joule when discharged. That’s twice the minimum. That’s deterrence.
]]>Simply buy Expansion Packs for the Base Camp model.
This is possible because Bear Sentries are modular: Backcountry and Base Camp models share the same powerful energizer and many common components; it's the posts and wire that distinguish them. So you can convert a Backcountry into a Base Camp and vice versa with the purchase of one model, and expansion packs for the other.
With “Two Bear Sentries in one” you can protect your campsite wherever or however you want to enjoy the wilderness.
So the bear won’t get ‘stuck’ to the fence from seized up muscles; instead, it will be released instantaneously to run away and think twice about approaching your or anyone else’s campsite again.
The outcome that lasts is not physical damage, then, but psychological deterrence.
Bear Sentries are actually “good” for bears, because zapping them modifies their behaviour: they learn to disassociate food from human spaces and avoid campsites and homes where they can end up in unfortunate conflicts with us (leading to what are called ‘defensive kills’, and more orphans sent to the Northern Lights Wildlife Shelter, if they’re lucky).
So when your Bear Sentry goes into action, it’s good for you and good for the bears.
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Feed the polywire into the ring terminal and wind it through. Using aviation snips (or any other strong shears) cut off the fused section. Pull back the polywire until about a 1/2” is left.
With an electrical crimping tool, crimp i.e. compress the narrow section of the ring terminal shaft onto the polywire end (you can use another tool as long as you get lots of pressure right on the centre.
Hook the ring terminal onto a low clip.
]]>For sure.
Bears do love beehives for their honey and pupae. A Bear Sentry can protect them from predation and damage, with a few considerations.
A bear would be highly motivated to cross the fence perimeter. While the Bear Sentry energizer is highly capable of delivering the shock required, it’s important that your set up provide the best circumstances for that big shock to happen, whether the bear hits the fence high or low, with its nose or thickly furred body (read about how an electrical connection is made under “Should I pack the volt meter?”).
The best Bear Sentry for the job would be the Base Camp model with possibly one or more expansion packs depending on the size of the apiary and the terrain.
String at least one extra polywire line on the lowest clip (in addition to the minimum 3 we recommend for Bear Sentries).
Ensure that all the lines remain taught. Position the step-in posts closer together than the 5m / 16’ maximum we normally recommend and use more posts with expansion packs if you have to. This will avoid potential sag in the lines. You can also use guy lines on the corner posts for more tension.
You’ll need access to your bees and this means setting up your fence for a door (see “Is there a gate for my Bear Sentry?”).
You’d have to hook up the energizer on the the outside of course, so that you can disconnect the fence before heading in. Just remember not to handle the hardware afterwards with sticky, sweet smelling hands or the bear will deactivate the fence for you.
We recommend using household/mains power with the AC adapter. If you’re off-grid, use 12V car battery power charged by a 100W solar panel.
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Output energy is the energy of the shock actually delivered (to a bear). It depends on the resistance of the line and the quality of the ground. With 20km of line and a good ground, the energizer "output" energy is rated at 1.0 Joules.
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Roughly 24 continuous hours (three 8-hour nights) with fresh alkaline batteries in optimal conditions. Don't forget that batteries are affected by the cold, so bring spares if out for more than two nights.
Long Answer:
Gotta start with these:
Power (Watts) = Current (Amps) x Electromotive Force (Volts)
Energy (Watt hour) = Power (Watts) x Time (hours)
A standard alkaline AA battery is rated for 1.5 V with about 2.8 Ah of charge. That means it has an energy capacity of roughly 4 Wh. When connected in series, you add the voltage and the energy rating of each battery, so a Bear Sentry battery pack (with alkaline batteries) provides 12 V and holds 32 Wh of energy.
The Bear Sentry energizer runs on that 12 V and is rated to draw 100 mA of current when the fence is operating (even when it's not being discharged). As such, it draws 1.2 W of power when electrified. For every hour it operates, it consumes 1.2 Wh of energy, so the pack can therefore charge the fence for 27 continuous hours. Assuming you only have the fence running while you sleep, the pack should do you for up to three 8-hour days.
The energizer releases a full 1.0 Joule pulse of energy when the hot wire is grounded. A Joule is a Ws, or 0.00028 Wh of energy. As such, shocks delivered by the energizer make no appreciable dent in the battery pack's capacity.
The fence works with such a small release of energy, because the fence energizer transforms the voltage of the system up to around 10,000 V while limiting the pulse to only 3/10,000 of a second. 1.0 J of energy delivered in such a tiny fraction of a second is an extremely painful experience, but does no damage.
Here's the rub: the type of batteries and the ambient temperature can make a fair amount of difference to the fence's longevity. We tested the system using standard alkaline batteries with temperatures around 20C and got results in line with the theory presented above. At colder temperatures however, longevity will be reduced.
Long and short of it is that if you're camping out for two nights or more, you should bring a spare set of batteries with you.
An alternative would be to bring along a solar charged power bank such as the one we offer. Ours has a rated 50 Wh capacity and can recharge in full sunlight at 1 W.
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