Choosing an Energizer
by Gary Duncan
Choosing the proper size energizer can be a frustrating or intimidating proposition. It may depend on the integrity or knowledge of the salesperson whom you are dealing with. There is a lot of myth and mystery about energizers in general, but it doesn’t have to be that way. Your first consideration should be power source.
· 110V or 220V plug in mains power: is probably where you get the most power for your dollar. Our general recommendation is that if you have a power outlet available, then use it and get more power for your dollar.
· Battery power is necessary for locations where conventional electric power is not available. You will pay a little more for this energizer option, plus the additional cost of a good deep cell marine type battery. You may also consider the cost of replacing a battery every 3rd or 4th year.
· Solar power is another option for remote locations. However, you will usually pay about as much for the solar panel as you did for the energizer. Large solar units may require more than one battery. In essense the solar panel serves to keep your battery(s) charged. If you have enough battery storage, under normal conditions they will operate fine with a week of cloudy weather. However the larger battery energizers (under heavy loads) can run a battery down in a hurry.
Don't judge an energizer by its case size. In the photo above the case sizes are the same but from left to right, they have 15, 22 or 37 output joules.
Sizing an Energizer: There really is no industry standard for comparing energizers. To generalize all of the manufacturers is not possible either. So here is my GENERAL SUGGESTION. Most Manufacturers say that their energizers will power approximately 10 miles per output joule, and in some cases they just say joules or stored joules. It is not consistent between manufacturers. So my suggestion is if they say their energizer will power 30 miles, it probably tells me that it is around a 3 output joule charger. If you dropped their estimate in half you would probably be safe in assuming that it will power 15 miles. If you use my rule of thumb that 1 output joule will power between 3 to 4 miles, then I would be saying that a 3 joule charger will power between 9 and 12 miles of fence. So, my suggestion in a summary is: don’t always believe what it says on the charger box. At least drop the manufacturers claim in half - you are going to be putting it in a pasture with grass loads, weeds and vines -- not in a laboratory.
Note: When comparing energizers please try to evaluate them on the same basis (“apples to apples”). Output Energy is the amount of energy that is delivered to the fence. Stored Energy is the amount of energy stored inside the energizer (in the capacitors). Stored energy does not necessarily relate to the amount of energy that is delivered to the fence.
Try to compare energizers by looking at the maximum OUTPUT ENERGY. Some manufacturers do not give you all of this information on the packaging. Some may only give you Stored Energy, thus making it look more powerful to the un-informed. A general approximation is that the Output Energy is generally about 70% of the Stored Energy. Thus, an energizer boasting 10 Stored joules will actually be putting out about 7 Output Joules.
What is a joule? Good question, but hard to explain. It is a measure of electrical energy in British Thermal Units. Something like 1 watt for 1 second, which doesn’t mean a lot to me or most of our customers. What is important to me, is how much fence 1 joule will power. While many manufacturers claim that 1 joule will power 10 miles of fence we would suggest a 3 to 1 ratio. One output joule will power approximately 3 miles of fence – considering vegetation loads, vines, weeds, grass load and minor shorts. So, for example, if you have 12 miles of fence (12 divided by 3 = 4) you will need an energizer with at least 4 output joules. Additionally, most electric fence systems are generally added on to at some point. We would suggest that you buy an energizer (based on the example above) in the 6 to 8 output joule range. That should give you plenty of power.
New Zealanders visiting the US often comment that we overbuild our electric hi-tensile fences, then under-power them. Hummm. We are proponents of suggesting that you put more power on your fence than you initially think you will need - basically because it will NOT cost you all that much more & it is likely that you will be adding more fence in the future. The cost of a $300 energizer spread over 15 miles of fence is $ 0.0037878 cents per foot. The cost of a $1000 energizer spread over 100 miles of fence is $ 0.0018939 per foot. Hardly seems worth the effort to try to save money here. Don't skimp on your energizer and don't undersize it.
On the other hand to be fair here is to say this: If you do put a very large energizer on a very small run of fence -- you could possibly damage the energizer. It is my opinion that some feedback of pulse may go back into the energizer thru the fence line. Those pulses go to the end of the fence and dont just dissappear. They may travel back up the fence wire towards the charger. I've never seen reason to test this scenerio, but personally feel that this may happen.
Multi-wire fences? How do you figure your total footage of fence wire? There really are a lot of variables here and it depends on the grass load that you may expect. For instance a single wire cross fence that is 34" off the ground will not have much load. On the other had if you have a wire 6" off the ground (and you don't spray) you will have a load when the grass is growing. It also depends greatly on how you hook up your jumper wires and route your power through out your system, even with multi- wire systems. I generally figure multi-wire fences by the running foot of fence and I don't loop wires back into my system. Take your total distance of fence divided by 3 to find the minimum output joule size of energizer needed to most efficiently energize your fence. Another example: if I had 30 miles of fence divided by 3 = 10. So I would want at least 10 output joules, but I may buy one in the 12 to 15 joule range, maybe more if I expect heavy loads.
Basing your energizer requirements on acreage ? Some manufacturers may also indicate how many acres a particular energizer will power. I feel that this is probably a poor estimate for power requirements. There are too many variables involved such as cross-fencing, number of strands, etc.
Powering Poliwire ? In general, poli products are intended for short runs of fence. However, in some cases we have seen people with miles of poliwire in use. Poli products have much more resistance due to the diameter of the conductors. You will normally need more power when charging long distances of poliwire.
Strip Grazer Energizers: These are small energizers that are made for charging short runs of fence, generally less than a mile in total length, that you will be moving on a regular basis. Most of these energizers have output joules of 0.17 to 0.25 output joules. They work quite well for what they are intended for, which is short runs of polywire fences of a temporary nature. However, if you choose to put them on longer distances, then don't expect them to have a lot of voltage and power over distance.
We hope this helps when you decide on an energizer. As always, please feel free to call us anytime. 417-741-1230
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