November 05, 2017
I am going to make several comments regarding your question because this topic comes up all the time to me. I think this is a good time to explain what is needed in putting in a good hot fencer system whether solar or AC. A solar fencer properly sized for the acres covered or miles of total fence line will equal any AC mains fencer. The main problem with solar fencers that come in a carry out box size, is they lack the joules of output to handle the larger size of field or pasture needed to energize. Small solar panels, and a small battery also contribute to a lot of issues keeping the fencer going on cloudy days as well as colder weather when the battery becomes less efficient. Grounding is the number one issue I have seen in at least 97% of every fix I have done for farmers/ranchers. You need to have at least 3'-4' of ground rod for every joule of output on a fencer. If you have a 5 joule fencer in output joules then you need 15'-20' of total ground rod length in the ground spaced at least 8' apart. Formula is: depth of rod in feet x 1.13 for distance between each ground rod. Use copper ground rods always if possible too along with copper no. 12 or no. 8 bare copper wire. Do not mix galvanized with copper or corrosion will occur on the two being mated. Galvanized does not work well long term in moist soil. It will rust and rust does not conduct well so your resistance of the ground systems goes up, and the efficiency goes down, which decreases joule output of the fencer, and wastes it by putting it back down into the ground system instead of going out on the HOT side of the fencer. Only if it is encapsulated in concrete will it last longer. Copper if properly installed will last up to 40 years with a good quality ground rod. If you are wanting a good rule of thumb for a fencer to operate well, do a 1:1 ratio instead of a 10:1 ratio for miles of fence to be charged. 1 mile to 1 joule output will get you a good hot fence heavily loaded with a good quality fencer. 10 miles to 1 joule, best wishes, won't cut it. Also, a good fence should never have less than 4k volts minimum on it. I like to see 7k or above at all times. A good test to do if you doubt grounding. Take an area where deer are abundant. Put out a small powered fencer with an average ground system and see what happens. Count the days the deer knock off the insulators. Then go buy a good quality fencer with a heavy transformer in it, install a proper ground rod system, and the deer won't touch it. So, with that said, most solar fencers out of the box will not cover much over 2 miles of heavy fencing, because most are under the 3 joule output range. But around say a corn stalk field using 14 ga. wire, with a good hot fencer may work satisfactory up to as much as 120 acres with good wire, but no vegetation. If you see low voltage with a clean fence you normally have 1 of 3 issues, a poorly installed ground rod system, an undersized jouled fencer, or a cheap made fencer with no horsepower, small transformer inside. Some fencer companies such as Gallagher advertise their units in stored joules, so that is not the output rating. Figure about 65-75% stored joule efficiency to get a good feel for actual output joules. So lets take a B300 Gallagher for example, it states 2.6 joules stored energy, so then 1.70-1.95 joule output would be closer to actual range when figuring true net output of energy. In summary, I would not recommend using anything over a 5:1 ratio maximum or you will be disappointed in results, especially in single wire configuration.