Electric fence charger - how do I charge my battery, and how long will it last?
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  1. #1
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    Default Electric fence charger - how do I charge my battery, and how long will it last?

    Long story short, I have an electric fence energizer that is battery powered.

    I also have a 120 amp hour 12 volt battery that I can attach to the charger and help it deter bears.

    Two questions, as I'm not the most informed on batteries:

    1) How do I charge the battery, exactly? Do I just hook it up to my car, using a typical jumper cable setup - and turn my car on...and just let it sit there for a half hour or so? 12 volt to 12 volt, that should work right?

    2) Once I figure out how to charge my 120 amp hour battery, how long will it last with a 6 joule energizer? You think I can get it to last 3-6 months on a single charge?

    3) Any recommendations on how to block the rain from hitting the battery and the charger?

    Thank you!!

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  3. #2
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Hello, welcome to the forum!
    First off, I don't have an electric fence personally, but I've seen plenty of them. Each brand is a little different, but I think the things I can state below should be almost identical for all brands:
    - I think 100% of the ones I have seen are solar recharged... A small panel is mounted on a pole near the fence controller, like a 10"x12" panel or something like that
    - The fence won't draw much power, and can stay mostly charged, as long as you keep any grass and veg away from the wires, or any other potential grounds (like bears). The more bears, the shorter the battery will last
    - Wherever the wire crosses a pole, make sure there is an insulator to eliminate parasitic grounds there too. The wire must remain totally isolated (except for the occasional bear)
    - The battery and leads should be inside a plastic box OFF THE GROUND that is well protected from water, high enough that it can't flood into the box in a big rain
    - The box must NOT be totally sealed, when batteries charge they release explosive hydrogen gas, so it needs to vent a bit
    - If the box is out of direct sun that can be nice too, batteries don't like lots of heat, but of course the panel needs to be facing the sun as much as possible
    - The panel controller should have a charge controller, so it is not trying the overcharge the battery if it is full. If it overcharges frequently, it'll kill the lifespan of the battery
    - Make sure the box is anchored, so a strong wind (or strong bear) can't just easily push it over and knock the battery leads off
    Does that help?
    USDA 6a, 8 frame equipment

  4. #3
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    I don't have a solar charger, just a battery and a battery powered energizer. Solar chargers of good quality that can keep out the 500 pound bears we have up here are $600+, and that's just too expensive.

    So I have a 12v 120amp hour battery, and a 6 joule charger, total was around $200.

    I did learn info on how to keep the battery protected from the elements, but I still don't know how to charge the battery, and how long it would last before recharging (no solar charger).

  5. #4
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by username00101 View Post
    I don't have a solar charger, just a battery and a battery powered energizer. Solar chargers of good quality that can keep out the 500 pound bears we have up here are $600+, and that's just too expensive.

    So I have a 12v 120amp hour battery, and a 6 joule charger, total was around $200.

    I did learn info on how to keep the battery protected from the elements, but I still don't know how to charge the battery, and how long it would last before recharging (no solar charger).
    The trick to the solar charger is that it doesn't NEED to charge much, since the fence doesn't draw much except for the occasional bear jolt. Hopefully the bears learn after a few times and the fence can stay charged even longer. I see that harbor freight even sells a 7 watt solar charger for $30, here is the link:

    https://www.harborfreight.com/7-watt...kit-64801.html
    USDA 6a, 8 frame equipment

  6. #5
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    A 6 joule charger is larger than commonly used for bee enclosures. I have a 6 joule on my pasture and paddock but it is 110 v ac fed. My bee fence is perhaps a 2 joule but it stays on a garden tractor battery with a solar panel/charge controller and it looks after itself. I dont know how long it would last between charges if not supported by the solar. I would only go for the periodic recharge setup in an emergency as a lead acid battery does not do well to be living in a discharged condition. I would seriously consider getting a solar panel with charge controller.

    You can charge it up from your vehicle as you suggest but pick up a cheap multi meter and check the battery a few times a week apart. This will give you a handle on how long between charges. Fully charged with no load it should read 13 volts and I dont think you should be drawing it down below 11 volts before topping it up. Do a google on lead acid battery sulphation to see why.
    Frank

  7. #6
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by username00101 View Post
    I did learn info on how to keep the battery protected from the elements, but I still don't know how to charge the battery, and how long it would last before recharging (no solar charger).
    Your fence charger setup will be best served by using a deep-cycle battery (as opposed to a regular automotive-style battery). As such, your fence application is quite similar to an electric trolling motor application, that is - a low discharge rate over a relatively long period of time. Whereas an automotive battery experiences a high demand (starting the engine) and then not much of a demand after that.

    So, you can learn a lot about charging your fence battery by reading this page on trolling motor battery charging:
    https://www.minnkotamotors.com/blog/...-cycle-battery

    I recommend NOT using your car to recharge your fence battery. Doing so will charge the fence battery in a short period of time, but high recharge rates are not the best way to extend battery life. The best way to do that would be using a 'smart' charger that likely does not deliver more than about 10 amps at any point in the recharge cycle. Ideally, you would have a spare battery that you would periodically swap out while doing a (slow) recharge on the primary battery.

    Even though you did not originally plan on a solar fence charger system, there is no reason that you couldn't add a solar cell to your existing setup. Even a relatively small (inexpensive) solar panel would extend the time between battery recharge/swap outs.

    If you were to add an up to 15 watt solar panel you could probably avoid adding a solar controller. Just be sure to measure the battery voltage periodically and be prepared to recharge/swap when the voltage is too low.
    Graham
    USDA Zone 7A Elevation 1400 ft

  8. #7
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by hockeyfan_019 View Post
    The trick to the solar charger is that it doesn't NEED to charge much, since the fence doesn't draw much except for the occasional bear jolt. Hopefully the bears learn after a few times and the fence can stay charged even longer. I see that harbor freight even sells a 7 watt solar charger for $30, here is the link:

    https://www.harborfreight.com/7-watt...kit-64801.html
    If your insulators are good and no weed contacts the fence wont draw as much current to restore the capacitor between pulses but there is some continuous current draw even if no creature is contacting it. The fence wires radiate as an electro magnetic antenna. I remember my wifes bicycle speedometer registering 8 km. per hour when it came within about 15 feet of the 6 joule chargers fence.
    Frank

  9. #8
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    I have a 120 amp hour deep cycle battery, it's not an automotive battery.

    Sounds to me like my best option here is to buy a solar trickle charger.

    I found one on amazon that does 15 watts for $40, which seems like it should

    I think that should answer most of my questions, now for the real challenge:

    How do I remove grounding rods if they're already pounded into the soil?

  10. #9
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by username00101 View Post

    How do I remove grounding rods if they're already pounded into the soil?
    Why do you want to remove the grounding rods? It may be easier to just get new ones.

  11. #10
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by username00101 View Post
    I have a 120 amp hour deep cycle battery, it's not an automotive battery.

    Sounds to me like my best option here is to buy a solar trickle charger.

    I found one on amazon that does 15 watts for $40, which seems like it should

    I think that should answer most of my questions, now for the real challenge:

    How do I remove grounding rods if they're already pounded into the soil?
    Don't try to just pull them out, you're fighting hydro lock and corrosion. Drive them in a little bit first, and then use a fence post puller. If you don't have one of those, you can always rig up a tripod of sorts over the rod and use a come-along. I've done this with numerous items over time, but usually it's just a stump or fence post that I'm trying to get out. If you can just drive it down flush and get a new one like Frank suggested, that's probably an easier proposition, but those rods are a few $$$. Since I'm so cheap, I'd probably try to get it out first.
    USDA 6a, 8 frame equipment

  12. #11
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by hockeyfan_019 View Post
    Don't try to just pull them out, you're fighting hydro lock and corrosion. Drive them in a little bit first, and then use a fence post puller. If you don't have one of those, you can always rig up a tripod of sorts over the rod and use a come-along. I've done this with numerous items over time, but usually it's just a stump or fence post that I'm trying to get out. If you can just drive it down flush and get a new one like Frank suggested, that's probably an easier proposition, but those rods are a few $$$. Since I'm so cheap, I'd probably try to get it out first.
    They're like $20 each.

  13. #12
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    Default

    20 watt solar panel $25 and solar charge controller for 6.50. Both EBay prices.

  14. #13
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by username00101 View Post
    They're like $20 each.
    Farm jack or old bumper jack, pipe wrench, a piece of chain, and a pimiento cheese sandwich. Or a 2x4 for a lever, a pipe wrench, some chain, and a pimiento cheese sandwich. If the top of the grounding rod is at ground lever, bring a shovel and don’t wear Crocs.
    David Matlock

  15. #14
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    David, You must make some amazing pimiento cheese sandwiches

  16. #15
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by Riverderwent View Post
    bring a shovel and donít wear Crocs.
    Wow, I can think of lots of places where such advice can be beneficial lol
    USDA 6a, 8 frame equipment

  17. #16
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by hockeyfan_019 View Post
    Wow, I can think of lots of places where such advice can be beneficial lol
    I put it on my refrigerator.
    Last edited by Riverderwent; 04-02-2020 at 03:16 PM.
    David Matlock

  18. #17
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    Quote Originally Posted by yruiz View Post
    20 watt solar panel $25 and solar charge controller for 6.50. Both EBay prices.
    I just spoke with my son. He says 20 watt panel is what he buys when they are on sale. 15 watt ones start getting behind sometimes as the days start to get shorter in the fall. He uses the Parmac Magnum fencers. Having a spare is a good idea.
    Frank

  19. #18
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    OK, last question.

    What is the amount of Amp hours that one needs on a deep cycle battery, assuming I have the 20W solar charger?

  20. #19
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    You really can't make those kinds of assumptions. The output of the solar charger will vary, based on the sun/cloud coverage. And the demand of the fence charger will vary based on weed contact, animal contact and battery condition. So you will still have to monitor the battery voltage. There really is no free lunch.
    Graham
    USDA Zone 7A Elevation 1400 ft

  21. #20
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    Default Re: Electric fence charger - how do I charge my battery, and how long will it last?

    You mentioned you had a 120 ampere hour battery. That should be enough flywheel effect to carry you through a fairly long rainy spell without having the battery voltage dip too much. Time spent, X the degree of discharge is the killer of lead acid batteries. My son buys automotive batteries from Costco or Walmart usually a size that fits some other piece of farm equipment. There are recreational batteries dubbed Marine or some such name that are supposedly more tolerant of deeper discharges but his experience is they are not worth the extra cost. Put your battery on the fencer fully charged and note how much voltage drop there is in a week without the solar, and you will find out. Buy a cheap multimeter if you dont have one.

    Many people make out with a battery the size used in riding mowers which are less than half the price of an automotive sized one. That is what I use on mine but I have about a 50 watt panel and it puts out enough juice even on cloudy days so the battery only has the dips that occur overnight.
    Frank

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