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



## username00101 (Apr 17, 2019)

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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## hockeyfan_019 (Dec 1, 2019)

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?


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## username00101 (Apr 17, 2019)

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).


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## hockeyfan_019 (Dec 1, 2019)

username00101 said:


> 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-solar-panel-kit-64801.html


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## crofter (May 5, 2011)

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.


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## Rader Sidetrack (Nov 30, 2011)

username00101 said:


> 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/article/how-charge-deep-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.


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## crofter (May 5, 2011)

hockeyfan_019 said:


> 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-solar-panel-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.


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## username00101 (Apr 17, 2019)

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?
*


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## elmer_fud (Apr 21, 2018)

username00101 said:


> *
> 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.


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## hockeyfan_019 (Dec 1, 2019)

username00101 said:


> 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.
> 
> ...


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.


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## username00101 (Apr 17, 2019)

hockeyfan_019 said:


> 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.


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## yruiz (Aug 22, 2019)

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


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## Riverderwent (May 23, 2013)

username00101 said:


> 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.


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## Ryan Williamson (Feb 28, 2012)

David, You must make some amazing pimiento cheese sandwiches


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## hockeyfan_019 (Dec 1, 2019)

Riverderwent said:


> bring a shovel and don’t wear Crocs.


Wow, I can think of lots of places where such advice can be beneficial lol


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## Riverderwent (May 23, 2013)

hockeyfan_019 said:


> Wow, I can think of lots of places where such advice can be beneficial lol


I put it on my refrigerator.


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## crofter (May 5, 2011)

yruiz said:


> 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.


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## username00101 (Apr 17, 2019)

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?


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## Rader Sidetrack (Nov 30, 2011)

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.


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## crofter (May 5, 2011)

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.


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## sjj (Jan 2, 2007)

username00101 said:


> ... but I still don't know how to charge the battery, ...


Users should consult the battery manufacturer for the charging instructions. For example: 
https://www.usbattery.com/wp-content/uploads/2019/04/usb_31DC_data_sheet_2019.2.pdf


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## Deepwoods (Jan 9, 2019)

Username,

A battery box like boaters use will protect your battery. For the fencer, try a cut off antifreeze jug. Example pic below. If you add a solar panel to your setup, a scavenged satellite tv dish make a great adjustable mount for a single solar panel.


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## Jim Given (Mar 15, 2012)

I'm frugal, so went to local Auto parts store and bought 2 discarded/used car batteries for $10. I charge them with battery charger and switch them out monthly. Been doing this for years. Batteries usually last 2-3 yrs I have found that way.


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## username00101 (Apr 17, 2019)

The 20 watt charger appears to be strong enough.


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## username00101 (Apr 17, 2019)

Holy crap.

The 100 amp hour battery died.

No idea why.

Worked perfectly for 3 weeks, suddenly just dead.

The grass grew up along the fence over the weekend, and I guess the grass was pulling the electric charge from the fence.

What a total waste of money, and effort. I had to go buy a new battery, and I still have absolutely no idea what went wrong.

Now the stupid battery is reading 9 volts.

I hate deep cycle batteries, they make no sense. Why won't it get back up above 12V, aren't they designed to deep cycle?

Why would a 20 watt solar charger suddenly fail after working perfectly for 3 weeks.


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## username00101 (Apr 17, 2019)

@$#*@

I think this is the answer here:

_To combat excessive weeds, use low impedance energizers, which are capable of increasing their energy output as fence load increases. As weeds touch the fence line, drawing voltage and amperage to earth, the low impedance energizer will begin to compensate for the power drain by releasing stored energy (joules). This boost overcomes the voltage loss caused by the weeds, and pushes energy to the rest of fence line. As long as the wire remains in contact with the energizer, the energy can flow past vegetation to keep the fence hot. 

...low impedance energizers are specifically designed to pump out more energy when the fence is registering low ohms. This allows our energizers to produce their maximum energy output when it is needed, rather than all the time. "
_

So I guess this means that the stupid grass growing along the fence was pulling out enough energy from the battery to croak the system in just a few days?


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## username00101 (Apr 17, 2019)

OK, so it was probably a combination of the grass and the fact that a 20W charger just doesn't seem to be enough. 

The electric fence energizer company didn't offer much advice.

Trial and error.


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## sjj (Jan 2, 2007)

username00101 said:


> ... Trial and error.


To react quickly you need a refractometer to measure the specific gravity of the battery acid. 
They have 3 scales.One of them is for battery fluid. (SG =1.10-1.40kg/l). 
The ATC feature helps to interpretthe readings in the field.


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## crab414 (Jan 6, 2020)

Raising pigs out on pasture, you and I have a lot of same challenges. I have ended up using Speedrite 1000 energizers. They store 2.5 jules and push 2. The units show you the charge of the battery, clearance of the fence line, gives different settings and strengths for day and night. On the low setting, the battery lasts for 42 days and 28 on the high setting. I'm using two now and I love them. 
The voltage runs 10000kv on the line. Kinda need that when your boar weighs 800#. I think I paid 146$ apiece at Premier Fencing. Also, I believe that they are American made, I could be wrong though.


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## username00101 (Apr 17, 2019)

After trial and error, solar charger must be over 50+ watts.

Energizer power makes a difference - a low powered energizer likely does not require as many watts.

The 2 joule energizer required 50 watts or higher. 

Financially, the most realistic option is a combo package and go for the higher watts.


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