Battery life..fence charger

I use 12 volt batteries to power remote electric fence energizers. I use short runs of fence to divide pastures for rotational grazing and to keep animals off fences. Because the fences are moved often I want to keep the charger and battery easily portable, so solar chargers that require a solid mounting, don't work for me. I have been rotating batteries...leave it on until the battery gets drained low, replace it with a fully charged battery and bring the discharged battery back to the barn and recharge it.

A couple questions: Does this constant cycling hurt battery life? Since it actually does not take much of a battery to run these chargers, will lawn mower batteries hold up as well as a regular battery? Is there any real advantage in using big marine deep cycle batteries (expensive and heavy to move)?

Thanks for your replies.

Repeated discharging below 75% full before recharge is harmful. The larger the battery,the longer it last's before requiring recharge. I don't understand why you feel solar chargers are difficult to use.

Auto batteries (car, tractor, motorcycle, lawn mower, etc.) are designed for "starting", and the more they get deeply discharged, the sooner they will fail. Deep cycle batteries are designed for being able to safely discharge down to 30% or even to 20%. AGM batteries will probably make you the happiest. They come in various different sizes, are sealed, spillproof, and can handle repeated discharge cycles if not TOO far. Would still highly recommend connecting a small solar panel to help keep the battery's charge lasting longer. This can be done by mounting a board on top of a wood post near the battery, then set the small solar panel on the board. Be sure to use some means of preventing a strong gust from blowing your panel off.

Although initial cost is high, we use Optima Yellow top deep cycle batteries on our electric fences in the same fashion you are talking. With the small solar panels I did not charge either battery during the season. We ran from mid June to beginning of October. We used Battery Tender solar panel chargers from Amazon that cost about $80 each. That being said our area was small, slightly over two acres, and only two wire for pigs. We also were diligent with keeping the fence line clean of grass and weeds. Both batteries got charged at the end of the season, and will again once they go out in May.

Can't say a cheaper non-deep cycle battery would be better but I had no issues and that is one less thing to worry about.

There is so much info about batteries, I sometimes have difficulty knowing what to believe. He is a clip from battery university.

A discharge/charge cycle is commonly understood as the full discharge of a charged battery with subsequent recharge, but this is not always the case. Batteries are seldom fully discharged, and manufacturers often use the 80 percent depth-of-discharge (DoD) formula to rate a battery. This means that only 80 percent of the available energy is delivered and 20 percent remains in reserve.

They also recommend not discharging a lead acid battery more than 1.75v per cell. Volts is easy to measure. 12v battery has 6 cells, 6x 1.75 = 10.5v

I find my lead acid batteries last longer charging at 8 amps and with a charger that will also desulfate and equalize.

I bought my last marine battery. They don't last me very long. A friend agrees, his marine battery doesn't last him very long either. He uses his on a trolling motor. He claims his friend uses a car battery on his boat and gets longer life out of battery.

Another way to measure the charge in a battery is using a hydrometer. Here is an estimate of what the specific gravity vs charge. I got a good hydrometer from Napa. It also measures the temperature of electrolyte and gives you a correction factor.

Charged Specific Gravity
100% 1.255-1.275
75% 1.215-1.235
50% 1.180-1.200
25% 1.155-1.165
0% 1.110-1.130

Measuring specific gravity may be more reliable than measuring voltage. Do both and decides which works best to extend battery life.

We always used car or tractor batteries that would no longer start the vehicle but would run the fence just fine. The older they got, they would discharge faster but we keep more than one around and try to keep a spare charged up. Swap out when checking or switching pastures. We purchased a new deep cycle battery a few years ago when we needed another battery and it will last several months on a charge.

On batteries designed for "starting", if they are repeatedly discharged to low amounts it creates more sulfation, which decreases its capacitance. Capacitance is the true measure of how much power a battery has, as you can measure 12v across the terminals, yet have no starting power.

There are quite a few videos out there about "How To Restore A Dead Battery". And while it IS possible to revive a battery, you can't bring it back to 100% capacitance. ...But now I'm getting a little off-topic.

Is there a golf course near you?
Electric hand carts and the larger buggies use brilliant deep cycle sealed batteries . When they won't go round 18 holes plus the car park and club house they get changed . A battery that will still go round 17 holes still packs a punch. I use these for all my tractors and lawn mowers and electric fences . They usually cost a few beers or a bottle of wine .

That's a great idea! Unfortunately for me, not many golf courses up here. They keep losing the balls in the snow! *LOL*

I used an old farm pickup as my battery, charger holder and battery charger. Worked good started the truck every three days or so for about 15 minutes or whatever time it took to check cattle in that paddock.

I just hang my solar fencer on a post, works well.

I run battery powered electronet for rotational grazing sheep. I use deep cycle marine batteries form Wally World. I used a Harbor Freight cheapy solar charger, but this year I want to get a better one with a controller in it. At that, I'll still probably need to rotate batteries.