Wanted solar panel and battery to power electric fence energizer

[bmeagle]

On my small holding I want to power the energizer for my electric fence purely with solar, no inverter needed.

Energizer supposedly uses about 27 Watts.

Nemtek wanted to sell me 140W panel and 100AH battery at exorbitant prices.

Energizer can pull up to 40 watt.

Any offers in centurion, midrand area?

I think 100Ah is to small to ensure long life, battery should last at least 3 years.

[viper_za]

I think with the small load of +-27w a 100Ah battery will be more than enough to carry the load for +- 2 days with no sun at all, this will put it on 50% DOD. 27w is not close to the C20 rating (100Ah) of the battery and you should easily get more then 100Ah out of the battery with the slow discharge rate.

What I would ask for is a bigger panel 180w and up maybe.

What charge controller did they recommend?

[bmeagle]

They sold me a 15A pwm controller.

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[Mark]

Out of interest.  I run an electric gate (12V ET Gate Motor) off a 102ah Sealed Lead Acid Battery, 15A Controller and 100W solar panel.  I also have an LED floodlight (12V, 10W) which comes on for 3 min every time the gate is opened.  Easily manages this...

[bmeagle]

Out of interest.  I run an electric gate (12V ET Gate Motor) off a 102ah Sealed Lead Acid Battery, 15A Controller and 100W solar panel.  I also have an LED floodlight (12V, 10W) which comes on for 3 min every time the gate is opened.  Easily manages this...

Your DOD is probably very low with such small loads.

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[KLEVA]

Have 2 Electric Fences at house, and although they post 38W as their usage (on the slip of paper that gives their specs), they can jump (very temporary) to over 200W for a few seconds or in error/fault. They are normally intelligent enough to correct themselves, but don't let your power input be unable to deliver that 200W when needed...

That aside, this is a single application and even if it sits with a 40W continuous load, it is still small.

As I advocate in many posts - Batteries are key (you can add/subtract other stuff later, not so with batteries), however 105Ah for your Energizer seems like enough (if you can afford a 200Ah battery, then all the better, and will last even longer and serve you probably 4x as many cycles), and more importantly can deliver the power for a 2-3 day period if there is no other power input, if the draw remains that low. (but as mentioned below, you must be able to charge it)

The maths on the panel feels wrong though, even with a low power draw, a battery bank needs between .3A and 4A just to remain at float... I am not sure that that panel is right (and you didn't mention a charger/invertor)... If you not feeding this with something else, then I think there is something wrong with the panels (I don't think they can charge a 105Ah battery in a day of 8 hours sunshine - but I haven't done the math yet), and surely you need more than one day of operation, what if yesterday was cloudy/rainy?

Another small note: Somewhere you are going to have an intelligent enough charger to be able to load the battery up to maybe 58 volts every so often and properly float (at about 54V), and then be able to cut everything off below +-42V... This wasn't in your discussion, but you can't do any of the above without a intelligent charger...