Solar panel for 12 volt fence charger??

How does one correctly check the output of a solar panel? Is it correct to attach ohm meter with it set on 20 volts DC? Attaching ohm meter as I described showed 19.5 volts which I think is too high. Can solar panel leads be attached directly to battery as long as polarity is correct? The reason I ask is I attached solar panel to battery but battery voltage got below 11.5 volts so fence charger quit electrifying fence. My bull thinks my neighbors 16 month old open heifers look appealing. To keep this tractor related I use my tractor to feed rd bales to my bull.
Thanks,Jim

Jim, I had those things for a few years, and
decided they were too expensive to keep up. Mine
is now on a 120 outlet in the barn, and the time
to run a jumper out to the fence was worth every
bit of it. The solar panels are OK, I guess, but
if it got cloudy for three days, the batteries
died and with it the fence. Another day or two
and we were chasing calves. During the summer,
they worked OK until the weeds killed the fence,
but during the winter, they only rarely worked. And, the gel cell batteries, or a larger wet cell battery is getting pretty expensive.
My advice- get a good, hot New Zealand charger and
forget the solar idea....

A typical 12 volt solar panel has will read 20-21
volts when there is only a volt meter hooked to it
and no load. That reading is called the "Voc."

The right way to check it is when in full sun,
hooked to a load that draws it's rated amp rating
along with a volt reading. A 100 watt "12 volt"
panel will be able to make 21.4 volts no-load, and
around 17 volts when making 6.2 amps of current at
17.4 volts.

Voc = Voltage open circuit - nothing attached to
the panel.

Vmp = Voltage maximum power - what the Voltage
would be under ideal conditions with the maximum
output current

Imp = Amps maximum power.

(quoted from post at 16:19:13 07/29/14) How does one correctly check the output of a solar panel? Is it correct to attach ohm meter with it set on 20 volts DC? Attaching ohm meter as I described showed 19.5 volts which I think is too high. Can solar panel leads be attached directly to battery as long as polarity is correct? The reason I ask is I attached solar panel to battery but battery voltage got below 11.5 volts so fence charger quit electrifying fence. My bull thinks my neighbors 16 month old open heifers look appealing. To keep this tractor related I use my tractor to feed rd bales to my bull.
Thanks,Jim

Click to expand...

I have had one set up for four years now it stays out there year round, 1.25 mile of fence.
I use one of the large panels roughly one foot by three foot.
It is hooked to an old 12 volt battery and the fencer is hooked to that.
Hooked direct no charge controler or regulator on mine.
Start of the grazing season year four I finally changed out the battery with another old car battery.
Without the battery connected the panel makes enough juice to run the fencer during the day.
Without the panel hooked up the battery will keep things going for 8-10 days.
Real simple and dependable system.
Half a dozen bulls here, not one has ever crossed the line.

"Attaching ohm meter as I described showed 19.5 volts which I think is too high"


Jim, the "open circuit" unloaded voltage output, Voc, may be in the 19 to over 20 volt range depending on the sunlight and angle and the panels rating, so that 19.5 volts doesnt surprise me. Its important to what the voltage is when connected to a load and to what voltage it might raise a given battery that tells you more.


"Can solar panel leads be attached directly to battery as long as polarity is correct?"

They could be connected direct without a charge controller in place and "work". Depending on the panel rating and sunlight and the battery I suppose there's "some" chance the battery could become overcharged, that's one reason for using a charge controller.

John T

Thanks for the replies. I'll check solar panel while it's attached to the battery.
Thanks,Jim

(quoted from post at 17:19:13 07/29/14) How does one correctly check the output of a solar panel? Is it correct to attach ohm meter with it set on 20 volts DC? Attaching ohm meter as I described showed 19.5 volts which I think is too high. Can solar panel leads be attached directly to battery as long as polarity is correct? The reason I ask is I attached solar panel to battery but battery voltage got below 11.5 volts so fence charger quit electrifying fence. My bull thinks my neighbors 16 month old open heifers look appealing. To keep this tractor related I use my tractor to feed rd bales to my bull.
Thanks,Jim

Click to expand...

How many watts and amps is the solar panel rated for ? Sounds like not enough charging capacity.

If it's one of those cheesy little 6"x6" solar panel fence chargers, there is no way it can keep the battery charged unless you get a LOT of sun.

First off check for shorts on the fence. That sucks down the battery faster.

Second off you need a much larger solar panel. One of those 45W setups from Harbor Freight is more like it.

(quoted from post at 08:48:05 07/30/14)

How many watts and amps is the solar panel rated for ? Sounds like not enough charging capacity.

Click to expand...

Actually I got this panel in "used condition" so I have no idea of watts/amps. Are the panels marked for watts/amps?

This fence charger is far from cheesy as it's a Gallagher Smart power MBX2500 that I have attached a 900CCA autio battery to. Solar panel is a 12" X 12" of unknown output.

Here's a link to a solar panel I've been using

The only thing since then is the charge controller died...so I bought 2 more, so I'd have a spare

Fred
Solar fencer

(quoted from post at 09:03:16 07/30/14)

(quoted from post at 08:48:05 07/30/14)

How many watts and amps is the solar panel rated for ? Sounds like not enough charging capacity.

Click to expand...

Actually I got this panel in "used condition" so I have no idea of watts/amps. Are the panels marked for watts/amps?

Click to expand...

Is there no charge controller or at least a diode that prevents the panel discharging the battery at night ?